Preparation and Characterization of PVA/Halloysite Composite Films

In this study, the characteristics of halloysite subjected to silane coupling treatment as a reinforcing agent are investigated. Halloysite is one of the natural substances that is currently recognized as having a nanotubular structure. Halloysite nanotubes are 50 nm in diameter, 0.5-1 μm in length and 15 nm of inner diameter. Polyvinyl alcohol (PVA) which is a synthetic polymer with characteristics such as biodegradability and solubility in water was used as the matrix. The halloysite/PVA films were characterized by tensile test, scanning electron microscopy (SEM), and optical transmittance. The tensile strength of PVA/untreated halloysite film was decreased, but Young’s modulus was increased compared with neat PVA film. In addition, silane coupling treatment was performed on halloysite to improve the interfacial adhesion between PVA and halloysite. PVA/silane-treated-halloysite film had improved elongation compared with PVA/untreated-halloysite films. SEM images revealed the fracture mode and the distribution of halloysite inside the composites. When the halloysite content was low, a fracture surface formed by dimples originating at the halloysite sites was observed. On the other hand, when the halloysite content was high, brittle fracture occurred. In the case of high halloysite content, agglomeration of nanotubes was observed. The optical transmittances of PVA/silane-treated-halloysite films with 8 wt% halloysite were over 80%.