Preparation and characterization of PTFE-g-GMA modified PTFE/SiO2 organic–inorganic hybrids

Abstract

In this paper, PTFE (polytetrafluoroethylene)/SiO2 organic–inorganic hybrids were prepared with PTFE emulsion and tetraethoxysilanes (TEOS) through in-situ Sol–gel process, and then modified by PTFE grafted polymer. The studies included Sol–gel manufacturing process, the effects of SiO2 content and graft polymer on the properties of the hybrids. The result showed that, cosolvent ethanol was not needed during the process of Sol–gel because it could make PTFE emulsion colloidal particles agglomerated. When the mass fraction of SiO2 was 1.05 %, the tensile strength reached 20.96 MPa, which was nearly twice as much as that of the pure PTFE sample. Hybrids were treated by PTFE grafted glycidyl methacrylate (PTFE-g-GMA) and silane coupling agent KH-550, after which the tensile properties of hybrids were all enhanced. SEM (scanning electron microscope) images showed that SiO2 changed the original fracture morphology of PTFE. The diameter of SiO2 could reach 110 nm in the hybrid, and the size of SiO2 was further refined by modification. Hybrids with different contents of SiO2 were also analyzed with TGA (thermogravimetric analyzer), through which it could be found that decomposition temperature were improved with an increasing SiO2 content. Furthermore, the crystallinity reached a maximum value 47.03 % measured by DSC (different scanning calorimetry) when the SiO2 content was 2.55 %. Additionally, more SiO2 could hinder the motion of chain segment and destroy the crystallization sequence length, so the crystallinity and crystallization velocity both decreased at the mass fraction of 7.37 %, but the crystallization behavior was enhanced after modification with graft polymer. It has been found that PTFE-g-GMA contributes to the compatibility between PTFE and SiO2.