Patent Description:
Lightweight components formed from lightweight polymer materials are used in many applications, such as food packaging and the automotive industry. One of the main challenges involving lightweight polymer materials lies in the development of increasingly light components, but retaining the mechanical properties of heavier components. A possible strategy for developing lightweight components may include foaming of a base material to reduce the weight or density. Foaming may include incorporating reinforcing and/or functional fillers into the foam to act as cell nucleating agents or promoters. Cell nucleating agents can be used in polymeric foaming processes to enhance cell nucleation. With the presence of nucleating agents, heterogeneous nucleation becomes the predominant mode of cell nucleation during polymer foaming processes.

Polypropylene foams are known, but they have reduced stiffness and mechanical strength compared to conventional polypropylene, and present foaming processes may be insufFicient to decrease the weight while retaining desirable mechanical properties. Increasing oil prices have also contributed to increased production costs of plastic resins and finished plastic products. Plastic resin costs typically amount to <NUM>% to <NUM>% of the total cost of any given plastic product; therefore, a reduction of resin amounts in plastics while at the same time maintaining mechanical and other properties of the plastic products could provide considerable economic benefit. <CIT> relates to polymer-based foams having a cellular structure and using talc as a nucleating agent.

A polymer foam can be described as a material with a cellular structure created by the formation of gas bubbles within a polymer. Polymer foams may offer certain advantages over their solid analogues, including lower density, higher thermal insulation, enhanced sound deadening, and tunable mechanical properties. In closed-cell polymer foams, the size and distribution of the foam cells may have an impact on the resulting physical properties. For example, foams with cell sizes smaller than the critical defect size of the polymer may limit fracture and may reduce the weight without sacrificing the mechanical properties. Therefore, developing straight-forward strategies to control the size and distribution of cells within a polymer foam would be desirable.

Accordingly, it may be desirable to provide a polymer-based foam having improved properties. It may also be desirable to provide a method of producing a polymer-based foam.

The present invention is defined in and by the appended claims. In accordance with a first aspect there is provided a polymer foam composition comprising: a polymer-based foam matrix; and a mineral nucleating agent within a cell of the polymer-based foam matrix, wherein the mineral nucleating agent comprises an alkaline earth metal silicate, wherein the alkaline earth metal silicate comprises calcium silicate, and wherein the alkaline earth metal silicate is present in an amount in a range from <NUM>% by weight to <NUM>% by weight of the polymer foam, wherein the polymer-based foam matrix comprises at least one of a polystyrene matrix, polypropylene matrix, polyurethane matrix, poly(ethyl vinyl acetate) matrix, polyethylene terephthalate matrix, or copolymer matrices thereof. There is described herein a method of producing a polymer foam which may include providing a polymer composition, introducing an alkaline earth metal silicate into the polymer composition, and foaming the polymer composition using a gas to form a polymer foam.

There is described herein a method of producing a polymer-matrix which may include providing a polymer composition, nucleating the polymer composition with an alkaline earth metal silicate, and using a blowing agent to form a polymer foam from the polymer composition. The alkaline earth metal silicate may facilitate nucleation of the cells in the polymer foam.

Introducing the alkaline earth metal silicate may include introducing the alkaline earth metal silicate into the polymer composition using an extrusion-mixing process.

The polymer composition may include at least one of a thermoplastic polymer or a thermoplastic elastomer. The polymer composition includes at least polymer selected from the group consisting of a polystyrene, a polypropylene, a polyurethane, a poly(ethyl vinyl acetate), a polyethylene terephthalate, and copolymers and blends thereof.

The polymer composition may include at least one of a thermoplastic polymer or a thermoplastic elastomer. The polymer composition includes at least one of polystyrene, polypropylene, polyurethane, poly(ethyl vinyl acetate) (EVA), polyethylene terephthalate (PET), or copolymers thereof.

The blowing agent may include at least one of CO<NUM>, N<NUM>, or an organic gas. An organic gas may include, for example, hexane, propane, butane, n-butane, i-butane, pentane, i-pentane, n-pentane, CHF<NUM>Cl, CF<NUM>ClCH<NUM>, CHF<NUM>CH<NUM>, CHCl<NUM>CF<NUM>, CHFClCF<NUM>Cl, CHFClCF<NUM>, CH<NUM>FCF<NUM>, CH<NUM>CF<NUM>, CFCl<NUM>, CF<NUM>Cl<NUM>, CFCl<NUM>CF<NUM>Cl, CF<NUM>ClCF<NUM>Cl, CH<NUM>Cl, or CH<NUM>Cl<NUM>.

The polymer composition may be the major component of the polymer foam. For example, the polymer composition may be present in an amount greater than about <NUM>% by weight of the polymer foam, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, or greater than about <NUM>% by weight of the polymer foam.

The alkaline earth metal silicate is present in an amount in a range from about <NUM>% by weight to about <NUM>% by weight of the polymer foam, such as, for example, in a range from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, or from about <NUM>% by weight to about <NUM>% by weight of the polymer foam. The nucleating agent may be present in an amount in a range from about <NUM>% by weight to about <NUM>% by weight of the polymer foam, such as, for example, in a range from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, or from about <NUM>% by weight to about <NUM>% by weight of the polymer foam.

The alkaline earth metal silicate comprises calcium silicate. The calcium silicate may include a synthetic calcium silicate. In another aspect, the calcium silicate may comprise a natural calcium silicate, such as, for example, a Wollastonite. The alkaline earth metal silicate may include a derived calcium silicate, such as, for example, diatomaceous earth-derived calcium silicate. The alkaline earth metal silicate may include a blend of alkaline earth metal silicates. The alkaline earth metal silicate may include a secondary mineral in addition to the alkaline earth metal silicate.

The alkaline earth metal silicate may include magnesium oxysulfate as a secondary mineral. The magnesium oxysulfate may have an aspect ratio ranging from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. The alkaline earth metal silicate may include a secondary mineral selected from a kaolin, a bentonite, a talc, a chloritic talc, a milled expanded perlite, and a diatomaceous earth.

The alkaline earth metal silicate may include a functionalized alkaline earth metal silicate. The functionalized alkaline earth metal silicate may have a surface treatment that may enhance interaction with one or more of the gas or the polymer composition. For example, the surface treatment may impart hydrophobic properties to the alkaline earth metal silicate. The surface treatment may include a silane, silicone oil, siloxane, fatty acid, salt thereof, or ester thereof. The fatty acid, salt thereof, or ester thereof may have a chain length of C8 or higher. The alkaline earth metal silicate may include a secondary mineral in addition to the alkaline earth metal silicate.

The alkaline earth metal silicate may include magnesium oxysulfate as a secondary mineral. The magnesium oxysulfate can have an aspect ratio ranging from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. The alkaline earth metal silicate may include a secondary mineral selected from a kaolin, a bentonite, a talc, a chloritic talc, a milled expanded perlite, and a diatomaceous earth. Talc or chloritic talc may include at least one of a lamellar talc, micro-lamellar talc, microcrystalline talc, and macrocrystalline talc.

The mineral nucleating agent, such as, for example, an alkaline earth metal silicate, may have a high aspect ratio.

The talc or chloritic talc may include one or more of a high aspect ratio talc, a high aspect ratio lamellear talc, a high aspect ratio micro-lamellar talc, a high aspect ratio chloritic talc, a high aspect ratio lamellar chloritic talc, and a high aspect ratio micro-lamellar chloritic talc.

A high aspect ratio of the mineral nucleating agent may be achieved by a wet-milling process.

The mineral nucleating agent may include a blend of a talc and a chloritic talc. For example, the mineral nucleating agent may include talc as a mineral and chloritic talc as a secondary mineral, or may include chloritic talc as a mineral and talc as a secondary mineral.

The polymer foam composition may have a flexural modulus greater than or equal to about <NUM> MPa, such as, for example, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, or greater than or equal to about <NUM> MPa.

The polymer foam composition may have a flexural modulus in a range from about <NUM> MPa to about <NUM> MPa, such as, for example, in a range from about <NUM> MPa to about <NUM> MPa, from about <NUM> MPa to about <NUM> MPa, or from about <NUM> MPa to about <NUM> MPa.

The polymer foam composition may have a first flexural modulus. The first flexural modulus may be greater than a flexural modulus of a comparative polymer foam composition having a mineral nucleating agent that includes one of the mineral and the secondary mineral individually.

The polymer foam composition having a mineral nucleating agent and a secondary mineral nucleating agent may have an impact resistance that is not adversely affected relative to a polymer foam composition having a mineral nucleating agent that includes one of the mineral and the secondary mineral individually.

The polymer foam composition may have a weight reduction greater than or equal to about <NUM>% as compared to the same volume of the non-foamed polymer, such as, for example, greater than or equal to about <NUM>%, greater than or equal to about <NUM>%, or greater than or equal to about <NUM>% as compared to the same volume of the non-foamed polymer.

The polymer foam composition may have a weight reduction in a range from about <NUM>% to about <NUM>% as compared to the same volume of the non-foamed polymer.

The mineral nucleating agent may have a lamellarity index greater than about <NUM>, such as, for example, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

The polymer foam may have an average cell size (φ) less than or equal to about <NUM>. For example, the polymer foam may have an average cell size (φ) less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, or less than or equal to about <NUM>.

The polymer foam may have an average cell size (φ) in a range from about <NUM> to about <NUM>. For example, the polymer foam may have an average cell size (φ) in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

The polymer foam may have an average cell size (φ) less than the critical defect size of the polymer composition.

The polymer foam may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer foam may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM>. <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, or greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>.

The polymer foam may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer foam may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, or from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>.

The alkaline earth metal silicate may have a BET surface area greater than or equal to about <NUM><NUM>/g. For example, the alkaline earth metal silicate may have a BET surface area greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, or greater than or equal to about <NUM><NUM>/g.

The alkaline earth metal silicate may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g. For example, the alkaline earth metal silicate may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, or from about <NUM><NUM>/g to about <NUM><NUM>/g.

The alkaline earth metal silicate may have a median particle size (d<NUM>) greater than or equal to about <NUM>, such as, for example, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

The alkaline earth metal silicate may have a median particle size (d<NUM>) in a range from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

The method may include a two-step extrusion-mixing and foaming process. The method may include a single-step injection-moulding foaming process.

The alkaline earth metal silicate may have an oil absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

The alkaline earth metal silicate may have a water absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

The alkaline earth metal silicate may have an aspect ratio in the range of from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

The alkaline earth metal silicate may have a basic pH. For example, the alkaline earth metal silicate may have a pH greater than <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

The polymer foam may have a relative density compared to the respective unfoamed base materials, in a range from about <NUM> to <NUM>, such as, for example, in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

A polymer foam composition may include a polymer-based foam matrix and a mineral nucleating agent within a cell of the polymer-based foam matrix.

The mineral nucleating agent includes alkaline earth metal silicate. The mineral nucleating agent may include at least one of magnesium oxysulfate, kaolin, talc, chloritic talc, perlite, expanded milled perlite, diatomaceous earth, glass cullet, feldspar, nepheline syenite, or bentonite. Talc or chloritic talc may include at least one of a lamellar talc, micro-lamellar talc, microcrystalline talc, and macrocrystalline talc.

In general, the individual platelet size, i.e., the median diameter as measured by the Sedigraph method, of an individual talc platelet (a few thousand elementary sheets) can vary from approximately <NUM> to over <NUM>, depending on the conditions of formation of the deposit. The individual platelet size determines the lamellarity of the talc. A highly lamellar talc will have large individual platelets, whereas a microcrystalline talc will have small platelets. Although all talcs may be termed lamellar, their platelet size differs from one deposit to another. Small crystals provide a compact, dense ore, known as microcrystalline talc. Large crystals come in papery layers, known as macrocrystalline talc. Known microcrystalline talc deposits are located in Montana (Yellowstone) and in Australia (Three Springs). In a microcrystalline structure, talc elementary particles are composed of small plates compared to macrocrystalline structures, which are composed of larger plates.

The mineral nucleating agent may have a high aspect ratio. The talc or chloritic talc may include one or more of a high aspect ratio talc, a high aspect ratio lamellear talc, a high aspect ratio micro-lamellar talc, a high aspect ratio chloritic talc, a high aspect ratio lamellar chloritic talc, and a high aspect ratio micro-lamellar chloritic talc.

The polymer-based foam matrix may include at least one of a thermoplastic polymer matrix or a thermoplastic elastomer matrix. The polymer-based foam matrix includes at least one of a polystyrene matrix, polypropylene matrix, polyurethane matrix, poly(ethyl vinyl acetate) (EVA) matrix, polyethylene terephthalate (PET) matrix, or copolymer matrices thereof.

The blowing agent used to form the polymer-based foam matrix may include at least one of CO<NUM>, N<NUM>, or an organic gas. An organic gas may include, for example, hexane, propane, butane, n-butane, i-butane, pentane, i-pentane, n-pentane, CHF<NUM>Cl, CF<NUM>ClCH<NUM>, CHF<NUM>CH<NUM>, CHCl<NUM>CF<NUM>, CHFClCF<NUM>Cl, CHFClCF<NUM>, CH<NUM>FCF<NUM>, CH<NUM>CF<NUM>, CFCl<NUM>, CF<NUM>Cl<NUM>, CFCl<NUM>CF<NUM>Cl, CF<NUM>ClCF<NUM>Cl, CH<NUM>Cl, or CH<NUM>Cl<NUM>.

The polymer-based foam matrix may be the major component of the polymer foam composition. For example, the polymer-based foam matrix may be present in an amount greater than about <NUM>% by weight of the polymer foam composition, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, or greater than about <NUM>% by weight of the polymer foam composition.

The alkaline earth metal silicate is present in an amount in a range from about <NUM>% by weight to about <NUM>% by weight of the polymer foam composition, such as, for example, in a range from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, or from about <NUM>% by weight to about <NUM>% by weight of the polymer foam composition. The nucleating agent may be present in an amount in a range from about <NUM>% by weight to about <NUM>% by weight of the polymer foam composition, such as, for example, in a range from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, or from about <NUM>% by weight to about <NUM>% by weight of the polymer foam composition.

The alkaline earth metal silicate includes calcium silicate. The calcium silicate may include a synthetic calcium silicate. The calcium silicate may include a natural calcium silicate, such as, for example, a Wollastonite. According to some embodiments, the alkaline earth metal silicate may include a derived calcium silicate, such as, for example, diatomaceous earth-derived calcium silicate. The alkaline earth metal silicate may include a blend of alkaline earth metal silicates.

The mineral nucleating agent may include a functionalized alkaline earth metal silicate. The functionalized mineral nucleating agent may have a surface treatment that enhances interaction with one or more of the gas or the polymer composition.

The polymer-based foam matrix may have an average cell size (φ) less than or equal to about <NUM>. For example, the polymer-based foam matrix may have an average cell size (φ) less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, or less than or equal to about <NUM>.

The polymer-based foam matrix may have an average cell size (φ) in a range from about <NUM> to about <NUM>. For example, the polymer-based foam matrix may have an average cell size (φ) in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

The polymer-based foam matrix may have an average cell size less than the critical defect size of the polymer.

The polymer-based foam matrix may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer-based foam matrix may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM>. <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, or greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>.

The polymer-based foam matrix may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer-based foam matrix may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, or from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>.

The mineral nucleating agent may have a BET surface area greater than or equal to about <NUM><NUM>/g. For example, the mineral nucleating agent may have a BET surface area greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, or greater than or equal to about <NUM><NUM>/g.

The mineral nucleating agent may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g. For example, the mineral nucleating agent may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, or from about <NUM><NUM>/g to about <NUM><NUM>/g.

The mineral nucleating agent may have a median particle size (d<NUM>) greater than or equal to about <NUM> , such as, for example, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

The mineral nucleating agent may have a median particle size (d<NUM>) in a range from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

The mineral nucleating agent may have an oil absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

The mineral nucleating agent may have a water absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

The mineral nucleating agent may have an aspect ratio in the range of from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

The polymer foam composition may have a relative density compared to the respective unfoamed base materials, in a range from about <NUM> to <NUM>, such as, for example, in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

Exemplary embodiments will be further illustrated by reference to the following figures:.

According to some embodiments, the present disclosure may provide for polymer foams prepared using an alkaline earth metal nucleating agent.

As used herein, "surface area" refers to a BET surface area. "BET surface area," as used herein, refers to the technique for calculating specific surface area of physical absorption molecules according to Brunauer, Emmett, and Teller ("BET") theory. BET surface area can be measured with an ASAP* <NUM> Surface Area and Porosimetry Analyzer using nitrogen as the sorbent gas, available from Micromeritics Instrument Corporation (Norcross, Ga.

According to some embodiments, the alkaline earth metal silicate may have an aspect ratio according to Jennings theory. The Jennings theory (or Jennings approximation) of aspect ratio is based on research performed by W. Gregorova, and C. Berthold, Department of Glass and Ceramics, Institute of Chemical Technology, Prague, and Institut für Geowissenschaften, Universität Tübingen, Germany, as described, e.g., in <NPL>.

Unless otherwise indicated herein, the cellular structure of the various foams described in this disclosure was studied using a HITACHI S-4300SE/N scanning electron microscope (SEM) from samples cryogenically fractured using liquid nitrogen and made conductive by sputter deposition of a thin layer of carbon. The average cell size (φ) and cell density (Nf) were directly obtained from low-magnification micrographs using the intercept counting method described in G. Sims and C. Khunniteekool, "Cell size measurement of polymeric foams," Cellular Polymers, <NUM>, <NUM> (<NUM>). In particular, cell density, Nf, was determined according to the following equation: <MAT> where n is the number of cells per area A (in cm<NUM>), and ρs and ρf are respectively the solid and foam densities.

The particle size properties for the minerals were measured according to the methods known to the skilled person in the art using light scattering of the particulate materials in a fully dispersed condition in an aqueous medium using a Microtrac S3500 laser diffraction machine supplied by Microtrac, a member of Nikkiso. The size of the particles is referred to as the "equivalent spherical diameter" (esd). The measured particle size can be provided as a plot of the cumulative percentage by weight of particles having a given size less than the esd values. The median particle size, d<NUM>, is the value determined to be the esd at which <NUM>% of the particles by weight have an esd less than that of the particular value.

The "lamellarity index" characterizes the shape of the particle, and more particularly, its flatness (large dimension/thickness). In the following description, the lamellarity index is measured by the difference between the value of the mean dimension of the particles of the powder obtained by a particle size measurement by Malvern laser diffraction using a wet method (standard AFNOR NFX11-<NUM>) and the value of the mean diameter d<NUM> obtained by a measurement by sedimentation using a "Sedigraph" (standard AFNOR X11-<NUM>), the difference being related to the mean diameter d<NUM>. Reference may be made to the article by <NPL>, which shows that this index is correlated to the mean ratio of the largest dimension of the particle to its smallest dimension. A high aspect ratio mineral, as used in this disclosure, is one with a lamellarity index greater than <NUM>.

According to some embodiments, alkaline earth metal silicates may be suitable for use as nucleating agents and/or fillers in the production of polymer foams. The polymer foams may be selected from thermoplastic materials, thermoplastic elastomers foamed with physical blowing agents, or other polymer foams, such as, for example, polystyrene, polypropylene, polyurethane, poly(ethyl vinyl acetate) (EVA), or polyethylene terephthalate (PET) foams. In some embodiments, polypropylene foams may be suited for use in the food packaging and the automotive industries. In some embodiments, polystyrene foams may be suitable for use as, for example, packaging products, insulating materials, or automotive products. In some embodiments, PET foams may be suitable for use in shipping materials, in structural components, such as automotive or aeronautical components, or in consumer goods, such as cups, boxes, or plates. In some embodiments, EVA foams may be suitable for consumer goods, such as shoes, surfboards, orthotics, or automotive or aeronautical components.

Furthermore, according to certain embodiments the compositions and methods disclosed herein may provide improved properties, regardless of whether they were produced using a two-step extrusion-mixing and foaming process, a single-step injection-moulding foaming process, or another suitable foaming process. According to some embodiments, when a single-step injection-moulding foaming process is used, advantageous physical properties may be obtained in both the flow direction (FD) of the moulding and the transversal direction (TD) to the moulding direction.

Polymer foams having desirable properties may be produced according to interactions between a blowing agent and the surface of a mineral nucleating agent, such as, for example, an alkaline earth metal silicate. Selection of the blowing agent and alkaline earth metal silicate can be used to reduce cell size in polymer foams and to encourage cell formation. Without wishing to be bound to a particular theory, it is believed that a nucleating agent surface with strong interactions with a gas (e.g., blowing agent) may reduce the activation energy for bubble nucleation in the foam, thereby increasing the cell nucleation rate and reducing the cell size. According to some embodiments, a high surface area, CO<NUM>-philic or N<NUM>-philic alkaline earth metal silicate may act as an efficient cell nucleator in polymer foams. When a blowing agent other than CO<NUM> or N<NUM> is used, such as, for example, an organic gas, the alkaline earth metal silicate may be selected to have an affinity to the blowing agent.

According to some embodiments, the size of cells within a polymer foam may be controlled by the bubble formation mechanism. For example, the cell size and distribution within a polymer foam can be controlled by a combination of the nucleation rate of bubbles and the growth rate of the bubbles. This nucleation and growth can be described by classic nucleation theory. Briefly, classic nucleation theory states that the formation of a bubble from a homogeneous polymer-gas solution is an energetically unfavorable process with an associated activation energy. The activation energy of the formation is inversely proportional to the cell nucleation rate. After a stable bubble forms, it then grows in size by depleting the surrounding solution of gas. In polymer foams, the activation energy associated with the bubble nucleation is the limiting factor in the number of bubbles created within a given volume.

According to some embodiments, the activation energy associated with bubble nucleation can be reduced through heterogeneous nucleation. In this heterogeneous nucleation, the surface between a nucleating agent and the polymer may promote bubble formation by increasing the interfacial order of the gas bubble. Increasing the interfacial order of the gas bubble may reduce the energetic barrier to nucleation by providing a favorable surface for nucleation. Such surfaces may have a surface energy that encourages wetting of the surface by the gas. In addition, these surfaces may have a high surface area in order to maximize the nucleation site density. Reducing the activation energy may provide a strategy for controlling the cell structure of polymer foams and controlling their mechanical properties.

According to some embodiments, a method of producing a polymer foam may include providing a polymer composition, introducing an alkaline earth metal silicate into the polymer composition, and foaming the polymer composition using a gas to form a polymer foam.

According to some embodiments, a method of producing a polymer-matrix may include providing a polymer composition, nucleating the polymer composition with an alkaline earth metal silicate, and using a blowing agent to form a polymer foam from the polymer composition. The alkaline earth metal silicate may facilitate nucleation of the cells in the polymer foam.

According to some embodiments, introducing the alkaline earth metal silicate may include introducing the alkaline earth metal silicate into the polymer composition using an extrusion-mixing process.

According to some embodiments, the polymer composition may include at least one of a thermoplastic polymer or a thermoplastic elastomer. The polymer composition includes at least one of polystyrene, polypropylene, polyurethane, poly(ethyl vinyl acetate) (EVA), polyethylene terephthalate (PET), or copolymers and blends thereof.

According to some embodiments, the polymer foams may include other fillers or additives. The fillers or additives may include, for example, additives, pigments, or reinforcing fillers. According to some embodiments, the additives or fillers may include, for example, talc, calcium carbonate, kaolin, diatomaceous earth, metal carbonates, or metal silicates.

According to some embodiments, the blowing agent may include at least one of CO<NUM>, N<NUM>, or an organic gas. An organic gas may include, for example, hexane, propane, butane, n-butane, i-butane, pentane, i-pentane, n-pentane, CHF<NUM>Cl, CF<NUM>ClCH<NUM>, CHF<NUM>CH<NUM>, CHCl<NUM>CF<NUM>, CHFClCF<NUM>Cl, CHFCICF<NUM>, CH<NUM>FCF<NUM>, CH<NUM>CF<NUM>, CFCl<NUM>, CF<NUM>Cl<NUM>, CFCl<NUM>CF<NUM>Cl, CF<NUM>ClCF<NUM>Cl, CH<NUM>Cl, or CH<NUM>Cl<NUM>.

According to some embodiments, the polymer composition may be the major component of the polymer foam. For example, the polymer composition may be present in an amount greater than about <NUM>% by weight of the polymer foam, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, or greater than about <NUM>% by weight of the polymer foam.

According to some embodiments, the alkaline earth metal silicate is present in an amount in a range from about <NUM>% by weight to about <NUM>% by weight of the polymer foam, such as, for example, in a range from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, or from about <NUM>% by weight to about <NUM>% by weight of the polymer foam. The nucleating agent may be present in an amount in a range from about <NUM>% by weight to about <NUM>% by weight of the polymer foam, such as, for example, in a range from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, from about <NUM>% by weight to about <NUM>% by weight, or from about <NUM>% by weight to about <NUM>% by weight of the polymer foam.

The alkaline earth metal silicate includes calcium silicate. In some embodiments, the calcium silicate may include a synthetic calcium silicate. In some embodiments, the calcium silicate may include a natural calcium silicate, such as, for example, a Wollastonite. According to some embodiments, the alkaline earth metal silicate may include a derived calcium silicate, such as, for example, diatomaceous earth-derived calcium silicate. The alkaline earth metal silicate may include a blend of alkaline earth metal silicates.

According to some embodiments, the alkaline earth metal silicate may include magnesium oxysulfate as a secondary mineral (a secondary mineral nucleating agent). In some embodiments, the magnesium oxysulfate may have an aspect ratio ranging from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>. In some embodiments, the alkaline earth metal silicate may include a secondary mineral selected from a kaolin, a bentonite, a talc, a chloritic talc, a milled expanded perlite, and a diatomaceous earth.

According to some embodiments, the alkaline earth metal silicate may include a functionalized alkaline earth metal silicate. The functionalized alkaline earth metal silicate may have a surface treatment that enhances interaction with one or more of the gas or the polymer composition.

According to some embodiments, the alkaline earth metal silicate may include a blend of a talc and a chloritic talc. For example, the alkaline earth metal silicate may include talc as a mineral and chloritic talc as a secondary mineral, or may include chloritic talc as a mineral and talc as a secondary mineral.

According to some embodiments, the polymer foam composition may have a flexural modulus greater than or equal to about <NUM> MPa, such as, for example, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, greater than or equal to about <NUM> MPa, or greater than or equal to about <NUM> MPa.

According to some embodiments, the polymer foam composition may have a flexural modulus in a range from about <NUM> MPa to about <NUM> MPa, such as, for example, in a range from about <NUM> MPa to about <NUM> MPa, from about <NUM> MPa to about <NUM> MPa, or from about <NUM> MPa to about <NUM> MPa.

According to some embodiments, the polymer foam composition may have a first flexural modulus. The first flexural modulus may be greater than a flexural modulus of a comparative polymer foam composition having an alkaline earth metal silicate that includes one of the mineral and the secondary mineral individually.

According to some embodiments, the polymer foam composition having a mineral nucleating agent and a secondary mineral nucleating agent may have an impact resistance that is not adversely affected relative to a polymer foam composition having a mineral nucleating agent that includes one of the mineral and the secondary mineral individually.

According to some embodiments, the polymer foam composition may have a weight reduction greater than or equal to about <NUM>% as compared to the same volume of the non-foamed polymer, such as, for example, greater than or equal to about <NUM>%, greater than or equal to about <NUM>%, or greater than or equal to about <NUM>% as compared to the same volume of the non-foamed polymer.

According to some embodiments, the polymer foam composition may have a weight reduction in a range from about <NUM>% to about <NUM>% as compared to the same volume of the non-foamed polymer.

According to some embodiments, the alkaline earth metal silicate may have a lamellarity index greater than about <NUM>, such as, for example, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

According to some embodiments, the polymer foam may have an average cell size (φ) less than or equal to about <NUM>. For example, the polymer foam may have an average cell size (φ) less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, or less than or equal to about <NUM>.

According to some embodiments, the polymer foam may have an average cell size (φ) in a range from about <NUM> to about <NUM>. For example, the polymer foam may have an average cell size (φ) in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

According to some embodiments, the polymer foam may have an average cell size less than the critical defect size of the polymer composition.

According to some embodiments, the polymer foam may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer foam may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM>. <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, or greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>.

According to some embodiments, the polymer foam may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer foam may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, or from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>.

According to some embodiments, the alkaline earth metal silicate may have a BET surface area greater than or equal to about <NUM><NUM>/g. For example, the alkaline earth metal silicate may have a BET surface area greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, or greater than or equal to about <NUM><NUM>/g.

According to some embodiments, the alkaline earth metal silicate may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g. For example, the alkaline earth metal silicate may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, or from about <NUM><NUM>/g to about <NUM><NUM>/g.

According to some embodiments, the alkaline earth metal silicate may have a median particle size (d<NUM>) greater than or equal to about <NUM>, such as, for example, greater than or equal to about <NUM> , greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

According to some embodiments, the alkaline earth metal silicate may have a median particle size (d<NUM>) in a range from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

According to some embodiments, the method may include a two-step extrusion-mixing and foaming process. The method may include a single-step injection-moulding foaming process.

According to some embodiments, the alkaline earth metal silicate may have an oil absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

According to some embodiments, the alkaline earth metal silicate may have a water absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

According to some embodiments, the alkaline earth metal silicate may have an aspect ratio in the range of from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

According to some embodiments, the polymer foam may have a relative density compared to the respective unfoamed base materials, in a range from about <NUM> to <NUM>, such as, for example, in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

The polymer foam composition includes a polymer-based foam matrix and a mineral nucleating agent within a cell of the polymer-based foam matrix.

The mineral nucleating agent includes alkaline earth metal silicate. According to some embodiments, the mineral nucleating agent may include at least one of magnesium oxysulfate, kaolin, talc, chloritic talc, perlite, expanded milled perlite, diatomaceous earth, glass cullet, feldspar, nepheline syenite, or bentonite. According to some embodiments, talc or chloritic talc may include at least one of a lamellar talc, micro-lamellar talc, microcrystalline talc, and macrocrystalline talc.

According to some embodiments, the mineral nucleating agent may have a high aspect ratio. According to some embodiments, the talc or chloritic talc may include one or more of a high aspect ratio talc, a high aspect ratio lamellear talc, a high aspect ratio micro-lamellar talc, a high aspect ratio chloritic talc, a high aspect ratio lamellar chloritic talc, and a high aspect ratio micro-lamellar chloritic talc.

According to some embodiments, a high aspect ratio of the mineral nucleating agent may be achieved by a wet-milling process.

According to some embodiments, the mineral nucleating agent may include a blend of a talc and a chloritic talc. For example, the mineral nucleating agent may include talc as a mineral and chloritic talc as a secondary mineral, or may include chloritic talc as a mineral and talc as a secondary mineral.

According to some embodiments, the polymer foam composition may have a first flexural modulus. The first flexural modulus may be greater than a flexural modulus of a comparative polymer foam composition having a mineral nucleating agent that includes one of the mineral and the secondary mineral individually.

According to some embodiments, the mineral nucleating agent may have a high aspect ratio.

According to some embodiments, the mineral nucleating agent may have a lamellarity index greater than about <NUM>, such as, for example, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

According to some embodiments, the polymer-based foam matrix may include at least one of a thermoplastic polymer matrix or a thermoplastic elastomer matrix. The polymer-based foam matrix includes at least one of a polystyrene matrix, polypropylene matrix, polyurethane matrix, poly(ethyl vinyl acetate) (EVA) matrix, polyethylene terephthalate (PET) matrix, or copolymer matrices thereof.

According to some embodiments, the blowing agent used to form the polymer-based foam matrix may include at least one of CO<NUM>, N<NUM>, or an organic gas. An organic gas may include, for example, hexane, propane, butane, n-butane, i-butane, pentane, i-pentane, n-pentane, CHF<NUM>Cl, CF<NUM>ClCH<NUM>, CHF<NUM>CH<NUM>, CHCl<NUM>CF<NUM>, CHFClCF<NUM>Cl, CHFClCF<NUM>, CH<NUM>FCF<NUM>, CH<NUM>CF<NUM>, CFCl<NUM>, CF<NUM>Cl<NUM>, CFCl<NUM>CF<NUM>Cl, CF<NUM>ClCF<NUM>Cl, CH<NUM>Cl, or CH<NUM>Cl<NUM>.

According to some embodiments, the polymer-based foam matrix may be the major component of the polymer foam composition. For example, the polymer-based foam matrix may be present in an amount greater than about <NUM>% by weight of the polymer foam composition, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, greater than about <NUM>%, or greater than about <NUM>% by weight of the polymer foam composition.

The alkaline earth metal silicate includes calcium silicate. In some embodiments, the calcium silicate may include a synthetic calcium silicate. In some embodiments, the calcium silicate may include a natural calcium silicate, such as, for example, a Wollastonite. According to some embodiments, the alkaline earth metal silicate may include a derived calcium silicate, such as, for example, diatomaceous earth-derived calcium silicate. According to some embodiments, the alkaline earth metal silicate may include a blend of alkaline earth metal silicates.

The mineral nucleating agent includes alkaline earth metal silicate. The mineral nucleating agent may include at least one of magnesium oxysulfate, kaolin, talc, chloritic talc, perlite, expanded milled perlite, diatomaceous earth, glass cullet, feldspar, nepheline syenite, or bentonite. According to some embodiments, talc or chloritic talc may include at least one of a lamellar talc, micro-lamellar talc, microcrystalline talc, and macrocrystalline talc.

According to some embodiments, the mineral nucleating agent may have a high aspect ratio. According to some embodiments, the talc or chloritic talc may include one or more of a high aspect ratio talc, a high aspect ratio lamellear talc, a high aspect ratio micro-lamellar talc, a high aspect ratio chloritic talc, a high aspect ratio lamellar chloritic talc, and a high aspect ratio micro-lamellar chloritic talc. In some embodiments, the mineral nucleating agent may include a secondary mineral nucleating agent (a secondary mineral).

According to some embodiments, the mineral nucleating agent may include a functionalized mineral nucleating agent. The functionalized mineral nucleating agent may have a surface treatment that may enhance interaction with one or more of the gas or the polymer composition. For example, the surface treatment may impart hydrophobic properties to the mineral nucleating agent. According to some embodiments, the surface treatment may include a silane, silicone oil, siloxane, fatty acid, salt thereof, or ester thereof. According to some embodiments, the fatty acid, salt thereof, or ester thereof may have a chain length of C8 or higher. According to some embodiments, the fatty acid may include stearic acid.

In some embodiments, the one surface treatment silanizes the mineral nucleating agent. The silanizing surface treatment may include at least one siloxane. In general, siloxanes are any of a class of organic or inorganic chemical compounds including silicon, oxygen, and often carbon and hydrogen, based on the general empirical formula of R<NUM>SiO, where R may be an alkyl group. Exemplary siloxanes may include, but are not limited to, dimethylsiloxane, methylphenylsiloxane, methylhydrogen siloxane, methylhydrogen polysiloxane, methyltrimethoxysilane, octamethylcyclotetrasiloxane, hexamethyldisiloxane, diphenylsiloxane, and copolymers or blends of copolymers of any combination of monophenylsiloxane units, diphenylsiloxane units, phenylmethylsiloxane units, dimethylsiloxane units, monomethylsiloxane units, vinylsiloxane units, phenylvinylsiloxane units, methylvinylsiloxane units, ethylsiloxane units, phenylethylsiloxane units, ethylmethylsiloxane units, ethylvinylsiloxane units, or diethylsiloxane units.

In some embodiments, the silanizing surface treatment may include at least one silane. In general, silanes and other monomeric silicon compounds have the ability to bond to inorganic materials, such as the mineral nucleating agent. The bonding mechanism may be aided by two groups in the silane structure, where, for example, the Si(OR<NUM>) portion interacts with the inorganic particulate material, while the organofunctional (vinyl-, amino-, epoxy-, etc.) group may interact with other materials.

In some embodiments, the mineral nucleating agent may be subjected to a surface treatment surface-treated with at least one ionic silane. Exemplary ionic silanes include, but are not limited to, <NUM>-(trimethoxysilyl) propyl-ethylenediamine triacetic acid trisodium salt and <NUM>-(trihydroxysilyl)propylmethylposphonate salt. In some embodiments, the mineral nucleating agent may be subjected to a surface treatment with at least one nonionic silane.

In a further embodiment, the mineral nucleating agent may be subjected to a surface treatment with at least one silane of Formula (I):.

(R<NUM>)xSi(R<NUM> )<NUM>-xR<NUM>     (I).

In some embodiments, silanization may proceed according to "wet" or "dry" silanization processes known to the skilled artisan.

According to some embodiments, the polymer-based foam matrix may have an average cell size (φ) less than or equal to about <NUM>. For example, the polymer-based foam matrix may have an average cell size (φ) less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, less than or equal to about <NUM>, or less than or equal to about <NUM>.

According to some embodiments, the polymer-based foam matrix may have an average cell size (φ) in a range from about <NUM> to about <NUM>. For example, the polymer-based foam matrix may have an average cell size (φ) in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

According to some embodiments, the polymer-based foam matrix may have an average cell size less than the critical defect size of the polymer.

The cell size distribution of the polymer-based foam matrix may be selectively controlled by selective addition of a mineral nucleator having a desired particle size distribution. According to some embodiments, this may allow for creation of a polymer foam having narrow or broad pore size distribution by utilizing a mineral nucleator having a likewise narrow or broad particle size distribution.

According to some embodiments, the polymer-based foam matrix may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer-based foam matrix may have a cell density (Nf) greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM>. <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>, or greater than or equal to about <NUM> × <NUM><NUM> per cm<NUM>.

According to some embodiments, the polymer-based foam matrix may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>. For example, the polymer-based foam matrix may have a cell density (Nf) in a range from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>, or from about <NUM> × <NUM><NUM> per cm<NUM> to about <NUM> × <NUM><NUM> per cm<NUM>.

According to some embodiments, the mineral nucleating agent may have a BET surface area greater than or equal to about <NUM><NUM>/g. For example, the mineral nucleating agent may have a BET surface area greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, greater than or equal to about <NUM><NUM>/g, or greater than or equal to about <NUM><NUM>/g.

According to some embodiments, the mineral nucleating agent may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g. For example, the mineral nucleating agent may have a BET surface area in a range from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, from about <NUM><NUM>/g to about <NUM><NUM>/g, or from about <NUM><NUM>/g to about <NUM><NUM>/g.

According to some embodiments, the mineral nucleating agent may have a median particle size (d<NUM>) greater than or equal to about <NUM>, such as, for example, greater than or equal to about <NUM> , greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, greater than or equal to about <NUM>, or greater than or equal to about <NUM>.

According to some embodiments, the mineral nucleating agent may have a median particle size (d<NUM>) in a range from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

According to some embodiments, the mineral nucleating agent may have an oil absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

According to some embodiments, the mineral nucleating agent may have a water absorption greater than or equal to about <NUM> wt%, such as, for example, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, greater than or equal to about <NUM> wt%, or greater than or equal to about <NUM> wt%.

According to some embodiments, the mineral nucleating agent may have an aspect ratio in the range of from about <NUM> to about <NUM>, such as, for example, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

According to some embodiments, the polymer foam compositions may have a relative density compared to the respective unfoamed base materials, in a range from about <NUM> to <NUM>, such as, for example, in a range from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or from about <NUM> to about <NUM>.

In this example, the cell size and distribution within a polymer foam was controlled through the addition of an alkaline earth metal silicate with a high surface area and favorable interaction with the blowing agent.

Synthetic calcium silicate was added to a commercially available <NUM> (<NUM> lb. ) two-part polyurethane foam provided by Morris Materials of Salt Lake City, Utah comprising <NUM>,<NUM>' methylene bis(phenylisocyanate), polymethylene polyphenyl isocyanates, and a polyol. The synthetic calcium silicate had a high surface area, about <NUM><NUM>/g, a high water absorption (about <NUM> wt%), and a high oil absorption (about <NUM> wt%). CO<NUM>, generated through the reaction of moisture and isocyanate, was used as the physical blowing agent.

To prepare the samples, <NUM> wt% of the synthetic calcium silicate relative to the total mass of the final polyurethane mixture was added to the polyol and mixed in a speedmixer for <NUM> minutes at <NUM> rpm. Next, an equal weight of isocynate mixture was added to the polyol and mixed for <NUM> seconds at <NUM> rpm until cream in color. The mixture was allowed to foam and cure at room temperature and pressure for <NUM> minutes. A control polyurethane foam was prepared under similar conditions, but without the synthetic calcium silicate nucleating agent.

To analyze the foam composition, the foam was fractured in ambient conditions and micrographs collected using a scanning electron microscope. Images of the foam composition having a calcium silicate nucleating agent as compared to a neat polyurethane foam without a nucleating agent are shown in <FIG>. The cell size of the nucleated and non-nucleated foams was computed using ImageJ software and averaged over <NUM> images for each foam. The control polyurethane foam exhibited an average cell diameter of <NUM> ± <NUM>. The exemplary nucleated foam having <NUM> wt% synthetic calcium silicate reduced average cell diameter by about <NUM>%, having an average cell diameter of <NUM> ± <NUM>.

The efficiency of cell nucleation was then investigated by varying the amount of the synthetic calcium silicate from <NUM> wt% to <NUM> wt % relative to the total mass. The polymers were prepared as described in this example with varying weight percent of synthetic calcium silicate and then foamed. The cell diameter as a function of the weight percent of synthetic calcium silicate was determined. A graph of the average cell diameter versus the weight percent of synthetic calcium silicate is shown in <FIG>. As shown in <FIG>, when calcium silicate is added in an amount up to about <NUM> wt%, the cell diameter is reduced. Above about <NUM> wt% synthetic calcium silicate, the cell diameter does not appear to be reduced further. Without wishing to be bound by a particular theory, it is believed that the apparent reduction limit in the cell size after about <NUM> wt% synthetic calcium silicate results from saturation of the material because of the limited availability of blowing agent. These findings indicate that synthetic calcium silicate may be a promising bubble nucleator for chemically blown systems.

The cell nucleation ability of calcium silicate was examined in a physically blown system using CO<NUM> as the blowing agent. Poly(ethyl vinyl acetate) (EVA) was dissolved in xylenes and was mixed with <NUM> wt% calcium silicate using a speedmixer for <NUM> minutes at <NUM> rpm. The resulting mixtures were dried at <NUM> in under reduced pressure (<NUM> of Hg in vacuum (<NUM> inches of Hg in vacuum)) and pressed with a carver press at <NUM> and <NUM> MPa to form <NUM> thick films. The films were then placed in a CO<NUM> environment at <NUM> MPa at <NUM> for <NUM> hours. Then, the pressure was rapidly reduced at a rate of <NUM> MPa/s and the composition was allowed to foam at <NUM> and ambient pressure. A control EVA foam was also prepared using the same method, except that no calcium silicate was added. The foams were cryofractured and characterized using a HITACHI S-4300SE/N scanning electron microscope (SEM). SEM micrographs of the control EVA foam and the calcium silicate-nucleated EVA foam are shown in <FIG>. The average cell diameter was determined as described in Example <NUM>.

As shown in <FIG>, the addition of calcium silicate as a nucleating agent reduces the average cell size of the EVA foam. For the control EVA foam, the average cell diameter was <NUM>. The addition of <NUM> wt% calcium silicate as a nucleating agent reduced the average cell diameter by about <NUM>% to <NUM>. <FIG> shows a further magnified image of the calcium silicate-nucleated EVA foam, which shows a correlation between the foam cell diameter and the diameter of the calcium silicate particle within the cell. As shown in <FIG>, the alkaline earth metal silicate may be seen in a cell of the polymer-based foam matrix. <FIG> also show SEM images of alkaline earth metal silicates used to nucleate cells in polymer foams, where the nucleating agent can be seen within the cell of the foam. Without wishing to be bound by a particular theory, it is believed that this correlation between cell size and particle size relates directly to the nucleation mechanism. Under such conditions, the CO<NUM> favorably interacts with the surface of the calcium silicate to facilitate the formation of a bubble and the amount of gas available for foaming will scale with the available surface area of the nucleating silicate. As a result, increasing particle size may result in an increase in the bubble size of the foam. This correlation may indicate that bubble nucleation is facilitated through the favorable interaction of a gas with the calcium silicate surface.

Tests and analytical results of unfilled and filled polyethylene terephthalate foams were prepared via a two-step extrusion-mixing and foaming process.

All materials were prepared by melt-mixing polyethylene terephthalate resin "PQB15-<NUM>", commercially available from PolyQuest, Inc. , with different nucleating agent using a Haake Rheomex PTW16 co-rotating twin-screw extruder. Table <NUM> shows the extrusion temperature profiles. The screw speeds were <NUM> rpm in this example.

Several minerals were tested as nucleating agents for polymer foams, which are shown below in Table <NUM>, along with the d<NUM> and BET surface area values of each mineral. The d<NUM> and BET surface area is measured as described above.

Each of samples A-D was added by mechanically mixing <NUM> wt% of mineral with polyethylene terephthalate ("PET"), then processing the composition inside a twin-screw extruder. For comparison purposes, a control material of PET without any mineral was also processed using identical processing conditions. At the exit of a circular extrusion die, all composites were cooled using a water bath at <NUM> and pelletized prior to solid foaming precursor preparation.

The composition of each PET-mineral composite was determined by calcination as the average of three values obtained according to UNE-EN ISO345-<NUM> using <NUM> of each sample material at <NUM>. Table <NUM> below shows that composition of each sample. Samples A and C are of the invention.

To prepare solid precursors for foaming, each of pelletized samples A-D were formed into a disk having a diameter of <NUM> and a thickness of <NUM> using a Haake MiniJet Pro piston injection molder system. The molding conditions are shown below in Table <NUM>.

Foaming was performed using either carbon dioxide (CO<NUM>) or nitrogen (N<NUM>) gas dissolution.

For the CO<NUM> dissolution, the solid foaming precursor discs were foamed using a two-step gas dissolution batch-foaming process with CO<NUM> as the physical blowing agent. Foams were obtained by saturating the discs in CO<NUM> in a high-pressure vessel at <NUM> at <NUM> MPa for <NUM> hours until the discs contained <NUM> wt. % dissolved CO<NUM>. The pressure was then released at a rate of <NUM> MPa/s. The saturated discs were then transferred to a Carver hot press and foamed at <NUM> for one minute.

For the N<NUM> dissolution, the solid foaming precursor discs were foamed using a two-step gas dissolution batch-foaming process with N<NUM> as the physical blowing agent. Foams were obtained by saturating the discs in N<NUM> in a high-pressure vessel at <NUM> at <NUM> MPa for <NUM> hours until the discs contained <NUM> wt% dissolved N<NUM>. The pressure was then released at a rate of <NUM> MPa/s. The saturated discs were then transferred to a Carver hot press and foamed at <NUM> for <NUM> minute.

The foamed and unfoamed composites were then characterized. The densities were measured according to ISO <NUM>, without removing the outer skins of the foamed specimens generated during the CO<NUM>-foaming and N<NUM>-foaming process. The relative density was also determined and refers to the ratio of the density between the foamed and unfoamed composites. The cellular structure of the various foams was studied using a HITACHI S-4300SE/N scanning electron microscope (SEM) from samples cryogenically fractured using liquid nitrogen and made conductive by sputter deposition of a thin layer of gold. The average cell diameter (φ) and cell density (Nf) were directly obtained from low-magnification micrographs using the intercept counting method described above.

The results of the CO<NUM>-foaming are shown below in Table <NUM>. SEM images of the CO<NUM>-foamed Samples A-D are shown in <FIG> for the center and <FIG> for the skin layer.

The results of the N<NUM>-foaming are shown below in Table <NUM>. SEM images of the N<NUM>-foamed Samples A-D are shown in <FIG>.

As shown in Tables <NUM> and <NUM> above and <FIG>, alkaline earth metal silicates, such as calcium silicate and magnesium silicate, may provide efficient nucleating agents in CO<NUM> and N<NUM> environments. In the N<NUM> environment, calcium silicate (such as, for example, Wollastonite) may provide an efficient agent to reduce the cell (bubble) size, which may improve the mechanical strength of the foamed composites.

Tests and analytical results of unfilled and filled polypropylene foams prepared according to an extrusion-mixing and injection-moulding foaming process are described in this example. The samples comprising Wollastonite are of the invention.

The production of foamed polypropylene was carried out using a chemical blowing additive during injection-moulding. Polypropylene block copolymer "PP56M10" (MFI of <NUM>/<NUM>; <NUM>, <NUM>), commercially available from Sabic, was foamed using Hydrocerol ITP <NUM> (<NUM>% active content of a blend of citric acid and sodium bicarbonate), which is commercially available from Clariant (<NUM> wt%) as the chemical blowing agent, to obtain ISO B bars of dimensions <NUM> × <NUM> × <NUM>. The mineral compositions incorporated were (i) talc, (ii) Wollastonite, (iii) a <NUM>:<NUM> blend by weight of talc and a Wollastonite, all present at a concentration of <NUM> wt% based on the total weight of the filled polymer. The injection-moulding machine "Arburg Allrounder 420C" has a closing force of <NUM> tons, maximum injection pressure of <NUM> bar, and a screw diameter of <NUM>. The temperatures of the injection unit are shown in Table <NUM>. The mould temperature was set to <NUM> for solid and <NUM> for foam with an in-mould cooling time of respectively <NUM> and <NUM> seconds. The talc used in this example was a blend of two talcs A and B. Talc A possessed a d<NUM> of <NUM> (laser) and <NUM> (Sedigraph) plus a BET surface area of <NUM><NUM>/g. Talc B possessed a d<NUM> of <NUM> (laser) and <NUM> (Sedigraph) plus a BET surface area of <NUM><NUM>/g. The Wollastonite possessed a d<NUM> of <NUM> (laser) and a BET surface area of <NUM><NUM>/g.

Foams were produced using the above described process. The polymer dosages and injection speeds for solid and foamed conditions are shown in Table <NUM>.

The various foams produced from the polypropylene comprising talc and Wollastonite and their unfoamed equivalents had the densities shown in Table <NUM>. The densities were measured according to ISO <NUM>.

The flexural modulus was analysed on the injection molded ISO bars according to the three points bending test at <NUM> following ISO <NUM> standards.

The foams produced according to the injection molding foaming process were analysed by the three points bending test characterisation as described above. The results are shown in Table <NUM>.

Claim 1:
A polymer foam composition comprising:
a polymer-based foam matrix; and
a mineral nucleating agent within a cell of the polymer-based foam matrix,
wherein the mineral nucleating agent comprises an alkaline earth metal silicate, wherein the alkaline earth metal silicate comprises calcium silicate, and wherein the alkaline earth metal silicate is present in an amount in a range from <NUM>% by weight to <NUM>% by weight of the polymer foam, wherein the polymer-based foam matrix comprises at least one of a polystyrene matrix, polypropylene matrix, polyurethane matrix, poly(ethyl vinyl acetate) matrix, polyethylene terephthalate matrix, or copolymer matrices thereof.