EFFECT OF MIXING CONDITIONS AND PARTICLE SIZES OF TITANIUM DIOXIDE ON MECHANICAL AND MORPHOLOGICAL PROPERTIES OF POLYPROPYLENE/TITANIUM DIOXIDE COMPOSITES

Abstract

Particles sizes and melt processing of TiO 2 play improtant role in thermoplastic systems. The mechanical and morphological properties of polypropylene (PP)/TiO 2 composites were investigated by preparing the compostie by melt mixing technique in a twin screw extruder. The results show that after adding TiO 2 particles of 42.3 nm (TD42.3) and TiO 2 130 nm (TD130) sizes, the tensile strengths of PP composites decreased with increasing filler content and their stress-at-break values increased after filler addition. The effect of particle size showed that TD130 improved the mechanical properties of PP in relation to TD42.3 of smaller size. TiO 2 of 130 nm size was added to PP using two different mixing conditions. PP composites prepared at screw speed of 50 rpm with 2 mixing cycles showed higher tensile strength, stress-at-break and Young's modulus relative to samples prepared by the same screw speed and 1 mixing cycle. The impact strength of the samples prepared by 2 mixing cycles was higher than those prepared by 1 mixing cycle. Apparently, the 2 mixing cycles improved the impact strength of the composites due to the improved interfacial interaction between TD130 and the matrix and increased energy absorption during the impact process. The higher screw speed led to low mechanical properties. The dispersion of TD130 particles was relatively good when operated at 50 rpm and 2 mixing cycles with less aggregations in PP matrix.