Drastic Modification of the Dispersion State of Submicron Silica during Biaxial Deformation of Poly(ethylene terephthalate)

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• 作者：Sté ; phane Jé ; ol ; Franç ; oise Fenouillot ; Alain Rousseau ; Karine Masenelli-Varlot ; Catherine Gauthier ; Jean-Franç ; ois Briois
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：May 1, 2007
• 年：2007
• 卷：40
• 期：9
• 页码：3229 - 3237
• 全文大小：1061K
• 年卷期：v.40,no.9(May 1, 2007)
• ISSN：1520-5835

文摘

Deformation-induced modification of the dispersion state of silica nanoparticles in poly(ethyleneterephthalate) (PET) has been characterized by means of transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD). We focused on the biaxial deformation applied at a temperature just above theglass transition temperature (110 C), during the free stretch-blowing process of amorphous PET modified withsubmicron silica. The first nanocomposite studied contains 2.5 wt % of fractal aggregated pyrogenic silica. Theparticles are well dispersed after the polymerization of PET, but they agglomerate and orient strongly parallel tothe elongation direction after biaxial deformation. They form long streams of particles (>2 m long) regularlyspaced by a distance of 50-100 nm. Interestingly, the silica organization is consistent with the hierarchical structurecommonly proposed for the strain-induced crystallization of PET. The particles are rejected from the highlyoriented domains induced by the strain, and their spatial organization reveals the superstructure. The secondnanocomposite contains 5% of spherical silica with a diameter of 20 nm. Its behavior is drastically different. Thesilica also forms streams of particles (1-2 m long); however, the streams are oriented perpendicular to theelongation direction, and that is hardly compatible with the presence of a microfibrillar structure. We assumethat this unexpected orientation is produced by the extended growth of mesophases and crystallites perpendicularto the orientation and that stacked lamellae are formed rather than microfibrils.