| Polyamide (PA66) is an engineering plastic with excellent mechanical strength,heat resistance, chemical resistance, self-lubricating, which has been widely used ineveryday life. However, PA66has poor wear resistance under dry wear conditions. Inrecent years, improving friction and wear properties of PA66in dry conditions is a hottopic, which has been widely studied. Basic magnesium oxysulfate whisker (MOS) isa kind of high performance inorganic non-metallic materials, it has large length todiameter ratio, low price, rich in the nature, flame-retardant, non-toxic, which isrecognized as environmentally friendly polymer filler material. Because of its uniquemolecular structure, polytetrafluoroethylene (PTFE) is an excellent wear resistancemodifier that has been widely used. Therefore, in this paper the basic magnesiumsulfate whisker is used as filler to prepared PA66/basic magnesium oxysulfatewhisker composites by melt blending. Not only the surface modification of basicmagnesium oxysulfate whisker, the mechanical properties of composite materials,friction and wear properties, and the wear mechanism has been studied and analyzed,but also the overall performance of composite materials after γ-ray radiation has beeninvestigated. The main results are shown as follows:(1)Different types of composite materials PA66/MOS was prepared by meltblending and the effects of whisker content on Composites properties has beenstudied. The tensile modulus,f lexural strength and flexural modulus of thePA66/MOS composites were improved by40.0%and261.5%,110.2%,329.3%compared with pure PA66. Friction coefficient and volume wear rates decreased by30%and28%. The heat distortion temperature is improved by141℃compared withpure PA66and the thermal expansion coefficient is decreased. Moreover, the impactstrength, break elongation of the composite material significantly decreased and thecomposite brittle fracture, under the whisker content satisfies the conditions ofprocessing. The compatibility with the matrix resin was effectively improved bymodificating the surface of basic magnesium sulfate whiskers. The effect ofsurfacemodification SG-Si900is better than KH560and KH570. Tensile strength andbending strength of the composite material was improved45.7%and77.5% compared with pure PA66, When the content of salicane coupling agent SG-Si900is1.5~2.0wt%.(2)When addition of PTFE, the mechanical properties, friction and wear propertiesof the composite was studied. The results show that it can greatly improve the frictionand wear properties level of PA66under dry friction conditions.The frictioncoefficient, wear rate of the composites are significantly reduced to75.0%and69.7%compared with PA66respectively.However, due to the ultrafine PTFE resin matrixprone aggregates, causing uneven dispersion, and then blended with the compositePA66/MOS, the mechanical properties of the composite material decline. Due toPTFE was aggregates easliy, which cannot disperse uniform in the resin matrix. Sothe mechenical properties were decresed with the PTFE additon. It can be seen thatPTFE can significantly improve the friction and wear properties of compositematerials. It Making the composite material self-lubricating.(3)Not only mechanical properties, thermal performance,heat distortiontemperature of the PA66/MOS/PTFE composites improved after a certain irradiation,but also the thermal expansion coefficient of the composites significantly decresed.(4)The friction mechanism of PA66and the composites were studied by SEM. Itshow that PA66was mainly adhesive wear, PA66/MOS and PA66/MOS/PTFEmainly mild abrasive wear and fatigue wear under the dry friction conditions. Itindicated that whiskers and irradiation could make the friction and wear behavior ofPA66matrix changed.(5) As the modulus of the composites increased and heat distortion temperatureimproved, the friction coefficient and the ware rate of the composite materialsreduced. As a result the friction and wear properties of the composites can beimproved. |
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