Polyolefins polymethylpentene

Fig. 11. Effect of polyolefin primers on bond strength of ethyl cyanoacrylate to plastics. All assemblies tested in accordance with ASTM D 4501 (block shear method). ETFE = ethylene tetrafluoroethylene copolymer LDPE = low-density polyethylene PFA = polyper-fluoroalkoxycthylene PBT = polybutylene terephthalate, PMP = polymethylpentene PPS = polyphenylene sulfide PP = polypropylene PS = polystyrene PTFE = polytetrafluoroethylene PU = polyurethane. From ref. [73].

Polymethylpentene is more permeable to gases than some other polyolefins. 

The polyolefins are high-molecular-weight hydrocarbons. They include low-density, linear low-density, and high-density polyethylene, polyallomer, polypropylene, and polymethylpentene. All are break-resistant, nontoxic, and... 

Within the family of polyolefins there are many individual families that include low density polyethylenes, linear low density polyethylenes, very low polyethylenes, ultra low polyethylenes, high molecular weight polyethylenes, ultra high molecular weight polyethylenes, polyethylene terephthalates, ethylene-vinyl acetate polyethylenes, chlorinated polyethylenes, crosslinked polyethylenes, polypropylenes, polybutylenes, polyisobutylene, ionomers, polymethylpentene, thermoplastic polyolefin elastomers (polyolefin elastomers, TP), and many others. 

Polyolefin homopolymers include polyethylene (PE), polypropylene (PP), poly-butene-1 (PB), polymethylpentene-1 (PMP), and higher polyolefins. Table 1.2 shows the structures of commercial polyolefin homopolymers. 

Polymethylpentene Thermoplastie stereoregular polyolefin obtained by polymerizing 4-methyl-1-pentene based on dimerization of propylene has low density, good transpar-eney, rigidity, dieleetrie and tensile properties, and heat and ehemieal resistanee. Proeessed by injection and blowmolding and extrusion. Used in laboratory ware, coated paper, light fixtures, auto parts, and electrical insulation. Also called PMP. 

Polymethylpentene (IPX) This polymer, like polybutylene, is a very young member of the polyolefins (1965). It appears as a polymer based on 4-methylpentene. 

Polymethylpentene has a high crystalline melting point of 240°C, coupled with useful mechanical properties at 204°C and retention of form stability to near the melt point. However, the polymer is brittle (fiber or rubber additives are usually advised for improved toughness), ages poorly (the use of antioxidants is recommended), has high gas permeability, and is relatively expensive. Polymethylpentene s chemical resistance is very good and typical of the polyolefins. Its transparency is close to the theoretical optimum for thermoplastics. Polymethylpentene also has excellent electrical properties with power factor, dielectic constant, and volume resistivity on the same order as PTFE fluorocarbon. 

Fortunately, for Phillips Petroleum Co., John Paul Hogan and Robert L. Banks followed up the Baily-Reid investigations and applied for patents on the synthesis of linear polyolefins including polyethylene, pol3q)ropylene and polymethylpentene. In 1951, A. Zletz of Standard Oil of Indiana, working with another classmate of mine, Don Carmody, also patented a low pressure process for making HDPE. 

The family of polyolefins includes polyethylene, polypropylene, ethylene-vinyl acetate, ionomers, polybutylene, polyisobutylene, and polymethylpentene. Because the chemical and electrical properties of the various polyolefins are basically similar, they often compete for the same applications. However, since the different strength and modulus properties vary greatly with the type and degree of crystallinity, as seen in the preceding tables and figures, the tensile, flexural, and impact strength of each polyolefin may be quite different. Their stress-crack resistance and useful temperature ranges may also vary with their crystalline structure. 

Polyolefins, such as polyethylene, polypropylene, and polymethylpentene, as well as polyformaldehyde and polyether, may be more effectively treated with a sodium dichro-mate- sulfuric acid solution. This treatment oxidizes the surface, allowing better wetting. Activated gas plasma treatment, described in the general section on surface treatments is also an effective treatment for these plastics. Table 7.17 shows the tensile-shear strength of bonded polyethylene pretreated by these various methods. 

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