Effect of the mixing sequence on the morphology and properties of a polypropylene/polydimethylsiloxane/nano-SiO₂ ternary composite

• Published in: Journal of applied polymer science 2008-11, Vol.110 (3), p.1457-1468
• Main Authors: Prakashan, K, Gupta, A.K, Maiti, S.N
• Format: Article
• Language: English
• Subjects: Applied sciences; Composites; crystallization; dispersions; Exact sciences and technology; Forms of application and semi-finished materials; mechanical properties; nanocomposites; poly(propylene) (PP); Polymer industry, paints, wood; Technology of polymers
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.28544

Ternary composites of polypropylene (PP), polydimethylsiloxane (PDMS) elastomer, and nano-SiO₂, prepared with three different mixing sequences, were studied for dispersion morphology and its effect on the crystallization of PP and the mechanical properties. The mixing sequence produced a significant effect on the dispersion morphology and, thereby, on the mechanical properties of the composites. A two-step mixing sequence, in which nano-SiO₂ was added in the second step to the PP/PDMS binary system, produced a significant encapsulation of nano-SiO₂ by PDMS, and this, in turn, resulted in the poor modulus and impact strength of the composite. A one-step mixing sequence of all three components produced a separated dispersion of PDMS and nano-SiO₂ phases in the PP matrix with the occurrence of a fine band of nano-SiO₂ particles at the boundaries of the PDMS domains and the presence of some nano-SiO₂ filler particles inside the PDMS domains. This one-step mixing sequence produced an improvement in the tensile modulus but a decrease in the impact strength with increasing nano-SiO₂ content. In the third sequence of mixing, which involved a two-step mixing sequence through the addition of PDMS in the second step to the previously prepared PP/nano-SiO₂ binary system, the morphology of the dispersion showed separately dispersed PDMS and nano-SiO₂ phases with a loose network of nano-SiO₂ particles surrounding the PDMS domains. This latter series of ternary composites had the highest impact strength and exhibited high shear deformation under tensile and impact conditions.