Preparation Of Conductive And Electromagnetic Shielding Polyolefin Composites

Polymer material has been widely used in electronic industry with its unique strengthssuch as light weight, corrosion resistance, low cost, easy processing and so on. This expandsthe commercial application and academic research on conductive polymer composites (CPCs).In recent years, academic papers about CPCs are focusing on the application of newconductive fillers such as carbon nanotubes (CNTs) and graphene. However, research on theinfluence of polymer matrix characters on conductivity and relations between shieldingeffectiveness and conductivity is rarely reported.In this study, we used High-Density Polyethylene (HDPE)(Grade2010,2100J,8916),Polypropylene (PP)(Grade T30s,160,1900) as matrices and carbon black (CB), carbon fiber(CF) as conductive fillers. In the research of CB filled single-component composites, theinfluence of polymer matrix characters like wetting property, melting viscosity andcrystallizing process on conductivity were discussed. For CB filled bi-component composites,we researched the effects of PP/HDPE melting viscosity ratio, filling sequence and PP/HDPEmass ratio on the conductivity of polymer composites. We also discussed the relationsbetween shielding effectiveness and conductivity of CPCs, and further explained the shieldingmechanism of CB filled composites. Finally, we explored the improvement of CF to theconductivity of CB filled single-component and bi-component composites.In the research of PP/CB, HDPE/CB composites, we found the conductivity of PP/CB ishigher than HDPE/CB, and PP160/CB has a lower percolation threshold, which is nearly1wt%.The results indicated that material with low wetness to CB, proper melting viscosity,crystallinity and size of crystal has higher conductivity.The research on9kinds of PP/HDPE/CB composites which contained different grades ofPP and HDPE, showed PPT30s/HDPE8916/CB has higher conductivity, and its percolationthreshold is about0.5~1wt%. We found the applying of high melting viscosity PP and lowmelting viscosity HDPE can improve the conductivity of composites. Further investigationindicated that the better filling sequence is (PP+HDPE)+CB and the better PP/HDPE massratio is50/50.The research on PP/CB and PP/HDPE/CB composites showed the shielding effectivenesshas direct proportion with CB content, and when the CB content is above a certain value, theshielding effectiveness will have a direct proportion relationship with conductivity. We alsofound the shielding effectiveness of PP/HDPE/CB is lower than PP/CB composite.Through the investigation on PP/CB/CF and PP/HDPE/CB/CF composites, we found CF can improve the conductivity of these materials. The results indicated PP/CB/CF compositewith2wt%5mm long CF and2wt%CB has the better conductivity and better mechanismproperties, and the volume resistivity is26Ω·cm. For PP/HDPE/CB/CF composite with2wt%5mm long CF, the percolation threshold is below0.5wt%.