Development of Biodegradable Poly(Lactic Acid)/Lignin Treated Alkyl Ketene Dimer Properties for Packaging Applications

Abstract

In this work, PLA/lignin treated AKD composites have been developed for packaging applications. The composites were prepared by a thermal processing. The lignin was prepared from the black liquor which is the waste of paper industry by extracting acetic acid and filtering. The resulting lignin has a structure of syringlyl unit (S) and guaiacyl unit (G) because use eucalyptus is a shaft wood use in the paper industry. The lignin contents the PLA matrix were 0.1, 0.3 and 0.5 phr and the improvement of lignin properties by using AKD in ratio 10:1 of lignin and AKD is caused by the reaction between the AKD and the OH group of lignin to from bond called β-ketone ester bond. The treatment of lignin with AKD showed the increase of hydrophobicity and good dispersion in PLA. SEM results of PLA/lignin and PLA/lignin treated AKD showed that when the lignin content increased, the surface roughness was observed except 0.5 phr of PLA/lignin treated AKD composites. The lignin addition decreased the tensile strength of PLA/lignin composites, whereas the PLA/lignin treated AKD at 0.5 phr had similar mechanical properties with neat PLA. Fourier-transform infrared (FTIR) spectroscopy found to be non-crystalline, consistent with differential scanning calorimeter (DSC) results indicated that the enthalpy of crystallization was equal to the enthalpy of melting. Moreover, X-ray diffraction (XRD) result did not appear the peaks. UV-vis analysis indicated the light transmission was protected with increasing lignin contents. Water contact angle test (WCA) results indicated that lignin had a decreasing effect on the waterproofing of the material, but the lignin treated with AKD has a water contact angle similar to that neat PLA.