Ethylene vinyl acetate rheological properties

Blends of ethylene-vinyl acetate (EVA) copolymer with metallocene-catalysed elastomeric ethylene-alpha-olefin copolymer were investigated and were found to be immiscible in the melt and solid state but mechanically compatible. The morphology (SEM), thermal (DSC), rheological (viscosity), mechanical (including tensile, shear thinning and elastic behaviour) and optical properties of EVA-rich and ethylene-alpha-olefin copolymer-rich blends were studied and the results are discussed in terms of processibility in film applications. 24 refs. 

The choice of binder is as important as the choice of solvent. The binder contributes to the overall rheological properties of the paste, but it must be removed completely during firing. Ethyl cellulose is a common binder for air-fired materials. Binders for firing in inert or reducing atmospheres must be chosen carefully to avoid leaving a carbon residue in the fired film suitable choices include nitrocellulose and copolymers of ethylene and vinyl acetate. 

The vinyl acetate content and the molecular weight range influence the hot melt rheology and particularly the adhesive properties. The higher the ethylene content, the better the specific adhesion to non-polar substrates, such as polyolefins, copolymers with a higher vinyl acetate content show an improved adhesion to polar substrates, such as paper. Comparatively low molecular weight polymers yield low-melt viscosity solid inks that are easier to process and apply. 

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