Synthetic plastic types

The characteristic property of elastomers is their rubber-elastic behavior. Their softening temperature lies below room temperature. In the unvulcanized state, i.e. without crosslinking of the molecular chains, elastomers are plastic and thermo-formable, but in the vulcanized state—within a certain temperature range — they deform elastically. Vulcanization converts natural rubber into the elastic state. A large number of synthetic rubber types and elastomers are known and available on the market. They have a number of specially improved properties over crude rubber, some of them having substantially improved elasticity, heat, low-temperature, weathering and oxidation resistance, wear resistance, resistance to different chemicals, oils etc. 

As with most synthetic plastic materials, they commence with the monomers Any of the common processes, including bulk, solution, emulsion, or suspension systems may be used in the free-radical polymerization or copolymerization of acrylic monomers. The molecular weight and physical properties of the products may be varied over a wide range by proper selection of acrylic monomer and monomer mixes, type of process, and process conditions. 

John Hyatt was the first to make plastics. He made celluloid in 1868. Leo Baekeland made bakelite. Synthetic plastics are made from petroleum products. There are two types of plastics thermoplastics and thermosetting plastics. 

The more significant sources of information concerning the properties and applications of plastics were determined by a breakdown and analysis of two plastics literature reviews covering the years 1950 and 1951 —yiz., the literature review published annually in the technical section of Modern Plastics, and the chapter on synthetic plastic insulation in the National Research Council s annual Digest of the Literature on Dielectrics. An appended bibliography lists the major sources of information. Searching for highly specialized types of information is discussed briefly. 

In 1851, hard rubber, or ebonite, was commercialized. In 1870 a patent was issued to I. Hyatt, of New York, for celluloid, a type of cellulose nitrate with low nitrate content produced at high temperature and pressure. This was the first commercially available plastic and the only one until the development of Bakelite by Baekeland in 1907. Bakelite is the oldest of the purely synthetic plastics and consisted of a resin obtained by the reaction of phenol and formaldehyde. 

Museum olgects are rarely collected for their material type alone but because of their origin, function, design, rarity, cultural, historical or artistic significance. Plastics are collected for the same reasons. Synthetic plastics have had a significant influence on industrial, domestic and cultural aspects of everyday life in the twentieth and twenty-first centuries. Their significance is reflected in... 

The manufacturing of component parts and panels from this material occurs at lower temperatures and the resulting parts show a lower shrinkage than those made from synthetic plastics. The mechanical behaviour, however, exhibits some similarities with wood and the measured properties depend strongly on the fibre type and content. The model product loudspeaker box combines an interesting noble wood like design with outstanding acoustic properties. They were injection moulded in different complex shapes at various wall thicknesses. 

Synthetic Plasticizers. The most important types of synthetic plasticizers are esters. Phthalate esters are used to improve elasticity and low-temperature flexibility, especially in NBR and CR vulcanizates. Common examples are dibutyl phthalate (DBP), di(2-ethyl-hexyl) phthalate (DOP), diisooctyl phthalate (DlOP), and diisononyl phthalate (DINP). They are generally used at levels of 5 to 30 phr. 

Triaryl phosphate n. A synthetic-ester type plasticizer derived from isopropylphenol feedstock, useful as a flame-retarding plasticizer in vinyl plastisols. 

However, thermal reprocessing of post-consumer waste plastics introduces changes into the materials that mean they may be unusable for the applications for which they were originally intended, even if the same synthetic polymer type is reprocessed. These changes are partly due to the differences in the formulation of plastics in different applications, and partly due to chemical and physical changes that occur during the thermal reprocessing of the material. 

Cellulosic is a family name that applies to a wide group of thermoplastics. They are not synthetic plastics but rather are made from a natui y occurring polymer, cellulose, which is obtained from wood pulp and cotton linters. Cellulose can be made into a film as cellophane or a fiber, rayon, but it must be chemically modified to produce TPs. Because it can be compounded with many different plasticizers in widely varying concentrations, its property range is broad. These plastics are normally specified by their flow, according to ASTM D 569, which is controlled by the plasticizer content. Cellulosics are all processed by conventional TP methods. They include the following types. 

PGC has been applied to the characterization of a number of different types of polymers besides the traditional paint chips and fiber evidence submitted to the crime laboratory. Synthetic plastics have been readily identified and differentiated by PGC (253). Hume et al. (265) applied PGC to the characterization of motor vehicle body fillers utilizing a 15-m Carbowax 20 M gas chromatographic column and a computer-based system to compare pyrograms. 

A homopolymer of (R)-3-hydroxybutyrate (PHB) is the most common type of PHA that bacteria accumulate in nature and has been studied and characterized extensively by many researchers. Poly (P-hydroxybutyrate) (PHB) has a number of interesting characteristics and can be used in various ways similar to maity conventional synthetic plastics now in use. The properties of polyhydroxyalkanoates viz. PHB, PHV and comparison with synthetic polymer polypropylene (PP) have been described by Sasikala and Ramana (1996). 

Synthetic plasticizers should be added to improve the cold flexibility of high vinyl acetate containing grades. Good results have been obtained by using adipate-and sebacate-type plasticizers. 

Degradability of other polyesters There are two main water-soluble polymer types commercially available polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH). PVOH is a readily biodegradable, water-soluble polymer. The degradation of PVOH is influenced by its crystallinity and molecular weight PVOH does not biodegrade, but simply dissolves in water or can be biodegraded by activated sludge treatment. EVOH is another water-soluble synthetic plastic. 

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