Polyethylene specific gravity

Ethylene. Under the influence of pressure and a catalyst, ethylene yields a white, tough but flexible waxy sohd, known as Polythene. Polyethylene possesses excellent electric insulation properties and high water resistance it has a low specific gravity and a low softening point (about 110°). The chemical inertness oi Polythene has found application in the manufacture of many items of apparatus for the laboratory. It is a useful lubricant for ground glass connexions, particularly at relatively high temperatures. 

In some cases, particularly with iaactive metals, electrolytic cells are the primary method of manufacture of the fluoroborate solution. The manufacture of Sn, Pb, Cu, and Ni fluoroborates by electrolytic dissolution (87,88) is patented. A typical cell for continous production consists of a polyethylene-lined tank with tin anodes at the bottom and a mercury pool (ia a porous basket) cathode near the top (88). Pluoroboric acid is added to the cell and electrolysis is begun. As tin fluoroborate is generated, differences ia specific gravity cause the product to layer at the bottom of the cell. When the desired concentration is reached ia this layer, the heavy solution is drawn from the bottom and fresh HBP is added to the top of the cell continuously. The direct reaction of tin with HBP is slow but can be accelerated by passiag air or oxygen through the solution (89). The stannic fluoroborate is reduced by reaction with mossy tin under an iaert atmosphere. In earlier procedures, HBP reacted with hydrated stannous oxide. 

Chlorinated polyethylene (CPE) has excellent o2one, oil, and heat resistance. In addition chlorinated polyethylene has replaced chloroprene elastomers. CPE has a lower specific gravity than chloroprene compounds and produces compounds that are similar to CR in properties but with lower costs. In addition, due to high levels of chlorine in the polymer, the flame resistance of the compounds of CPE are high. 

Here Ceq is the ethylene concentration equilibrium to the concentration in a gaseous phase, Kp the propagation rate constant, N the concentration of the propagation centers on the catalyst surface, Dpe the diffusion coefficient of ethylene through the polymer film, G the yield of polymer weight unit per unit of the catalyst and y0at, ype are the specific gravity of the catalyst and polyethylene. 

High-Density Polyethylene Foams These foams are defined by the specific gravity (ca. 0.96 g/cc) and melt index of the basic resin. They have been used extensively in the U.S. and Europe, particularly for materials-handling applications, such as boxes, crates, and pallets because, imtil recently, they were much cheaper than polypropylene (13). 

Materials. High density polyethylene (HDPE) having different molecular weights, and specific gravity of 0.951 (Marlex 5202, HXM 50100, made by Phillips 66 Co), were used for extrusion applications. Polyamides used were a semicrystalline copolyamide of adipic acid, hexamethylene diamine and caprolactam, and a copolyamide containing isophthalic acid as well. An anhydride modified polyethylene (3-5) as an interlaminar adhesive/compatibilizer was also used. The combinations are generally included in "Selar" barrier materials supplied by E. I. du Pont de Nemours Co. 

Polyethylene is manufactured in various polymeric forms, differing by their molecular weight and linearity, or presence of irregularities, or branches, unsaturations, and so on. This in turn determines the density, or specific gravity of the polymer, which is nsed as the principal classification feature of polyethylenes. The main forms of polyethylenes are as follows ... 

Polypropylenes are subdivided to homopolymers and copolymers. Homopolymers are more crystalline, have a rather well-defined melting temperature at 161-165°C (322-329°F), softens at about 155°C (311°F), and have a rather narrow molecular weight distribution. Copolymers typically contain some amount of ethylene comonomer and in turn are subdivided to random and block copolymers. Their melting points are in the range of 140-155°C (284-311°F). Polypropylenes have a specific gravity (density) of 0.90-0.91 g/cm which is approximately equal to that of very low-density polyethylene and lower than that of majority of polyethylenes, particularly HDPE (0.941-0.965 g/cm ). PP homopolymers are stiffer than copolymers, with their flexural modulus of 165,000-290,000 psi and 130,000-175,000 psi, respectively. PP homopolymers, in turn, are generally stiffer compared to HDPE, which has flex modulus in the range of 125,000-... 

Let us consider an example of, say, a Trex deck board. It consists of 50% w/w polyethylene (LDPE/LLDPE and/or HDPE) and 50% w/w of wood flour. Specific gravity of LDPE/LLDPE is 0.925 g/cm and that of HDPE is 0.96 g/cm Specific gravity of wood flour is 1.30 g/cm These two ingredients define the density of the composite material at their natural compaction, which would be... 

There are no data available on the effect of WPC density on the slip coefficient. However, it is known that polyethylene of lower density has a better traction than that of a higher density. In other words, HDPE is characterized by a low coefficients of friction, and the higher the density (specific gravity), the lower the static (and dynamic) coefficient of friction. For polyethylene density of 0.915 g/cm, coefficient of friction equals to 0.50 for 0.932 g/cm, it is equal to 0.30, and for 0.965 g/cm, it is equal to 0.10 [3]. 

Detrimental effects in WPC, 96 Thermal degradation, 95 Hemicellulosic materials, 77, 92, 94, 95, 180 Hemp fiber, 82, 83, 86, 101, 110 Cellulose content, 110 Eiber diameter, 110 Lignin cintent, 110 Specific gravity, 110 Heteropolysaccharides, 92 High density polyethylene (HDPE), 52, 55, 67, 68, 363, 371,... 

The specific gravity of PVC at room temperature is close to 1.4 g/cm. Compared with other commodity polymers (PE, PP) it is a very high density. For the same volume of product one has to use about 60% more PVC as compared with polyethylene or polypropylene. The very high density of PVC is most likely the biggest disadvantage of PVC which contributes to increased weight of Ihe product and the cost of raw materials required to produce it. 

The wet and washed chips are le-slumed in rinse water in an agitated tank, and pumped through a set of hydrocyclones to separate the "light" components (polyethylene base cups and polypropylene labels) from the "heavy" components (PET and aluminum bottle tops). The specific gravities are as follows ... 

The specific heat of dry wood does not have a strong dependence on specific gravity and is roughly 0.324 cal/(g K) or 1360 J/(kg K) [17]. This is about half the specific heat of common polyolefins such as polypropylene and polyethylene, for which values are approjdmately 2-3000 J/(kg K.)... 

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