Characterization and degradation characteristics of poly(ε-caprolactone)-based composites reinforced with almond skin residues

Poly(ε-caprolactone), PCL, degradation by microorganisms is a very interesting feature for its potential use in massive applications, such as food packaging. Blends of PCL with natural fibres, such as those from agricultural and food processing wastes, have proved effective by permitting a substantial reduction of the material costs, but also playing a role as reinforcement in mechanical properties. This study is focused on the evaluation of morphological, mechanical, thermal, barrier properties and degradation in composting environment of new bio-composites based on PCL and almond skin (AS) filler at different contents (0, 10, 20 and 30 wt%). Results showed a clear improvement in mechanical properties, corresponding to a gain in elastic modulus of 17% at 10 wt% particle loading. Lower melting and crystallization enthalpies and higher crystallinity values were obtained for bio-composites compared with neat PCL. Some decrease in thermal stability and increase in oxygen and water vapour barrier properties were also observed for composites with increasing filler content. PCL/AS composites showed higher biodegradability than pure PCL, which can be explained in terms of the depressed crystallization enthalpy of the polymer matrix and improved hydrophilicity. PCL-based composites reinforced with almond skin filler at 10 wt% loading have shown as promising environmentally-friendly materials for food packaging showing a high disintegration rate, increasing the added-value potential of agricultural wastes and reducing the packaging cost. Spanish Ministry of Economy and Competitiveness (MAT-2011-28468-C02-01). Arantzazu Valdés acknowledges Conselleria de Educación (Spain) for ACIF/2010/172 Predoctoral Research Training Grant.