Herein certain terms are used, and they are defined below:
By a “thermoplastic” is meant a polymer, preferably having a weight average molecular weight of about 10,000 or more, more preferably about 20,000 or more, and which has a glass transition temperature and/or at least one melting point above 30° C., more preferably above about 50° C. and especially preferably above about 100° C. Preferably at least one of these melting points (if there is more than one) has a heat of fusion associated with it of 3 J/g or more, preferably at least about 5 J/g or more. Melting points, heats of fusion, and glass transition temperatures are measured by ASTM Method D3418, at a heating rate of 10° C./minute, using measurements on the second heat. The melting point is taken as the peak of the endotherm. The glass transition point is taken as the midpoint (inflection point) of the transition. Thus thermoplastics may include both semicrystalline and amorphous polymers.
By a “partially aromatic polyamide” is meant a polyamide or blend of polyamides in which at least 5 mole percent of all repeat units in the polyamide or blend of polyamides have an aromatic ring, which means thermoplastic polyamides having all repeat units containing an aromatic ring may be used. However, preferably no more than 60 mole percent of the repeat units have an aromatic ring. By an aromatic ring is meant a group such as phenyl or phenylene, naphthyl or naphthylylene, biphenyl or biphenylene, or pyridyl or pyridylylene. Preferably the aromatic ring is in the main chain of the polymer, i.e., is not a “side group” in the repeat unit. Units in the main chain would include those derived from terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 1,4-diaminobenzene, 1,3-diaminobenzene, 1,4-bis(aminomethyl)benzene, 1,3-bis(aminomethyl)benzene, 4,4′diaminobiphenyl, 4-aminobenzoic acid, and 3-aminobenzoic acid. Repeat units with aromatic side groups include those derived from 3-phenyl-1,6-diaminohexane and 2-(4-pyridyl)succinic acid. If more than one polyamide is present (a blend of polyamides) then all repeat units in all polyamides are used in this calculation, whether any particular polyamide has any repeat units containing aromatic groups or not.
By a “polyamide” is meant a polymer in which at least 90 mole percent of the groups linking the monomers together are amide groups, preferably at least 98%.
By a “chopped” fiber is meant a fiber whose number average length is about 5 cm or less, preferably about 2.5 cm or less, more preferably about 1.3 cm or less, and especially preferably less than about 0.6 cm, when measured on the final composition, or in the case of a shaped article, the shaped article. Fiber lengths may be measured by standard optical or electron microscopy methods (as appropriate, depending on the diameter of the fiber, the magnification required is such that at least 90% of the fibers are visible at that magnification).
Glass fibers typically used as fillers/reinforcing agents for thermoplastics may be used, and preferably the glass fiber has a diameter of about 30 μm or less, more preferably about 20 μm or less, and especially preferably have a diameter of about 5 to about 13 μm. The glass fiber may be sized or unsized, but it is preferred that the glass fiber be sized, especially with a sizing, as now commercially available, designed for the particular thermoplastic(s) being used. Preferably the glass fiber has a tensile modulus of about 30 GPa or more.
Carbon fibers typically used as fillers/reinforcing agents for thermoplastics may be used, and preferably the carbon fiber has a diameter of about 20 μm or less, more preferably about 10 μm or less. The carbon fiber may be sized or unsized, but it is preferred that the carbon fiber be sized, especially with a sizing, as now commercially available, designed for the particular thermoplastic(s) being used. The carbon fiber may be made in a number of ways, for instance it may be “pitch based” or made from polyacrylonitrile. Preferably the carbon fiber has a tensile modulus of about 150 GPa or more.
Preferably the minimum amount of fiber component (glass fiber plus carbon fiber) is about 52 weight percent, more preferably about 55 weight percent, while the maximum amount of fiber component is 70 weight percent, more preferably about 65 weight percent, and especially preferably about 62 weight percent. It is to be understood that any maximum amount of fiber component can be combined with any minimum amount of fiber component to form a preferred fiber component range.
Herein the ratio of glass fiber to carbon fiber (glass:carbon) ranges from a maximum of about 13:1.0 to a minimum of about 1.0:1.0 Preferably the maximum is about 8:1.0, more preferably 6:1.0, and preferably the minimum is about 2.0:1.0, more preferably 3.0:1.0. It is to be understood that any such maximum amount may be combined with any such minimum amount to form a preferred ratio range.
Virtually any kind of thermoplastic may be used, including poly(oxymethylene) and its copolymers; polyesters such as PET, poly(1,4-butylene terephthalate), poly(1,4-cyclohexyldimethylene terephthalate), and poly(1,3-poropyleneterephthalate); polyamides such as nylon-6,6, nylon-6, nylon-12, nylon-11, and partially aromatic (co)polyamides; polyolefins such as polyethylene (i.e. all forms such as low density, linear low density, high density, etc.), polypropylene, polystyrene, polystyrene/poly(phenylene oxide) blends, polycarbonates such as poly(bisphenol-A carbonate); fluoropolymers including perfluoropolymers and partially fluorinated polymers such as copolymers of tetrafluoroethylene and hexafluoropropylene, poly(vinyl fluoride), and the copolymers of ethylene and vinylidene fluoride or vinyl fluoride; polysulfones such as poly(p-phenylene sulfone), polysulfides such as poly(p-phenylene sulfide); polyetherketones such as poly(ether-ketones), poly(ether-ether-ketones), and poly(ether-ketone-ketones); poly(etherimides); acrylonitrile-1,3-butadinene-styrene copolymers; thermoplastic (meth)acrylic polymers such as poly(methyl methacrylate); and chlorinated polymers such as poly(vinyl chloride), vinyl chloride copolymer, and poly(vinylidene chloride). Also included are thermpoplastic elastomers such as thermoplastic polyurethanes, block-copolyesters containing so-called soft blocks such as polyethers and hard crystalline blocks, and block copolymers such as styrene-butadiene-styrene and styrene-ethylene/butadiene-styrene block copolymers. Polymers which may be formed in situ, such as (meth)acrylate ester polymers are also included. Also included herein are blends of thermoplastic polymers, including blends of two or more semicrystalline or amorphous polymers, or blends containing both semicrystalline and amorphous thermoplastics.
Preferred types of thermoplastics include polyamides, especially partially aromatic polyamides, polyesters, poly(etherimides), and polysulfones. Another preferred type of thermoplastic is a semicrystalline thermoplastic, that is thermoplastics with melting points as described above.
These compositions may contain other materials that are conventionally found in thermoplastic compositions other than those described in the claims. For instance these may include other fillers/reinforcing agents, stabilizers, mold releases or lubricants, antioxidants, tougheners, other types of polymers, crystallization promoters, flame retardants, and antistatic agent(s). If other polymeric materials are present is the composition the percentage of the filler component is based on the total weight of all polymers present plus the weight of the filler component.
By a toughener is meant a polymeric material which typically is an elastomer or has rubbery characteristics. It may be a thermoplastic as defined herein, but it will often have a high elongation to break. The toughener may or may not contain functional groups which react with the “matrix” resin. Typical tougheners are EP rubber, EPDM rubber grafted with maleic anhydride, sytrenic block copolymers, and copolymers of ethylene and various acrylic esters. Some of these acrylic esters may contain reactive functional groups such as epoxy. Such tougheners are well known in the art, see for instance C. R. Bucknall, Toughened Plastics, Applied Science Publishers, Ltd., London, 1977, and E. A. Flexman Toughened Semicrystalline Engineering Polymer: Morphology, Impact Resistance and Fracture Mechanisms in C. K. Riew, et al., Ed., Advances in Chemistry Series 233, Toughened Plastics I, American Chemical Society, Washington D.C., 1993.
Preferably the present compositions have a tensile modulus of 25 GPa or more when measured by ASTM Method D638, at an extension rate of 5.8 mm/min (0.20″/min), using a Type IV bar, and/or a notched Izod of about 80 Nm/m (1.5 ft.lb./in) or more when measured by ASTM Method D256, more preferably 107 Nm/m (2.0 ft.lb./in.) or more. Both measurements are preferably made on specimens 0.32 cm (⅛ in.) thick.
The present compositions may be made by methods well known in the art for making thermoplastic compositions with fillers/reinforcing agents (and optionally other materials) present. The polymer may be melt mixed with the carbon and glass fibers in typical melt mixing equipment such as single or twin screw extruders, kneaders, and other similar devices. In melt mixing the thermoplastic is heated above its melting point to mix in the various ingredients, including the glass and carbon fiber. While it is preferred that both of these fibers be added in their chopped form this is not necessary since normally such mixers will cut the fibers to the desired length anyway. In order to preserve the fiber lengths, it may be desirable to “side feed” the chopped fiber(s) in order to minimize shear degradation of the fiber lengths. Other than side feeding, no particular order of adding the ingredients is preferred. Alternatively the glass and/or carbon fiber may be added during the synthesis of the thermoplastic and dispersed during that process. No matter what process is used, in the resulting composition, as is well known in the art for all similar thermoplastic compositions, the ingredients should preferably be well dispersed.
The compositions may also be made by making “masterbatches” containing glass fiber and/or carbon fiber and blending pellets of the proper concentrations of these fillers with other pellets containing no or lesser amounts of these fibers in order to form the desired composition in a melt mixer such as an extruder. This is sometimes called cube blending.
The composition may be formed into shaped articles by many processes known in the art in general for forming thermoplastic parts. By a shaped article is meant a part with one, two or three definite, and normally desired dimensions, and includes films, sheets, two dimensional extrusions, and three dimensional parts. The parts may be formed by heating the composition to either soften (but not melt) it or heated above the melting point to melt it. Whether softened or melted the composition is then “forced” into or through some sort of mold or die that shapes the composition. Processes that require melting include injection molding, melt extrusion, and blow molding. A process that requires softening is thermoforming. Processes that require one or both of melting and softening include rotomolding, and compression molding. All of these processes are well known in the art. Preferred forming processes are injection molding, extrusion, and compression molding, and injection molding is especially preferred.
The present compositions are especially useful as shaped parts wherein high stiffness and tensile strength are needed, especially in combination with some toughness.
In the Examples tensile properties were determined using ASTM Method D638, using a Type IV bar and an extension rate of 5.08 mm/min (0.20″), and notched Izod was measured by ASTM Method D256. All test pieces were 0.32 cm (⅛″) thick. Elongation is percent tensile elongation to break. In the Examples, unless otherwise noted, all parts are parts by weight.
In the Examples certain ingredients are used. They are:
The compositions were made by mixing in a Werner & Pfleiderer 30 mm twin screw extruder at a nominal rate of about 13.6 kg/h at barrel temperatures of 290-340° C. depending on the partially aromatic polyamide used. The extruder had one feeder at the rear for all of the ingredients except the carbon and glass fibers, each of which was separately side fed through a feeder. They were molded into 0.32 cm thick standard ASTM test specimens on a 6 oz. Model 200 HPM Injection Molding Machine. Compositions and physical properties are given in Table 1.
The compositions were made by mixing in a Werner & Pfleiderer 30 mm twin screw extruder at a nominal rate of about 13.6 kg/h at barrel temperatures of 290-340° C. depending on the partially aromatic polyamide used. The extruder had one feeder at the rear for all of the ingredients except the carbon and glass fibers, each of which was separately side fed through a feeder. They were molded into 0.32 cm thick standard ASTM test specimens on a 6 oz. Model 200 HPM Injection Molding Machine. Compositions and physical properties are given in Table 2.
The compositions were made by mixing in a Werner & Pfleiderer 30 mm twin screw extruder at a nominal rate of about 13.6 kg/h at barrel temperatures of 280-290° C. The extruder had one feeder at the rear for all of the ingredients except the carbon and glass fibers, each of which was separately side fed through a feeder. They were molded into 0.32 cm thick standard ASTM test specimens on a 6 oz. Model 200 HPM Injection Molding Machine. Compositions and physical properties are given in Table 3.
The compositions were made by mixing in a Werner & Pfleiderer 30 mm twin screw extruder at a nominal rate of about 13.6 kg/h at barrel temperatures of 280-290° C. The extruder had one feeder at the rear for all of the ingredients except the carbon and glass fibers, each of which was separately side fed through a feeder. They were molded into 0.32 cm thick standard ASTM test specimens on a 6 oz. Model 200 HPM Injection Molding Machine. Compositions and physical properties are given in Table 4.
The compositions were made by mixing in a Werner & Pfleiderer 30 mm twin screw extruder at a nominal rate of about 13.6 kg/h at barrel temperatures of 280-290° C. The extruder had one feeder at the rear for all of the ingredients except the carbon and glass fibers, each of which was separately side fed through a feeder. They were molded into 0.32 cm thick standard ASTM test specimens on a 6 oz. Model 200 HPM Injection Molding Machine. Compositions and physical properties are given in Table 5.
The compositions were made by the same method used to make the compositions of Examples 9-10 and Comparative Examples M-O, except Polymer E was used instead of Polymer D. Compositions and properties are shown in Table 6.
Using the same procedure as used for Example 5 and Comparative Examples E-G, the a composition was prepared and test pieces made. The composition and physical properties are shown in Table 7.
The results in the Tables show that high modulus with relatively good toughness (Notched Izod test, the higher the value the tougher the composition) can be achieved with the composition of the present invention. This combination of properties wasn't achieved by glass or carbon fibers alone.
This application claims the benefit of U.S. Provisional Application No. 60/802,608, filed May 23, 2006 and U.S. Provisional Application No. 60/818,574, filed Jul. 5, 2006.
Number | Date | Country | |
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60818574 | Jul 2006 | US | |
60802608 | May 2006 | US |