Effect of lignocellulose nanofibril and polymeric methylene diphenyl diisocyanate addition on plasticized lignin/polycaprolactone composites

Abstract

Kraft lignin was plasticized with ε-caprolactone via twin-screw extrusion at 150 °C, and its glass transition temperature was decreased from 155 to 96 °C. The lignin or plasticized lignin (p-lignin)/polycaprolactone (PCL) composites with and without lignocellulose nanofibril (LCNF) or polymeric methylene diphenyl diisocyanate (pMDI) were prepared, and their properties were compared. The p-lignin was better dispersed in the PCL than neat lignin, and the p-lignin/PCL composites exhibited a homogenous fractured surface despite the addition of LCNF. An increase in the lignin or p-lignin content decreased the tensile strength and elastic moduli but increased the melt flow index (MFI). With the addition of pMDI and LCNF, the tensile properties and MFI improved and declined, respectively. The strength improvement by pMDI and LCNF was better in the p-lignin/PCL composite than in the lignin/PCL composite.