第3项共6 6.F 11.F 7.F 12.F 13.F 14F 10.F 15.T VI.Give a simple answer to the following questions(15points) 1.What are the two types aspects are they different from each other?(2pts The two types of glass fibers are E-glass and S-glass.They are different in composition. modulus of elasticity,and applications. 2.How does the crystallinity affect the optical properties of plastics?Give examples to explain the。 Tect.(3pts) The optical properties of plastics will be reduced by increasing the crystallinity of polymers.For examples.HDPE has a higher degree of crystallinity than LDPE therefore,HDPE is opaque while LDPE is transparent. 3.Name the polymerization ap an example to explain how the properties of polymers are improved by using this approach.(4pts) The polymerization approaches to improving the properties of polymers include copolymerization.terpolymerization.and multicomponent polymerization.For example. butyrene is tough but weak,and polystyrene is a britte polymer that has limited toughness and poor chemical t th with styrene,it is possible to obtain a chemically resistant,more rigid,and stronger plastic.Copolymerization of butadiene and styrene results in an elastomer;and the terpolymerization of acrylonitrile,butadiene,and styrene produces ABS plastics that are though and elastomeric,and have good chemical resistance. 4.Describe three methods in which adhesives develop their cured attraction between the substrate and the adherent.(3pts) The cured attraction between the substrate and the adherent can be developed by 1) removal of solvent;2)removal of external heat sources;3)blocking oxygen;4)Mix the separately stored resin and catalyst together tocause cross-inking of the resin. 5.What are the three major differences between carbon and graphite fibers?(3pts)第 3 页 共 6 页 3 6. F 7. F 8. F 9. T 10. F 11. F 12. F 13. F 14. F 15. T VI. Give a simple answer to the following questions (15points) 1. What are the two types of glass fibers and what aspects are they different from each other? (2pts) The two types of glass fibers are E-glass and S-glass. They are different in composition, modulus of elasticity, and applications. 2. How does the crystallinity affect the optical properties of plastics? Give examples to explain the effect.(3pts) The optical properties of plastics will be reduced by increasing the crystallinity of polymers. For examples, HDPE has a higher degree of crystallinity than LDPE, therefore, HDPE is opaque while LDPE is transparent. 3. Name the polymerization approaches to improving the properties of polymers. Give an example to explain how the properties of polymers are improved by using this approach. (4pts) The polymerization approaches to improving the properties of polymers include copolymerization, terpolymerization, and multicomponent polymerization. For example, butyrene is tough but weak, and polystyrene is a brittle polymer that has limited toughness and poor chemical resistance. But through copolymerization of acrylonitrile with styrene, it is possible to obtain a chemically resistant, more rigid, and stronger plastic. Copolymerization of butadiene and styrene results in an elastomer; and the terpolymerization of acrylonitrile, butadiene, and styrene produces ABS plastics that are though and elastomeric, and have good chemical resistance. 4. Describe three methods in which adhesives develop their cured attraction between the substrate and the adherent. (3pts) The cured attraction between the substrate and the adherent can be developed by 1) removal of solvent; 2) removal of external heat sources; 3) blocking oxygen; 4) Mix the separately stored resin and catalyst together to cause cross-linking of the resin. 5. What are the three major differences between carbon and graphite fibers? (3pts)