Copolymers ethylene vinyl acetate, peroxide

H5V was used as grafting monomer for atactic polypropylene, ethylene/propylene copolymer, ethylene/vinyl acetate copolymer, poly(methyl acrylate) and poly(methyl methacrylate) (32). In all cases, grafting was achieved in chlorobenzene with ditertiarybutyl peroxide as the initiator. Up to now, we have not succeeded in grafting 2H5P under the same conditions onto these polymers. 

Organic peroxides are used in the polymer industry as thermal sources of free radicals. They are used primarily to initiate the polymerisation and copolymerisation of vinyl and diene monomers, eg, ethylene, vinyl chloride, styrene, acryUc acid and esters, methacrylic acid and esters, vinyl acetate, acrylonitrile, and butadiene (see Initiators). They ate also used to cute or cross-link resins, eg, unsaturated polyester—styrene blends, thermoplastics such as polyethylene, elastomers such as ethylene—propylene copolymers and terpolymers and ethylene—vinyl acetate copolymer, and mbbets such as siUcone mbbet and styrene-butadiene mbbet. 

Ethylene-vinyl acetate copolymers have been available for several years from Bayer (Levapren 450) and these contain about 45% of vinyl acetate units. As with EPM these rubbers cannot be cured with accelerated sulphur systems but by peroxides. 

Because of their content of hydrogen atoms, which can be separated by a radical reaction, ethylene-vinyl acetate copolymers have a good basis for grafting. In earlier papers on the radical crosslinking of EVA copolymers with peroxides, we showed that polyunsaturated compounds, such as triallyl cyanurate, can be incorporated completely in the copolymers by graft reactions (2). 

A crosslinked polymer synthesised [50] by crosslinking ethylene-vinyl acetate copolymer with dicumyl peroxide gave two large signal at 31.8 and... 

The two pottant materials studied in this report are plasticized polyvinyl butyral (plPVB) which is easily available and used in safety glass, and a highly stabilized, peroxide crosslinked ethylene/vinyl acetate (EVA) copolymer containing about 33 weight % vinyl acetate (.7). The outer cover/insulator materials studied include polyvinyl fluoride (PVF) and a butyl aerylate/methyl methacrylate graft copolymer (BAgMMA) both are blown films. 

The use of these monomers for radiation cross-linking of polyethylene has been suggested [66]. With benzophenone as a photosensitizer, atactic as well as isotactic polypropylene is crosslinked with allyl acrylate by UV radiation. In this process both types of double bonds react [67]. Elastomers such as ethylene-vinyl acetate copolymer have been cross-linked with this monomer on a roller mill at 150°C using dicumyl peroxide as the initiator. Such cross-linked elastomers exhibit little or no swelling with aromatic solvents or chloroform after 24 hr at 30°C, conditions under which the uncured elastomers ordinarily dissolve [68]. Despite these interesting applications for such monomers, the bulk of the commercially produced allyl methacrylate finds application as a synthetic intermediate rather than as a monomer. 

Vinyl Acetate, Homo- and Copolymer Latexes Vinyl Acetate Comonomer (butyl acrylate, ethylene, vinyl ester of versatic add) Partially Hydrolyzed Polyvinyl Alcohol Sodium Bicarbonate Hydrogen Peroxide (35%) Sodium Formaldehyde Sulfoxylate Water 70.0-100.0 0.0-30.0 6.0 0.3 0.7 0.5 80.0... 

Peroxides are vulcanizing agents for elastomers, which contain no sites for attack by other types of vulcanizing agents. They are useful for ethylene-propylene rubber (EPR), ethylene-vinyl acetate copolymers (EAM), certain millable urethane rubbers, and silicone mbbers. They generally are not useful for vulcanizing butyl rubber (poly[isobutylene-co-isoprene]) because of a tendency toward chain scission, rather than crosslinking, when the polymer is subjected to the action of peroxide. 

Vinyl acetate residues in ethylene-vinyl acetate copolymers reduce the regularity of polyethylene. This reduces crystallinity in the polymer. Materials containing 45% vinyl acetate are elastomers and can be crosslinked with peroxide. 

The letter preceding the four-digit numeric indicates that the product concerned is a copolymer or speciality (A = ethyleneacrylic copolymer V = ethylene-vinyl acetate copolymer XL = contains peroxide crosslinker). 

C2, C3 Fitting constants in the Gibson and Ahsby equations Mean cell size Mean cell wall thickness Collapse or yield stress Density of the foam Density of the solid polymer Dicumyl peroxide Ethylene vinyl acetate copolymer Ethylene styrene interpolymer Effective diffusion coefficient fraction of material in the struts or edges... 

Some specific recent applications of the GC-MS technique to various types of polymers include the following PE [49,50], poly(l-octene) [51], poly(l-decene) [51], poly(l-dodecene) [51], 1-octene-l-decene-l-dodecene terpolymer [51], chlorinated polyethylene [52], polyolefins [53, 54], acrylic acid methacrylic acid copolymers [55], polyacrylates [56], styrene-butadiene and other rubbers [57-59], nitrile rubber [60], natural rubbers [61, 62], chlorinated natural rubber [63, 64], polychloroprene [65], PVC [66-68], silicones [69, 70], polycarbonates [71], styrene-isoprene copolymers [72], substituted PS [73], polypropylene carbonate [74], ethylene-vinyl acetate copolymers [75], Nylon [76], polyisopropenyl cyclohexane a-methyl styrene copolymers [77], m-cresol-novolac epoxy resins [78], polymeric flame retardants [79], poly(4-N-alkyl styrenes) [80], polyvinyl pyrrolidone [81], vinyl pyrrolidone-methyl acryloxysilicone copolymers [82], polybutylcyanoacrylate [83], polysulfide copolymers [84], poly(diethyl-2-methacryloxy)ethyl phosphate [85], ethane-carbon monoxide copolymers [86], polyetherimide [87], bisphenol A [88], ethyl styrene [89], styrene-isoprene block copolymer [89], polyvinyl alcohol-co-vinyl acetate [90], epoxide thiol [91], maleic acid-propylene copolymer [92], P-hydroxy butyrate-P-hydroxy valerate copolymer [93], polycaprolactams [39,94], PS [95,96], polypyrrole [95,96], polyhydroxy alkanoates [97], poly(p-chloromethyl) styrene [81], polybenzooxazines and siloxy substituted polyoxadisila-pentanylenes [98,99] poly benzyl methacrylates [100], polyolefin blends after ageing in soil [101] and polystyrene peroxide [43]. 

Vinyl Acetate—Ethylene Copolymers. In these random copolymers, the ratio of ethylene to vinyl acetate (EVA) is varied from 30—60%. As the vinyl acetate content increases, the oil and heat resistance increases. With higher ethylene content the physical strength, tensile, and tear increases. The polymers are cured with peroxide. The main properties of these elastomers include heat resistance, moderate oil and solvent resistance, low compression set, good weather resistance, high damping, exceUent o2one resistance, and they can be easily colored (see Vinyl polymers, poly(VINYL acetate)). 

Ethylene has also been copolymerised with a number of non-olefinic monomers and of the copolymers produced those with vinyl acetate have so far proved the most significant commercially . The presence of vinyl acetate residues in the chain reduces the polymer regularity and hence by the vinyl acetate content the amount of crystallinity may be controlled. Copolymers based on 45% vinyl acetate are rubbery and may be vulcanised with peroxides. They are commercially available (Levapren). Copolymers with about 30% vinyl acetate residues (Elvax-Du Pont) are flexible resins soluble in toluene and benezene at room temperature and with a tensile strength of about lOOOlbf/in (6.9 MPa) and a density of about 0.95 g/cm. Their main uses are as wax additives and as adhesive ingredients. 

The first free radical initiated copolymerization was described by Brubakerl) in a patent. A variety of peroxides and hydroperoxides, as well as, 02, were used as initiators. Olefins that were copolymerized with CO included ethylene, propylene, butadiene, CH2=CHX (X—Cl, OAc, CN) and tetrafluoroethylene. A similar procedure was also used to form terpolymers which incorporated CO, C2H4 and a second olefin such as propylene, isobutylene, butadiene, vinyl acetate, tetrafluoroethylene and diethyl maleate. In a subsequent paper, Brubaker 2), Coffman and Hoehn described in detail their procedure for the free radical initiated copolymerization of CO and C2H4. Di(tert-butyl)peroxide was the typical initiator. Combined gas pressures of up to 103 MPa (= 15,000 psi) and reaction temperatures of 120—165 °C were employed. Copolymers of molecular weight up to 8000 were obtained. The percentage of CO present in the C2H4—CO copolymer was dependent on several factors which included reaction temperature, pressure and composition of reaction mixture. Close to 50 mol % incorporation of CO in the copolymer may be achieved by using a monomer mixture that is >70 mol% CO. Other related procedures for the free radical... 

The polymerization of vinyl monomers in liquid and supercritical CO2 has been studied extensively. Patents were issued in 1968 to the Sumitomo Chemical Company [81] and in 1970 to Fukui et al. [82] for the preparation of homopolymers of polystyrene, poly(vinyl chloride), poly(acrylonitrile) (PAN), poly-(acrylic acid) (PAA), and poly(vinyl acetate) (PVAc), as well as the random copolymers PS-co-PMMA and PVC-co-PVAc. Additionally, a patent was issued in 1995 to Bayer AG [83] for the preparation of styrene/acrylonitrile copolymers in SCCO2. In 1986, the BASF Corporation was issued a Canadian patent for the precipitation polymerization of 2-hydroxyethylacrylate and various N-vinylcarboxamides in compressed carbon dioxide [84]. In 1988, Terry et al. attempted to homopolymerize ethylene, 1-octene, and 1-decene in SCCO2 for the purpose of increasing the viscosity of CO2 for enhanced oil recovery [85]. These reactions utilized free-radical initiation with benzoyl peroxide and r-butylperoctoate at 71 °C and 100-130 bar for 24-48 h. Although the resulting polymers were not well characterized, they were found to be relatively... 

Copolymers of ethylene with a small amount of vinyl acetate are often preferred for peroxide cross-linking because the latter promotes the cross-linking process. Large amounts of carbon black may be incorporated into polyethylene that is to be cross-linked. The carbon black is believed to take part in the cross-linking process, and the mechanical properties of the resulting product are superior to those of the unfilled material. 

Ethylene can be free radically copolymerized with vinyl acetate. Copolymerization with 0%-35% vinyl acetate is carried out in bulk at 1000-2000 bar, that of 35%-100%at 100-400 bar in /-butanol, and that of 60%-100%at 1-200 bar in emulsion. Products with vinyl acetate contents of over 10% give shrinkable films those with up to 30% vinyl acetate give thermoplastic films, and those with over 40% vinyl acetate give clear films. Products of still higher vinyl acetate content are elastomers, fusion, and solvent adhesives or modifiers for PVC. The products can be cross-linked with lauroyl peroxide on the addition of, for example, triallyl cyanurate. Copolymers of ethylene and ethyl acrylate have similar properties. 

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