Effect of particle size and a processing aid on the crystallization and melting behavior of iPP/red pine wood flour composites

The growth of wood–polymer composites (WPCs) as sustainable materials is generating a steadily increasing impact in various industrial and consumer sectors. A detailed analysis of the thermal stability and crystallization and melting behavior of isotactic polypropylene (iPP) with red pine wood flour, under dynamic and isothermal conditions in the presence of a processing aid with varying filler particle sizes, is presented. Only small variations were found in the thermal stability. The wood particles have a heterogeneous nucleating effect on iPP crystallization that reduces the free energy of nucleation and increases the overall crystallization rate to a greater extent in composites with smaller particle size prepared without the processing aid. With the processing aid the formation of a fraction of β-iPP crystals was found, independent of wood particle size. Competition between heterogeneous nucleation and auto nucleation processes was found.