Effect of lignocellulosic filler type and content on the behavior of polycaprolactone based eco-composites for packaging applications

This study was based on the influence of lignocellulosic fillers and content on the morphology, crystallization behavior and thermal, mechanical and barrier properties of fully biodegradable eco-composites based on polycaprolactone for packaging applications. The biodegradation in soil as a function of time was also analyzed. Composites with 5 and 15 wt% of cotton (CO); cellulose (CE) and hydrolyzed-cellulose (HCE) were prepared by melt-mixing. It was determined that, whereas lower content of CO and CE produced a decrease on the crystallinity of the matrix, HCE did not affect it. Increasing the filler content, the crystallinity degree of the matrix decreased at less extent, which was independent on the filler type. A clear reduction on the theoretical melting point, attributed to heterogeneous nucleation sites, took place for the lower content of CO and CE. Induction and half-crystallization times diminished when fillers were incorporated but the effect was less notorious at higher filler contents. All fillers enhanced the Young's modulus of the matrix but the optimal mechanical properties were not obtained with HCE, as was expected, but with CE. After analyzing the main parameters that affect the mechanical properties of the composite; such as morphology, hydrophilicity, crystallinity, mechanical properties and thermal stability of the fillers themselves, interface interaction, filler dispersion and thermal aspects of the composites, we concluded that the parameters responsible for such behavior were the larger aspect ratio, better dispersion and enhanced interface interaction of the CE filler. These parameters also affected the barrier properties and the process of biodegradation in soil of the composites.