Prepararion And Properties Of Conductive Polypropylene Composites

In recent years,with the development of industry and technology,thermal conductivity materials have been more and more widely used in chemical,electronic packaging and other fields.There is also higher request of these materials' performance.Metals as traditional thermal conductive materials have apparent disadvantages.The difficult processing and poor corrosion resistance limit the application in some special field.Polymers have excellent chemical corrosion resistance,fatigue resistance and easy processability.However,most polymer resins are thermally insulating.Thus the development of new functional polymer materials with good thermal conductivity has received much attention.In this study,platelet-shaped graphite and rod-shaped carbon fiber were used as conductive fillers to successfully prepare thermal conductive polypropylene.Firstly,polypropylene/graphite/carbon fiber composites were prepared via melting compounding and the influence of filler contents,filler particle size and filler distribution on thermal conductivity,mechanical properties,thermal properties were researched in detail.Secondly,PP/PE/ graphite and PP/PBT/graphite were prepared via the same method and the influence of two-phase incompatible systems on thermal conductivity,mechanical properties,thermal properties were researched in detail.Finally,with small mass fraction of filler,select the best ratio of filler and two-phase matrix to prepare the thermal conductive polypropylene.The results were given:(1)The addition of thermal conductive filler obviously increase the thermal conductivity of polypropylene and because of the anisotropy of carbon materials,the in-plane thermal conductivity is apparently higher than through-thermal conductivity.Controlling the mass fraction of filler is 40wt%,the in-plane and through-plane thermal conductivity of polypropylene rise to 2.818 W/(m·K)and 0.967 W/(m·K)respectively at a graphite/carbon fiber ratio of 6:1.(The in-plane and through-plane thermal conductivity of polypropylene with 40% graphite are merely 0.508 W/(m·K)and 1.801 W/(m·K).)The formation of two phase structure is beneficial for more graphite fillers to aggregate at the interface of two phases,which results in the higher thermal conductivity.The in-plane and through-plane thermal conductivity of polypropylene increase to 2.347 W/(m·K)and 1.376 W/(m·K)respectively with 10% PBT as well as 5% compatilizer PP-g-MAH.(The in-plane and through-plane thermal conductivity of polypropylene without PBT and PP-g-MAH are merely 0.508 W/(m·K)and 1.801 W/(m·K).)Control the ratio of graphite/carbon fiber is 6:1 and the ratio of PP/PBT is 9:1,the in-plane and through-plane thermal conductivity of polypropylene rise to 1.896W/(m·K)and 0.665W/(m·K).(The in-plane and through-plane thermal conductivity of polypropylene with 10% graphite are merely 0.23W/(m·K)and 0.745W/(m·K).)(2)As for mechanical properties(tensile strength,impact strength and bending strength),the PP/graphite/carbon fiber composites tends to decline firstly and increase then with the increasing addition of carbon fillers.In case of two-phase system,the addition of PE and PBT significantly improve the tensile strength but the impact strength and bending strength have slight decrease.The combination of two kinds of fillers effectively improves the tensile strength of PP/PBT system.(3)Additionally,PP composites show excellent thermal stability compared to pure PP which is beneficial for wider application.The addition of fillers also effectively enhances the crystallinity of PP and improves its heat resistance.