Physical, dielectric and biodegradation studies of PVC/silica nanocomposites based on traditional and environmentally friendly plasticizers

PVC/nano-SiO₂ nanocomposites based on a bio-based plasticiser (castor oil) and dioctyl phthalate (DOP) were prepared using solution casting method. Castor oil (CO) was used as a complete alternate plasticiser of dioctyl phthalate (DOP) in PVC. The prepared films were characterised by different techniques. In addition, the biodegradation of the films was tested by soil burial, hydrolytic and enzymatic degradation tests. The presence of CO facilitates the dispersion of SiO₂ in PVC matrix and enhances the thermal stability. Besides, it has a significant contribution in reduction of HCl emission during the decomposition of PVC nanocomposites. FTIR spectra of the nanocomposite films showed a considerable change in the intensity of the characteristic peaks of the functional group by addition of SiO₂ and after proceeding hydrolytic and enzymatic degradation as well. Additionally, the presence of SiO₂ plays a dominant role in improving the migration stability and volatility of the plasticiser. Further, the permittivity (ε'), loss factor (tanδ), electric modulus (M') and conductivity (σ) of PVC were also investigated. It is found that the values of ε' and σ of PVC/CO/SiO₂ nanocomposites are higher compared to those of PVC/DOP/SiO₂ nanocomposites. Moreover, electric modulus (M’) demonstrates two dielectric relaxation processes. The conductivity values revealed that PVC nanocomposites can perform as antistatic materials. This makes them a good choice for electronic components packaging. (paper)