The blending of bydroxypropyl lignin with poly(methylmethacrylate) and poly(vinyl alcohol)

Abstract

Polymer blends consisting of hydroxypropyl lignin (HPL ) and commercially available poly(methyl methacrylate) (PMMA ) and poly(vinyl alcohol) (PVA) were evaluated in terms of their morphology, viscoelastic properties and mechanical properties. In the case of HPL/PMMA blends experimental variables included HPL molecular weight, HPL content and method of preparation. Methods of preparation included injection molding and solution casting with THF (a hydrogen bonding solvent ) and chloroform (a non-hydrogen bonding solvent) . SEM results indicated that all HPL/ PMMA blends formed two phase systems. However the domain-matrix interphase varied with the method of preparation and HPL molecular weight. Most notably was that solution cast blends showed domains that were "pulled away" from the matrix whereas injection molded blends showed HPL striations that were closely associated with the matrix. Injection molded blend's Tg values were found to more closely follow predicted Tg values (Flory-Fox equation) and injection molded blends also showed consistently superior material properties. Polymer blends of HPL and PVA were prepared by solution casting and evaluated in terms of HPL content and PVA's solubility parameter. Blends of HPL and PVA formed homogeneous materials over a much broader range of solubility parameters than would be predicted from the theory of matching solubility parameters. It was concluded that hydrogen bonding between hydroxyl groups on both polymers was responsible for the formation of at least partially miscible systems over a wider than expected range of solubility parameters.