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Plastic Product Material and Process Selection Handbook Part 4

Tham khảo tài liệu 'plastic product material and process selection handbook part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 2 Plastic property 89 . I . iiHMwwOT barrier properties of PET allow for its use in carbonated beverages and many types of food containers. However PET barrier properties are deficient for packaging beer and certain foods that are highly sensitive to oxygen unless coinjected with suitable materials. PET can be reinforced with glass fibers to produce an injection molded product with high heat resistance and high stiffness. The resistance of PET to chemicals and solvents is greatly enhanced as the crystallinity of the polymer increases. PET s broad range of properties make them ideal replacements in certain applications for such metals as die-cast aluminum or zinc also in thermoset switches relays sensors etc. Applications include packaging particularly stretched injection blow molded beverage bottles and film appliances electrical electronics etc. PET finds applications in such diverse end uses as fibers for clothing films bottles food containers and engineering plastics for precision molded parts.118-120 A wide range of applications is possible because of the excellent balance of properties PET possesses and because the degree of crystallinity and the level of orientation in the finished product can be controlled. PET plastics are hygroscopic so require proper drying before processing. They can be extruded blow molded and thermoformed on conventional equipment if dried to a moisture content of less than 50 ppm. Recycling all types of PET materials is easily accomplished. Of the 2002 total USA 49.4 million units of PET beverage container market 57 contain carbonated soft drinks and 24 contain water.485 Polyethylene Terephthalate Glycol The clear amorphous glycol-modified polyester PETG is polymerized from dimethyl ester DMT or terephthalic acid PTA and ethylene glycol. The addition of glycol prevents polymer crystallization providing a broader process window than PET. PETG parts such as blow molded bottles have good clarity toughness and ESCR environmental stress .