Friction And Wear Properties Of Food Contact PTFE Composite Coating

Teflon,synthesized by American scientists R.S.Plunkett in 1938,has been widely used in industries due to its superior performance.However,PTFE only found limited application in industrial because of its poor mechanical properties,big linear expansion coefficient,bad creep resistance,poor wear resistance.Nowadays,research on wear properties of PTFE composites are mostly based on experience,or limited to specific test conditions.There are no throughout studies which are devoted to estimate the service life for PTFE nonsticking coating under different load and speed.Furthermore,tribological performance of coating under heat treatment and different media need further research.In this thesis,two common PTFE nonsticking coating are chosen and their service life under load and speed are evaluated.The tribological performances of PTFE coating under different media are evaluated.The influences of heat treating temperature on the tribological performance of PTFE coating are also investigated.We hope to provide support for daily usage of non-stick pan.The main results are showed as the follows:(1)Research shows that load and rotating speed both show extremely significant effects on the lifetime of the PEFE coating by response surface methodology.The test values(F)are less than 0.0001.The lifetime of PTFE coatings is shortest under high speed and high load,whereas the lifetime is longest under low speed and low load.A second order relationship between lifetime with speed and load is established which can accurately predict the life of the coating.(2)Compared with tribological performance of PTFE coating in dry sliding contact,the lower friction coefficient(COF)is observed when deionic water,NaCl solution,Na2CO3 solution ? acetic acid solution and ethanol solution is existed in the sliding contact.The most striking effect in decreasing COF is observed for Na2CO3 solution,acid solution,ethanol solution.Furthermore the wear of PTFE coating increases when deionic water and NaCl solution are existed,whereas lower wear has found for other solution.Especially,in the Na2CO3 solution,the wear of PTFE coating is only one thirdof that under dry sliding.(3)Heat treatment can significantly affect the tribological properties of PTFE coating.Below 300?,there is no change in wettability,surface morphology and tribological performance of PTFE coating.However,with the heat treatment temperature increasing to 500?,there is a clear damage in certain degree for PTFE coating.When the heat treatment temperature reached 550?,the surface of coating has completed destructed.