Thermophysical properties and biodegradation behavior of green composites made from polyhydroxybutyrate and potato peel waste fermentation residue

Abstract

Polyhydroxybutyrate (PHB) is one of most biodegradable bioplastic, but its high cost and brittleness limits its applications. In this study, low-value waste byproduct from a fermentation process of potato peel waste, called the potato peel waste fermentation residue (PPW-FR) fibers, were recovered and compounded with PHB to form biocomposites of tunable properties. The mechanical and thermal properties of pure PHB and biocomposites were investigated by thermogravimetric analysis (TGA), tensile and flexural tests, and dynamic mechanical analysis (DMA). Fiber content was shown to have a significant effect on the surface hydrophobicity and water absorption of the biocomposites. All absolute and specific mechanical properties and water absorption (by normalizing the measured parameters against the measured density (ρ)) were investigated. The biodegradability of PHB and biocomposites were evaluated in soil over 8 months. The surface morphology, chemistry and melting/crystallization behavior were monitored and characterized by microscopy, FTIR spectroscopy and differential scanning calorimetry (DSC), respectively. The biocomposites showed poor mechanical properties but extremely higher biodegradation rate as compared with pure PHB, especially when the fiber content was >15%. The degradation rate increased with increasing fiber content and positively correlated to the water absorption showing more cracks and deeper pits. FTIR spectroscopic analysis showed that the plant polysaccharides and PHB within the biocomposite were degraded with exposure time. At 50% fiber content the biocomposites were completely degraded by 8 months. These PPW-FR based biocomposites offer new opportunities for fast degrading biomaterials in agricultural and horticultural applications.