Preparation and characterization of wood-to-wood bonding adhesive by glycidyl methacrylate grafting natural rubber

In this study, a wood adhesive obtained from natural rubber (NR) was prepared by grafting glycidyl methacrylate (GMA)/styrene (St) at a weight ratio of 9/1 (NR- g -GMA) with the aid of a cumene hydroperoxide (CHP)/tetraethylene pentamine (TEPA) initiating system. The effect of reaction time on lap shear strength and the adhesion mechanism were investigated. A water contact angle on NR- g -GMA decreased from 95° to 54°; attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy confirmed the introduction of oxirane rings and St onto the NR; subsequently a ring-opening reaction in basic media occurred. In addition, dynamic mechanical analysis (DMA) showed that the storage modulus (G‘) of NR- g -GMA increased, whereas the glass transition temperature (T g ) slightly shifted to lower temperature and the height of tan δ decreased as compared to NR. The lap shear strength of NR- g -GMAs increased with increasing reaction time together with the hydroxyl content due to the ring-opening reaction, whereas the percentage grafting efficiency and the carbonyl content decreased after 4 h of reaction time. X-ray photoelectron spectroscopy (XPS) and ATR-FTIR showed that C–H, C O, and OH groups were mainly chemical compositions of wood and NR- g -GMA adhesive. Therefore, we propose that adsorption and molecular interaction were the main mechanisms determining adhesive strength.