Synergistic effect of sisal fiber reinforcement and boric acid cross-linking on the water absorption of PVA

Plastics play a crucial role in modern human life. While plastics have versatile applications, they are mainly serving for packing purposes. Many of the plastics used for packaging applications are petrochemical derivatives. Even though they fulfill most of the criteria as good packing materials, they are not biodegradable. This causes serious environmental pollution. As a result, biodegradable plastics have emerged as an alternative to conventional plastics. Polyvinyl alcohol (PVA) is one of the biodegradable polymers that have potential applications for various purposes because of its availability, non-toxicity, and biodegradability. However, high water absorption hinders its application. To overcome this drawback, locally extracted natural biodegradable sisal fiber was used as reinforcement in this report. The sisal fiber was extracted from the sisal plant found in the Ethiopian highlands. After the extraction of the fiber, 10%NaOH was used for treatment to enhance interfacial adhesion between the sisal fiber and the matrix. Sisal fiber reinforced composites with weight percentage of 0%, 5%, 10%, 20%, and 25% sisal fiber with respect to PVA were prepared using the solution casting technique. In addition to this, a cross-linker (boric acid) was used to crosslink PVA chains. The water absorption and degradation of the samples were studied. The result showed that the water absorption PVA was reduced from 170% for pure PVA to 32% for the synergy of 25% w/w reinforcement and 5.68% w/w of cross-linker concentration. The biodegradability study showed that all the samples were degradable. However, both reinforcement and cross-linkers did not show a significant change in the degradation of PVA. The synergy between boric acid cross-linking and natural sisal fiber reinforcement might be responsible for the reduction of water absorption.