1. Formulating Ethylene Vinyl Acetate Hot Melt Adhesives

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.