Thermoplastic starch/wood composites: interfacial interactions and functional properties

Péter Müller; Károly Renner; János Móczó; Erika Fekete; Béla Pukánszky

doi:10.1016/j.carbpol.2013.10.083

Thermoplastic starch/wood composites: interfacial interactions and functional properties

Carbohydr Polym. 2014 Feb 15:102:821-9. doi: 10.1016/j.carbpol.2013.10.083. Epub 2013 Nov 5.

Authors

Péter Müller¹, Károly Renner², János Móczó³, Erika Fekete², Béla Pukánszky²

Affiliations

¹ Laboratory of Plastics and Rubber Technology, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, P.O. Box 91, H-1521 Budapest, Hungary.
² Laboratory of Plastics and Rubber Technology, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, P.O. Box 91, H-1521 Budapest, Hungary; Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary.
³ Laboratory of Plastics and Rubber Technology, Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, P.O. Box 91, H-1521 Budapest, Hungary; Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary. Electronic address: jmoczo@mail.bme.hu.

PMID: 24507352
DOI: 10.1016/j.carbpol.2013.10.083

Abstract

Thermoplastic starch (TPS)/wood composites were prepared from starch plasticized with 36 wt% glycerol. The components were homogenized by dry-blending, extruded and injection molded to tensile bars. Tensile properties, structure, deformation, water adsorption and shrinkage were determined as a function of wood content, which changed between 0 and 40 vol% in 7 steps. The modification of TPS with wood particles improves several properties considerably. Stiffness and strength increases, and the effect is stronger for fibers with larger aspect ratio. Wood fibers reinforce TPS considerably due to poor matrix properties and strong interfacial interactions, the latter resulting in the decreased mobility of starch molecules and in the fracture of large wood particles during deformation. Strong interfacial adhesion leads to smaller water absorption than predicted from additivity, but water uptake remains relatively large even in the presence of wood particles. The shrinkage of injection molded TPS parts is very large, around 10%, and dimensional changes occur on a very long timescale of several hundred hours. Shrinkage decreases to a low level already at 15-20 vol% wood content rendering the composites good dimensional stability.

Keywords: Interfacial adhesion; Particle characteristics; Shrinkage; TPS/wood composites; Water absorption.