Functionalized cork-polymer composites (CPC) by reactive extrusion using suberin and lignin from cork as coupling agents

High density polyethylene (HDPE) and cork powder were compounded in a co-rotating twin-screw
extruder to obtain cork-polymer composites (CPC) with improved properties. Benzoyl peroxide (BPO)
was used as initiator agent, and suberin or lignin isolated from cork enhanced filler-matrix bonding
and promoted mechanical reinforcement with environmental benefits. The novel composites were characterised
in terms of dimensional stability, evolution of morphology, thermal and mechanical properties
and their performance was compared with that of composites containing polyethylene-grafted maleic
anhydride (PE-g-MA) as coupling agent. As expected, composites with coupling agent present higher
mechanical properties, lower water uptake and thickness swelling variation. Suberin acts as plasticizer
with antioxidant benefits, while lignin works as a coupling agent, improving tensile modulus and
maximum strength. Increasing lignin content does not improve the mechanical properties but improves
thermal stability.