Barrier Engineering Plastics

Copolymers are typically manufactured using weU-mixed continuous-stirred tank reactor (cstr) processes, where the lack of composition drift does not cause loss of transparency. SAN copolymers prepared in batch or continuous plug-flow processes, on the other hand, are typically hazy on account of composition drift. SAN copolymers with as Httle as 4% by wt difference in acrylonitrile composition are immiscible (44). SAN is extremely incompatible with PS as Httle as 50 ppm of PS contamination in SAN causes haze. Copolymers with over 30 wt % acrylonitrile are available and have good barrier properties. If the acrylonitrile content of the copolymer is increased to >40 wt %, the copolymer becomes ductile. These copolymers also constitute the rigid matrix phase of the ABS engineering plastics. 

Aortal Aery Me ABS Alkyd Alloy /Blands Barrier Resin CeliAwie Diallyl Phthalates Engineering Plastics Epoxies Fluorepdlymars Liquid Crystal Melamine Nitrile Resins Nylon Phenolic Polyamlde-lmide Polycarbonate polyester Polyethylene Polyimictes Polypropylene Polyurethanes PVC... 

Chapters 1-4 of the book deal with the mechanical, electrical and thermal properties of a wide range of unreinforced and reinforced engineering plastics. Chapter 5 discusses various miscellaneous properties such as wear, abrasion resistance, frictional hardness properties, surface properties and weathering, and chemical resistance. In addition, this chapter covers a particular property of food packaging plastics, namely their gas barrier properties. 

Polyolefins are a major class of commodity synthetic polymers. The technology for the production of these important polymers is well estabUshed, from catalyst synthesis to polymerization reactor technology. Despite constant advancements in polyolefin production technology, applications of polyolefins are stiU mainly limited to commodity products. The recent interest in the production of polyolefin-clay nanocomposites extends the use of polyolefins to specialty and engineering plastic appHcations. Polyolefin-clay nanocomposites are lighter than conventional composites, but have thermal stability, barrier, and mechanical properties that are comparable to those of engineering plastics. 

GE Plastics has introduced Lexan EXE, an extra tough polycarbonate with added impact resistance and low temperature ductility. These attributes, plus its light weight, make it a great material for a variety of applications including telecommunications, portable electronics and outdoor equipment. It can replace metal and other engineering plastics. Lexan EXE sheet is finding new opportunities in vacuum formed parts, sound barriers and architectural applications. 

Unsubstituted and nonheat-reactive phenolic resins are used to a very limited extent due to their nonfilm-forming character. These resins are generally used as hardeners with epoxy resins to produce thermoset systems with high-quality engineering plastic properties. The base-catalyzed curing produces a crosslinked polyether structure, as shown in reaction (30), which is resistant to chemicals and heat and shows good barrier properties against moisture vapour. 

The structural materials used by engineers are not soft, but only deform plastically at large applied stresses. These result from a variety of extrinsic barriers to dislocation motion. Thus dislocations move freely between the barriers, but then stop until enough stress is applied to overcome the barriers. 

---