Abstract:
Poly (vinyl chloride) (PVC) is widely used in many fields due to its excellent non-flammable, corrosion and wear resistant properties. However, its thermal and optical stabilities are very poor which dramatically limit its outdoor application. The most effective way to improve PVC optical stability is the addition of light stabilizers. However, most of the currently used light stabilizers are poorly transparent which thereby restricts their use. In addition, most of the light stabilizers are small molecules, which are easily volatilized or migrated during their applications. In the present study, a novel organic/inorganic composite UV absorber was prepared by the combination of nano silica (SiO
2) with a panchromatic UV absorber polybenzimidazole (PBI), which was used to improve the UV resistance of PVC. In order to enhance the compatibility between nano SiO
2 and PBI, silane coupling agent
γ-aminopropyltriethoxysilane was used to modify nano SiO
2 (MSiO
2), after which PBI was coated onto the resultant MSiO
2 (PBI@MSiO
2). The PVC/PBI@MSiO
2 composites were subsequently prepared by melt blending. The UV absorption, mechanical properties, morphology and thermal stability of the obtained composites were investigated and compared. The SEM observation reveals that PBI@MSiO
2 particles disperses homogenously in the PVC matrix, and the PVC/PBI@MSiO
2 composites exhibit excellent thermal stability, UV-aging resistance and good mechanical properties. In the presence of 6% (mass fraction) PBI@MSiO
2, the initial thermal decomposition temperature of the composite is significantly increased by about 34℃ compared with that of pure PVC. Additionally, the UV-absorbance at 375 nm can reach 99%, and the yield strength is 63.3 MPa.