Question: What alternatives do I have for high-strength bonding to surfaces like polyethylene and polypropylene?
Answer: Cyanoacrylates can be used with special primers to get very high strengths on these low-energy plastics. However, cyanoacrylates are expensive, which normally limits their applications to relatively small bond areas. Two-part acrylic systems have been available for some time and provide good strengths on these plastics, but have been based on the use of methyl methacrylate monomer (the so-called “MMA” adhesives). While being very effective in promoting adhesion, methyl methacrylate has a noxious odor and is quite flammable.
Recently, a few companies have introduced acrylic adhesives using much less volatile and flammable monomers based on novel cure systems using complexed boron alkyls as the key component of their cure system. The boron alkyls appear to react with hydrogen atoms on the polyolefins. These adhesives have successfully bonded a range of low-energy plastics, including polyethylene, polypropylene and thermoplastic olefins, to themselves or to metals
The major limitations of these adhesives are their very long fixture times (typically 2-3 hrs), which limits their range of applications. I have recently gotten very decent shear strengths with these adhesives on ultra-high-molecular-weight polyethylene (UHMWPE), a plastic that has a very low frictional coefficient and is used very frequently in wear situations. ASI
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