Although polymer adhesives can form excellent and robust bonds between many materials, some materials are more difficult to bond to than others. In fact, there are some materials that are prohibitively difficult to bond, and chemical adhesives should be cautiously considered due to their inferior bonding capabilities. Materials from this end of the spectrum are designated as “hard-to-bond”.
Hard-to-bond materials include:
Polyolefins such as Polypropylene and Polyethylene
Fluoropolymers such as teflon and Hyflon
Acetal resins such as Delrin
Thermoplastic vulcanizates such as Santoprene
Due to the surface energy, porosity, and polarity of these materials, chemical adhesives have a hard time forming robust surface bonds. Of all the chemical adhesive options, cyanoacrylates, hot melts and UV acrylates typically yield the best results.
Surface preparation can somewhat remedy the issue. However, depending on the required adhesive strength and exposure conditions, fastening or other bonding methods should be considered over chemical adhesives.