Non-isothermal cold crystallization, melting, and moisture barrier properties of silver-loaded kaolinite filled poly(lactic acid) films

Abstract

Silver-loaded kaolinite (AgKaol), an antibacterial agent along with a barrier enhancer, was incorporated into poly(lactic acid) (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and tetrabutyltitanate (TBT) blend resulting in the formation of polymer composite. The introduction of AgKaol could improve the barrier and the crystallization properties of PLA/PBAT/TBT blend. The barrier property of composite polymer was investigated by water vapor permeability (WVP) to study the influence of AgKaol content (0.0, 1.0, 2.0, 3.0 and 4.0 phr) in polymer matrix. The values of WVP decreased with increasing AgKaol content and amount of crystallite in PLA composite. The cold crystallization property of this PLA/PBAT/TBT composited with 0.0, 2.0 and 4.0 phr of AgKaol was completely investigated by the non-isothermal differential scanning calorimetry (DSC) technique. From the non-isothermal DSC analysis, the crystallization rates (dX(T)/dt) of PLA composite increased with increasing of the heating rate and AgKaol content. The Avrami, Ozawa and Liu models were applied to describe the non-isothermal crystallization kinetics and determine crystallization parameters for PLA/PBAT/TBT/AgKaol composite. The crystallization mechanism of PLA/PBAT/TBT/AgKaol composite was proposed thorough the nucleation and three dimension growths. The activation energies of crystallization (Ea) were determined by the Kissinger-Akahira-Sunose (KAS) isoconversional method. The determined Ea for the crystallizations of PLA/PBAT/TBT with 4.0 phr of AgKaol were lower than 2.0 and 0.0 phr, respectively. Polarized optical microscopy (POM) showed more and larger spherulites with a nanocrystal structure of PLA/PBAT/TBT/AgKaol composite than neat PLA. The nucleating effect of AgKaol on PLA/PBAT/TBT blend might be useful for preparation of PLA composite as a gas barrier protection material in the future. Corresponding to the melt flow index (MFI) results, PLA composites could produce as a film with promising antibacterial packaging due to silver nanoparticles in AgKaol.