Polymer composite containing recycled carbon fibers
A polymer composition is described well suited for being combined with relatively short fibers. The fibers, for instance, can have a mean fiber length of less than 1,000 microns, such as less than 700 microns, such as less than 500 microns. The polymer formulation allows for intimate mixing with the fibers without having to use a sizing agent. In one embodiment, the composition contains a polybutylene terephthalate polymer combined with a thermoplastic polymer having lower crystallinity.
1. A reinforced polymer composition comprising:
a first polyester polymer;
a second polyester polymer blended with the first polyester polymer, the second polyester polymer being less crystalline than the first polyester polymer, the second polyester polymer being present in the polymer composition in an amount from about 2% by weight to about 35% by weight; and
carbon fibers combined with the first and second polyester polymers, the carbon fibers being present in the polymer composition in an amount from about 5% by weight to about 50% by weight, wherein the carbon fibers are substantially free of a sizing agent, and wherein the carbon fibers have a mean fiber length of from about 10 microns to about 1,000 microns.
2. A reinforced polymer composition as defined in claim 1 , wherein the carbon fibers have a mean fiber length of from about 50 microns to about 500 microns.
3. A reinforced polymer composition as defined in claim 1 , wherein the carbon fibers have a mean fiber length of from about 50 microns to about 200 microns, and wherein the carbon fibers are present in the composition in an amount from about 10% to about 45% by weight.
4. A reinforced polymer composition as defined in claim 1 , wherein the first polyester polymer has a crystallinity of greater than about 40%.
5. A reinforced polymer composition as defined in claim 1 , wherein the second polyester polymer has a crystallinity of less than about 40%.
6. A reinforced polymer composition as defined in claim 1 , wherein the first polyester polymer comprises polybutylene terephthalate.
7. A reinforced polymer composition as defined in claim 1 , wherein the second polyester polymer comprises polyethylene terephthalate.
8. A reinforced polymer composition as defined in claim 1 , wherein the composition further contains a fatty acid ester.
9. A reinforced polymer composition as defined in claim 8 , wherein the fatty acid ester comprises an ester of montanic acid.
10. A reinforced polymer composition as defined in claim 1 , wherein the composition further contains a nucleating agent.
11. A reinforced polymer composition as defined in claim 10 , wherein the nucleating agent comprises talc and wherein the nucleating agent is present in the composition in an amount from about 0.001% to about 0.5% by weight.
12. A reinforced polymer composition as defined in claim 1 , wherein the composition contains a heat stabilizer and an antioxidant.
13. A reinforced polymer composition as defined in claim 12 , wherein the heat stabilizer comprises a diphosphite or triphosphite and wherein the antioxidant comprises a sterically hindered phenolic compound.
14. A reinforced polymer composition as defined in claim 1 , wherein the composition is in a compounded form.