Polymer Bulletin, Vol.77, No.5, 2737-2747, 2020
Preparation and characterization of natural rubber bio-based wood adhesive: effect of total solid content, viscosity, and storage time
Natural rubber (NR) grafted by methyl methacrylate (MMA) was used to produce bio-based wood adhesive. The effect of total solid content (%TSC) at 55, 57, and 60%, represented as 55NR-g-MMA, 57NR-g-MMA, and 60NR-g-MMA, respectively, and the effect of storage time on lap shear strength were investigated. It was found that contact angle sharply decreased from 95 degrees for NR to approximately 65 degrees for all of NR-g-MMAs. Because the MMA groups were incorporated into various NR-g-MMA samples and the highest relative amount of grafted MMA was obtained by 57-NR-g-MMA which is determined by peaks intensities ratio between wave number at 1725 (C=O stretching) and 1450 (CH2 stretching), investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). These influences resulted in an increase in storage modulus (E '), whereas tan delta was decreased as compared to that of NR, characterized by dynamic mechanical analyzer (DMA). In addition, the apparent viscosity performed by plate-and-plate rheometer trended to increase with total solid content and storage time. However, the highest lap shear strength was achieved by 57NR-g-MMA. It means that the lap shear strength was not only governed by viscosity as well as total solid content, but the amount of grafted MMA also plays an important role.