Reaction mechanism of carboxymethyl starch-based wood adhesive
Yong Zhang, Lixia Li
Faculty of Modern Agricultural Engineering, Kunming University of Science and Technology, Kunming, China
The technology involved in manufacturingcarboxymethyl starch-based adhesive was studied with the aim of enhancing its water-resistance. The optimum formula was based on previous research using a quadratic orthogonal rotation combination design to synthesise the carboxymethyl starch-based wood adhesive. Compared with the original starch, carboxymethyl starch improves the performance of starch adhesive due to its advantageous properties such as hydrophilicity and stability during freezing and thawing etc. Infrared spectroscopy and scanning electron microscopy were used to analyse the synthesis of the carboxymethyl starch-based adhesive. Many functional groups could be identified by their characteristic Fourier transformation infrared vibration frequency and this was used to explain the structural changes. At the same time, the microstructure of the adhesive was analysed by scanning electron microscopy (SEM), and porous, round or elliptical granules in the carboxymethyl starch were observed. An SEM of the main starch agent revealed a network structure; the granules did not aggregate together to form large groups due to the polyvinyl alcohol that prevented granule agglomeration. However, the SEM of the starch adhesive showed a smoother and more compact network structure, due to the large number of strong chemical bonds that were formed by the association of isocyanate with the main starch agent.