Ethylene homopolymer

Crystallinity and Density. Crystallinity and density of HDPE resins are derivative parameters both depend primarily on the extent of short-chain branching in polymer chains and, to a lesser degree, on molecular weight. The density range for HDPE resins is between 0.960 and 0.941 g/cm. In spite of the fact that UHMWPE is a completely nonbranched ethylene homopolymer, due to its very high molecular weight, it crystallines poorly and has a density of 0.93 g/cm. ... 

The number of branches in HDPE resins is low, at most 5 to 10 branches per 1000 carbon atoms in the chain. Even ethylene homopolymers produced with some transition-metal based catalysts are slightly branched they contain 0.5—3 branches per 1000 carbon atoms. Most of these branches are short, methyl, ethyl, and -butyl (6—8), and their presence is often related to traces of a-olefins in ethylene. The branching degree is one of the important stmctural features of HDPE. Along with molecular weight, it influences most physical and mechanical properties of HDPE resins. 

The chemical iadustry manufactures a large variety of semicrystalline ethylene copolymers containing small amounts of a-olefins. These copolymers are produced ia catalytic polymerisation reactions and have densities lower than those of ethylene homopolymers known as high density polyethylene (HDPE). Ethylene copolymers produced ia catalytic polymerisation reactions are usually described as linear ethylene polymers, to distiaguish them from ethylene polymers containing long branches which are produced ia radical polymerisation reactions at high pressures (see Olefin POLYMERS, LOWDENSITY polyethylene). 

A copolymer, on the other hand, results from two different monomers hy addition polymerization. For example, a thermoplastic polymer with better properties than an ethylene homopolymer comes from copolymerizing ethylene and propylene ... 

The compositions consist of a heat-plastified mixture of an ethylene homopolymer or copolymer, about 3 to 30 pbw of an elastomer, a stability control agent, which is a partial ester of a long chain fatty acid with a polyol, higher allyl amine, fatty acid amide or olefinically unsaturated carboxylic acid copolymer, and a hydrocarbon blowing agent having from 1 to 6 carbon atoms and a boiling point between -175 and 50C. 

The Surlyn A ionomers (E. I. du Pont de Nemours Co.) are believed to be derived from copolymers of ethylene with minor amounts of methacrylic acid which are treated subsequently, so that substantial amounts of the carboxylic acid are converted to the sodium or other metal carboxylate. Resins similar to the one studied in this work contain about 10 weight % methacrylic acid. The ash (sodium carbonate) indicates about 40% neutralization. This resin, which contains 0.05% Santo-white Powder (Monsanto Chemical Co.), a phenolic antioxidant, is of medium molecular weight—i.e., probably corresponding to an ethylene homopolymer with a melt flow index around 20 (17). The molecular weight distribution is broad (17). 

Chauve et al. [253] utilized the same technique to examine the reinforcing effects of cellulose whiskers in EVA copolymer nanocomposites. It was shown that larger energy is needed to separate polar EVA copolymers from cellulose than for the nonpolar ethylene homopolymer. The elastomeric properties in the presence of spherical nanoparticles were studied by Sen et al. [254] utilizing Monte Carlo simulations on polypropylene matrix. They found that the presence of the nanofillers, due to their effect on chain conformation, significantly affected the elastomeric properties of nanocomposites. 

An ethylene homopolymer (Allied Corporation) was also used as a filler for the IPNs. A 10% addition of this material to the 50/50 urethane/epoxy IPN sample had similar effects as those shown by the 10% mica-filled sample of Figures 7 and 8. A clear difference in this case was a shift of the loss tangent peak to lower frequencies, resulting in a lower tan A value in the frequency range of the display, (see Figure 12). 

DYALL DYLAN DYLAN SUPER DYLAN WED 205 DYNH DYNK 2 ELTEX ELTEX 6037 ELTEX A 1050 EPOLENE C EPOLENE C 10 EPOLENE Clin EPOLENE E EPOLENE E 10 EPOLENE E 12 EPOLENE N ETHENE POLYMER ETHERIN ETHEROL E ETHYLENE HOMOPOLYMER ETHYLENE POLYMER ETHYLENE POLYMERS (SCI) 23F203 FABRITONE PE FB 217 FERTENE FLAMOLIN MF 15711 FLOTHENE FM 510 FORTIFLEX 6015 ... 

SOREFLON 604 TARFLEN TEFLON (various) TETRAFLUOROETHENE HOMOPOLYMER TETRAFLUOROETHENE POLYMER TETRAFLUORO-ETHYLENE HOMOPOLYMER TETRAFLUOROETH-YLENE POLYMERS TETRAN PTFE UNON P VALFLON VELFLON ZITEX H 662-124... 

The high-temperature solution process is state-of-the-art for the production of ethylene homopolymers as well as ethylene/1-olefin copolymers with a wide range of average molecular mass and copolymer composition [15]. This process is performed in a CSTR or in a cascade of two reactors, like the low-temperature process. Only the downstream equipment is different. The diluent is an aliphatic hydrocarbon such as cyclohexane, n-hexane, or a Cg-Cio alkane fraction. Homogeneous catalyst and co-catalyst are fed into the polymerization reactor mixed with solvent. Ethylene, hydrogen to regulate average molecular mass, and the comonomer are injected either as a gas or as a liquid. Temperature can be con-... 

The unique structure of the ethylene homopolymers obtained results from a propensity of the metal centers to run along the growing polymer chain between insertions (a similar behavior had been observed previously for 1-olefm polymerization by a neutral nickel catalyst by Fink et al.) [58, 59]. An extensive patent on fhese polymerizations was filed by Brookhart and DuPont, and McLain demonstrated in several examples that fhese polymerizations can also be carried out in water [60]. Detailed investigations by Mecking et al. revealed that in fhis suspension-type aqueous polymerization fhe catalyst is remarkably stable, efhylene being polymerized at a steady rate for several days [61, 65]. At slightly elevated ethylene pressures of 20 bar, with 5 a activities of 10 TO h , similar to... 

Tirpak,G.A. Detection of ethylene homopolymer in ethylene-propylene block copolymers. J. Polymer Sci. A, 2, 705-709 (1964). 

During the past four years, linear low-density polyethylene (LLDPE) has probably become the most important of the thermoplastic copolymers. In contrast to the customary practice of producing branched ethylene homopolymer in a high-pressure reaction, a system of copolymerizing ethylene with a-C g olefins at low pressure is used to make LLPDE copolymer. This random copolymerization is commercially carried out in gas-phase, slurry, and solution processes in the presence of a transition metal catalyst 1-butene, 1-hexene, 4-methyl-l-pentene, or 1-octene are choices of comonomer. In the face of plant overcapacity and idle equipment existing at this time, LLDPE can also be made in high-pressure autoclaves and tubular reactors. 

The three major classes of polyethylene are described by the acronyms HOPE. LDPE. and LLDPE. High-density polyethylene (HOPE) is a linear, semicrystalline ethylene homopolymer Tm 135 °C) prepared by Ziegler—Natta and chromium-based coordination polymerization technology. Linear low-density polyethylene (LLDPE) is a random copolymer of ethylene and a-olefins (e.g.. 1-butene. 1-hexene, or... 

A typical structure of an ethylene/methyl acrylate (E/MA) copolymer is very similar to an ethylene homopolymer produced by the same a-diimine palladium catalysts, see Figure 3. The EMA copolymers are amorphous, highly branched materials with about 100 branches per 1000 carbon atoms and with glass-transition temperatures typically ranging from —50 to —70 Simultaneous RI and UV... 

The ability to predictably prepare linear low-density polyethylenes from ethylene alone represents an opportunity to design ethylene homopolymers for target applications. 

Silica supported chromium catalysts that polymerize ethylene to polyethylene with as many as 12 methyl branches/1000 carbon atoms have been reported. The small amount of branching observed in the ethylene homopolymers prepared by these supported chromocene catalysts was attributed to a chain isomerization process (a) Karol, F. J. Karapinka, G. L. Wu,... 

The measured surface energy of the pure ethylene homopolymer (plasma power input 300 W) was 36 mj nT, which is in the range of commercial polyethylene [1]. The polar component was also near zero, which qualifies the ethylene homopolymer as a pure chain-extending component in the copolymer and confirms the appropriateness of copolymers with ethylene sequences as a model surface with a variable concentration of exclusively one type of functional group. 

The dispersion component was determined to be 35 mJ m . Thus, the existing imperfections in the structure of the pulsed-plasma ethylene homopolymer (C=C double bonds, branched structures, and other inhomogeneities) did not influence the dispersion component noticeably. The pulsed-plasma polymerized poly(allyl alcohol) homopolymer possesses a surface energy of 51.6 mJ m. The butadiene homopolymer produced with 300 W has a surface energy of... 

EVA copolymers represent the largest-volume segment of ethylene copolymer market and are the products of low-density polyethylene (LDPE) technology. Commercial preparation of EVA copolymer is based on the same process as LDPE with the addition of controlled comonomer stream into the reactor. EVA copolymers are thermoplastic materials consisting of an ethylene chain incorporating 5-20 mol% vinyl acetate (VA), in general. The VA produces a copolymer with lower crystallinity than conventional ethylene homopolymer. 

Ethylene Polymers Ethylene polymers include ethylene homopolymers and copolymers with other unsaturated monomers, most importantly, olefins such as propylene and polar substances such as vinyl acetate. The properties and uses of ethylene polymers depend on the... 

The sheer size and value of the polyethylene industry ensure that there is continued research, progress, and development in catalysis, for their potential commercial impact. Although this whole subject is not within the scope of this chapter, we mention a couple of aspects of the progress, which offer the potential to impact this industry. In 1995, DuPont introduced work, carried out with them at the University of North Carolina—via the largest patent applicafion ever in the USA. They disclosed what are described as post-metallocene catalysts. These are transition and late transition metal complexes with di-imine ligands, which form part of the DuPont Versipol technology. Such catalysts create highly branched to exceptionally linear ethylene homopolymers and linear alpha-olefins. Late transition metals offer not only the potential for the incorporation of polar comonomers, which until now has only been possible in LDPE reactors, but also their controlled sequence distribution, compared to the random composition of free radical LDPE copolymers. Such copolymers account for over 1 million tons per annum [20]. Versipol has so far only been cross-licensed and used commercially by DuPont Dow Elastomers (a former joint venture, now dissolved) in an EPDM plant. 

---