Plasticizers, antioxidants and reinforcement fillers from hazelnut skin and cocoa by-products: Extraction and use in PLA and PP

The selective and serial extraction of natural additives from hazelnut skin and cocoa by-products has been carried out for giving a high-added value to poly(lactic acid) and poly(propylene) (PLA and PP). Through the proposed process, three fractions mainly containing plasticizers, antioxidants and reinforcement fillers have been consecutively separated. These have been subsequently characterized from the chemical and thermal point of view (assessed by infrared spectroscopy, differential scanning calorimetry and thermogravimetry), and then melt-blended with PLA or PP. Thus, the first fraction has been used for plasticizing PLA, the second one for UV-protecting PP, and the last one for reinforcing both matrices. The collected results by dynamic mechanical thermal analysis have shown that the first fraction partially plasticized PLA. The second fraction turned out to be consisting of UV absorbers as well as thermal stabilizers that increased PP oxidation induction time (of 30%) in the case of hazelnut skin, and PP thermal stability (of 26 °C in air) in the case of cocoa, respectively. The last fraction was capable to increase the storage modulus of PLA and PP up to 30 and 20% (with 30 wt.-% of filler content), respectively.