Thermoplastic materials commodity plastics

Plastics are not, as many people believe, new materials. Their origin can be traced to 1847 when Shonbein produced the first thermoplastic resin, celluloid, by reaction of cellulose with nitric acid. However, the general acceptance and commercialization of plastics began during the Second World War when natural polymers, such as natural rubber, were in short supply. Thus, polystyrene was developed in 1937, low density polyethylene in 1941, whereas other commodity plastics such as high density polyethylene and polypropylene were introduced in 1957. 

A singularly important development in recent years is the invention of the ubiquitous plastic material. It was about 60 years back when science yielded the first commodity thermoplastic material. It was an immediate and astounding success with increasing quantities of plastics manufactured each subsequent year to meet the demands of an expanding base of practical applications. There is no argument that plastics have made our lives interesting, convenient, and safe. But like any other material or technology, the use of plastics comes with a very definite price tag. 

Thermoplastics represent more than 80% of all plastics manufactured. Of these, the four major commodity plastics PE, PP, PS and PVC represent nearly 75% of all synthetic polymers produced annually, or about 75 million tons worldwide. Filled thermoplastics represent a huge and growing market for all types of manufactured products. It is estimated that each year 20 million tons of fillers are used in plastic materials. Currently, the most important fillers are calcium carbonate, talc, silica, mica, clay, aluminium trihydrate, glass fibres, starch and cellulosic powders. 

The development of plastic materials is one of the most successful stories of the twentieth century. In the sixties, plastics represented a small fraction of the total annual consumption of materials, but 20 years later they surpassed metallic materials (mostly iron-based) in terms of consumed volume. At the end of the century, plastics reached the astonishing total amount of 150 million metric tons produced per year. Of this amount, 70% is comprised by the so-called commodity plastics (HDPE, LDPE, PP, PVC, and PS), 11% by thermoset resins, 7% by elastomers, and 12% by engineering thermoplastics. 

PLA offers unique features of biodegradability, thermoplastic processibility and ecofiiendliness that offer potential applications as commodity plastics as in packaging, agricultural products and disposable materials. On the other hand, the polymer also has a bright future for applications in medicine, smgery and pharmaceuticals. The fundamental polymer chemistry of PLA allows control of certain fiber properties that make the fiber suitable for a wide variety of technical textile fiber applications, especially for apparel and performance apparel applications ... 

Currently more than 80% of all thermoplastic materials are based on the so-called mass polymers or commodities, for example, polyethylenes, polypropylenes, polystyrene, and poly(vinyl chloride). Compared to these, the contribution of the so-called engineering polymers is reiatively small poly(methyl methacrylate), polyamides, and polycarbonates together account for about 4%. High-performance plastics such as poly(phenylene suifide), poly(ether ether ketone), or fluoro-... 

Maximum continuous use temperatures are based upon the Underwriters Laboratories (UL) rating for long-term (100,000 hours) continuous use, and specifically on the elevated temperature which causes the ambient temperature tensile strength of the material to fall to half its unexposed initial value following exposure to that elevated temperature for 100,000 hours. The tests provide a continuous use temperature for a plastic in the absence of stresses. The maximum use temperature of PP is compared with other thermoplastics in Table 13. It can be seen that other commodity plastics and some other engineering plastics have a significantly lower maximum continuous use temperature than PP. However, polycarbonate has a higher maximum continuous use temperature in comparison to PP. 

Microbial PHA first received widespread attention during the petroleum crisis of the 1970s as a potential substitute for petrochemical-based plastics. Besides being a thermoplastic with properties comparable to that of PE, PHA are also completely biodegradable. The ability to produce PHA from renewable carbon sources also ensures a sustainable green chemistry process. A considerable amount of work has been focused on the production of various types of PHA for applications as commodity plastics. Initially, PHA were used to make everyday articles such as shampoo bottles and packaging materials. 

The materials mentioned above namely, PE, PP, PS and PVC are among the largest volume thermoplastics utilized. They are used in a maximum munber of applications, mostly in those which do not require high performance or special properties. In terms of cost they are among the cheapest of the thermoplastics. Hence they are often referred to as commodity plastics. 

The materials covered in this chapter are the crystalline members of the so-called engineering thermoplastics . They are rigid and robust, but somewhat more expensive than the commodity plastics, PE, PP, PS and PVC. Polyamides and saturated polyesters are used principally in fibres production, but plastics applications are important indeed, some materials have been developed specifically for plastics uses, notably polyamide 11, polyamide 12 and poly(butylene terephthalate). Polyacetals find application as plastics only. 

It is difficult to agree on a precise definition of a high performance plastic. There is indeed a clear overlap across the entire classification spectrum of thermoplastic materials. Some commodity plastics can be modified through reinforcements to compete with traditional engineering resins. Glass fibre-reinforced polypropylene is a good example of a standard thermoplastic material that is challenging polyamide and ABS in many different fields of application. 

The term commodity plastics is used to describe a category of thermoplastic materials that are widely used and readily available around the world—Whence the term commodity. While they can be used for structural purposes, they are typically used in cost-sensitive, high-volume applications such as packaging, clothing, and personal items intended for shortterm use. Key commodity plastics include the following. 

An Overview oe Thermoplastic Materials Table 4.1 A List of Commodity Plastics—cont d... 

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