Polyethylene homopolymers

Similarly, the random introduction by copolymerization of stericaHy incompatible repeating unit B into chains of crystalline A reduces the crystalline melting point and degree of crystallinity. If is reduced to T, crystals cannot form. Isotactic polypropylene and linear polyethylene homopolymers are each highly crystalline plastics. However, a random 65% ethylene—35% propylene copolymer of the two, poly(ethylene- (9-prop5lene) is a completely amorphous ethylene—propylene mbber (EPR). On the other hand, block copolymers of the two, poly(ethylene- -prop5iene) of the same overall composition, are highly crystalline. X-ray studies of these materials reveal both the polyethylene lattice and the isotactic polypropylene lattice, as the different blocks crystallize in thek own lattices. 

The Phillips-type catalyst can be used in solution polymerization, slurry polymerization, and gas-phase polymerization to produce both high density polyethylene homopolymers and copolymers with olefins such as 1-butene and 1-hexene. The less crystalline copolymers satisfy needs for materials with more suitable properties for certain uses that require greater toughness and flexibiUty, especially at low temperatures. 

Figure 10.7 shows that the tensile strength is improved as polystyrene is incorporated. Data for conventional melt-blended samples (Fayt et al., 1989) are provided for comparison. We note that the ductile-to-brittle transition for our system is shifted toward much higher polystyrene content. Fayt and others have shown that conventionally prepared polyethylene/ polystyrene blends are relatively poor materials (Barentsen and Heikens, 1973 Wycisk et al., 1990). Blends of most compositions are weaker than polystyrene or polyethylene homopolymers because of the poor interfacial adhesion between the two immiscible polymers. The electron micrographs and the mechanical data for the blends described here indicate that poly-... 

The early studies of Capaccio and Ward >, which led to the discovery of high modulus polyethylene, were based on drawing low molecular weight polyethylene homopolymer at comparatively low temperatures. Subsequent investigations were addressed at three major extensions of this work ... 

From the similarity of the pyrolysis products of the copolymer with that of polyethylene, it can be inferred that the pyrolysis process takes place by a free radical mechanism. The cleavage of the polyethylene segments generates the portion of the pyrolysate identical to that of the polyethylene homopolymer. Similar reactions take place for the poly(methacrylic acid) segments. From a free radical ending with a methacrylic acid unit, the formation of 2-methyl-2-propenoic acid by p-cleavage to the atom bearing the unpaired electrons is shown below. 

The maximum temperatures permissible for homopolymers in a number of diluents are listed in Table 75. These temperatures were determined in two ways, first, by laboratory swelling tests of a homopolymer in the particular hydrocarbon and, second, by actual experience in the production of homopolymers with the hydrocarbons in a pilot slurry reactor. Also shown in Table 75 is the degree of branching of each hydrocarbon, which is defined as the ratio of the number of methyl carbon atoms to the total number of carbon atoms. The swelling temperature correlates nicely with this ratio. Isobutane was chosen for commercial use as the best compromise between being highly branched and not too expensive. It permits a maximum operating temperature of about 111 °C for polyethylene homopolymer. 

The reactor can produce polyethylene homopolymer, or copolymers with butane, octane, etc. so the overall crystallinity of the product can be controlled. The molecular weight is controlled by additions of hydrogen, and the width of the molecular weight distribution can be changed by modifying the catalyst. 

Paxon 4700. A medium molecular-weight, high density polyethylene homopolymer film resin. 

The chemical structure of a linear polyethylene homopolymer is solely defined by the molar mass distribution (MMD) of the resin. This important distribution, together with the additives incorporated and the final morphology achieved in the processing, defines the polymer performance in a given application. 

Chem. Descrip. Polyethylene homopolymer CAS 9002-88-4 EINECS/ELINCS 200-815-3 Uses Additive wax in adhesives, inks, floor finishes, paper coatings, personal care, pharmaceuticals, plastics, rubber, textiles, wax blends, solv.-based polishes, inks, paints, lacquers defoamer in food-contact coatings, paper gellant for oils in personal care prods. film-former oil or fragrance encapsulant nonirritating abrasive emollient heat stabilizer food pkg. adhesives, coatings, paper/paperboard, cellophane, rubber articles, textiles, lubricants... 

Ciiem. Descrip. Micronized oxidized polyethylene homopolymer... 

---