Biodegradable polycaprolactone (PCL) was melt-compounded in a Werner & Pffe
iderer twin-screw extruder (ZSK25) together with wood flour (WF) and lignin
with maleic anhydride-grafted polycaprolactone (PCL-g-MA) used as a compat
ibilizer. The grafting of maleic anhydride onto PCL was achieved with react
ive extrusion in the presence of 2,5-dimethyl-2,5-di-(t-butylperoxy)hexan a
s an initiator. The graft copolymers were analyzed with size exclusion chro
matography and titration. As a function of the initiator and maleic anhydri
de addition, the grafted maleic anhydride content varied from 1.4 to 3.1 wt
%. Compounds compatibilized with PCL-g-MA exhibited improved mechanical pr
operties: a compatibilized PCL compound containing 40 wt % WF gave a Young'
s modulus of 2300 MPa with respect to 400 MPa for neat PCL and a 100% incre
ase in yield stress. The content of WF, lignin, and PCL-g-MA was varied sys
tematically to examine stress-strain and impact behavior. Low contents of g
rafted maleic anhydride and PCL-g-MA were required to improve both mechanic
al properties and interfacial adhesion. Biodegradation was investigated. Li
gnin addition was found to retard biodegradation. (C) 2001 John Wiley & Son
s, Inc.