Normal polyethylene

Figure 3 Light permeability of the high-pressure polyethylene sample as a function of thickness I-3-quenched polyethylene 4-6-normal polyethylene 1 and 4-50 jlc thick 2 and 5-200 /jlc thick 3 and 6-350 fic thick.

Figure 6 Light transmission of quenched cured polyethylene as a function of the sample thickness (vulcanization temperature 160°C, time 15 min.). 1-sample of normal polyethylene 2 mm thick 2, 3, and 4-quenched cured samples of different thickness 2-1 mm, 3-2 mm, 4-4 mm.

Columns 1 and 3 refer to normal polyethylene columns 2 and 4 refer to the transparent one. 

On exposure to ultraviolet irradiation over a period of 25 hours, specific elongation of normal polyethylene decreases by half, and complete decomposition is observed after a 50-hour exposure. At the same time, specific elongation of quenched polyethylene, when exposed to irradiation not greater than 50 hours, is little affected, but when exposed over a period of 100 hours, its specific elongation amounts to 100%. 

Polyethylene cured by the chemical and radiation-chemistry methods undergoes thermal destruction upon heating as in normal polyethylene. Thermoslabiliz-... 

A series of polyamine disulphides (polyaniline disulphide, polyamine disulphide, and polyparaphenylenedi-amine disulphide) represent effective thermostabilizers of cured polyethylene, and provide a decrease in gel fraction 2.5-3 times as large as that in case of inhibited thermal destruction. Stabilizers of normal polyethylene (Neozone D , Santonox R ) are inefficient as stabilizers of cured polyethylene, these substances decompose and even initiate thermal destruction of cured polyethylene. 

Vapor barrier- A building product installed on exterior walls and ceilings under the drywall and on the warm side of the insulation. It is used to retard the movement of water vapor into walls and prevent condensation within them. Normally, polyethylene plastic sheeting is used. 

Fig. 6.6. Change of g-values for normal polyethylene with temperature O, A radical X, B-radical , meanscompletecoincidence of O and X (Ref,...

Normally polyethylene is insoluble in all solvents. It is also resistant to being soluble in polar solvents, vegetable oils, water, alkalis and most concentrated acid including hydrofluoric acid (HP) at room temperature. 

According to generally accepted theories (42, 43) the self-diffusion coefficient D of polymer melts is inversely proportional to the square of the chain length. For long chains, this leads to extremely low values of D. Since th mean square displacement of a particle in a specified direction, measure small D values is limited by the spatial resolution of the experimental technique. For instance, the first data on self-diffusion in a polymer melt were obtained following the diffusion of deuterated polyethylene into normal polyethylene by IR spectroscopy (44) and this technique could resolve only distances of 0.1 mm thus, experiments extending over a day could... 

The theoretical analysis of self diffusion of long flexible chain molecules by de Gennes and by Doi and Edwards has stimulated much experimental testing of their predictions. Klein and Brisoe followed the diffusion of deuterated polyethylene into normal polyethylene by IR spectroscopy, Gilmore et al followed the diffusion of poly(vinyl chloride) in polycaprolactone by a combination of scanning electron microscopy and energy dispersive X-ray analysis, and Shiah and Morawetz followed, by fluorescence techniques, the self diffusion of naphthalene donor and pyrene acceptor labelled polymers. 

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