Study On High Temperature Polymer PTC Composites

In this thesis,study aims to explore and prepare lower room temperature resistivity,higher switching temperature PTC composite materials and testing its room temperature resistivity,PTC intensity repeatability.which is in order to weaken or eliminate the NTC effect,develop the better stability of polymer PTC materials.At first,we choose a kind of crystalline engineering plastics called PPS with high melting point of 280? as matrix for preparing PTC composite material with its Curie temperature beyond 200?.PTC composite material of PPS/GP and PPS/CB are prepared by adjusting the content of conductive filler and adopting different filler size,in the same time,testing its resistivity and resistivity temperature characteristic,the results show that idea that taking PPS as matrix to prepare PTC composite material with high switch temperature and high temperature resistance is feasible.But thus leading to its room temperature resistivity is not ideal and low PTC intensity,we have to find a way to improve it.Then,we conduct further exploration.we choose anther kind of crystalline polymer called PTFE with high melting point and high heat stability as binary matrix for preparing system of PPS/PTFE/conductive filler in order to weaken or eliminate the NTC effect and enhance stability.Adding the binary matrix is regarded as the simplest and the most efficient method to eliminate the NTC effect.The system PPS/PTFE/GP obtains high stability,no NTC effect and Its PTC strength is 4.0 when the mass ratio of PPS/PTFE is 7/3.At last,we perform the further exploration because the PTC property of PPS/PTFE/GP system is good.Whether the property of PTC composite material is good or not if taking the PTFE as matrix alone.For that,we choose three different kinds of conductive filler(CB,GP,CNF)to fill in PTFE with different content.Result show that PTC phenomenon of the system PTFE/CNF is weak and less than 1.0;For system PTFE/BP2000,when the content of BP2000 is 1wt%,its intensity is 2.6;As for system PTFE/GP,when the content of GP is 8wt%,its intensity is 3.6,which is the best of systems.In addiction,the system PTFE/conductive filler obtain low room temperature conductivity about 100?·cm and its switch temperature is close to the melting point about 325?.