Fluoropolymer addition to an epoxy: phase inversion and tribological properties

Morphology, elastic modulus, static and dynamic friction of a commercial epoxy resin+fluorinated poly(aryl ether ketone) (12F-PEK) system have been studied. The system was cured at 24 and 70°C. We have obtained significant friction lowering, namely 30% less than the value for the plain epoxy at the 12F-PEK concentration of only 10 wt% after curing at 24°C. By contrast, after curing at 70°C, increases in both static and dynamic friction are observed. At 24°C, the SEM analysis shows that a phase separation starts at 10% 12F-PEK; completely phase-inverted morphology was found above 30% of the fluoropolymer. The system cured at 70°C has more compact structure and the phase separation process is shifted towards higher fluoropolymer concentrations. We explain the phase inversion at low fluoropolymer concentrations by the low free surface energy of 12F-PEK; as a consequence, we observe its accumulation on the surfaces of the samples. The samples with high 12F-PEK concentrations exhibit elevated elastic modulae and are highly ductile.