Preparation And Tribological Properties Of Porous Self-lubrication Melamine-Formaldehyde Materials

In this thesis,Melamine-Formaldehyde(MF)prepolymer was used as the external phase(continuous phase)and liquid paraffin as the internal phase(dispersed phase)and the effect of different emulsifiers(block copolymers,amphiphilic particles)on the morphology and stability of the emulsions was investigated.Subsequently,oil-containing porous materials with different porosity were fabricated by one step synthesis using emulsions with different internal phase ratios as templates.The tribological properties of porous materials with different oil ratios were investigated.TAPA-MF oil-containing materials with a mesoporous structure were prepared by introducing cross-linking agents.As a comparison,micron-sized macroporous oil-bearing materials were also prepared by the emulsion template method.The lubrication and wear mechanism of porous oil-containing MF materials were discussed.The details were as follows:The effect of different block copolymers on the stability of MF prepolymer-liquid paraffin emulsion was evaluated.The results demonstrate that the droplets of F68 emulsion have a complete morphology and the porous morphology after emulsion curing is relatively regular.When the oil content of the material increased to 30vol%,the average friction coefficient and wear rate of the composite decreased to 0.160 and 2.31×10^-7mm³/N·m,respectively,which account for 74.44%and 97.38%decrease compared with those of the oil-free MF material.Different kinds of cationic surfactants were selected to modify the surface of Ti₃C₂T_X-Mxene in order to tune the hydrophilic-lipophilic ability of MXene.And finally,CTAB was fixed as the best surface modifier for MXene.Meanwhile the optimal CTAB/MXene ratio was 1:1.The structure of porous MF materials prepared by MXene-Pickering emulsion template method is regular.When the oil content of the porous material is 10vol%,the average friction coefficient and wear rate are 75.23%and 94.44%lower than those of oil-free MF materials.The results show that Mxene not only stabilizes the Pickering emulsion in the prepared porous MF material,but also plays a synergistic effect with liquid paraffin during the friction process to achieve a good anti-friction and anti-wear effect.By introducing rigid molecule Tris(4-aminophenyl)amine(TAPA)into the Melamine-Formaldehyde(MF)prepolymer,the mesoporous TAPA-MF material could be obtained by the cross-linking strategy.When the molar ratio of TAPA:MA is 1:7,the saturated oil absorption capacity of TAPA-MF is 19.20wt%.Meanwhile,the average friction coefficient of the sample is 0.216,and the wear rate is 2.50×10^-7mm³/N·m,which is 66.51%and 90.73%reduce compare with those of MF pure sample,indicating that the saturated oil-absorbing mesoporous TAPA-MF materials has good friction reduction and anti-wear effect.The TAPA-MF material with macroporous structures was prepared by combining the emulsion template method as well.For low oil content TAPA-MF porous materials,the liquid paraffin released during the friction process is low and fails to form sufficiently thick lubricant film,while the presence of micron-sized pores reduces the load-bearing capacity of the material,resulting in a higher wear rate.The 50 vol%oil content of the macroporous TAPA-MF material has the lowest coefficient of friction and wear rate.