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ABSTRACT:Residual cellulose fibers from the paper industry have been used as reinforcements in recycled polypropylene (PP) composites. The main obstacle to obtaining good properties with this biocomposite is deficiencies in the compatibility between the nonpolar matrices and the polar cellulose fibers used as reinforcements. The aim of this work was to improve the compatibilization between these cellulose fibers and the PP matrix with four different methods: modification by the addition of polypropylene-maleic anhydride copolymer (PPgMA) during the process of blending, preblending modification of the cellulose with a solution of PPgMA, modification of cellulose by silanes (vinyltrimethoxysilane), and acetylation of cellulose. Blends with all of the differently modified celluloses were prepared with the cellulose content varied up to 40%, and then all of the blends were subjected to thermal (differential scanning calorimetry and thermogravimetric analysis) and thermomechanical (dynamic mechanical thermal analysis) analyses. The results showed that the addition of cellulose fibers improved the thermomechanical behavior of the PP, increasing the value of the log of the dynamic modulus, and affected the thermal and thermooxidative behavior. Moreover, an advantage of the use of a recycled PP containing a small quantity of ethyl vinyl acetate (EVA) as a prime material in the composition was the enhancement of mechanical properties. The use of these methods for the modification of cellulose led to more desirable thermal and thermooxidative stabilities.

A technique for poly-3-hydroxybutyrate (P(3HB)) extraction with safer, non-chlorinated solvents, was developed, aiming to attain high recovery yields and purities. A wide range of solvents was selected from the GlaxoSmithKline guide as sustainable industrial solvents and the solubility of P(3HB) on those solvents calculated using predictive equations from literature. Anisole, * Corresponding author: Tel.: +351 21 8419137; Fax: +351 21 8419062. e-mail address: teresa.cesario@tecnico.ulisboa.pt + Current address: Politecnico di Milano, Dipartimento di Chimica Materiali e Ingegneria Chimica "Giulio Natta". Via Mancinelli, 7 -20131 Milano MI 2 cyclohexanone and phenetole were used as extraction solvents and the relevant process variables (extraction temperature, extraction time and mass of cells/solvent volume ratio) were optimized.Polymer recovery yields of 97% and 93% were obtained with anisole and cyclohexanone, respectively, at 120-130°C using a cell/solvent ratio of 1.5% (w/v). Maximum polymer purities using these experimental conditions were 98% for both solvents. Recovery yields and polymer purity attained with chloroform (reference solvent) were 97 and 98%, respectively. Higher cell/solvent ratios of 6.0 % (w/v) showed slightly lower recovery yields and purities The average molecular weight and the thermal properties of the polymers extracted with the alternative solvents were comparable to those of the polymers obtained by chloroform extraction, showing that the applied conditions did not significantly alter the properties of the extracted P(3HB).

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