Boundary lubrication of thermoplastic polymers in model fluids

et al. 1997

Four kinds of polytetrafluoroethylene(PTFE)-based composites, such as pure PTFE, PTFE/30%(v)PbO, PTFE/30%(v)Pb 3 O 4 , and PTFE/30%(v)Cu 2 O composite, were prepared. The friction and wear properties of these metal oxides filled PTFE composites sliding against GCr15 bearing steel in both dry and lubricated conditions were studied by using an MHK-500 ring-block wear tester. Then the worn surfaces of these PTFE composites and the transfer films of these PTFE composites formed on the surface of GCr15 bearing steel were examined by using a Scanning Electron Microscope (SEM) and an Optical Microscope, respectively. Experimental results show that the friction and wear properties of these metal oxide-filled PTFE composites can be greatly improved by liquid paraffin lubrication, and the friction coefficients can be decreased by one order of magnitude. Meanwhile, the interactions between liquid paraffin and metal oxide-filled PTFE composites, especially the absorption of liquid paraffin into the surface layers of these PTFE composites, reduce the mechanical strength and the load-carrying capacity of these metal oxide-filled PTFE composites. This leads to the deterioration of the friction and wear properties of these PTFE composites. Investigations of the frictional surfaces show that Pb 3 O 4 , Cu 2 O, and PbO enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, and thus promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel. Therefore, they greatly reduce the wear of the PTFE composites. However, the transfer of these PTFE composites onto the counterfaces can be greatly reduced by lubrication with liquid paraffin.

Section: Sem Investigation Of Worn Surfacessupporting

confidence: 91%

“…Before each test, the surfaces of PTFE composite block and GCr15-bearing steel ment. Briscoe et al 13,14 studied the lubricated wear of some polymers. They pointed that the abring were cleaned by rubbing with a soft cloth dipped in acetone and then dried in air.…”

Section: Introductionmentioning

confidence: 99%

Friction and wear characteristics of PTFE composites filled with metal oxides under lubrication by oil

et al. 1997

“…The creation and the development of these cracks under load reduce the mechanical strength and loadsupporting capacity of the PTFE composites. 10,11 This would lead to the deterioration of the friction and wear properties of the PTFE composites under higher loads (Ͼ600N) in liquid paraffin lubrication. The above analysis results are consistent with the results of friction and wear tests.…”

Section: Sem Examination Of Worn Surfacesmentioning

confidence: 99%

Friction and wear characteristics of metal sulfides and graphite-filled PTFE composites under dry and oil-lubricated conditions

et al. 1999

Five kinds of polytetrafluoroethylene (PTFE)-based composites, pure PTFE, PTFE ϩ 30(v)% MoS 2 , PTFE ϩ 30(v)% PbS, PTFE ϩ 30(v)% CuS, and PTFE ϩ 30(v)% graphite (GR) composites, were first prepared. Then the friction and wear properties of these PTFE composites, sliding against GCr15-bearing steel under both dry and liquid paraffin-lubricated conditions, were studied by using an MHK-500 ring-on-block wear tester. Finally, the worn surfaces and the transfer films of the PTFE composites formed on the surface of GCr15 bearing steel were investigated by using a scanning electron microscope (SEM) and an optical microscope, respectively. Experimental results show that filling with MoS 2 , PbS, CuS, or graphite to PTFE can reduce the wear of the PTFE composites by two orders of magnitude compared to that of pure PTFE under dry friction conditions. However, the friction and wear-reducing properties of these PTFE composites can be greatly improved by lubrication with liquid paraffin. Investigations of transfer films show that MoS 2 , PbS, CuS, and graphite promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel under dry friction conditions, but the transfer of the PTFE composites onto the surface of GCr15-bearing steel can be greatly reduced by lubrication with liquid paraffin. SEM examinations of worn surfaces show that with lubrication of liquid paraffin, the creation and development of the cracks occurred on the worn surfaces of the PTFE composites under load, which reduces the load-supporting capacity of the PTFE composites. This would lead to the deterioration of the friction and wear properties of the PTFE composites under higher loads (Ͼ600N).

“…The creation and development of the cracks under load reduces the mechanical strength and load-supporting capacity of the PTFE composites, which would lead to the deterioration of the friction and wear properties of the PTFE composites under higher loads in liquid paraffin lubrication. 18,19 Meanwhile, with increase of the addition content of CeO 2 , CeF 3 , and La 2 O 3 in PTFE, the microdefects in the PTFE composites also increase; this would lead to increase of the cracks that occurred on the worn surfaces of the PTFE composites under load in liquid paraffin lubrication and, so, in turn, lead to the reduction of the limit loads of the PTFE composites. Therefore, the limit loads of CeO 2 -, CeF 3 -, and La 2 O 3 -filled PTFE composites decrease with increase of the addition content of CeO 2 , CeF 3 , and La 2 O 3 in PTFE under lubrication of liquid paraffin.…”

Section: Sem Investigation Of Worn Surfacesmentioning

confidence: 97%

Friction and wear behavior of PTFE composites filled with rare earth compounds under oil-lubricated conditions

et al. 1999

Polytetrafluoroethylene (PTFE)-based composites, filled with CeO 2 , CeF 3 , and La 2 O 3 in volume contents of 5, 10, 15, 20, and 30%, were prepared. Then, the friction and wear behavior of these PTFE composites sliding against GCr15 bearing steel under both dry and liquid paraffin-lubricated conditions was evaluated using an MHK-500 ring-on-block wear tester. Finally, the worn surfaces and the transfer films of these PTFE composites were investigated using a scanning electron microscope (SEM) and an optical microscope. Experimental results showed that filling CeO 2 , CeF 3 , and La 2 O 3 into PTFE can reduce the wear of the PTFE composites by 1-2 orders of magnitude. When the content of CeO 2 in PTFE is 15%, the friction and wear properties of the CeO 2 -filled PTFE composite are the best. Meanwhile, when the content of La 2 O 3 in PTFE is between 15 and 20%, the PTFE composite filled with La 2 O 3 exhibits excellent friction and wear-reducing properties. However, the friction coefficient of the CeF 3 -filled PTFE composite increases but its wear decreases with increase in the content of CeF 3 from 5 to 30%. The friction and wear-reducing properties of CeO 2 -, CeF 3 -, and La 2 O 3 -filled PTFE composites can be greatly improved by lubrication with liquid paraffin, but the limit loads of the PTFE composites decrease with increase in the content of CeO 2 , CeF 3 , and La 2 O 3 in PTFE (from 5 to 30%) under the same conditions. Investigations of worn surfaces show that the interaction between liquid paraffin and the CeO 2 -, CeF 3 -, and La 2 O 3 -filled PTFE composites, especially the absorption of liquid paraffin into the microdefects of the PTFE composites, creates some cracks on the worn surfaces of the PTFE composites and that the creation and development of the cracks reduces the mechanical strength and the load-supporting capacity of the PTFE composites. However, with increase of the content of CeO 2 , CeF 3 , and La 2 O 3 in the PTFE, the microdefects in the PTFE composites also increase, which would lead to increase in the number of the cracks on the worn surfaces of the PTFE composites under load and, so, in turn, lead to the reduction of the limit loads of the CeO 2 -, CeF 3 -, and La 2 O 3 -filled PTFE composites under lubrication with liquid paraffin.