| Polypropylene?polypropylene?is a crystalline polymer.Polypropylene thermoplastic has many advantages,such as low price,light quality,water resistance,acid and alkali resistance.It has production application in electronic industry,packaging industry,machinery manufacturing,national defense and military and so on.Polypropylene,however,is an electrical insulator with low thermal conductivity,which limits its use in semiconductor manufacturing and geothermal energy applications.In order to improve the thermal conductivity of polypropylene,the effects of carbon fiber on the morphology,mechanical properties and thermal conductivity of polypropylene composites were studied with short cut carbon fiber?Carbon Fiber?as the main material.The specific research content and results are as follows:First,three kinds of CF,0.5mm,3mm and 7mm,were dispersed into polypropylene by melt blending to prepare polypropylene composites with different carbon fiber content.The morphology,mechanical and thermal properties of the composites were studied.The results show that the tensile strength and bending strength of the composites increase with the increase of CF content,and the impact strength of the notch increases first and then decreases,and the thermal conductivity increases.With the increase of CF length,thermal conductivity shows an upward trend.However,when the CF content is greater than 20phr,the thermal conductivity of 0.5mmCF/PP composites is better.When the content of 0.5mmCF is 25phr,the thermal conductivity of the PP/CF composite is 0.77 W·?m·K?-1,which is 285%higher than that of pure PP(0.2 W·?m·K?-1),indicating that the addition of short cut CF has a good effect on improving the thermal conductivity of the composite.Secondly,PP composites were filled with carbon fibers respectively with graphene nanosheets?GNSs?and flake graphite.The flexural modulus of PP/3mm CF/GNSs composites increased significantly with the addition of GNSs.With the increase of GNSs content,the thermal conductivity of the composites increased obviously.The thermal conductivity of PP/3mm CF/GNSs composites at GNSs 5phr is 0.47W·?m·K?-1,which is 105%and 18%higher than pure PP and PP/GNSs?5phr?(0.40W·?m·K?-1)composites.For PP/CF/flake graphite composites,the thermal conductivity of composites increased with the increase of flake graphite,and the mechanical properties decreased.When the content of the flake graphite is 30phr,the heat conduction channel is formed in the system.The thermal conductivity of the PP/3mmCF/scale graphite composite is 1.3 W·?m·K?-1,which is increased by 550%compared with the pure PP.At the same time,the addition of CF and flake graphite or graphene nanosheets has obvious synergistic effect,and the thermal conductivity enhancement effect is remarkable.Finally,nylon 6 was further introduced into PP CF/flake graphite composite,and PP/PA6/CF/flake graphite composite material was prepared.The effect of PA6 on the mechanical properties and thermal stability of PP/PA6 alloy was studied.The effect of PA6/PP alloy matrix on the thermal conductivity and morphology of PP/PA6/CF/flake graphite composite was studied.The best ratio of PP/PA6 is 70/30.At this time,10 PP-g-MAH is the best.The thermal conductivity of the PP/PA6/CF/scale graphite?30phr?composite is 1.53 W·?m·K?-1,which is increased by 18%compared to the PP/CF/scale graphite?30phr?composite(1.3 W·?m·K?-1).Compared with PP matrix,PA6in PP/PA6 alloy matrix is dispersed phase,and graphite tends to aggregate at both interfaces,thereby enhancing thermal conductivity. |
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