PVA wood adhesive modified with sodium silicate cross-linked copolymer
Poly (vinyl alcohol) (PVA) is a water-soluble synthetic polymer with excellent adhesive property. But the water resistance is poor. The aim of this study is to explore the suitable formula for PVA cross-linking with sodium silicate to form new kind of wood adhesive which has the perfect bonding strength as well as water resistance. When PVA and sodium silicate are mixed directly, they then become gel immediately. Through cross-linking in batch with the help of emulsifier OP-10 and weak acids and with the bonding strength as the evaluation indicator, the orthogonal experiment method is used to choose the suitable formula. Stable translucent white latex was made by PVA and sodium silicate. The results show that the most suitable condition is mass ratio of PVA/sodium silicate/OP-10/weak acids=20:3:0.05:2.5. With the adhesive under this prescription, the bonding strength of poplar plywood reached 0.75MPa and 24h thickness swell (TS) is 4.5% which is much better than the second class plywood standard.