Improving the adhesion strength and moisture resistance of poly(vinyl acetate) latex as wood adhesive via blending with gelatin

Abstract

Gelatin can act as wood adhesive for fabrication of numerous structures. Polyvinyl acetate (PVAc) is also used as wood adhesive because it provides excellent adhesion. Unfortunately, its bonds are sensitive to humid atmospheres especially at elevated temperatures. The current work explores hybridization of PVAc emulsion with finite amounts of gelatin and the resulting latex was fully characterized using different techniques, where it was found that gelatin insertion caused densification of the latex structure without affecting its stability while the viscosity increased without visual phase separation, indicating strong interactions emerged between both. Dynamic light scattering (DLS) and transmission electron microscope (TEM) confirmed a mean size of the latex particles increasing from 265 nm to 290 nm in presence of elevated doses of gelatin, with the surface charge decreasing from −42 mV to −33 mV. Turbidity measurements revealed the latex particles became more likely to coagulate in presence of increasing amounts of gelatin and formation of a more compact film that provides higher resistance to water permeation and stronger adhesion as supported by shear strength evaluations. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) proved strong interactions between PVAc with gelatin, causing higher thermal stability and possibility of use at relatively higher temperatures. X-ray diffraction (XRD) showed broadening of the peak at 2θ = 21° indicating partial destruction of the triple helical structure of gelatin, which can be correlated with the spectra of Fourier transform infrared (FTIR) that showed obvious shifts of the main peaks of PVAc due to effective insertion of gelatin.