Views:49 Author:Site Editor Publish Time: 2019-11-05 Origin:Site
Formulating Ethylene Vinyl Acetate Hot Melt Adhesives
Introduction Key Material Properties Required for Hot Melt Adhesives Formulation of EVA Hot Melt Systems Advances in EVA Hot Melt Adhesives Introduction Hot melt adhesives are increasingly becoming popular because of their fast setting speed, relatively low cost (materials and processing), and low environmental impact. Hot melt adhesive systems also have broad formulation latitude so that a multiplicity of products can be produced for specific end-uses and substrates. Primary hot melt applications are high-speed applications such as packaging, attaching labels and wood veneer, bookbinding, and textiles. Hot melt adhesives can also be manufactured in various forms including pellets, slugs, and blocks for bulk application or stick and continuous rope forms for heated gun applicators. Films are also available for high area assembly and continuous laminating. Hot melt adhesives are primarily made from thermoplastic polymers including ethylene vinyl acetate (EVA), block copolymers such as styrene butadiene styrene (SBS) or styrene isoprene styrene (SIS), polypropylene (atactic), polyethylene, polyamide, polyester, and polyurethane. Of these, EVA is the most popular due to their high versatility. EVA resins are highly flexible products, compatible with many other polymers and additives, and easy to process. They have high cohesive strength and excellent adhesion to a wide range of substrates. EVA copolymers can be used in soft, permanently tacky pressure sensitive adhesives or in tough rigid hot melt compositions used for semi-structural applications. Table 1 identifies the major advantages and limitations associated with EVA based hot melt adhesives.