Development Of High Thermal Conductivity AF/POM Wear Resistant Composite Based On Micro-structure Control

In order to make up for the deficiencies of low thermal conductivity and poor thermal stability of polyoxymethylene(POM)and widen its application in complex environment,aluminum foam(AF)was used to combine with POM to prepare AF/POM composites with interpenetrating structure(IPC).Meanwhile,a series of micro-structural control of interpenetrating composites were carried out to improve the performance of interpenetrating phase and the combination of two phases.In this paper,nano-alumina(aA12O3)and sulfonated graphene(S-GNS)complexes(S-GNS-aA12O3)were prepared by electrostatic self-assembly method to modify POM for the POM phase.For AF phase,KH-550,graphene oxide(GO),S-GNS and graphene(GS)coatings were prepared on the hole surface of AF by electrodeposition.The coated AF/modified POM interpenetrating composites were prepared by injection moulding.The thermal conductivity and tribological properties of coated AF/modified POM interpenetrating composites were studied.At the same time,the thermal conductivity and friction and wear mechanism of IPC were further investigated by means of scanning electron microscopy(SEM),X-ray Diffraction Analysis(XRD)and infrared spectrum analysis(FT-IR).The following conclusions are drawn:(1)The chemical composition,structure and properties of S-GNS and S-GNS-aA12O3 complexes are determined.Hydrophilic sulfonic acid group(-SO3H)is successfully grafted onto S-GNS carbon atom plane.Compared with GO and GS,S-GNS has the largest lamellar spacing of 1.3 8nm,and the best dispersion and stability In water.In the S-GNS-αAl2O3 complexes,S-GNS and αAl2O3 are combined by physical action,and S-GNS reduces the surface energy of αAl2O3 and improves the agglomeration of αAl2O3.(2)The synergistic effect of aA12O3 and S-GNS on the thermal conductivity and tribological properties of POM is investigated.The thermal conductivity of S-GNS-αAl2O3/POM increases with the addition of S-GNS-αAl2O3 complex content.S-GNS plays an important role in heat transfer and improves the interface bonding between αAl2O3 and POM,while αAl2O3 exerts a small size effect and a high thermal conductivity filler.The addition of S-GNS-αAl2O3 reduces the friction coefficient and wear loss of POM composites.The friction coefficient of 5%S-GNS-αAl2O3/POM composites(POMc)is 0.276,the wear loss is only 32mg,which is 66.6%lower than pure POM.The main wear forms are adhesive wear and plough groove cutting.So the tribological properties of 5%S-GNS-αAl2O3/POM are the best.(3)The preparation process and structural characteristics of AF surface coating are investigated.GO and S-GNS coatings can be successfully prepared on the hole surface of AF at the electrodeposition voltage of 15V solution concentration of 0.lmg/mL and deposition time of 5min.All kinds of coatings are combined with AF by physical adsorption.No new chemical bonds are formed.(4)The effects of different coatings on thermal conductivity and tribological properties of AF/POMc interpenetrating composites are summarized.The thermal conductivity of coated AF/POMc composites is effectively improved by coating as interface transition layer,and S-GNS-AF/POMc interpenetrating composites has the highest thermal conductivity of 2.25W/(m.K)The friction coefficient and wear loss of coated AF/POMc composites decrease significantly.Among them,the friction coefficient of S-GNS-AF/POMc composites is 0.34 and the wear loss is 82.2 mg,which are 10.3%and 42.1%lower than that of AF/POMc.S·CfNS plays the role of homogenizing friction、transferring friction heat and improves the thermal stability of the composites.So the tribological properties of S-GNS-AF/POMc are the best.(5)The effect of coating on the interfacial bonding of AF/POMc interpenetrating composites is investigated.The two-phase interface of composites with coating has good bonding and no cracks.The thermal resistance of the interface can be effectively reduced by inserting coatings into the two,phase interface,thus improving the thermal conductivity of the AF/POMc interpenetrating composites.(6)The effect of coating on heat transfer of AF/POMc interpenetrating composites is simulated and analyzed.The internal temperature difference of S-GNS-AF/POMc composite is less than that of AF/POMc,and the S-GNS coating increases the heat flow path greatly.The high heat flux area is concentrated in the coating area,which improves the thermal conductivity of composite.