Study On Interfacial Modification And Properties Of Polylactic Acid/Glass Fiber Composites

Polylactic acid (PLA) is a biodegradable polyester that has excellent tensile strength, but its applications are limited by its high cost and inherent brittleness. In this paper, the siloxane coupling agent (KH550) and isocyanate-terminated polylactic acid oligomers were used as the interfacial modifiers. The composites [(PLA/GF)s] of PLA with glass fiber(GF) were then prepared, their mechanical and crystalline performances were investigated systematically.The GF surface was modified by KH550via both dry and wet methods, respectively. The effect of the modified GF concentration on the mechanical properties of composites [(PLA/GF)]s was explored. The results showed that the composite (mPLA:mGF=7:3) with wet-modified GF containing1.2%of KH550possessed the highest mechanical properties. Its impact, bending and tensile strength, was20.76kJ/m2,120.74MPa and78.32MPa, respectively.The isocyanate-terminated polylactic acid oligomers (OCN-PLA-NCO)s with different molar ratio of NCO and OH groups were synthesized from the pre-prepared polylactic acid oligomer (HO-PLA-OH) and diphenyl methane diisocyanate (MDI) as an end-capping reagent. The OCN-PLA-NCO-modified GF was prepared and mixed PLA by melt blending using (OCN-PLA-NCO)s as interfacial compatibilizers. The composites obtained were characterized by means of FE-SEM, mechanical property measurement, FT-IR, GPC and DSC, and the enhancing and toughening mechanisms were illustrated. The impact, bending and tensile strength of the composite (nNCO:nOH=3) reached to25.30kJ/m2,133.42MPa and91.83MPa, respectively, under optimum conditions.DSC and X(t)-t curves were obtained by DSC measurement, respectively. The isothermal crystallization behavior was described for PLA composites with different glass fiber content by modification methods. The crystallization rate of PLA increased with the increases of glass fiber content and heating rate. PLA’s crystallinity increased because of the incorporation of glass fiber. The composite with1%of GF had the highest crystallinity. The non-isothermal crystallization curves of (PLA/GF)s obtained using Jeziorny and Mo equations showed good linear relationships.