Preparation and Properties of Nano-Silica Filled Self-Reinforced Polypropylene
To improve the properties of polypropylene (PP), a new route that combines nanoparticles filling with self-reinforced technique was applied in this work. That is, nano-silica particles were firstly modified by graft polymerization to increase interfacial interaction between nanoparticles and matrix. Then the grafted nanoparticles were melt-compounded with PP producing composites sheets, and the sheets were stretched under a temperature slight lower than the melt point of PP at a constant velocity. Finally, the stretched sheets were film-stacked with random PP copolymer by a special designed mold and were hot pressd at different processing temperature (T=150-175°C) and holding pressure (2.0-5.0MPa) under constant holding time of 5min. The resultant self-reinforced nanocomposite are much stronger and stiffer than the unfilled polymer as characterized by mechanical test. The results show that the optimum processing conditions for hot consolidation are 160°C and 2.5MPa. Addition of nanoparticles increases crystallinity of PP, and induces the formation of craze and cause much more surrounding matrix polymer to involve in large-scale plastic deformation, which might ensure an overall improvement of mechanical properties.
Prof. Alan Kin Tak Lau, Dr. J. Lu, Vijay K. Varadan, Fu-Kuo Chang, J.P. Tu and Pou Man Lam
W. H. Ruan et al., "Preparation and Properties of Nano-Silica Filled Self-Reinforced Polypropylene", Advanced Materials Research, Vols. 47-50, pp. 318-321, 2008