Green plastics: Direct production from grocery wastes to bioplastics and structural characterization by using synchrotron FTIR

Abstract

Lignocellulosic bioplastics were produced using four different green wastes: hemp, parsley stem, pineapple leaves and walnut shell. Two different solutions were used to dissolve the green wastes: trifluoroacetic acid (TFA) and pure water. The changes in their natural structures and the solvent effect during the regeneration in biofilm formation were investigated by using Synchrotron FTIR Microspectroscopy (SR-mu FTIR). The presence of cellulose, hemicellulose and lignin components in the water-based biofilms was confirmed. After dissolving in TFA, the spectra demonstrated some additional bands especially in the hemicellulose region. This is due to the hydrolysis of ester bonds and conversion to carboxylic acids. Principal component analysis showed grouping due to different solvents and polymer addition. Hemp-PVA (Polyvinyl Alcohol) composite biofilms were obtained by adding polyvinyl alcohol to the hemp solution to give extra strength to the hemp biofilms. It has been shown that water-based hemp-PVA biofilms do not cause any significant spectral changes, comparing with pure hemp and PVA spectra. However, after dissolving in TFA, unlike water-based biofilms, it appears that TFA molecules are retained by PVA through hydrogen bonds of TFA's carboxylic acid and hydroxyl groups and distinct spectral regions belong to TFA bands are clearly identified.