Structure high density polyethylene

Structural Components. In most appHcations stmctural foam parts are used as direct replacements for wood, metals, or soHd plastics and find wide acceptance in appHances, automobUes, furniture, materials-handling equipment, and in constmction. Use in the huil ding and constmction industry account for more than one-half of the total volume of stmctural foam appHcations. High impact polystyrene is the most widely used stmctural foam, foUowed by polypropylene, high density polyethylene, and poly(vinyl chloride). The constmction industry offers the greatest growth potential for ceUular plastics. 

The most common backbone structure found in commercial polymers is the saturated carbon-carbon structure. Polymers with saturated carbon-carbon backbones, such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyacrylates, are produced using chain-growth polymerizations. The saturated carbon-carbon backbone of polyethylene with no side groups is a relatively flexible polymer chain. The glass transition temperature is low at -20°C for high-density polyethylene. Side groups on the carbon-carbon backbone influence thermal transitions, solubility, and other polymer properties. 

High-density polyethylene has more CH2 groups per unit volume than low-density polyethylene. Explain why this is so in terms of the structures of the two forms of the polymer. 

Fig. 11.2 Structural model of the composite of hydroxyapatite particles and high density polyethylene.

Morpholine chromate, molecular formula, properties, and uses, 6 562t Morphology. See also Structure of carbon fibers, 26 737-739 of high density polyethylene, 20 162 of polymer blends, 20 356 of polymer colloid, 20 386-388 of PVC particles, 25 658-661, 661-663, 664-665... 

Density is a consequence of structure and allows low, medium and high density polyethylene material to be distinguished. 

Examples of crystalline polymers are nylons, cellulose, linear polyesters, and high-density polyethylene. Amorphous polymers are exemplified by poly(methyl methacrylate), polycarbonates, and low-density polyethylene. The student should think about why these structures promote more or less crystallinity in these examples. 

FIGURE 2.1 Simulated structure of linear high-density polyethylene (HDPE) contrasted with the structural formula of linear or normal decane. 

Low- and high-density polyethylene, polypropene, and polymers of other alkene (olefin) monomers constitute the polyolefin family of polymers. All except LDPE are produced by coordination catalysts. Coordination catalysts are also used to produce linear low-density polyethylene (LLDPE), which is essentially equivalent to LDPE in structure, properties, and applications (Sec. 8-1 lc). The production figures given above for LDPE do not include LLDPE. The production of LLDPE now exceeds that of LDPE, with about 10 billion pounds produced in 2001 in the United States. (Copolymers constitute about one-quarter of all low density polyethylenes see Sec. 6-8b.)... 

The data from this table illustrate the semicompatibility of the phase between isotactic polypropylene and the high density polyethylene with block copolymer without gross interference in the domain structure or the crystalline phases that exist in these TPR s. 

Focusing collectors are usually cast acrylic Fresnel lenses, or mirrors of aluminized polyester film in frames of aluminum. These reflectors are either enclosed in a bubble of poly(vinyl fluoride) film, or under polycarbonate glazing, which may be covered with a fluorocarbon film to reduce the reflectivity. The absorbers for active systems are copper or aluminum since the temperatures are too high (325—370°C) for plastics. The frames, however, can be molded ABS, high density polyethylene or polyurethane, either solid or structural foam. Polybutylene or chlorinated PVC can be used for piping hot water, and tanks can be made of either reinforced polyester or blow- or rotational-molded, high density polyethylene (12—15). 

Filaments about 0.12 mm in diameter were obtained from unfractionated high-density polyethylene (Mi] = 8.0 x 104) by a melt-spinning at 220 ° C with a draft ratio of about 17. They were next stretched at 100 °C in polyethylene glycol with a molecular weight of 380—400 to different draw ratios, which are defined as the ratios of the drawn length to the original. NMR spectroscopy was carried out for the drawn filaments randomly packed into a glass tube 18 mm diameter. The three-component analysis of the spectrum at different temperatures was performed the results are discussed in relation to the phase structure of samples. 

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