A study of chemically modified poly(vinyl butyral)
Poly (vinyl butyral) (PVB) is prepared-by the-acetalisation-of-poly-(vinyl - alcohol) with butanal. Due to the random nature of the reaction, some of the hydoxyl groups are left unreacted. The residual hydroxyl groups greatly influence its solution behaviour leading to aggregate formation in many solvents. A number of modified samples of PVB were prepared by esterification of the hydroxyl groups with butanoic anhydride, benzoic anhydride, trifluroacetic anhydride, phthalic anhydride and succinIcanhydriue: - These modified samples were examined by size exclusion chromatography (SEC) and dilute solution viscometry. The degree of modification was determined by chemical determination of the residual hydroxyl groups, by nuclear magnetic resonance spectroscopy (NMR) or Fourrier transform infrared spectroscopy (FTIR). Viscosity measurements showed that modification with non-polar ester groups diminished the degree of aggregate formation in THF while modification. with the cyclic anhydrides showed an increased tendency towards aggregation in THF while the aggregates were efficiently disrupted by methanol. The miscibility of the modified PVB with a polyester, a polyurethane, polyethylenimine and poly (vinyl pyrrolidone) was investigated by dynamic mechanical thermal analysis (DMTA). It was found that samples modified with non-polar. ester groups showed reduced miscibility with these polymers, while samples modified with cyclic anhydrides showed improved miscibility with these polymers and formed macromolecular complexes with polythylenimine and poly (vinyl pyrrolidone). It was concluded that intermolecular hydrogen bonding ~fected the viscosity behaviour of PVB in various sole vents and was the main thermodynamic reason for promoting miscibility with the polymers studied.