Plastics with very low surface energy, such as polyethylene and polypropylene, make it difficult for most adhesives to wet the surface and make a strong bond.
Polyethylene is a lightweight thermoplastic material that splits into two families: HDPE (high density polyethylene) and LDPE (low density polyethylene), used in storage containers, packaging, tanks, and other widely used items. Bonding polyethylene is extremely difficult because it is a relatively non-stick surface. To glue polyethylene materials, you need a glue made especially for HDPE and LDPE.
Polypropylene is also a low surface energy plastic, and is used in food storage and other types of containers because it repels liquids easily.
Epoxy will not bond polyethylene and polypropylene materials. Neither will polysulfide adhesives such as BoatLIFE Life-Calk, or polyurethane adhesives such as 3M 5200 or Sika-flex.
Methacrylates are generally the type of adhesive to use to bond these dissimilar plastics. An example would be 3M Scotch-Weld DP 8005 Structural Plastic Adhesive. Its two-part structural formulation effectively bonds low surface energy plastics such as polyethylene and polypropylene with other materials, without pre-treating the surface.
