Polyolefins are generally not thought of as adhesives because as a substrate they are so hard to bond. However, polyolefin resins make excellent hot melt adhesives because they do have a low surface energy and wet most polymeric and metallic substrates.
Adhesives that are based on polyolefin resins are used mainly as hot melt adhesives in either block or film form. In film form, they provide excellent peel strength as a hot laminating adhesive for plastic films and metallic foils. Polyethylene adhesive films are also used in extrusion coating. In this application a ply of polyethylene is extruded onto a structure to provide a heat sealing medium for later bonding.
RESULTING PROPERTIES
Polyolefin hot melt adhesive have good thermal stability (minimal color changes and reduced gel formation on standing in the melter). Ring and ball softening points are generally I the 100-130°C range. Melt viscosities can have a wide range due to molecular design and additives. Polyolefins are compatible with many tackifers. Many are also approved by FDA for direct food contact and are oil and water resistant. The formulations above describes hot melt adhesives for manufacturing multiwall paper bags that are based on polyethylene. Such adhesives are often used in packaging applications especially due to good adhesion to plastic film and FDA approval for food contact.
