Multiphase materials with lignin: 1. Blends of hydroxypropyl lignin with poly(methyl methacrylate)

Abstract

Polymer blends consisting of hydroxypropyl lignin (HPL) and poly(methyl methacrylate) (PMMA) were prepared by injection moulding and by solution casting (tetrahydrofuran and chloroform). Blend morphology and material properties were determined by scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis and tensile testing. Results were interpreted in relation to HPL content, HPL molecular weight and method of preparation. All blends produced two-phase materials with morphology varying with method of preparation and HPL content. A surprising degree of compatibility was revealed by thermal analysis (differential scanning calorimetry and dynamic mechanical thermal analysis). The behaviour suggests significant plasticization or antiplasticization for all blends. Even the highly phase-separated solution-cast blends showed single T g values at all HPL contents. These results were explained with transitional smearing, and with some degree of polymer-polymer interaction. The addition of HPL to PMMA was found to cause an increase in modulus and a decrease in ultimate properties. Blends prepared by injection moulding had consistently better material properties than those prepared by solution casting.