Polyethylene mechanical damage

For process water, steel pipes are used unless iron pickup is to be minimized. Plastic pipes (polyethylene and polyvinylchloride) are used but they sometimes need external protection from solvents present in industrial atmospheres, ultraviolet radiation (including sunlight), freezing and mechanical damage. 

In the special case of pipelines operating at relatively high temperatures such as for the transmission of heavy fuel oil at up to 85°C, heat insulation and electrical insulation are provided by up to 50 mm of foam-expanded polyurethane. As a further insurance against penetration of water, and to prevent mechanical damage, outer coatings of polyethylene (5 mm), butyl laminate tape (0-8 mm) or coal-tar enamel reinforced with glass fibre (2-5 mm) have been used. 

Stabilized with 0.2% amine antioxidant High Density Polyethylene. Extrusion grades of hlgh-denslty polyethylene protected by 2.5% channel type black of 19 my particle size were exposed In a Weather-O-Meter for 10,000 hours without any evidence of serious mechanical damage, as measured by low temperature brittleness and elongation tests. This represents the useful limit In our accelerated weathering test, since as described In an earlier paper,(2) fllm-like deposits form on... 

Chitin, one of the most abundantly available natural polysaccharides, can be readily modified by acetylation reactions to form chitosan (CHI) [37]. CHI was modified with the four-member oxetane (OXE), followed by cross-Hnking with trifunctional hexamethylene di-isocyanate (HDI) in the presence of polyethylene glycol to form heterogeneous cross-linked polyurethane (PUR) network. When there is mechanical damage of the network, self-repairing occurs upon exposure of the damaged area to UV radiation. While the reactions leading to network formation are shown... 

Polyethylene glycol (which is related in chemical structure to pluronic polyols) and PVA have been tested more recently as protectants against aeration and agitation cell damage (Michaels et al, 1991). Both appear to offer mechanical protection as good as F-68, without any detrimental effects on the cells they have been tested on (Chinese hamster ovary (CHO) and hybridoma cells CRL 8018). 

L. D Esposito of Dlgllabs we have made some Fourier transform IR measurements to complement those on our conventional equipment. These studies on polyethylene compare the bond rupture kinetics due to y-ray damage and mechanical degradation at various temperatures as measured by ESR and IR spectroscopy. 

Polyethylene glycol (PEG) is a fiisogen (Fig. 5.5). It has been shown to mechanically repair damaged cellular membranes and reduce secondary axotomy after... 

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