Development of Okara/PVA-based hydrophobic composite aerogel

Abstract

Okara or Solid Curb Residue (SCR) is a soybean oil or tofu processing waste. It was by-produced from tofu processing. As tofu consumption increases annually, the amount of Okara has correspondingly become abundant at an alarming rate. If left untreated, it can serve to detriment the environment. Therefore, an environmental-friendly method to recycle Okara material is crucial. In this project, Okara was mixed with Poly (Vinyl Alcohol) (PVA) as main ingredients for organic aerogel. Water was used as a solvent to dissolve PVA/Okara blend to fulfill environmental-friendly requirements. The solution was then freeze-dried to form a highly porous material known as aerogel. Furthermore, Methyl-tri-methoxy-silane (MTMS) was also coated onto the aerogel for enabling a hydrophobic surface. The variables which were used for this experiment are chemical composition and freezing temperature. Its effect on thermal conductivity, water contact angle, and compressive Young’s modulus will be discussed. As a result, a contact angle up to 150o was obtained. Interestingly, hydrophobic layer was formed not merely on the outer surface but also inside the bulk structure. The compressive Young’s modulus which indicates the stiffness of material was achieved as high as 929 KPa. Furthermore, higher PVA may serve to enhance the bending toughness of aerogel. Lastly, the thermal conductivity was found to be in the range of 0.034-0.037 W/m.K. With such properties, PVA/Okara aerogel coated with MTMS can be used in thermal insulation.