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Ethylene polymer

Ethylene Polymers. Depending on the polymerization conditions, three major types of polyethylene are manufactured low-density polyethylene (LDPE) by free-radical polymerization, linear low-density polyethylene (LLDPE) by copolymerization of ethylene with terminal olefins, and high-density polyethylene (HDPE) by coordination polymerization. The processes yield polymers with different characteristics (molecular weight, molecular weight distribution, melt index, strength, crystallinity, density, processability). [Pg.770]

A number of processes have been developed to obtain products of different physical properties. The nature of the product is affected by the addition of diluents or other additives before carrying out the polymerization. Autoclaves or stirred-tank reactors, and tubular reactors, or their combinations have been developed for the industrial production of high-pressure polyethylene.206,440 Pressures up to 3500 atm and temperatures near 300°C are typically applied. [Pg.771]

Linear low-density polyethylene (LLDPE)440-442 is a copolymer of ethylene and a terminal alkene with improved physical properties as compared to LDPE. The practically most important copolymer is made with propylene, but 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene are also employed.440 LLDPE is characterized by linear chains without long-chain branches. Short-chain branches result from the terminal alkene comonomer. Copolymer content and distribution as well as branch length introduced permit to control the properties of the copolymer formed. Improvement of certain physical properties (toughness, tensile strength, melt index, elongation characteristics) directly connected to the type of terminal alkene used can be achieved with copolymerization.442 [Pg.771]

Incorporation of a small amount of propylene in ethylene polymerization lowers crystallinity, density, and melting point of the product. The copolymer thus formed has a narrower molecular weight distribution and exhibits better optical properties. [Pg.771]

With larger amount of propylene a random copolymer known as ethylene-propylene-monomer (EPM) copolymer is formed, which is a useful elastomer with easy processability and improved optical properties.208,449 Copolymerization of ethylene and propylene with a nonconjugated diene [EPDM or ethylene-propylene-diene-monomer copolymer] introduces unsaturation into the polymer structure, allowing the further improvement of physical properties by crosslinking (sulfur vulcanization) 443,450 Only three dienes are employed commercially in EPDM manufacture dicyclopentadiene, 1,4-hexadiene, and the most extensively used 5-ethylidene-2-norbomene. [Pg.772]


In practice, synthetic polymers are sometimes divided into two classes, thermosetting and thermo-plMtic. Those polymers which in their original condition will fiow and can be moulded by heat and pressime, but which in their finished or cured state cannot be re softened or moulded are known as thermo setting (examples phenol formaldehyde or urea formaldehyde polymer). Thermoplastic polymers can be resoftened and remoulded by heat (examples ethylene polymers and polymers of acrylic esters). [Pg.1014]

Polyethylene (Section 6 21) A polymer of ethylene Polymer (Section 6 21) Large molecule formed by the repeti tive combination of many smaller molecules (monomers) Polymerase chain reaction (Section 28 16) A laboratory method for making multiple copies of DNA Polymerization (Section 6 21) Process by which a polymer is prepared The principal processes include free radical cationic coordination and condensation polymerization Polypeptide (Section 27 1) A polymer made up of many (more than eight to ten) amino acid residues Polypropylene (Section 6 21) A polymer of propene Polysaccharide (Sections 25 1 and 25 15) A carbohydrate that yields many monosacchande units on hydrolysis Potential energy (Section 2 18) The energy a system has ex elusive of Its kinetic energy... [Pg.1291]

The compositional distribution of ethylene copolymers represents relative contributions of macromolecules with different comonomer contents to a given resin. Compositional distributions of PE resins, however, are measured either by temperature-rising elution fractionation (tref) or, semiquantitatively, by differential scanning calorimetry (dsc). Table 2 shows some correlations between the commercially used PE characterization parameters and the stmctural properties of ethylene polymers used in polymer chemistry. [Pg.368]

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). [Pg.394]

Fig. 22.1. (a) The ethylene molecule or monomer (b) the monomer in the activated state, ready to polymerise with others (<)-(f) the ethylene polymer ("polyethylene") the chain length is limited by the addition of terminators like —OH. The DP is the number of monomer units in the chain. [Pg.229]

Crystalline Olefin Polymers (Eds. raff, r. a. v. and doak, k. w.). Interscience, New York (1964) Polythene—the Technology and Uses of Ethylene Polymers (Eds. Renfrew, a. and Morgan, r), Iliffe, London, 2nd Edn (1960)... [Pg.245]

R. Halle, Structure, properties and blown film processing of a new family of linear ethylene polymers, SME Blown Film Technology Seminar, Oct 1993, USA. [Pg.165]

The chloro-nitro-ethylene polymer explds when heated over an open flame Emits dangerous fumes on decompn Refs 1) Beil 1, [166] 2) Sax (1968), 961... [Pg.325]

Radiolytic ethylene destruction occurs with a yield of ca. 20 molecules consumed/100 e.v. (36, 48). Products containing up to six carbons account for ca. 60% of that amount, and can be ascribed to free radical reactions, molecular detachments, and low order ion-molecule reactions (32). This leaves only eight molecules/100 e.v. which may have formed ethylene polymer, corresponding to a chain length of only 2.1 molecules/ ion. Even if we assumed that ethylene destruction were entirely the result of ionic polymerization, only about five ethylene molecules would be involved per ion pair. The absence of ionic polymerization can also be demonstrated by the results of the gamma ray initiated polymerization of ethylene, whose kinetics can be completely explained on the basis of conventional free radical reactions and known rate constants for these processes (32). An increase above the expected rates occurs only at pressures in excess of ca. 20 atmospheres (10). The virtual absence of ionic polymerization can be regarded as one of the most surprising aspects of the radiation chemistry of ethylene. [Pg.266]

Linear polycarbosilanes and polycarbosiloxanes-especially those containing arylene units in the chain-have specific physico-chemical properties which can be applicable in heat-resistant materials [29-31]. Phenylene-silylene-ethylene-polymers, which may serve as potential substrates for applications as membrane materials are usually obtained in the presence of platinum catalysts [32], although other transihon-metal complexes have also been tested in this process. [Pg.349]

Chemisorphon of the complexes [Cp MR2], [Cp MR3] or [MR4] (Cp = Cp, Cp M = Zr, Ti, Th R = Me, CH2 Bu, CH2TMS) onto superacidic sulfated zirconia (ZRS , where x refers to activation temperature) [81, 91] and sulfated y-alumina (AIS) [90] afforded active benzene hydrogenation catalysts and ethylene polymer-izahon catalysts. The most active catalyst system for the hydrogenation of benzene (arene Zr = 1.5 1, 25 °C, no solvent, 0.1 MPa H2) was [Cp ZrMe2] -ZRS400, which achieved a TOP of 970 h. The activity of this adsorbate catalyst rivals or exceeds those of the most active heterogeneous arene hydrogenahon catalysts known. The... [Pg.196]

Improved compositions useful for the production of foamed rotomoulded articles are provided. The compositions of the invention are comprised of a first thermoplastic resin component which is an ethylene polymer in pellet form containing a foaming agent and a second thermoplastic resin component which is a powder consisting of a mixture of different particle size and melt index ethylene polymers. An improved process for producing foamed rotomoulded articles having uniformly foamed interiors and smooth exterior skins which are snbstantially free of surface defects is also provided. [Pg.67]

These comprise at least one homogeneously branched ethylene polymer and at least one blowing agent. They are particularly suitable for sealing food and liquid containers and do not contribute to taste and/or odour of the packaged product. [Pg.74]

Patent Number US 5554661 A 19960910 CLOSED CELL, LOW DENSITY ETHYLENIC POLYMER FOAM PRODUCED WITH INORGANIC HALOGEN-FREE BLOWING AGENTS... [Pg.80]

Patent Number US 5407965 A 19950418 CROSS-LINKED ETHYLENIC POLYMER FOAM STRUCTURES AND PROCESS FOR MAKING... [Pg.94]

Disclosed is a crossUnked ethylenic polymer foam structure of an ethylenic polymer material of a crosslinked, substantially linear ethylenic polymer. The ethylenic polymer in an uncrossUnked state has (a) a melt flow ratio greater than or equal to 5.63 (b) a molecular weight distribution defined by a given equation and (c) a critical shear rate at onset of surface melt fracture of at least 50% greater than the critical shear rate at the onset of surface melt fracture of a linear ethylenic polymer having about the same melt flow ratio and molecular weight distribution. Further disclosed is a process for making the above foam structure. [Pg.94]

Patent Number US 5405883 A 19950411 ETHYLENE POLYMER FOAMS BLOWN WITH ISOBUTANE AND 1,1-DIFLUOROETHANE AND A PROCESS FOR MAKING... [Pg.95]

Disclosed is an ethylene polymer foam structure having enhanced processing and physical properties. The foam structure comprises an ethylenic polymer material and a blowing agent of isobutane and 1,1-difluoroethane. Further disclosed is a process for making the foam structure. [Pg.95]

These comprise an ethylenic polymer and a blowing agent, which contains a primary blowing agent of isobutane and a secondary blowing agent of 1,1,1-trifluoroethane, 1,1,12-tetrafluoroethane or a blend thereof. They exhibit enhanced processing and physical properties. [Pg.96]

Patent Number WO 9425255 A1 19941110 ETHYLENE POLYMER FOAMS BLOWN WITH... [Pg.97]


See other pages where Ethylene polymer is mentioned: [Pg.381]    [Pg.440]    [Pg.213]    [Pg.1969]    [Pg.209]    [Pg.280]    [Pg.277]    [Pg.325]    [Pg.325]    [Pg.464]    [Pg.114]    [Pg.166]    [Pg.214]    [Pg.335]    [Pg.305]    [Pg.35]    [Pg.56]    [Pg.80]    [Pg.94]    [Pg.96]    [Pg.97]   
See also in sourсe #XX -- [ Pg.208 ]

See also in sourсe #XX -- [ Pg.208 ]

See also in sourсe #XX -- [ Pg.234 ]

See also in sourсe #XX -- [ Pg.208 ]




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