Preparation by melt mixing and characterization of isotactic polypropylene/SiO2 nanocomposites containing untreated and surface-treated nanoparticles

In the present study two series of isotactic polypropylene (iPP)/SiO2 nanocomposites containing 1, 2.5, 5, 7.5, and 10 wt % SiO2 nanoparticles were prepared by melt‐mixing on a twin‐screw corotating extruder. In the first series untreated fumed silica nanoparticles were used, whereas in the second n...

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Bibliographic Details
Published in:Journal of applied polymer science 2006-05, Vol.100 (4), p.2684-2696
Main Authors: Bikiaris, Dimitris N., Papageorgiou, George Z., Pavlidou, Eleni, Vouroutzis, Nikolaos, Palatzoglou, Paraskevas, Karayannidis, George P.
Format: Article
Language:English
Subjects:
Applied sciences
Composites
Exact sciences and technology
Forms of application and semi-finished materials
isotactic polypropylene
morphology
nanocomposites
Polymer industry, paints, wood
silica
Technology of polymers
tensile properties
thermal properties
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Summary:In the present study two series of isotactic polypropylene (iPP)/SiO2 nanocomposites containing 1, 2.5, 5, 7.5, and 10 wt % SiO2 nanoparticles were prepared by melt‐mixing on a twin‐screw corotating extruder. In the first series untreated fumed silica nanoparticles were used, whereas in the second nanoparticles were surface‐treated with dimethyldichlorosilane. In both cases, the average size of the primary nanoparticles was 12 nm. Tensile and impact strength were found to increase and to be affected mainly by the type and content of silica nanoparticles. A maximum was observed, corresponding to samples containing 2.5 wt % SiO2. These findings are discussed in light of the SEM and TEM observations. By increasing the amount of nanoparticles, large aggregates of fumed silica could be formed, which may explain the reduction of mechanical properties with higher concentrations of SiO2. However, it was found that surface‐treated nanoparticles produced larger aggregates than did those derived from untreated nanoparticles, despite the increased adhesion of the iPP matrix, as was postulated from yield strength. This behavior negatively affected mechanical properties. In addition, an effort was made to determine if toughening theories, mainly the critical interparticle distance for rubber toughening or composites, also might be applicable in nanocomposites. From DSC measurements it was demonstrated that silica nanoparticles acted as effective nucleating agents, increasing the crystallization rate and the degree of crystallinity of iPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2684–2696, 2006
ISSN:0021-8995
1097-4628
DOI:10.1002/app.22849