Ethylene vinyl acetate copolymer properties

Ethylene vinyl acetate copolymer (EVA) forms a soft, tacky film with good water-vapor barrier but very poor gas-barrier properties. It is widely used as a low temperature initiation and broad-range, heat-sealing medium. The film also serves for lamination to other substrates for heat-sealing purposes. 

The low vinyl acetate ethylene—vinyl acetate copolymers, ie, those containing 10—40 wt % vinyl acetate, are made by processes similar to those used to make low density polyethylene for which pressures are usually > 103 MPa (15,000 psi). A medium, ie, 45 wt % vinyl acetate copolymer with mbber-like properties is made by solution polymerisation in /-butyl alcohol at 34.5 MPa (5000 psi). The 70—95 wt % vinyl acetate emulsion copolymers are made in emulsion processes under ethylene pressures of 2.07—10.4 MPa (300—1500 psi). 

Poly(ethylene-i (9-vinyl alcohol) is made by saponification of ethylene—vinyl acetate copolymers. The properties of these materials depend on the amount of vinyl alcohol present in the copolymer. High vinyl alcohol content results in more hydrophilic materials possessing higher densities, stiffness, and moduh. They are used commercially as barrier resins for packaging. Important producers include Du Pont and EVALCA (74) (see Barrier polymers). 

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 ... 

Several authors have discussed the ion exchange potentials and membrane properties of grafted cellulose [135,136]. Radiation grafting of anionic and cationic monomers to impart ion exchange properties to polymer films and other structures is rather promising. Thus, grafting of acrylamide and acrylic acid onto polyethylene, polyethylene/ethylene vinyl acetate copolymer as a blend [98], and waste rubber powder [137,138], allows... 

The properties of ethylene-vinyl acetate copolymers vary widely with their ester content. At the lowest levels of vinyl acetate, they have physical properties that are similar to those of low density polyethylene. As the comonomer content increases, the material becomes less crystalline and more elastic. Copolymers made with the highest comonomer levels contain no measurable crystallinity. The resulting products are tough, flexible, and clear. The ester... 

How does the vinyl acetate content in ethylene vinyl acetate copolymer affect the properties of the polymer ... 

ISO 4613-1 1993 Plastics - Ethylene/vinyl acetate (E/VAC) moulding and extrusion materials - Part 1 Designation and specification ISO 4613-2 1995 Plastics - Ethylene/vinyl acetate (E/VAC) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 8985 1998 Plastics - Ethylene/vinyl acetate copolymer (EVAC) thermoplastics -Determination of vinyl acetate content... 

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]... 

Properties Poly(methyl pentene), unfilled Low-density Medium-density High-density Ultra high-molecular-weight Glass-fiber- reinforced, high-density Ethylene-vinyl acetate copolymer... 

Camino, G., Maffezzoli, A., Braglia, M., De Lazzaro, M., and Zammarano, M., Effect of hydroxides and hydroxycarbonate structure on fire retardant effectiveness and mechanical properties in ethylene-vinyl acetate copolymer, Polym. Deg. Stab., 74(3), 457-A64, December, 2001. 

Clerc, L., Ferry, L., Leroy, E., and Lopez-Cuesta, J.M., Influence of talc physical properties on the fire retarding behavior of (ethylene-vinyl acetate copolymer/magnesium hydroxide/talc) composites, Polym. Degrad. Stab. 2005, 88, 504. 

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,... 

A limited number of patents concern sPS blend which are not compatible. In these cases the properties that are described are functional ones and not related to the poor toughness of sPS. For instance, blends of sPS and partially saponified ethylene-vinyl acetate copolymers exhibit improved gas barrier properties (entry 11) small amounts of sPS added to polyethylene terephthalate) (although the patent actually claims a wide range of compositions) are useful to increase the polyester crystallization rate (entry 5). 

Ethylene vinyl acetate copolymers have a wide variety of industrial uses. Properties of ethylene vinyl acetate copolymer films in terms of oxygen and moisture transfer rate are related... 

The most widely used thermoplastic polymer is the ethylene—vinyl acetate copolymer, which is obtainable in a wide range of molecular weights as well as in a variety of compositions. Often flexibilizers or plasticizers are added in order to improve both the mechanical shock resistance and the thermal properties of the adhesive. Polybutenes, phthalates, and tricresyl phosphate have been used as plasticizers. Tackifying agents can also be added. Because hot-melt adhesives are frequendy ethylene-based, they are subject to oxidation if, as in a typical situation, the adhesive sits in an applicator for long periods before use. Thus, antioxidants such as hindered phenols are often used, as are fillers. Fillers are added to opacify or to modify the adhesive s flow characteristics, as well as to reduce cost. Wax is also a very important component. Wax alters surface characteristics by decreasing both the liquid adhesive s surface tension and its viscosity in the melt. Upon solidification, however, the wax acts to increase the strength of the adhesive. Both paraffin and microcrystalline wax are used (see Waxes). 

To obtain a higher effidency of photocrossiinking and to improve technological properties of prepared films (smoothness of the surface, transparoic ), 3 to 5% of ethylene-vinyl acetate copolymer having about 12% of vinyl acetate groups ate added [90], Increase of the molecular mass of the added copolymer leads to the increase of insoluble gel which indicates that this copolymer incorporates into the polyethylene network. The decrease or increase of vinyl acetate content in the cx>polymer below/ above an optimum value always reduces the effidency of photoo-osdinldng. 

Wang, B., Wang, X., Shi, Y. et al. 2012. Effect of vinyl acetate content and electron beam irradiation on the flame retardancy, mechanical and thermal properties of intumescent flame retardant ethylene-vinyl acetate copolymer. Radiation Physics and Chemistry 81 308-315. 

Ethylene Copolymers. Ethylene-vinyl acetate copolymers differ according to their vinyl acetate content and molecular mass. With increasing vinyl acetate content, compatibility with paraffin waxes decreases, but that with other binders increases. Low molecular mass types containing 25-40% vinyl acetate are readily or sufficiently soluble in solvents. With a 40% vinyl acetate content, they can be combined with polar resins and nitrocellulose. Terpolymers with free carboxyl groups exhibit improved adhesion. Ethylene-vinyl acetate copolymers are primarily added to waxes to improve their properties, but are also used to increase flexibility and adhesion in paints, printing inks and adhesives, and for hot melt coatings. Ethylene-vinyl acetate copolymers have low water vapor and gas permeabilities (barrier effect). 

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