In an example, a material includes a cellulosic nanomaterial and multiple polymer chains chemically bonded to the cellulosic nanomaterial. Each polymer chain includes a styrene-butadiene copolymer.

I. FIELD OF THE DISCLOSURE

The present disclosure relates generally to flame-retardant impact modifiers (e.g., for blending with a polymer).

Plastics are commonly derived from petrochemicals, resulting in price fluctuations and supply chain instability. Replacing non-renewable petroleum-based polymers with polymers derived from renewable resources may be desirable. However, in certain contexts, there are limited alternatives to petroleum-based polymers. To illustrate, particular renewable polymers may have less than desirable material properties, such as low impact resistance or flame resistance. Such material properties can sometimes be improved by blending the polymers with additive compounds. The additive compounds generally include other polymers. If the additive compounds are not from renewable sources, blending renewable polymers with the additive compounds reduces the portion of non-renewable petroleum-based polymers replaced with polymers derived from renewable resources.

III. SUMMARY OF THE DISCLOSURE

According to an embodiment, a renewable material can be used as an additive to other polymers, especially other renewable polymers. When blended with another polymer, the renewable material improves impact resistance of the blend. Further, in some embodiments, the renewable material improves other material properties of the blend. For example, the renewable material may include flame retardant functional groups which may increase the flame retardancy or flame quenching properties of the blend. Additionally, the renewable material may include a rheology modifier, which may improve rheological properties of the blend.

In a particular embodiment, a material (e.g., a polymer blend additive) includes a cellulosic nanomaterial and multiple polymer chains chemically bonded to the cellulosic nanomaterial. Each polymer chain includes a styrene-butadiene copolymer.

In another embodiment, a polymer blend includes at least one polymer and an impact modifier blended with the at least one polymer. The impact modifier includes a cellulosic nanomaterial and multiple polymer chains chemically bonded to the cellulosic nanomaterial. Each polymer chain includes a styrene-butadiene copolymer.

In another embodiment, a method includes combining a methyl methacrylate-functionalized cellulosic nanomaterial with at least a first monomer and a second monomer. The method also includes initiating a reaction of the methyl methacrylate-functionalized cellulosic nanomaterial, the first monomer and the second monomer to form a reactant including multiple polymer chains chemically bonded to the methyl methacrylate-functionalized cellulosic nanomaterial.

A renewable polymer blend additive can be used to improve material properties of other polymers. The renewable polymer blend additive may be especially useful when blended with renewable polymers to maintain an overall percentage of renewables in a final product. The renewable polymer blend additive may enable use of renewable polymers in circumstances where non-renewable polymers may otherwise be used due to inability of renewable polymers to satisfy specified material properties, such as impact resistance, flame retardance, etc.

V. DETAILED DESCRIPTION

The present disclosure relates to polymeric materials, especially renewable polymers. One hurdle in the use of renewable polymers in some industries is that many renewable polymers tend to have unsatisfactory ignition resistance characteristics. One approach that is used to address this concern is to blend a renewable polymer with another material (e.g., a filler) that has flame retardant properties. In some cases, such fillers may include relatively small molecules in the form of particles. In such cases, to provide adequate flame retardance, loading levels of these flame retardant fillers can run as high as 30%. Such high loading levels can compromise mechanical properties of the resulting polymer blend. For example, the impact resistance, tensile strength, modulus, or other properties of such a polymer blend may be unsatisfactory.

Thus, for some bio-derived or renewable polymers, adding a filler to improve a polymer blend's mechanical properties (such as impact resistance) may degrade the polymer blend's ignition resistance. Additionally, adding a filler to improve the polymer blend's ignition resistance may degrade the polymer blend's mechanical properties. Embodiments disclosed herein provide a polymeric filler material that improves both mechanical properties and ignition resistance of a polymer blend. The polymeric filler material can be bio-derived or renewable. Accordingly, adding the polymeric filler material to a polymer blend does not decrease a percentage or proportion of renewable content of the polymer blend.

In a particular example, the polymeric filler material incorporates orthogonal functionality on an impact modifier to address shortcomings present in other filler materials. To illustrate, to form the polymeric filler material a cellulosic nanomaterial (such as a cellulose nanocrystal or cellulose nanofiber material) may be functionalized with methyl methacrylate. The functionalized cellulosic nanomaterial may be copolymerized with constituent monomers to form a styrene-butadiene-based impact modifier material. In some examples, the polymeric filler material may be rendered flame retardant by copolymerizing the constituent monomers with small amounts of a monomer that has flame retardant characteristics, such as an acrylic, styrenic, or otherwise vinylic monomers containing flame-quenching functionalities (e.g., phosphorus, halogens, etc.) and capable of polymerizing via radical polymerization. The resulting flame-retardant impact modifier may be blended with one or more polymers (e.g., bio-renewable polymers, such as polylactic acid (PLA), polycaprolactone (PCL), polyamide (PA), polyglycolic acid (PGA), polyhydroxybutyrate (PHB), polyhydroxyalkanoates (PHA), polyethylene terephtalate (PET), polypropylene (PP), polyethylene (PE), PLA/starch material (PSM), polycarbonate (PC), or a combination or copolymer thereof).

In some implementations, the polymeric filler material may be formed by functionalizing the cellulosic nanomaterial with methyl methacrylate via nucleophilic acyl substitution. For example, the cellulosic nanomaterial may be reacted with an acyl halide (e.g., methacryloyl chloride), an acrylic acid (e.g., methacrylic acid), or an acrylic anhydride (e.g., methacrylic anhydride). The methyl methacrylate-functionalized cellulosic nanomaterial may be copolymerized with a mixture of styrene and butadiene. To make the resultant product flame retardant, a flame retardant monomer may also be copolymerized with the styrene, the butadiene and the methyl methacrylate-functionalized cellulosic nanomaterial. The copolymerization may be initiated using a thermal initiator, a UV initiator, or another radical polymerization initiator. After polymerization, the resultant product (e.g., a cellulosic nanomaterial impact modifier/filler with the flame retardant groups coupled to poly(methyl methacrylate-co-styrene-co-butadiene)) may be compounded with a polymer or polymer blend.

In some implementations, the methyl methacrylate-functionalized cellulosic nanomaterial may have unreacted hydroxyl groups (i.e., hydroxyl groups of the cellulosic nanomaterial that were not replaced with methyl methacrylate groups). In such implementations, rather than (or in addition to) blending, the cellulosic nanomaterial impact modifier/filler may be reacted with a polymer, polymer blend, or one or more monomers to covalently link the cellulosic nanomaterial impact modifier/filler to the polymer, polymer blend or monomers via the previously unreacted hydroxyl groups.

FIG. 1is a chemical reaction diagram100illustrating a particular embodiment of preparation of a methyl methacrylate-functionalized cellulosic nanomaterial. As illustrated inFIG. 1, a cellulosic nanomaterial102may be reacted to form a methyl methacrylate-functionalized cellulosic nanomaterial106. For example, the cellulosic nanomaterial102may undergo nucleophilic acyl substitution when mixed with an acyl halide, such as methacryloyl chloride104. In other examples, the cellulosic nanomaterial102may be reacted with methacrylic acid or methacrylic anhydride to form the methyl methacrylate-functionalized cellulosic nanomaterial106.

The cellulosic nanomaterial102may include or correspond to a cellulose nanocrystal, a cellulose nanofiber, or another cellulosic material having a characteristic dimension (e.g., a length) on the order of a nanometer (e.g., less than about 1000 nanometers, less than about 100 nanometers, or less than about 10 nanometers). The cellulosic nanomaterial102may include a plurality of hydroxyl groups. During the reaction illustrated inFIG. 1, the oxygen of the hydroxyl group attacks the acyl carbon. This nucleophilic attack may be promoted by a base or a catalyst, such as pyridine. After the nucleophilic attack, the halide (e.g., the Cl) is eliminated (e.g., leaves to potentially form HCl). If a catalyst such as pyridine is used the catalyst may also act as a proton scavenger, neutralizing the HCl and helping the reaction proceed By controlling stoichiometric ratios of the acyl halide and the cellulosic nanomaterial102, the reaction can be used to produce a cellulosic nanomaterial with multiple methyl methacrylate functional groups, such as the illustrative methyl methacrylate-functionalized cellulosic nanomaterial106ofFIG. 1.

As described further below, the methyl methacrylate groups of the methyl methacrylate-functionalized cellulosic nanomaterial106may be used to modify the cellulosic nanomaterial102to form an additive or filler having particular properties, such as flame-retardance or impact resistance.

FIG. 2is a chemical reaction diagram200illustrating a particular embodiment of preparation of a compound that may be used as an impact modifier. As illustrated inFIG. 2, the methyl methacrylate-functionalized cellulosic nanomaterial106may be reacted with a plurality of monomer compounds to form a material206(e.g., the compound that can be used as an impact modifier). For example, as illustrated inFIG. 2, the monomer compounds may include a styrene202(or another compound having a styrenic functional group) and butadiene204. In this example, the styrene202and butadiene204may react to form a plurality of polymer chains, such as a first polymer chain208and a second polymer chain210. In the example ofFIG. 2, each polymer chain208,210includes a copolymer of styrene202and butadiene204(e.g., polybutadiene-styrene (PBS)).

The polymer chains208,210are chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups (e.g., each polymer chain208,210is coupled to the cellulosic nanomaterial102via a corresponding methyl methacrylate group). Thus, the material206includes the cellulosic nanomaterial102with multiple polymer chains208,210chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups.

As described above, the polymer chains208,210may include a styrene-butadiene copolymer. Styrene-butadiene copolymers tend to have good impact resistance. Accordingly, the material206may be blended with another polymer (or set of polymers) as an additive to improve impact resistance of the blended polymer(s). If the styrene202, the butadiene204, and the cellulosic nanomaterial102are derived from renewable sources, the material206can be used as a renewable impact modifier. Thus, blending the material206with another polymer causes a quantity of renewable content in a final product (including the other polymer and the material206) to increase. Thus, as much of the material206as desired to achieve particular impact resistance levels can be added without negatively affecting the proportion of renewable content in the final product.

Additionally, cellulosic nanomaterials, such as the cellulosic nanomaterial102, are sometimes added to polymers to modify rheology characteristics of the polymers. Thus, the material206may be added to a polymer blend as a rheology modifier, as an impact modifier, or as both a rheology modifier and an impact modifier. Using a single material (e.g., the material206) as both a rheology modifier and an impact modifier may reduce costs associated with formulating a polymer blend (e.g., by simplifying supply chain management, reducing a number or cost of polymer additives, etc.).

FIG. 3is a chemical reaction diagram300illustrating a particular embodiment of preparation of a compound that may be used as a flame-retardant impact modifier. As illustrated inFIG. 3, the methyl methacrylate-functionalized cellulosic nanomaterial106may be reacted with a plurality of monomer compounds to form a material304(e.g., the compound that can be used as a flame-retardant impact modifier). For example, as illustrated inFIG. 3, the monomer compounds may include styrene202(or another compound having a styrenic functional group), butadiene204, and a flame-retardant monomer302. The flame-retardant monomer302includes a compound that is capable of radical polymerization and that has a flame-retardant or a flame-quenching functional group (FR). For example, the flame-retardant monomer302may include an acrylic compound, a styrenic compound, or an otherwise vinylic compound, that has a flame-retardant or a flame-quenching functional group. The flame-retardant or flame-quenching functional group may include a phosphorous-based or halogen-based group. Specific, non-limiting, examples of flame-retardant monomers302are described with reference toFIGS. 4 and 5.

In the example ofFIG. 3, the styrene202, the butadiene204, and the flame-retardant monomer302may react to form a plurality of polymer chains, such as a first polymer chain306and a second polymer chain308. Thus, each of the polymer chains306,308includes a copolymer of styrene202, butadiene204, and the flame-retardant monomer302. The polymer chains306,308are chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups (e.g., each polymer chain306,308is coupled to the cellulosic nanomaterial102via a corresponding methyl methacrylate group). Thus, the material304includes the cellulosic nanomaterial102with multiple flame-retardant and impact resistant polymer chains306,308chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups.

Flame retardant properties of the material304may be related to a quantity of the flame-retardant monomer302used in the reaction illustrated inFIG. 3. For example, reacting the styrene202, the butadiene204, and the methyl methacrylate-functionalized cellulosic nanomaterial106with more of the flame-retardant monomer302may result in the material304having more of the flame retardant functional groups, which may improve flame retardancy of the material304. Conversely, reacting the styrene202, the butadiene204, and the methyl methacrylate-functionalized cellulosic nanomaterial106with less of the flame-retardant monomers302may result in the material304having fewer of the flame retardant functional groups, which may decrease flame retardancy of the material304.

The material304may be blended with another polymer (or set of polymers) as an additive to improve impact resistance of the blended polymer(s), to improve flame retardancy of the blended polymer(s), to modify rheological properties of the blended polymer(s), or a combination thereof. If the styrene202, the butadiene204, the flame-retardant monomers302, and the cellulosic nanomaterial102are derived from renewable sources, the material304can be used as a renewable filler in the blended polymer(s). Thus, blending the material304with another polymer causes a quantity of renewable content in a final product (including the other polymer and the material304) to increase. Accordingly, as much of the material304as desired to achieve particular impact resistance levels, particular flame retardance characteristics, or both, can be added without negatively affecting the proportion of renewable content in the final product. Using a single material (e.g., the material304) as a rheology modifier, an impact modifier, and a flame retardance modifier may reduce costs associated with formulating a polymer blend (e.g., by simplifying supply chain management, reducing a number or cost of polymer additives, etc.).

FIG. 4is a chemical reaction diagram400illustrating another particular embodiment of preparation of a flame-retardant impact modifier compound.FIG. 4illustrates a specific, non-limiting example of flame retardant monomers that can be used to form the flame-retardant impact modifier compound. InFIG. 4, the methyl methacrylate-functionalized cellulosic nanomaterial106may be reacted with the styrene202(or another compound having a styrenic functional group), the butadiene204, and a flame-retardant monomer or multiple flame retardant monomers. InFIG. 4, the flame retardant monomer(s) include 4-(diphenylphosphino)styrene402, or a combination of 4-(diphenylphosphino)styrene402and diphenyl(4-vinylphenyl)phosphine oxide404.

In the example ofFIG. 4, the styrene202, the butadiene204, and the flame-retardant monomer(s) may react to form a plurality of polymer chains, such as a first polymer chain408and a second polymer chain410. Thus, each of the polymer chains408,410includes a copolymer of styrene202, butadiene204, and the flame-retardant monomer(s). The polymer chains408,410are chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups (e.g., each polymer chain408,410is coupled to the cellulosic nanomaterial102via a corresponding methyl methacrylate group). Thus, the material406includes the cellulosic nanomaterial102with multiple flame-retardant and impact resistant polymer chains408,410chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups.

Flame retardant properties of the material406may be related to a quantity of the flame-retardant monomer(s) used in the reaction illustrated inFIG. 4. For example, reacting the styrene202, the butadiene204, and the methyl methacrylate-functionalized cellulosic nanomaterial106with more of the flame-retardant monomer(s) may result in the material406having more of the flame retardant functional groups, which may improve flame retardancy of the material406. Conversely, reacting the styrene202, the butadiene204, and the methyl methacrylate-functionalized cellulosic nanomaterial106with less of the flame-retardant monomer(s) may result in the material406having fewer of the flame retardant functional groups, which may decrease flame retardancy of the material406.

The material406may be blended with another polymer (or set of polymers) as an additive to improve impact resistance of the blended polymer(s), to improve flame retardance of the blended polymer(s), to modify rheological properties of the blended polymer(s), or a combination thereof. If the styrene202, the butadiene204, the flame-retardant monomer(s), and the cellulosic nanomaterial102are derived from renewable sources, the material406can be used as a renewable filler in the blended polymer(s). Thus, blending the material406with another polymer causes a quantity of renewable content in a final product (including the other polymer and the material406) to increase. Accordingly, as much of the material406as desired to achieve particular impact resistance levels, particular flame retardance characteristics, or both, can be added without negatively affecting the proportion of renewable content in the final product. Using a single material (e.g., the material406) as a rheology modifier, an impact modifier, and a flame retardance modifier may reduce costs associated with formulating a polymer blend (e.g., by simplifying supply chain management, reducing a number or cost of polymer additives, etc.).

FIG. 5is a chemical reaction diagram500illustrating another particular embodiment of preparation of a flame-retardant impact modifier compound.FIG. 5illustrates another specific, non-limiting example of a flame retardant monomer502that can be used to form the flame-retardant impact modifier compound. InFIG. 5, the methyl methacrylate-functionalized cellulosic nanomaterial106may be reacted with the styrene202(or another compound having a styrenic functional group), the butadiene204, and the flame retardant monomer502. InFIG. 5, the flame retardant monomer502includes an acrylic monomer with a phosphorus-based flame retardant moiety.

In the example ofFIG. 5, the styrene202, the butadiene204, and the flame-retardant monomer502may react to form a plurality of polymer chains, such as a first polymer chain506and a second polymer chain508. Thus, each of the polymer chains506,508includes a copolymer of styrene202, butadiene204, and the flame-retardant monomer502. The polymer chains506,508are chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups (e.g., each polymer chain506,508is coupled to the cellulosic nanomaterial102via a corresponding methyl methacrylate group). Thus, the material504includes the cellulosic nanomaterial102with multiple flame-retardant and impact resistant polymer chains506,508chemically bonded to the cellulosic nanomaterial102via the methyl methacrylate groups.

Flame retardant properties of the material504may be related to a quantity of the flame-retardant monomer(s) used in the reaction illustrated inFIG. 4. For example, reacting the styrene202, the butadiene204, and the methyl methacrylate-functionalized cellulosic nanomaterial106with more of the flame-retardant monomer502may result in the material504having more of the flame retardant functional groups, which may improve flame retardancy of the material504. Conversely, reacting the styrene202, the butadiene204, and the methyl methacrylate-functionalized cellulosic nanomaterial106with less of the flame-retardant monomer502may result in the material504having fewer of the flame retardant functional groups, which may decrease flame retardancy of the material504.

The material504may be blended with another polymer (or set of polymers) as an additive to improve impact resistance of the blended polymer(s), to improve flame retardance of the blended polymer(s), to modify rheological properties of the blended polymer(s), or a combination thereof. If the styrene202, the butadiene204, the flame-retardant monomer502, and the cellulosic nanomaterial102are derived from renewable sources, the material504can be used as a renewable filler in the blended polymer(s). Thus, blending the material504with another polymer causes a quantity of renewable content in a final product (including the other polymer and the material504) to increase. Accordingly, as much of the material504as desired to achieve particular impact resistance levels, particular flame retardance characteristics, or both, can be added without negatively affecting the proportion of renewable content in the final product. Using a single material (e.g., the material504) as a rheology modifier, an impact modifier, and a flame retardance modifier may reduce costs associated with formulating a polymer blend (e.g., by simplifying supply chain management, reducing a number or cost of polymer additives, etc.).

FIG. 6is a flow diagram illustrating a particular embodiment of a method600of forming an impact modifier compound. The method600may be used to form any one or more of the material206ofFIG. 2, the material304ofFIG. 3, the material406ofFIG. 4, or the material504ofFIG. 5. Alternatively or in addition, a portion of the method600may be used to form the methyl methacrylate-functionalized cellulosic nanomaterial106ofFIG. 1.

The method600may include, at602, combining an acyl halide (e.g., methacryloyl chloride), an acrylic acid (e.g., methacrylic acid), or an acrylic anhydride (e.g., methacrylic anhydride) with a cellulosic nanomaterial. For example, as illustrated inFIG. 1, the methacryloyl chloride104may be combined with the cellulosic nanomaterial102. The method600may also include, at604, initiating a reaction to form a methyl methacrylate-functionalized cellulosic nanomaterial. For example, the acyl halide, the acrylic acid, or the acrylic anhydride may react with the cellulosic nanomaterial to form the methyl methacrylate-functionalized cellulosic nanomaterial106ofFIG. 1. In some examples, rather than forming the methyl methacrylate-functionalized cellulosic nanomaterial via reaction of the cellulosic nanomaterial with one or more reagents, the methyl methacrylate-functionalized cellulosic nanomaterial may be obtained via an alternate mechanism, such as purchased as a reagent compound for use in forming an impact modifier.

The method600includes, at606, combining the methyl methacrylate-functionalized cellulosic nanomaterial with at least a first monomer and a second monomer. For example, the methyl methacrylate-functionalized cellulosic nanomaterial106may be combined with styrene, butadiene, one or more other radical polymerizable monomers, or a combination thereof. In some embodiments, the monomers may include an acrylic compound, a styrenic compound, or an otherwise vinylic compound, that has a flame-retardant or flame-quenching functional group.

The method600also includes, at608, initiating a reaction (e.g., a radical polymerization reaction) of the methyl methacrylate-functionalized cellulosic nanomaterial, the first monomer and the second monomer to form a compound including multiple polymer chains chemically bonded to the methyl methacrylate-functionalized cellulosic nanomaterial. For example, as described with reference toFIG. 2, the methyl methacrylate-functionalized cellulosic nanomaterial106, the styrene202and the butadiene204may be reacted to form the material206, which includes multiple polymer chains208,210chemically bonded to the methyl methacrylate-functionalized cellulosic nanomaterial. As another example, as described with reference toFIG. 3, the methyl methacrylate-functionalized cellulosic nanomaterial106, the styrene202, the butadiene204, and the flame-retardant monomer302may be reacted to form the material304, which includes multiple polymer chains306,308chemically bonded to the methyl methacrylate-functionalized cellulosic nanomaterial. Additional examples are described with reference toFIGS. 4 and 5.

In some embodiments, the method600may also include blending the compound including multiple polymer chains chemically bonded to the methyl methacrylate-functionalized cellulosic nanomaterial (e.g., the material206, the material304, the material406, or the material504) with one or more base polymers to form a polymer blend. In such embodiments, the compound may function as a filler for the polymer blend. The filler may modify rheological characteristics of polymer blends relative to the base polymer(s). Alternatively, or in addition, the filler may modify impact resistance characteristics of polymer blends relative to the base polymer(s). Alternatively, or in addition, the filler may modify fire-retardant characteristics of polymer blends relative to the base polymer(s). In particular embodiments, reactants used to form the filler can be renewable (e.g., biologically derived). In such embodiments, adding the filler to the polymer blend may improve characteristics of the polymer blend without decreasing a proportion of renewable materials in the polymer blend.