Poly(lactic acid) /kenaf fiber composites: effect of microfibrillated cellulose on interface-sensitive properties

摘要

Ecologically friendly composites consist of a biodegradable matrix and natural fibers (such as cotton, sisal,udkenaf, bamboo, etc.), which have been successfully used for reinforcing of different polymer matrices. Quiteudrecently, poly(lactic acid) (PLA) was used as a matrix for biodegradable eco-composites.udNatural fibers (NFs) offer both cost savings and a reduction in density when compared to glass fibers.udThough the strength of NFs is not as great as glass, the specific properties are comparable.udOne of the most undesirable properties of NFs is their dimensional instability due to the swelling caused byudmoisture absorption. However, a strong fiber/matrix interfacial adhesion can help to diminish the waterudpenetration, avoiding the worsening of mechanical performances of composites exposed to humidudconditions.udAccording to the literature, kenaf fibers exhibit higher strength values in terms of tensile and flexuraludproperties, as compared to other NFs, when reinforcing PLA.udThe aim of this work was to study the mechanical behavior of PLLA-based composites reinforced with kenafudfibers, and the influence of micro-fibrillated cellulose (MFC) on overall composite properties.udComposites of PLLA and kenaf fibers were prepared by melt mixing the components in a Rheocordudapparatus, and consequent compression molding at 180 oC for 3 min at 50 MPa. The amount of MFC in theudmixture was varied from 5-15 %, while the content of PLLA was kept constant, 50%.udThe results have shown that the addition of MFC influence the interface sensitive properties of PLLA/kenafudfiber composites, increasing the interfacial energy release rate for about 20% at MFC loading of 10%.udFlexural strength and modulus of the composites were also improved by the presence of MFC, reachingudvalues of 57 MPa and 5.9 GPa, corresondingly.