Effect of Lauric Acid on the Thermal and Mechanical Properties of Polyhydroxybutyrate (PHB)/Starch Composite Biofilms

Joemer A Adorna,Ruey-An Doong,Camelle Kaye A Aleman,Jey-R S Ventura,Kim Marie D Sisican,Jamela N Pangasinan,Van Dien Dang,Ian Lorenzo E Gonzaga,Ruby Lynn G Ventura

doi:10.1155/2020/7947019

Abstract

Polyhydroxybutyrate (PHB) is a biopolymer of natural origin, one of the suitable alternatives for synthetic plastics. However, pure PHB has a high production cost, is relatively brittle, and has poor processability, hence its limited application. Combining PHB with biomass fillers and plasticizers can significantly improve the properties of the polymer, leading to its commercial usage. In this study, PHB was incorporated with starch (S) as a cheap biomass filler and lauric acid (LA) as a potential plasticizer. The PHB/S/LA composites were prepared using a modified solvent casting method with the incremental addition of LA. The PHB/S ratio was maintained at a ratio of 80/20 (w/w). Physicochemical characterization via EDS, XRD, and FTIR proved that the composite components have blended through nucleation and plasticization processes. The morphology of the PHB/S blends was found to be a heterogeneous matrix, with decreased inhomogeneity upon the addition of LA in the composite. Thermal characterization done by TGA and DSC showed that the thermal properties of PHB/S films improved with the addition of LA. Mechanical tests (UTM) proved that the elastic strain of the films also increased with the addition of LA, although the tensile strength decreased slightly compared to pure PHB/S. Overall, the results of this study provide baseline information on the improvement of PHB-based bioplastics.

Highlights

The management of plastic wastes is a prevailing concern worldwide
The characteristic peaks in the Fourier Transform Infrared Spectroscopy (FTIR) spectra showed that the addition of lauric acid (LA) as a plasticizer promoted the formation of hydrogen bonds between the PHB, starch, and LA components
This can be observed in the Scanning Electron Microscopy (SEM) images where a decrease in the inhomogeneity of the samples can be seen, as well as a decrease in the surface roughness as the amount of LA added was increased

Summary

Introduction

The management of plastic wastes is a prevailing concern worldwide. Commercially used synthetic plastics degrade very slowly when disposed and have a relatively unknown decomposition rate [1]. PHB is still in the developmental stage due to its relatively high production cost [21], poor mechanical properties due to brittleness [22], and poor formability during processing [23] Addressing these problems can be carried chemically by blending with compounds that can improve PHB properties, forming a composite. LA, or dodecanoic acid, is a saturated fatty acid ester with hydroxyl moieties from its carboxylic acid groups that can form bonds with other polymers In this bioplastic composite, LA promotes hydrogen bond formation to reduce the intramolecular forces between PHB and starch molecules, effectively decreasing the glass temperature of the material [27]. 480/120/10 480/120/20 use of LA as a plasticizer in PHB/S has not been explored by existing literature

Materials and Methods

Characterization of the Bioplastic Composites

Effect of Lauric Acid Addition on the Morphology of the Bioplastic Composite

Conclusions