Synthesis of modified Natural Rubber with grafted poly(acetoacetoxyethyl methacrylate‐co‐methyl methacrylate) and performance of derived adhesives with GTA crosslinker

The main objective of this study is to develop wood adhesives that can be cured at room temperature, based on modified natural rubber (NR) latex. Two types of modified NR, namely poly(acetoacetoxyethyl methacrylate)‐grafted NR, NR ‐g‐ PAAEM, and poly(acetoacetoxyethyl methacrylate ‐co‐ methyl methacrylate)‐grafted NR, NR ‐g‐ P(AAEM ‐co‐ MMA), were synthesized. Emulsion polymerization technique was exploited to synthesize the graft copolymers. The hydrophilicity of NR after grafting modifications was examined by means of contact angle. These results reveal that the NR become more hydrophilic after being modified with poly(acetoacetoxyethyl methacrylate), PAAEM, and/or poly(methyl methacrylate), PMMA. Adhesion properties in terms of lap shear strength were studied for wood adhesives derived from both types of NR graft copolymers, with glutaraldehyde (GTA) as the crosslinking agent. The results show that adhesives based on the NR graft copolymers gave higher lap shear strength than the NR latex adhesive. For the graft copolymers, the NR ‐g‐ P(AAEM ‐co‐ MMA) adhesive exhibited much higher lap shear strength than the NR ‐g‐ PAAEM adhesive. This indicates that the incorporation of PMMA chains into the NR ‐g‐ PAAEM molecules significantly increased the cohesive strength of the resulting adhesive, which is probably due to increased modulus and hardness of the adhesive film. POLYM. ENG. SCI., 58:1610–1618, 2018. © 2017 Society of Plastics Engineers