Enhancing Gas Barrier Properties of Poly (Ethylene-Terephthalate) via 2D Boron Nitride Nanosheets Incorporation through Solution Processing

Abstract

Beverage industry has been facing gas barrier problems ever since the PET polymer became their favorite packaging material for carbonated drinks. Objective of the conducted research was focused on enhancing the inherent gas barrier abilities of the said polymer. Present research finds its unprecedentedness in the discovery of a facile and swift method for PET films fabrication i.e., Temperature induced phase separation (TIPS) using NMP as the common solvent. Nanosheets of Hexagonal Boron Nitride (BNNs) a polymorph of Boron Nitride and often referred to as white Graphite owing to their similarities in molecular structure was used as filler for the aforementioned objective. PET/h-BN nanocomposite films were synthesized using solution processing and were characterized accordingly. Films were tested for their permeation abilities and a remarkable reduction in CO2 and O2 permeation was observed, additionally films were completely non-selective and permeation reduction for both CO2 and O2 were similar. Experimental results were compared with theoretical models and it was found that Cussler model closely fits our experimental results. 96% reduction in permeation was achieved using only .010wt% BNNs filler, however, permeation tests were conducted for 8hrs only. A dense SEM imagery of nanocomposites further aided the permeation results and it was observed that with increasing filler loading,pores and their distribution decreased, and a fully dense morphology was obtained for 0.050wt% nanocomposite film. An increase in tensile strength was also observed, signifying the reinforcement capabilities of the filler used, however, a decrease in the young modulus of nanocomposites was seen due to enhanced strain induced by filler.Through FTIRand XRD it was confirmed that filler and polymer interaction was strictly physical and not chemical, in FTIR no formation of new bonds was observed, and no peak shift was observed in XRD.Based on lab results prototype PET bottle was manufactured. A hybrid solution and melt processing setup was employed for nanocomposite preform fabrication, BNNS suspension (20mg/mL) was added at a rate to synthesize a 0.003wt% preform samples. After successful testing according to PCI (Pepsi Cola International) standards, preforms were blown into bottles. ASC (Accelerated Stress Cracking) was performed on 4 sample bottles which were a success and afterwards CO2 retention test was performed for 2months using 48 samples. No improvement as compared to the pristine bottle in CO2 retention was observed due to extremely low volume fraction.