Noncrystalline plastic

Polystyrene is one of the oldest commercially produced thermoplastic polymers. The homopolymer, frequently referred to as GPPS, is a highly versatile product that has found acceptance in widely diverse applications. The strengths of this brilliant, clear, noncrystalline plastic are processing ease, rigidity, dimensional stability and clarity. However, the low impact strength of polystyrene limits its use. 

Cross-linking produces some dimensional stability and improves toughness in a noncrystalline type of plastic above the Tg, but... 

Substantially crystalline plastics in the range between Tg and Tm are referred to as leathery, because they are made up of a combination of rubbery noncrystalline regions and stiff crystalline regions. The result is that such plastics as PE and PP are still useful at the higher temperatures. 

Amorphous free silica (Noncrystalline) Diatomaceous earth A soft, gritty amorphous silica composed of minute siliceous skeletons of small aquatic plants. Used in filtration and decoloration of liquids, insulation, filler in dynamite, wax, textiles, plastics, paint, and rubber. Calcined and flux-calcined diatomaceous earth contains appreciable amounts of cristobalite, and dust levels should be the same as for cristobalite. 

Amorphous Silicon An alloy of silica and hydrogen, with a disordered, noncrystalline internal atomic arrangement, that can be deposited in thin layers (a few micrometers in thickness) by a number of deposition methods to produce thin-film photovoltaic cells on glass, metal or plastic substrates. 

In temperate and cold regions structures of nearly all kinds require good thermal insulation to reduce heating costs. In the construction industry, thermal insulators made from materials such as fiberglass and foamed plastics have been used widely because they are noncrystalline and incorporate a large void space with high entrapped air content. 

The plastic deformation exhibited by nonductile crystalline ceramics is not significant enough for deformation processes to be of much use in the fabrication of bulk articles. Noncrystalline materials (e.g. glasses) deform by the same mechanism as liquids, viscous flow. However, in a glass the effect is only pronounced at temperamres elevated enough to decrease the viscosity. 

Glasses and ceramics are inorganic materials that have been produced for thousands of years see Oxides Solid-state Chemistry and Noncrystalline Solids). Traditionally they are made from natural raw minerals such as clays or sand. Crystalline ceramics are shaped by adding water to clays in order to produce a plastic material and then heated in a furnace. Amorphous glasses are made from the melt and shaped by moulding near their softening temperatme. In both cases, high temperatmes are required. 

The ease of rotation of chain segments has a great influence on the properties of a polymer structure. As previously discussed, this is a function of polymer structure and temperature. The glass transition temperature of a polymer is that temperature at which backbone segments begin to rotate. An ideal noncrystalline polymer is a glass below the transition temperature and a non-Newtonian viscous liquid at temperatures above Tg. Thus, normally, plastics have Tg values above the use temperature, while elastomers have Tg values below the use temperature. 

Some noncrystalline solids, called amorphous solids, have no well-defined, ordered structure. Examples include rubber, some kinds of plastics, and amorphous sulfur. 

Laboratory Reaction Tests. It was necessary to understand the reaction parameters for the modifiers dipentene, styrene, and dicyclopentadiene to aid future field stabilization tests. Laboratory tests were performed to define the typical character of the material in the liquid and solid state. The conditions necessary to form completely plastic noncrystalline sulfur with each modifier were also established. 

Plastics can be classified according to the physical properties imparted to them by the way in which their individual chains are arranged. Thermoplastic polymers have both ordered crystalline regions and amorphous noncrystalline regions. Thermoplastic polymers are hard at room temperature, but soft enough to be molded when heated, because the individual chains can slip past one another at elevated temperatures. Thermoplastic polymers are the plastics we encounter most often in our daily lives—in combs, toys, switch plates, and telephone casings, for example. They are the plastics that are easily cracked. 

Due to scattering at interfaces, a crystalline plastic with myriads of crystallite regions bounded by interfaces is translucent. Crystalline polyethylene is thus translucent at room temperature, but, on warming, the crystallites disappear and the material becomes transparent. It can thus be inferred that plastics which are transparent at room temperature, such as polystyrene or poly(methyl methacrylate), are of the noncrystalline type and without fillers. 

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