Plasticizing and crosslinking effects of borate additives on the structure and properties of poly(vinyl acetate)†
As an environmentally friendly, low-cost and widely used polymer, poly(vinyl acetate) (PVAc) is worth modifying to achieve better properties. Here, we report on the influence of borate additives on the structure and properties of partially hydrolysed PVAc. In addition to the general crosslinking function of borate additives, an extraordinary plasticizing effect was found. By controlling the pH from 4 to 11 during sample preparation, the plasticizing and crosslinking effects can be shifted. In alkaline conditions, the degree of crosslinking in the PVAc/borate sample is increased; however, this increase declines gradually with an increase in the borate additive content, which impacts the morphology of the PVAc latex particles, as well as the mechanical and thermal properties of the PVAc/borate films. In contrast, in acidic conditions, the PVAc/borate films are plasticized by borate additives; thus, their ultimate mechanical strength, elastic moduli and thermal stabilities decrease, while the water diffusivities increase.