Biodegradable polyvinyl alcohol nanocomposites made from rice straw fibrils: Mechanical and thermal properties

Rice straw (Oryza sativa L.) pulp was treated using a high-pressure homogenizer to make fibril and fibril aggregates. The rice straw fibril and fibril aggregate material was used as reinforcement in a rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposite that was prepared by casting film under air-dry and freezing-thawing conditions, respectively. The material's tensile strength was increased by adding the rice straw fibril and fibril aggregates material into the polyvinyl alcohol matrix. The mechanical properties were higher in rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites cast under freezing-thawing conditions than those casting under air-drying conditions. Dynamic thermomechanical analysis testing showed that the storage modulus (E') of the rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites was higher than that of polyvinyl alcohol alone when 2% rice straw fibril and fibril aggregates material was added into the polyvinyl alcohol matrix. The glass transition temperature (T-g) rose in neat polyvinyl alcohol and rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites cast under freezing-thawing conditions. Differential scanning calorimetry analysis revealed that the melting temperature (T-m), melting enthalpy (Delta H-C) and crystallinity (X-C) in rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites increased to higher values compared to those in neat polyvinyl alcohol when cast under the two conditions. Thermogravimetric analysis showed that the polymer matrixes were stabilized against thermal decomposition by the addition of rice straw fibril and fibril aggregates. The shift of the -OH stretching peak of rice straw fibril and fibril aggregates/polyvinyl alcohol nanocomposites in Fourier transform infrared spectroscopy spectra indicated a good compatibility between rice straw fibril and fibril aggregates and the polyvinyl alcohol matrix in nanocomposites.