Investigation of the graft length impact on the interfacial toughness in a cellulose/poly(ε-caprolactone) bilayer laminate

Interfacial adhesion between immiscible cellulose-polymer interfaces is a crucial property for fibrous biocomposites. To tailor the interfacial adhesion, the grafting of polymers from cellulose films was studied using ring-opening polymerization of ε-caprolactone. The poly(ε-caprolactone) (PCL) grafted cellulose was analyzed with FTIR, AFM and water CA measurements. The graft length was varied by the addition of a free initiator, enabling tailoring of the interfacial toughness. Films of microfibrillated cellulose were grafted with PCL and hot-pressed together with a PCL film to form a bilayer laminate. Interfacial peeling toughness correlates very strongly with PCL degree of polymerization (DP). PCL grafts form physical entanglements in the PCL matrix and promote significant plastic deformation in the PCL bulk, thus increasing interfacial peeling energy.