Patent Description:
Additive manufacture, or '3D printing' can been used to make articles of almost arbitrary shape and size. In additive manufacture, a solid, real-world article is built up, layer-by-layer, based on a digital model that defines the topology of the article. The result is a high-fidelity realization of the digital model, obtained without dedicated tooling and with minimal human intervention. In variants in which a thermoplastic-polymer article is desired, a thermoplastic-polymer feedstock is conducted through a heated nozzle positioned at a locus of the article where material is to be deposited. The position of the locus is controlled in real time by moving the article with respect to the nozzle and/or rastering the nozzle over the article. Upon exiting the nozzle, the thermoplastic-polymer material cools and adheres to the underlying layer of the article.

A wide range of thermoplastic-polymer materials have been used in additive manufacture, but some materials present particular challenges. One challenge relates to the additive manufacture of articles comprising high molecular-weight polymers that exhibit desirable mechanical properties, thermal stability, and/or chemical resistance. Similar challenges occur with polymers having functional groups that impart rheologically significant steric bulk.

<CIT> states, according to its abstract, that a resin composition for solid freeform fabrication includes one or more thermoplastic resins containing a liquid crystal resin having a content rate of from <NUM> to <NUM> percent by mass to the one or more thermoplastic resins.

<CIT> states, according to its abstract, a thermoplastic filament comprising multiple polymers of differing flow temperatures in a geometric arrangement and an interior channel containing a structural or functional thread therein. A method for producing such a filament is also described. Because of the difference in flow temperatures, there exists a temperature range at which one polymer is mechanically stable while the other is flowable. This property is extremely useful for creating thermoplastic monofilament feedstock for three-dimensionally printed parts, wherein the mechanically stable polymer enables geometric stability while the flowable polymer can fill gaps and provide strong bonding and homogenization between deposited material lines and layers. These multimaterial filaments can be produced via thermal drawing from a thermoplastic preform, which itself can be three-dimensionally printed. Furthermore, the preform can be printed with precisely controlled and complex geometries, enabling the creation of a filament or fiber with an interior thread contained within the outer, printed filament or fiber. This thread adds structural reinforcement or functional properties, such as electrical conductivity or optical waveguiding, to the filament.

<CIT> states, according to its abstract, that an apparatus has a dispensing unit that causes a feedstock to flow out of an orifice of the dispensing unit where the flow exits toward a build surface. The feedstock has a functional material and a flowable material. The build surface and dispensing unit are moved relative to one another such that the flow exiting the orifice additively manufactures a part. A field generator emits a field onto the fluid flow to align the functional material. The field changes over time such that functional material has selectably variable orientation within a volume of the part.

<CIT> states, according to its abstract, that a recycling method of selective laser sintering (SLS) nylon waste powder is disclosed. The recycling method of SLS nylon waste powder has the effects that expensive nylon powder materials exert the effect again, the economic benefits are generated, and the materials are environmentally friendly. The method comprises the steps that the nylon powder is modified, the modified materials are extruded and granulated through double screws, through a fused deposition molding (FDM) dedicated single-screw extruder, extruding is carried out, and a wire is formed and is used as an FDM process raw material. The wire is smooth in surface, uniform in roundness, good in mechanical property, suitable for the FDM process, free of blocking a printer nozzle and small in product warping deforming amount.

<CIT> states, according to its abstract, that a polymeric composite material is provided for melt-laminated three-dimensional (3D) printers using carbon fiber, containing <NUM>-<NUM> parts by weight of a thermoplastic resin and <NUM>-<NUM> parts by weight of the carbon fiber. According to the present disclosure, it is possible to improve mechanical properties such as tensile strength, tensile elastic modulus, bending strength, and bending elastic modulus.

<CIT> states, according to its abstract, that a thermoplastic molding composition comprises, based on the thermoplastic molding composition, a) as component A, at least one thermoplastic matrix polymer selected from poly-amides, polyesters, polyacetals, and polysulfones, where this can also take the form of polymer blend, b) as component B, from <NUM> to <NUM>% by weight of at least one highly branched or hyperbranched polymer which has functional groups which can react with the matrix polymer of component A, and c) as component C, from <NUM> to <NUM>% by weight of conductive carbon fillers selected from carbon nanotubes, graphenes, carbon black, graphite, and mixtures thereof, with the exclusion of specific thermoplastic molding compositions.

<CIT> states, according to its abstract, that it belongs to the technical field of polymer materials, and particularly relates to a polyaryletherketone sheet or board with the characteristics of high strength, high-temperature resistance, corrosion resistance and the like. Based on the sum of the components being 100wt%, the polyaryletherketone sheet or board comprises <NUM>-<NUM>. 0wt% of polyaryletherketone resin, <NUM>-<NUM>. 0wt% of high-temperature lubricant and <NUM>-<NUM>. 0wt% of hyperbranched polyaryletherketone. The extrusion molding method of the polyaryletherketone sheet or board comprises high-temperature melt extrusion of resin, filtering of melt, introduction of melt to a slit-type neck mold, formation of melt material sheets in the neck mold, introduction of the melt material sheets to a three-roller calender for cooling and molding and other steps. By controlling the molding temperature of the three-roller calender, hypocrystalline or amorphous sheets can be prepared. The prepared polyaryletherketone sheet has the characteristics of high strength, high heat-resistant temperature, corrosion resistance and the like, and has wide application in the high-technology fields, such as aviation and aerospace, weapons and equipment, electronics, automobiles, machinery, petrochemical industry and the like.

<CIT> states, according to its abstract, that a method for producing a polymer composite fiber comprises a polymer matrix with filaments incorporated therein whose lengthwise dimensions are substantially oriented with the axial dimension of the composite fiber, the method comprising subjecting a melt comprised of a polymer matrix and filaments to an extrusion process in which the melt is extruded into a fibrous form in the absence of screw extruders and in the substantial absence of shear forces that result in breakage of the filaments, followed by cooling and solidification of the extruded melt to provide the polymer composite fiber. Integration of these polymer composite fibers with additive manufacturing technologies, particularly rapid prototyping methods, such as FFF and 3D printing, are also described. The resulting polymer composite fibers and articles made thereof are also described.

<CIT> states, according to its abstract, that a method of forming a composite component by additive layer manufacturing includes the steps of applying a stretching force to an elongate tape of carbon nanotubes (CNTs) whereby to align the CNTs to the tape and form an aligned tape, impregnating the tape with resin matrix material <NUM>, forming the aligned tape into portions and transferring the portions to a component build location whereby to form the component, layer by layer. The tape may be impregnated before being formed into portions, the portions being deposited as a series of layers having a cross sectional shape corresponding to that of the component; or the impregnated aligned tape may be chopped into aligned particles which are subject to a powder bed process in which an aligning influence (i.e. ultrasonic agitation, an electric or magnetic field) may be used to align the particles in each layer prior to selective consolidation. Further embodiments are provided wherein the aligned tape may be marked with a material sensitive to a magnetic field, the aligned tape may be chopped into particles which are deposited in an additive manufacture process wherein a magnetic field is applied which interacts with the markers and rotates the particles to a common orientation. A further embodiment uses a LIFT (Laser Induced Forward Transfer) process to transfer portions of the aligned tape to a build location. An apparatus for forming a composite component by additive manufacturing is further provided.

<CIT> states, according to its abstract, a composite composition and a method of making such a composite that is composed of a matrix material and dispersed reinforcement nanotubes that are substantially aligned along at least one specified direction or axis. Also a method for making a continuous fiber-reinforced composite object by combining a reinforcement fiber tow with a solidifying matrix material to form a preimpregnated tow or towpreg, providing a dispensing head capable of dispensing the towpreg onto a base member positioned a distance from this head with the head and base member being driven by motion devices electronically connected to a motion controller regulated by a computer, and operating and moving the head relative to the base member to dispense multiple layers of towpreg in accordance with a CAD-generated deposition path along which the dispensing head can be allowed to trace out individual layers by following a selected algorithm so that the number of path interruptions at which the towpreg must be tentatively cut off from the dispensing head is minimized.

In view of the context above, the invention relates to an additively manufactured article as defined in claim <NUM>.

Further, the invention relates to a material adapted as a feedstock for additive manufacture as defined in claim <NUM>.

Further, the invention relates to a process for additive manufacture of an article as defined in claim <NUM>.

This disclosure will be better understood from reading the following Detailed Description with reference to the attached drawing figures, wherein:.

Additive manufacture of articles comprising thermoplastic polymers can be problematic due to the limited flowability of the polymer feedstock. Generally speaking, the polymer chains of many commonly available, high molecular-weight polymers are randomly oriented and significantly entangled. These features reduce the flowability of such polymers at all temperatures. Steric bulk in polymer sidechains may also reduce flowability, even in relatively lower molecular-weight polymers. Due to the decreased flowability, undesirably high temperature and/or pressure may be required in order to conduct a thermoplastic polymer through the nozzle of an additive-manufacture apparatus. Such conditions may increase manufacturing costs and, in scenarios in which very high temperatures are employed, may limit the range of usable polymers and/or degrade the desirable material properties of the polymers, such as optical transparency.

The inventors herein have recognized the above issues and have discovered several related innovations that may improve the processability of thermoplastic polymers in additive manufacturing. The disclosed examples utilize the incorporation of an alignment additive into the polymer matrix of the thermoplastic-polymer feedstock provided to an additive-manufacture apparatus. The alignment additive is a molecular or macromolecular species configured to induce alignment of the polymeric chains in the flowing polymer. In some examples, alignment parallel to the flow direction is achieved. In the aligned state, the polymeric chains are more flowable than in the randomly oriented, entangled state. Accordingly, a polymer matrix comprising the alignment additive can provide a suitable feedstock for additive manufacture of thermoplastic articles.

The alignment additive used in the present invention is a liquid-crystal compound as recited in claims <NUM>, <NUM> and <NUM>. These species align naturally in the flow direction of the polymer under fluid-dynamic forces and induce alignment of neighboring polymeric chains via intermolecular forces. In addition, an alignment additive may include a hyperbranched macromolecule, such as a dendrimer, a nanotube, and a nanowire. Hyperbranched macromolecules may reduce the viscosity of a flowing high molecular-weight polymer and thereby accelerate the alignment of the polymeric chains due to shear forces.

This disclosure is presented by way of example and with reference to the attached drawing figures. Components, process steps, and other elements that may be substantially the same in one or more of the figures are identified coordinately and are described with minimal repetition. It will be noted, however, that elements identified coordinately may also differ to some degree. It will be further noted that the figures are schematic and generally not drawn to scale. Rather, the various drawing scales, aspect ratios, and numbers of components shown in the figures may be purposely distorted to make certain features or relationships easier to see. As used herein, the phrase 'one or more of' prepends an inclusive enumeration of options. Accordingly, a phrase of the form, 'one or more of A and B' equates to 'one or more members of the set {A, B}. That phrase neither excludes nor requires one or more instances of A concurrent with one or more instances of B.

Before describing in detail, the additive manufacture of a thermoplastic article, an example application context for such an article will be presented. <FIG> shows aspects of an example manufactured product in the form of an aircraft <NUM>. The aircraft includes, inter alia, an aerostructure <NUM>, power plant <NUM>, skin <NUM>, and cabin interior <NUM>.

Virtually all of the structural and/or functional components of aircraft <NUM> may be optimized for mechanical strength. In addition, many of the same components, among others, may be optimized for reduced weight. As such, various airframe components are constructed from high-strength metals, such as steel and titanium, whereas other components may be constructed from so-called 'performance polymers', a term that includes selected high molecular-weight, thermoplastic polymer materials.

One non-limiting example of a high molecular-weight, thermoplastic polymer material with applicability to aircraft manufacture is polyether ether ketone (PEEK). The chemical structure of PEEK is shown in <FIG>. PEEK has a melting temperature (Tm) of <NUM> and a glass-transition temperature (Tg) of <NUM>. In some examples, the molecular weight of a high molecular-weight polymer can be <NUM>,<NUM> Daltons or greater.

PEEK is a semi-crystalline thermoplastic exhibiting high thermal resistance, chemical resistance, and wear resistance, in addition to fatigue and creep resistance. PEEK exhibits exceptional tensile properties, which are retained even at elevated temperatures. Accordingly, the service temperature range of a PEEK article may extend to <NUM>. Above the service temperature range, the material remains virtually non-flammable and emits very little smoke or gas when burned. PEEK articles can be further strengthened via fiber reinforcement. When reinforced with carbon fiber, for example, a tensile strength of <NUM> MPa (<NUM>,<NUM> psi (lbf/in<NUM>)) can be achieved. Additional properties of filled and unfilled PEEK materials are summarized in Table <NUM>.

Returning to <FIG>, polymer articles comprising PEEK and/or other suitable thermoplastics may be incorporated into various portions of aircraft <NUM>, to exploit desirable material properties as noted above. In aerostructure <NUM>, for example, thermoplastic-polymer articles may be used for bearings and bushings, and as reinforcement for composite panels including hard points, thermal isolators, and fasteners. In power plant <NUM>, heat- and chemical-resistant thermoplastic-polymer articles may be used in fuel systems, turbines, and nacelles, and for dry and lubricated material contacts. In skin <NUM>, ultraviolet (UV)-stable and moisture-resistant thermoplastic-polymer articles may provide superior resistance to weathering. Low-flammability thermoplastic polymer articles may also be used in cabin interior <NUM> and in conduits to protect wires and fiber optic filaments. To form such components, a thermoplastic polymer such as PEEK may be processed conventionally via injection molding, extrusion molding, and compression molding. However, the use of some thermoplastics, such as PEEK, in state-of-the-art additive manufacture is problematic for the reasons discussed hereinabove. The same limitations and many of the same benefits may exist for various other thermoplastics, such as polyether ketone ketone (PEKK), having the structure shown in <FIG>, and various nylon compounds, such as nylon-<NUM> (poly(dodecano-<NUM>-lactam)).

It will be understood that the examples illustrated in this disclosure in no way limit the applicability of the underlying methodologies. Indeed, the processes described herein can be applied to the additive manufacture of a wide range of articles. Such articles may or may not be specifically configured to optimize mechanical strength relative to weight, or to provide heat, chemical, or weather resistance, or fire safety.

<FIG> shows aspects of an example apparatus <NUM> configured for additive manufacture of a thermoplastic-polymer article <NUM>. Apparatus <NUM> includes a chamber <NUM> that supports the article during the additive-manufacture process. The chamber includes a platen <NUM> to which the article is secured during the additive-manufacture process. In the particular example illustrated in <FIG>, substrate <NUM> of article <NUM> is secured to a rotating chuck <NUM>, which is coupled mechanically to platen <NUM>. A 'substrate', as used herein, is a base portion of the article to be formed via additive manufacture. In some examples, the substrate is a portion of relatively simple topology, which can be formed by conventional processing. Rotating chuck <NUM> can be used for the additive manufacture of articles having rotational symmetry, such as a bushing. In other examples, a vice or clamp can be used in lieu of the chuck to secure the substrate or any other portion of the article to the platen.

In apparatus <NUM>, article <NUM> is formed in layers by spatially selective addition of thermoplastic-polymer material to the underlying layer of the article, starting with substrate <NUM>. Accordingly, apparatus <NUM> includes a material reservoir <NUM> configured to store a supply of thermoplastic-polymer material <NUM>. The thermoplastic-polymer material can comprise a filament, pellets of any dimension, granules, or a coarse or fine powder, for example.

Apparatus <NUM> includes a material conveyor <NUM> configured to convey thermoplastic-polymer material <NUM> from material reservoir <NUM> and to deliver the thermoplastic-polymer material to nozzle <NUM>. The nozzle comprises an aperture in the conduit through which the thermoplastic-polymer material is conducted. In some implementations, the nozzle aperture is normal to the direction of flow through the conduit and cuts across the full diameter of the conduit, while in other implementations the nozzle aperture may have any other suitable configuration. The nozzle-aperture diameter can be about one millimeter in some examples. In other examples, the nozzle-aperture diameter can be about five millimeters, or larger. In some implementations, the material conveyor can be configured to forcibly conduct thermoplastic-polymer material <NUM> through nozzle <NUM>.

<FIG> shows aspects of an example material reservoir 320B and material conveyor 324B suitable for storing and conveying thermoplastic polymer material 322B in the form of pellets, granules, and/or powders. In this example, material conveyor 324B includes a screw feeder <NUM>.

<FIG> shows aspects of another example material reservoir 320C and material conveyor 324C suitable for storing and conveying thermoplastic-polymer material 322C in the form of a filament. In this example, material reservoir 320C includes a spool <NUM> around which the filament is wound, and material conveyor 324C includes a filament feeder <NUM>.

Returning now to <FIG>, nozzle <NUM> of apparatus <NUM> is arranged over locus <NUM> where thermoplastic-polymer material is to be added to article <NUM>. Nozzle heater <NUM> is coupled thermally to nozzle <NUM>. The nozzle heater is configured to heat the nozzle and thereby heat the thermoplastic-polymer material flowing through the nozzle to a desired setpoint temperature or range of temperatures. In some examples, nozzle heater <NUM> is a resistive heater powered electrically via a proportional-integral-derivative (PID) -based temperature controller, which is operatively coupled to a thermocouple or other form of temperature sensor. In this manner, the setpoint temperature of the flowing thermoplastic-polymer material is achieved via closed-loop control. In some examples, apparatus <NUM> may include additional heaters, as described hereinafter.

Apparatus <NUM> includes a translational stage <NUM> mechanically coupled to platen <NUM>. As articles are formed layer-by-layer in apparatus <NUM>, the translational stage can be configured to gradually lower the height of the platen as successive layers of the article are built up. The translational stage can also be configured to move the platen laterally to controllably vary the relative position of locus <NUM> relative to the frame of reference of the platen and, accordingly, of article <NUM>. The translational stage can include two or more component translational stages (e.g., linear actuators) configured to move the platen in two or more corresponding directions, which may include Cartesian X, Y, and Z axes, for instance. In some examples, one or more component rotational stages are used in lieu of, or in addition to the one or more component translational stages. In other examples equally consonant with this disclosure, a translational or rotational stage is coupled mechanically to nozzle <NUM>, and the platen may be stationary. In still other examples, the platen as well as the nozzle can be controllably actuated.

Apparatus <NUM> further includes a computer <NUM>. Computer <NUM> is operatively coupled to translational stage <NUM> and configured to control in real time the relative position of locus <NUM> relative to the frame of reference of platen <NUM>, via a series of actuator-control signals. In addition, the computer is operatively coupled to material conveyor <NUM> and configured to control in real time, via one or more material-conveyance control signals, the rate of flow of the thermoplastic-polymer material through nozzle <NUM>. Computer <NUM> is further configured to receive a digital model <NUM> that represents the topology of the article to be formed. The nature and/or digital data structure of the digital model is not particularly limited. The digital model may include a CAD file in some examples. The computer is configured to vary the actuator- and material-conveyance control-signal outputs based on the digital model, so as to achieve additive manufacture of the article as defined by the digital model.

<FIG> illustrates aspects of an example process <NUM> for additive manufacture of a thermoplastic-polymer article. Process <NUM> can be implemented using apparatus <NUM> of <FIG>, as described hereinabove. It will be understood, however, that process <NUM> may implemented using any other suitable apparatus, which, in some implementations, may differ significantly from apparatus <NUM>.

At optional step <NUM> of process <NUM>, a substrate of the article is secured to a platen of an additive-manufacture apparatus. The substrate can be secured via a vice, clamp, or chuck, for instance. In some examples, the substrate may comprise a thermoplastic polymer, although that aspect is not strictly necessary. More generally, the substrate may comprise any structure to which the thermoplastic feedstock material will adhere upon solidification. In some examples, the substrate is milled, lathed, or abrasively roughened, or chemically treated to promote adhesion of the thermoplastic feedstock material to be added.

At <NUM> of process <NUM>, a thermoplastic-polymer material adapted as a feedstock for additive manufacture is conveyed through a heated nozzle to form a flowing mass. In examples in which the thermoplastic-polymer material takes the form of a filament or wire, the thermoplastic-polymer material is conveyed via a filament feeder. In some examples in which the thermoplastic-polymer material takes the form of a pellet, granule or powder, the thermoplastic-polymer material is conveyed via a screw feeder.

The thermoplastic-polymer material conveyed at <NUM> comprises a polymer matrix including a plurality of polymeric chains. The polymer matrix is configured, by virtue of its macromolecular structure, to form a flowable mass at an elevated temperature. Aspects of the macromolecular structure that provide this feature include, for instance, the backbone structure including heteroatoms (if any), pendent side-chains and functional groups (if any), and the extent of cross-linking (if any), which influence both Tm and the viscosity at temperatures above Tm. In some examples, the polymer matrix comprises PEEK or PEKK. In some examples, the polymer matrix comprises a nylon polymer. In some examples, the polymer matrix comprises two or more different thermoplastic polymers. An example 'elevated temperature', as used herein, is any temperature in a range extending from the melting temperature Tm of the polymer matrix to a temperature at which the polymer decomposes observably on the timescale of processing. In one particular example, an elevated temperature by include a temperature of <NUM> above Tm.

The thermoplastic-polymer material conveyed at <NUM> further comprises an alignment additive dispersible within the polymer matrix. In some examples, the alignment additive comprises between <NUM> and <NUM>% by mass of the thermoplastic-polymer material. In more particular examples, the alignment additive comprises between <NUM> and <NUM>% by mass of the thermoplastic-polymer material. The alignment additive is configured, by virtue of its molecular or macromolecular structure, to align the plurality of polymeric chains in a direction of flow through a conduit of the additive-manufacture apparatus. The alignment additive may increase the melt-flow index of the thermoplastic-polymer material beyond that of polymer matrix having no alignment additive. A particular alignment additive incorporated in a thermoplastic-polymer material can be chosen empirically in some examples, based on its ability to do so.

The alignment additive comprises a liquid-crystal (LC) material comprising numerous liquid-crystal molecules. Both smectic and nematic liquid crystals may be used. The smectic liquid-crystal materials used as an alignment additive include <NUM>-(heptyloxy)benzoic acid, <NUM>-(octyloxy)benzoic acid, and <NUM>-(decyloxy)benzoic acid. Having the structure shown in <FIG>, <NUM>-(heptyloxy)benzoic acid exhibits a melting point of <NUM> and a transition to the isotropic phase at <NUM>. Having the structure shown in <FIG>, <NUM>-(octyloxy)benzoic acid exhibits a melting point of <NUM> to <NUM> and a transition to the isotropic phase at <NUM>. Having the structure shown in <FIG>, <NUM>-(decyloxy)benzoic acid exhibits a melting point of <NUM> and a transition to the isotropic phase at <NUM> to <NUM>. The nematic liquid crystal materials used as alignment additives include <NUM>,<NUM>'-azoxyanisole, <NUM>-isothiocyanatophenyl-<NUM>-pentylbicyclo[<NUM>. <NUM>]octane-<NUM>-carboxylate, and <NUM>-methoxycinnamic acid. Having the structure shown in <FIG>, <FIG>,<NUM>'-azoxyanisole exhibits a melting point of <NUM> to <NUM> and a transition to the isotropic phase at <NUM>. Having the structure shown in <FIG>, <NUM>-isothiocyanatophenyl-<NUM>-pentylbicyclo[<NUM>. <NUM>]octane-<NUM>-carboxylate exhibits a melting point of <NUM> to <NUM> and a transition to the isotropic phase at <NUM>. Having the structure shown in <FIG>, <NUM>-methoxycinnamic acid exhibits a melting point of <NUM> to <NUM> and a transition to the isotropic phase at <NUM>.

The liquid-crystal material is selected such that it undergoes a phase transition between an aligned (e.g., smectic or nematic) phase and an isotropic phase at or below the melting temperature Tm of the polymer matrix into which the alignment additive is incorporated. Such liquid crystal materials are dispersed in the isotropic phase at elevated processing temperatures and transition to an aligned phase prior to solidification of the thermoplastic-polymer material, and can help to align the polymer chains via this transition.

Table <NUM> presents melt-flow data collected on thermoplastic feedstock materials having different concentrations of <NUM>-(heptyloxy)benzoic acid as a liquid-crystal alignment additive.

The data in Table <NUM> demonstrate significant increase in flowability with increasing concentration of the alignment additive, both for PEEK and Nylon-<NUM> polymers. Table <NUM> presents additional data on the PEEK feedstock material.

More specifically, the data in Table <NUM> show that the thermal resistance of PEEK is substantially unchanged upon addition of the alignment additive, even at <NUM>%.

It will be understood that other suitable high-aspect ratio species can be incorporated into a thermoplastic-polymer matrix as an alignment additive to promote alignment of the polymer chains therein. In other examples, the alignment additive additionally comprises a nanotube or nanowire material comprising numerous nanotubes or nanowires, respectively. More particular examples include carbon nanotubes and silver nanowires, although nanotubes and nanowires comprising other elements are also envisaged.

Further, in some examples, the alignment additive additionally comprises a plurality of hyperbranched macromolecules, such as a dendrimers. Example dendrimers include poly(amidoamine) (PAMAM) and polypropylene imine) (PPI). The macromolecular structure of a PPI dendrimer is shown in <FIG>. As shown in Table <NUM>, PPI dendrimers may be nanosized, with a diameter that varies smoothly with generation number.

Due to its steric morphology, a dendrimer typically exhibits low intrinsic viscosity and depresses the viscosity of the polymer matrix into which it is dissolved. Furthermore, the intermolecular interactions between a dendrimer and a high molecular-weight thermoplastic matrix may be tuned by controlling the surface functionality of the dendrimer.

In some examples, the thermoplastic-polymer material conveyed at <NUM> is a composite material, such as a fiber-composite material. More particularly, the thermoplastic-polymer material, in some examples, further comprises a reinforcing additive or filler, such as a fiber additive. Glass fibers and carbon fibers are among the fiber additives envisaged herein.

Continuing now in <FIG>, at <NUM> of process <NUM>, at least a portion of the polymeric chains of the thermoplastic-polymer material are spontaneously aligned along a direction of flow through the heated nozzle, via the influence of the alignment additive.

In examples in which alignment additive includes a molecular or macromolecular species having a high aspect ratio, such as a liquid-crystal molecule, nanotube, and/or nanowire, the alignment additive may align naturally in the flow direction of the polymer under fluid-dynamic forces within and fluidically upstream of the heated nozzle. When aligned in this manner, the alignment additive may induce alignment of neighboring polymeric chains via intermolecular forces, such as the van der Waals force, molecular dipole force, hydrogen bonding, etc. In examples in which the alignment additive includes a relatively low molecular-weight, hyperbranched macromolecule, such as a dendrimer, the alignment additive may reduce the viscosity of a flowing high molecular-weight polymer and thereby accelerate the alignment of the polymeric chains due to shear forces within and fluidically upstream of the heated nozzle.

At <NUM> of process <NUM>, the flowing mass of the thermoplastic-polymer material is released from the heated nozzle at the intended locus position of the article being formed-e.g., on the substrate of the article. At <NUM>, the thermoplastic-polymer material is allowed to solidify at the locus.

At <NUM> subsequent layers of the thermoplastic-polymer material are added to the layer of the thermoplastic-polymer material already formed. This step can be repeated any number of times, based on the article topology as defined in the digital model, until the desired article has been built up.

At <NUM> the article is removed from the additive-manufacture apparatus and optionally annealed under controlled-temperature conditions for an appropriate period of time. Annealing may serve to reduce the density of defect sites in the additively manufactured article and thereby increase the strength of the article.

Returning now to <FIG>, apparatus <NUM> can be adapted to the process of additive manufacture from a thermoplastic-polymer feedstock comprising a polymer matrix and an alignment additive as described herein. More particularly, apparatus <NUM>, in some examples, includes an elongate conduit <NUM> coupled to nozzle <NUM>, fluidically upstream of the nozzle. The elongate conduit may be <NUM> to <NUM> (one to four inches) long, for instance. In other examples, the elongate conduit may be up to <NUM> (thirty inches) long. Elongate conduits of other length ranges are also envisaged. More generally, the elongate conduit may be of sufficient length to promote at least partial alignment of the polymeric chains of the thermoplastic-polymer material, via the influence of the alignment additive, when the thermoplastic-polymer material flows through the elongate conduit at the elevated temperature. In this adaptation, the cross-sectional dimensions of the elongate conduit may correspond to the cross-sectional dimensions of the feedstock material, and the extrusion rate can be unchanged relative to the rate of extrusion of the unmodified feedstock. Nevertheless, faster and slower rates of extrusion are also envisaged. The setpoint temperature of the elongate conduit is greater than the melting temperature of the thermoplastic-polymer material.

In these and other examples, material conveyor <NUM> is configured to convey the thermoplastic-polymer material through the elongate conduit and through the nozzle. The apparatus as illustrated also includes a conduit heater <NUM> coupled thermally to elongate conduit <NUM> and configured to heat the elongate conduit to an elevated temperature. Taken together, conduit heater <NUM> and nozzle heater <NUM> are configured to heat the elongate conduit <NUM> and nozzle <NUM> to allow the material to flow within the conduit and through the nozzle. Elongate conduit <NUM> is of sufficient length to promote at least partial alignment of the polymeric chains of the thermoplastic-polymer material, via the influence of the alignment additive, when the thermoplastic-polymer material flows through the elongate conduit at the elevated temperature. In some examples, conduit heater <NUM> and nozzle heater <NUM> can be separate heating units, as illustrated. In other examples, the conduit heater and nozzle heater may be integrated into a single heating unit capable of providing a desired temperature of nozzle <NUM> and a desired temperature of elongate conduit <NUM>, even if those temperatures are different.

<FIG> shows aspects of an example additively manufactured article <NUM> that can be formed according to process <NUM> of <FIG>. In the illustrated example, article <NUM> includes a substrate <NUM> in addition to thermoplastic-polymer material <NUM>, which is added to the substrate via additive manufacture. In some examples, the article can be formed without a substrate and may comprise only the thermoplastic-polymer material. In either case, thermoplastic-polymer material <NUM> comprises a polymer matrix <NUM> including a plurality of aligned polymeric chains <NUM>. The polymer matrix can include PEEK or PEKK, but other polymers are also envisaged.

It will be understood that the illustration in <FIG> is highly schematic. In real-world examples, the plurality of polymeric chains <NUM> need not be perfectly aligned, but may be partially aligned. In other words, alignment may be observed between a portion of one polymeric chain and a portion of another polymeric chain. The alignment may involve many such chains and may extend over relatively long distances in polymer matrix <NUM>. In some examples, the degree of alignment of the polymeric chains in article <NUM> can be assessed via x-ray diffractometery and/or other methods that differentiate between isotropic and ordered molecular configurations, as understood in the art of condensed-phase chemistry. For instance, a matrix of aligned polymeric chains may give rise to relatively sharp peaks in an x-ray diffraction spectrum, whereas an isotropic matrix of identical composition may give rise to a more featureless x-ray diffraction spectrum.

In accordance with the invention, the thermoplastic-polymer material also includes an alignment additive <NUM>, as recited in claims <NUM>, <NUM> and <NUM> dispersed within polymer matrix <NUM>. In some examples, the alignment additive comprises between <NUM> and <NUM>% by mass of thermoplastic-polymer material <NUM>, or between <NUM> and <NUM>% by mass of thermoplastic-polymer material in more particular examples. In some examples, the alignment additive further includes one or more of a nanotube, and nanowire. In the examples in accordance with the invention, in which alignment additive <NUM> includes a plurality of liquid-crystal molecules, the liquid-crystal molecules and at least some of the polymeric chains may be aligned substantially in parallel. This feature also can be assessed using x-ray diffractometry and other suitable analytical methods. In addition, alignment additive <NUM> can include a hyperbranched macromolecule, as noted above. In the example shown in <FIG>, thermoplastic-polymer material <NUM> also includes a strengthening filler in the form of a fiber additive <NUM>. In other examples, the fiber additive may be omitted. When included, the fiber additive can include glass and/or carbon fibers, for instance.

Table <NUM> presents test data collected on an article that was additively manufactured according to the process of <FIG>.

The data in Table <NUM> were acquired in accordance with American Society for Testing and Materials (ASTM) standard protocol ASTM D638 (Standard Test Method for Tensile Properties of Plastics), using a constant-rate-of-crosshead-movement type testing machine. The data reveal that the tensile strength of the PEEK matrix is degraded only marginally even at significant concentrations of the alignment additive. These data can be examined in view of the data from Table <NUM>, which show a <NUM>-fold improvement in the flowability of the PEEK feedstock with <NUM>% of the alignment additive.

No aspect of the foregoing drawings or description should be construed in a limiting sense, because numerous variations, extensions, and omissions are also envisaged.

For instance, in implementations in which the feedstock material takes the form of a filament, that filament may be pre-processed in order to provide still greater flowability when used in an additive-manufacture apparatus. In the process of forming such a filament, thermoplastic-polymer material <NUM> with alignment additive <NUM>, in any suitable physical form, is conducted through a heated elongate conduit and nozzle analogous to elongate conduit <NUM> and nozzle <NUM> of additive-manufacture apparatus <NUM>. In flowing through the elongate conduit and nozzle, the alignment additive may cause the polymeric chains of the polymer matrix to align in the direction of flow through the nozzle. When the feedstock material emerges from the nozzle and subsequently cools, the alignment of the polymeric chains in the length direction of the cooled filament is locked in. The extruded filament pre-processed in this manner is now usable as a feedstock in the additive-manufacture apparatus.

In some examples, the alignment of the polymeric chains in the above feedstock may be further increased by mechanically drawing the partially solidified feedstock material downstream of the nozzle. The extruded, drawn filament pre-processed in this manner may also be used as a feedstock in the additive-manufacture apparatus. In some scenarios, filaments as described above may even be used in additive-manufacture apparatuses not specifically adapted with elongate conduit <NUM>, as the increased flowability is already provided by virtue of the pre-processing.

Claim 1:
A material (<NUM>, <NUM>) adapted as a feedstock for additive manufacture, the material comprising:
a polymer matrix (<NUM>) including a plurality of polymeric chains (<NUM>), the polymer matrix configured to form a flowable mass at an elevated temperature; and
an alignment additive (<NUM>) dispersible within the polymer matrix, the alignment additive being configured to align the plurality of polymeric chains in a direction of flow through a conduit (<NUM>) of an additive-manufacture apparatus (<NUM>), wherein a melt-flow index of the material is preferably greater than a melt-flow index of the polymer matrix (<NUM>) without the alignment additive (<NUM>), wherein the alignment additive (<NUM>) comprises a liquid-crystal material that undergoes a phase transition between an aligned phase and an isotropic phase at or below the elevated temperature, wherein the liquid-crystal material includes <NUM>-(heptyloxy)benzoic acid, <NUM>-(octyloxy)benzoic acid, <NUM>-(decyloxy)benzoic acid, <NUM>,<NUM>'-azoxyanisole, <NUM>-isothiocyanatophenyl-<NUM>-pentylbicyclo[<NUM>.<NUM>]octane-<NUM>-carboxylate, or <NUM>-methoxycinnamic acid.