Ethylene-vinyl acetate copolymer additives

A further class of ethylene-vinyl acetate copolymer exists where the vinyl acetate content is of the order of 3 mole %. These materials are best considered as a modification of low-density polyethylene, where the low-cost comonomer introduces additional irregularity into the structure, reducing crystallinity and increasing flexibility, softness and, in the case of film, surface gloss. They have extensive clearance as non-toxic materials. 

Among the different pressure sensitive adhesives, acrylates are unique because they are one of the few materials that can be synthesized to be inherently tacky. Indeed, polyvinylethers, some amorphous polyolefins, and some ethylene-vinyl acetate copolymers are the only other polymers that share this unique property. Because of the access to a wide range of commercial monomers, their relatively low cost, and their ease of polymerization, acrylates have become the dominant single component pressure sensitive adhesive materials used in the industry. Other PSAs, such as those based on natural rubber or synthetic block copolymers with rubbery midblock require compounding of the elastomer with low molecular weight additives such as tackifiers, oils, and/or plasticizers. The absence of these low molecular weight additives can have some desirable advantages, such as ... 

It has been found that, for a fixed mineral filler content, the viscosity of PMF-based composites increases when the coat is made of polyethylene [164, 209, 293], poly(vinyl chloride) [316] and polypropylene [326, 327], The picture was different, however, for composites based on the ethylene/vinyl acetate copolymer to which kaolin with grafted poly (vinyl acetate) was added [336]. Addition of PMF with a minimum quantity of grafted polymer results in a sharp drop of flowability (rise of viscosity), in comparison to addition of unmodified filler but with a further increase of the quantity of grafted polymer the flow gradually increases and, depending on the kaolin content and quantity of grafted polymer, may even become higher than in specimens with unmodified filler, for equal concentrations. 

The monomers used to make an addition polymer need not be identical. When two or more different monomers are polymerized into the same chain, the product is a copolymer. For instance, we routinely copolymerize ethylene with small percentages of other monomers such as a-olefins (e.g., 1-butene and 1-hexene) and vinyl acetate. We call the products of these reactions linear low density polyethylenes and ethylene-vinyl acetate copolymer, respectively. We encounter these copolymers in such diverse applications as cling film, food storage containers, natural gas distribution pipes, and shoe insoles. 

Ethylene Vinyl Acetate Copolymers 203 Table 7.2 Cold Filter Plugging Points with Certain Additives (26)... 

Properties of Explosive Compositions With and Without Addition of Ethylene/Vinyl Acetate Copolymer (EVA) Binder... 

R. Reed, Moldable Ethylene/Vinyl Acetate Copolymer , USP 4090894 (1978) CA 39, 148908 (1978) [Vinyl acetate copolymerized with ethylene is used as a desensitizer and binder for moldable expl compns of cyclic nitramines such as RDX. From 82 to 98 wt % of binder is used, and various ratios of ethylene to vinyl acetate moieties in the resin are utilized to modify molding and extrusion properties. Prepn of typical compns consists of dissolving the copolymer in benz and addition with stirring to an RDX/w slurry, which is stirred until mixt is complete, followed by filtration and drying. Table 1 presents properties of sample compns with and without the ethylene/vinyl acetate copolymer (EVA). The inventor also states that the EVA, unlike other polymeric binders, endothermically breaks down at high temps and acts as a heat sink for the expl content]... 

TVy blending with any one of a multitude of additives, PVC can be transformed into a broad spectrum of resins ranging from highly plasticized to impact resistant. The use of polymeric plasticizers has attracted a great deal of attention because they provide superior permanence in physical properties over their low molecular weight counterparts. Recently a terpolymer of ethylene, vinyl acetate, and carbon monoxide was reported to be miscible with PVC (1,2). The system is of interest because blends of PVC and ethylene-vinyl acetate copolymers range from incompatible to miscible, depending on the content of vinyl acetate in the copolymer (3,4,5). We have therefore undertaken x-ray,... 

Poly(vinyl alcohol) is utilized as a component of starch-based adhesives.11121114 Other patents report the use of partially oxidized starch,1115 dextrins,1116 dextrins and urea,1117 borax,1118 boric acid,1119 and vinyl methyl ether-maleic acid copolymers.1120 Other patents indicate the use of poly (vinyl alcohol) with partially hydrolyzed poly(vinyl acetate),1121 nonhy-drolyzed poly(vinyl acetate),1122 and poly(vinyl chloride).1123 A few patents have reported such poly acrylic additives as poly (acrylic acid)1124 and its salts,1125 poly(acrylamide),1126 1127 A-methylacrylamide or poly(A-acryl-amide),1128 and polyethyleneimine.1129 Polystyrene has also been used,1130 as well as more complex copolymers such as a maleic acid monobutyl ester-methyl vinyl ether copolymer, together with dextrin and polyacrylamide),1131 carboxylated ethyl acrylate-styrene zinc salt copolymer,1132 ethylene-methyl acrylate-vinyl acetate copolymer,1133 vinyl acetate-vinyl pyr-rolidone copolymer,1134 and ethylene-vinyl acetate copolymer.1135 Some adhesives are compounded with SBR latex1136 1138 and phenol-formaldehyde resins.1139... 

Other examples from the research group of Koenig (2000-2002) include details of the dissolution behavior of polymers in different solvents (partly with the addition of nonsolvents) or a mixture of solvents. From these investigations, a nonuniform dissolution of the polymer at the interface could be observed for several solvent systems [7-11]. Further results of diffusion measurements were presented in 2002 by Rafferty and Koenig, and later in 2005 by Bobiak and Koenig [12, 13], in which the diffusion of nicotine into an ethylene-vinyl acetate copolymer was analyzed. 

In addition to, or instead of, polystyrene and oils, polymers such as polypropylene, polyethylene, or ethylene-vinyl acetate copolymer can be blended with these block copolymers. Blends with S-B-S or (S-B) -X block polymers usually show greatly improved ozone resistance (S-EB-S already has excellent ozone resistance). In addition, these blends have some solvent resistance. In certain cases, some oils that are stable to UV radiation reduce the stability of the blends however, the effects can be minimized by the use of UV stabilizers and absorptive or reflective pigments (e.g., carbon black or titanium dioxide). 

Zurina, M., Ismail, H., Ratnam, C. T., Effect of trimethylolpropane triacrylate (TMPTA) on the properties of irradiated epoxidized natural rubber (ENR-50), ethylene- (vinyl acetate) copolymer (EVA), and an ENR-50/EVA blend. Journal of Vinyl and Additive Technology 2009,15(1), 47-53. 

Adhesive applications can be widespread including contact cmnents, pressure-sensitive adhesives and hot melts. In solid compounded articles footwear is a large volune application such as molded-ln-place soling or unit soles to be cemented to uppers. Additional uses are in toys, milk tubing, cove base, mats and miscellaneous coatings or molded parts. Potential uses include blends with ethylene-propylene rubber and ethylene-vinyl acetate copolymers to provide ozone-resistant fomulations or blends to improve crack- or impact-resistance of plastics. 

Ethylene-vinyl acetate copolymers can be thought of as modified high pressure polyethylenes. Because of the free-radical polymerization process they have structural characteristics such as short-chain and long-chain branching in addition to the effects due to the incorporation of the vinyl acetate comonomer. Ethylene and vinyl acetate have a reactivity ratio which is close to 1 and as a result EVA copolymers contain vinyl acetate which is homogeneously distributed among the polymer chains. The major effect of the VA on polymer properties is to reduce... 

In a more recent study, Kelusky, Elston and Murray [11] demonstrated the use of analytical TREF for the analysis of a wide range of polyethylene-based blends. As with the work described above, their analytical TREF system used very small sample and column size, a programmed oven and an IR detector to achieve the necessary reproducibility and resolution. In addition to confirming the effectiveness of TREF for the characterization of blends of LLDPE and LDPE, they showed examples of LDPE/medium density PE blends (Fig. 38) and of ethylene vinyl acetate copolymer/LLDPE blends (Fig. 39). 

Water-based dispersions or emulsions such as polyvinyl acetate, acrylics, polyvinyl chloride and polyvinyl alcohol with plasticizers and tackifiers. In addition, this range can include urea formaldehyde and phenolic adhesives, resins, natural adhesives produced from starch, dextrin, casein, animal glues (see Polyvinyl alcohol in adhesives, Phenolic adhesives single-stage resoles. Phenolic adhesives two-stage novolacs. Animal glues and technical gelatins) and rubber latex (see Emulsion and dispersion adhesives). Solvent-free 100% solids such as polyurethane. Hot melt adhesives include Ethylene-vinyl acetate copolymers, polyolefins, polyamides, polyesters with tackifiers and waxes. More recent additions include cross-linkable systems. 

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