Utilisation of waste wool through fabrication of 3D water-resistant polyvinyl alcohol composite: Impact of micro-sized wool powders

Polyvinyl alcohol (PVA) is a biodegradable polymer having applications in several industries, such as textiles and paper manufacturing. Due to the water solubility, it is also a useful solvent in 3D dispensing to extrude printable solutions at a low temperature. However, its hydrophilicity is a drawback when considering the property of the end-use material if water contact is required. Using the water solubility of PVA as a benefit during 3D dispensing but avoiding the hydrophilicity in the printed material is tricky and unresolved. This study proposes a technique to achieve this phenomenon by taking advantage of the natural hydrophobicity of wool waste by using it as a filler in PVA. There is no previous knowledge on how wool could impact the water resistance characteristic of PVA. Three types of micro-sized wool powder (22.2 to 46.3 μm) were used and their impact on the wool/PVA (25/75) 3D composite properties was investigated. The wool powders reinforced in PVA were able to resist water drops from penetrating the surface for the full length of the experiment (10 min). Water solubility test also showed a greater resistance of the 3D composite samples due to the incorporation of wool powders. Though tensile strength and crystallinity of PVA were decreased by including the wool particles, powders prepared with finer wool showed minimum influence on this reduction. The rheology and thermal properties also suggested better compatibility in the wool/PVA system when finer wool was used. Overall results indicate that wool waste could be effectively utilised to naturally induce water-resistant performance in PVA composite. This finding could be beneficial not only in 3D dispensing, but also in many other areas, such as packaging, where the use of PVA is still limited due to its sensitivity to water.