Question: What tips can you provide for bonding plastics and composites with adhesives?
Answer: Adhesives are often a better way to assemble plastics than by using mechanical assembly with fasteners. For example, fiberglass composites are routinely bonded with epoxy or reactive acrylic adhesives in the automotive and marine industries because they give high strength and durable bonds. However, caution must be exercised in some cases. The inherent flexibility of plastics can induce peel and cleavage stresses in bonds. In addition, the high thermal expansion coefficients of plastics can also be an issue. Although it is not usually a problem in bonding plastics to plastics because plastics and adhesives often have similar thermal expansion coefficients, it can be an issue when bonding plastics to metals. Also, be aware that some acrylic adhesives can cause stress cracking in thermoplastics—there are warnings from manufacturers not to use anaerobic adhesives on several thermoplastics.