Thermoplastic materials specialty plastics

The plastics industry was launched nearly 150 years ago with the production of certain derivatives of cellulose. However, its real emergence as a growth industry of immense proportions and importance has occurred since World War II with the sustained strong growth of thermoplastics and specialty elastomers. The importance of the polymers industry in modern society is underscored by the myriad of uses already developed for these materials, with more being developed almost daily. Although there are a multitude of polymers that are derived from hydrocarbons, we will only briefly discuss the more common thermoplastics that are made from relatively simple monomers from petroleum. 

An Overview oe Thermoplastic Materials Table 4.3 A list of Specialty Plastics—cont d... 

The selection of the thermoplastic material itself is usually driven by structural requirements first, and then the type and amount of conductivity required will dictate what additives are to be used. The use of conductive plastics is a specialty field, but is growing rapidly. Often times, a specialty compounder can provide in-depth technical guidance. 

Extrusion. Sheet, film, and profiled articles are made by extrusion (20). The resin is melted and forced through a die plate or head. Variations include multilayer and blown film applications. In multilayer coextrusions, different combinations of plastics are separately but concurrently extruded to form layered sheet or film. In the packaging industry, specialty resins such as high barrier ethylene—vinyl alcohol copolymers are combined with heat- and impact-resistant thermoplastics for food packages. The properties of each resin layer are additive, as opposed to the "averaging of property" in blends. Multilayers are also used for blow-molded containers, films, and sheet products (see also Film AND sheeting materials). 

With the use of "plastics" in automobiles predicted to increase significantly in the 1980s (96) one would expect the use of thermoplastic rubbers of all types to Increase also. New thermoplastic rubbers with higher service temperatures and/or solvent resistance, particularly at lower prices than the present specialty materials, should accelerate this trend. It has been estimated (97) that the U.S. use of thermoplastic rubbers in automobiles will be greater than 0.5 billion lb in 1986. 

While any plastic material, irrespective of its chemical composition and character, may be made into pipe or tubing, by far the greatest amount of pipe is made from thermoplastics (TPs) that are adaptable to extrusion processes (Chapter 5). Specialty pipe is made in small amounts from TS materials such as phenolic and polyester, but very large of commercial pipe is made from polyethylene, polyvinyl chloride, acrylonitrile butadiene copolymers, and acrylonitrile butadiene styrene types of alloys. Specialty tubing in relatively small amounts is made of acrylates and acrylate copolymers, as well as other transparent materials (Chapter 3). 

The term filler is very broad and encompasses a very wide range of materials. We arbitrarily define in this book as fillers a variety of natural or synthetic solid particulates (inorganic, organic) that may be irregular, acicular, fibrous or flakey and are used in most cases in reasonably large volume loadings in plastics, mostly thermoplastics. Continuous fibers or ribbons are not included. Elastomers are also not included in this definition as well as many specialty additives that are used at low concentrations (e.g. pigments, lubricants, catalysts, etc). 

An early description of the cast film process was published in Modem Plastics in 1952 [26] which was very similar to the cast-film scheme shown in Figure 6.19 which represents the process used today. The cast film process involves the extrusion of polyethylene through a die to form a thin molten layer of material that is drawn down to a thinner gauge based on the difference between the rate the molten polymer exits the extruder and the rate that the molten polymer is cooled onto a chill roll. The film cools very rapidly on the chill roll and film orientation is only in the machine direction. Optical properties are usually better with cast film as compared to blown film and line rates may be higher with the cast film process. A cast film line may also involve coextrusion of several layers of different types of thermoplastics to fabricate specialty films with improved properties. A... 

The world demands for thermoplastic elastomers are forecast to expand by 7.5% per year to 2.6 million metric tons in 2006. TPEs will continue to find the majority of their applications as replacements for natural and synthetic rubbers, as well as rigid thermoplastics and metals. The global TPE industry will remain heavily concentrated in the USA, Western Europe and Japan, particularly for specialty materials, such as polyester elastomers. Prom the two trends of application of polyester elastomers as engineering plastics and functional materials, the second one is prioritized. In terms of engineering applications, the PEE production will remain closely related to the motor vehicle industry, sporting goods, hoses, and small household goods. 

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