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| Author(s): |
Adair Rangel de Oliveira Junior
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Química |
| Defense date: | 2006-06-10 |
| Examining board members: |
Maria do Carmo Gonçalves;
Raquel Santos Mauler;
Elias Hage Junior;
Ana Flávia Nogueira;
Maria Isabel Felisberti
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| Advisor: | Maria do Carmo Gonçalves; Inez Valéria Pagotto Yoshida |
| Abstract | |
The purpose of this work was to obtain expanded clay by modifying clay with organosilane, and its incorporation into polypropylene resin to prepare a polypro-pylene-clay nanocomposite. Natural sodium montmorillonite (GelMax, Polenita) as well as organophylic clay (Viscogel ED) were used for this purpose. Three types of silanes were used to modify the clay: Aminopropyltrimethoxysilane (APS), glyci-doxypropyltriethoxysilane (GPS) and methacryloxypropyltrimethoxysilane (MPS). The expanded clay was strongly affected by reaction conditions, such as silane type and concentration, solvent and pH. According to XRD analysis, the higher basal distance was achieved in aqueous dispersion (pH 8-10) using the APS as a modifier. Modified clay showed superior thermal stability in comparison to organo-phylic clay, using thermogravimetric analysis. Besides the clay modification pro-cess, the screw profile influence on nanocomposite properties was also evaluated. An organophylic clay (Viscogel) was used to optimize the extrusion conditions, in this study. The composite processing was carried out in a twin screw extruder with higher shear screw profile. In this way, an exfoliated nanocomposite was obtained, where the clay layer thickness was between 5 and 15 nm. The flexural modulus of such nanocomposite was 30% higher than virgin polypropylene. This higher shear screw profile was used to extrude the polypropylene/aminopropylsilane-modified clay. Based on the X-ray diffraction and transmission electron microscopy results, a satisfactory exfoliation degree for silane-modified clay was not achieved, as observed for organophylic clay. In spite of the low exfoliation level of silane-modi-fied clay, the mechanical properties of its composite were similar to the organo-phylic clay based nanocomposite. This fact was attributed to better adhesion between polypropylene-silane modified clay than the polypropylene-organophylic clay system (AU) | |