Non-isothermal crystallization kinetics of poly(lactic acid)/kenaf fiber composites

Abstract

The non-isothermal crystallization behavior of poly(lactic acid) (PLA)/kenaf fiber (KF) composites was investigated using differential scanning calorimetry (DSC) at different cooling rates (1, 2.5, 5, and 7.5 °C/min) with various KF sizes from 25 to 300 µm. The modified Avrami, Ozawa, and Mo methods were applied to study the non-isothermal crystallization kinetics of neat PLA and PLA/KF composites. It was found that KF size of 80-106 µm acts as nucleating agent during non-isothermal crystallization of PLA/KF composites since the values of half-time of crystallization (t1/2) of PLA80 were the fastest as compared to neat PLA and other PLA/KF composites at a given cooling rate. The AvramiJeziorny crystallization rate constant (Zc ) increased upon increased of cooling rates for both neat PLA and PLA/KF composites indicating the improvement in crystallization. However, only the Zc values for PLA80 were faster than PLA/ KF composites but slower than neat PLA at a certain cooling rate. The Ozawa method did not apply satisfactorily for both neat PLA and PLA/KF composites. Meanwhile, the results showed that the Mo method can be successfully applied by providing a good fitting for all cooling rates of neat PLA and PLA/KF composites. The Kissinger activation energy (ΔE) of PLA80 recorded the lowest value indicating the size of KF between 80-106 µm accelerated the noncrystallization of PLA.