Polymer crosslinked polyethylene

Sometimes, part design requires multiple polymer layers. For example, an automotive gasoline tank can consist of both nylon and crosslinked polyethylene to provide combined chemical [-, resistance and strength, To produce multilayered parts, the first polymer, which will form... 

Journal of Polymer Science Polymer Physics Edition 39, No.18, 15th Sept.2001, p.2159-67 RHEOLOGICAL PROPERTIES AND FOAM PROCESSABILITY FOR BLENDS OF LINEAR AND CROSSLINKED POLYETHYLENES Yamaguchi M Susuki K-I Tosoh Corp. 

Cellular Polymers 111. Conference proceedings. Coventry, 27th-28th April 1995, paper 13. 6124 CELL STRUCTURE DEVELOPMENT IN COMPRESSION MOULDED CROSSLINKED POLYETHYLENE AND ETHYLENE-VINYL ACETATE FOAM Sims G L A Khunniteekool C UMIST... 

New theories and findings on the formation of ionic species and radicals, which become trapped in the polymers, are discussed in the first two chapters, written by the two European authorities, Chapiro and Charlesby. The kinetics of crosslinking polyethylene is the subject of the American authority, Dole. A higher yield of crosslinking polyolefins was observed in the presence of nitrous oxide by the Japanese scientist, Okada. 

Multi-polymer Materials. The literature for multi-polymer materials is extensive but is less than that for blends and grafts composed of two polymers. A ternary graft copolymer, semi-IPN is described by Rogers and Ostler (43, 44) an original crosslinked polyethylene graft-poly-(potassium acrylate) was swelled with styrene and radiation polmerized. The authors comment that most of the grafting of polymer 3 was on polymer 2, the poly (potassium acrylate). This reaction sequence can be described ... 

The high-density polymer is virtually linear and can be obtained from ethylene using a coordination type catalyst (alkyl aluminum and TiCU) or by polymerization on a metal oxide catalyst. The structure of both polymers is usually indicated by the structure (-CH2CH2-)n, although the branching in the low density polymer implies the presence of -CH< groups. The same type of bonds may be present in crosslinked polyethylene. 

Sarathi, R. Das, S. Kumar, C.R.A. Velmurugan, R. Analysis of failure of crosslinked polyethylene cables because of electrical treeing a physicochemical approach. J. Appl. Polym. Sci. 2004, 92, 2169-2178. 

The mechanical properties of most polymers are modified by irradiation. They usually deteriorate in polymers undergoing predominant chain scission. In crosslinked polymers, the mechanical properties strongly depend on the temperature at which the measurements are performed and improvements are often obtained, especially above the melting point. Crosslinked polyethylene, for instance, is a rubbery solid above its crystalline melting point instead of being a viscous liquid if not irradiated. At room temperature, the elastic modulus and tensile strength are often increased by irradiation. Results on individual polymers will be discussed in section 5. 

In some cases, polymer crosslinking may be effected by a post-addition of peroxide to the shaped polymer. The process is performed by sorption of peroxide from the surface of the extruded tube following its deposition [101]. Conditions of crosslinking are adjusted so that diffusion into the bulk of polymer precedes the decomposition of peroxide. The rate of diffusion depends on the kind of peroxide, used and for the same peroxide also on the type of polyethylene and its thermal history [102]. 

The reduction of the lamdlar thickness of crystallites leads to a decrease of T. On the other hand, the crosslinks stabilize the arrangement of macromolecules which contributes to an increase of T. Actual values of T , for a given sample of crosslinked polyethylene depend on initial ciystallinity of a polyrnCT, temperature at which the crosslinking is conducted, as well as on conditions of crystallization before a measurement of melting temperature of polymer crystallites. The effect of crosslinkmg on the... 

Simunkova D, G l E (1988) Sulphur containing antioxidants in crosslinked polyethylene, 7th lUPAC Conference on Modified Polymers, Bratislava, 1988, p 19, p 37... 

The rate dependence of fatigue strength demands carefiil consideration of the potential for heat buildup in both the fatigue test and in service. Generally, since the buildup is a function of the viscous component of the material, the materials that tend toward viscous behavior will also display sensitivity to cyclic load frequency. Thus, TPs, particularly the crystalline polymers like polyethylene that are above their glass-transition temperatures, are expected to be more sensitive to the cyclic load rate, and highly crosslinked plastics or glass fiber reinforced TS plastics are much less sensitive to the frequency of load. 

The aosslinking of polyethylene typically occurs during the degradation of the polymer, but PE crosslinked in a controlled way has useful properties. Methods for intentionally crosslinking extruded and molded PE have created an important niche of applications crosslinked polyethylene (XLPE or PEX) is used for more resilient foams, tubing, film, sheet, cable coverings, and rotational moldings. 

Uses Reinforcing agent, extender in EPDM, SBR, nitrile, crosslinked polyethylene, most other polymers, wire and cable compds.. non-aq. coatings, adhesives and inks... 

Hassanpour, S., BGroylou, R, Jabbarzadeh, E., Thermal degradation of electron beam crosslinked polyethylene and (ethylene-vinylacetate) blends in hot water. Journal of Applied Polymer Science 2003,89,2346-2352. 

Commercial hybrid grafts include structures in which organic polymers are grafted onto a polysiloxane chain, such as polyethyleneoxide graft polydimethyl-siloxane surfactants, or structures in which alkoxysilanes are grafted onto organic polymers such as crosslinkable polyethylenes. 

Matty polymers may be used for produetion of wire and cable. These include polyethylene, crosslinked polyethylene, chlorosnlfonated polyethylene, ethylene-propylene rubber, polyvinylchloride, bntyl robber, styrene bntadiene rubber, silicone rubber, natural robber, polyisoprene robber, polyurethane, nitrile butadiene rubber, polychloroprene, polysulfone, thermoplastie elastomers, polyimide, and polyamides. Selection of polymer(s) depends on projected conditions of service such as temperature, presence of corrosive liquids, surrounding temperature, quality of insulation, etc. 

Piping in transfer lines should be free of loops and pockets. Unloading connections may be flexible hose (typically 50-mm) lined with acid-resistant rubber, crosslinked polyethylene, or a fluorocarbon polymer. These hoses should not have quick disconnects. They should be inspected after every use. A sight glass on the transfer line will let the operator know when transfer is complete. 

Peroxide degrades some plastics, such as polypropylene (PP). Consequently, in peroxide crosslinked TPVs, polymers like PP degrade and polymers like polyethylene crosslink. In phenolic resin cured TPVs, thermoplastics like PP do not degrade but moisture is always an issue, because the stannous chloride or zinc chloride that are used as Lewis acid are hygroscopic. 

Crosslinked polyethylene (CURE) has crosslinking between the linear strands of monomers that are bonded together, producing a polymer that s extremely tough. The lid on that HOPE milk Jug is probably CLPE. Soft drink bottle caps are cdso CLPE. The soft drink bottles are made of another type of pol5oner that I discuss a little later in the chapter. 

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