Effects of Plasticizers on Structures of Chemical Functional Groups, Morphologies, Water Vapor Permeability, and Thermal Properties of HPMC/BW Biopolymer Films

Abstract

Food preservation is one of the fields that many researchers are interested in, especially in the epidemic period like COVID-19 today. The better food or agricultural products are preserved for a long time, the more it ensures social stability for state management related to food security for people. This paper introduces one kind of biopolymer films with investigation on effect of plasticizers to its characteristics. In order to produce biopolymers, the most popular types of plasticizers were polyols. On that basis, this research used Glycerol (G), Propylene Glycol (PG), and Polyethylene Glycol 400 (PEG400) with a content of 1% to 3% to study their impact on Hydroxypropyl Methylcellulose/Beeswax (HPMC/BW) biopolymer films. Fourier transform infrared (FTIR) spectra assess changes in composite films structures of HPMC/BW when combined with different plasticizers, the amplitudes of these major vibrations were different compared among the HPMC and BW spectra due to the interaction among the components in the polymer networks and the formation of intramolecular bonds. Cutting surface observations of scanning electron microscopy images (SEM) show the degree of uniform dispersion, the appearance of defects in the membrane structure, influence on the change of water vapor permeability (WVP) values through the membrane from 68.2 to 28.6 g.mm/day.m².kPa. Differential scanning calorimetric graphs (DSC) analysis showed that the glass transition temperature (Tg) of the composite film created was within the Tg range of HPMC and BW, it indicated the relative match between the ratio of crystal and amorphous in the film formula, formed a stable composite emulsion and better dispersion. Plasticizers have been used to improve flexibility and processability of polymers, changing in plasticizers types and concentration significantly affect the film properties.