Influence of CaCO3/glass fiber hybrid fillers on the mechanical and thermal properties of polytetrafluoroethylene

With the large demand of various types of composite materials, many inorganic fillers have been introduced to polymer matrix to fabricate high-performance polymer composites. Heavy calcium carbonate (CaCO3) and glass fiber (GF) were selected as two fillers to incorporate into polytetrafluoroethylene (PTFE) matrix in this work by taking consideration of their low cost and wide sources. Fillers were first modified with paraffin through wet and dry modification technique, and then PTFE/CaCO3 binary composites and PTFE/CaCO3/GF ternary composites were prepared through die pressing and sintering process. Infrared spectroscopic analysis and compatibility test were used to investigate structure changes of the fillers before and after modification. The effect of modification methods on the mechanical properties and thermal properties of composites was investigated. Results revealed that both dry and wet modification methods would improve the elongation at break and tensile strength of PTFE/CaCO3 binary composites, and wet modification method was more efficient in enhancing the mechanical properties than that of other ways. Large differences in mechanical strength appeared between the wet modification and unmodified method for binary composites when CaCO3 content reached 30 wt%. Moreover, the elongation at break for composites with 30 wt% of CaCO3 through wet modification can still exceed 200%. Vicat softening temperature of PTFE/CaCO3 binary composite with 15 wt% of wet-modified CaCO3 was increased by 138.5% than that of PTFE/CaCO3 binary composite with same content of unmodified CaCO3.