The Dispersion And Coagulation Of Carbon Nano-particles In Polymeric Matrix

This paper presented two "impurity-free" modification methods for carbon nano-particles. One is grafting multi-walled carbon nano-tubes (MWNT) by poly D-lactic acid (PDLA). PDLA and poly L-lactic acid (PLLA) matrix could form stereo-complex crystals as the strong interactions between PDLA and PLLA, which promoted the dispersion of MWNT in PLLA effectively. It was found that the formation of MWNT conductive network can promote the formation of stereo-complex crystals network, and improve the heat resistance of the PLLA-based conductive composites significantly with a low PDLA amount. Materials’ Tg increased by15-20℃as MWNT network significantly delayed the glass transition.The other method is using self-degradated low molecular poly (amic acid)(PAA) as impurity-free dispersant. Carbon black (CB) and PAA/N-methyl-2-pyrrolidone (NMP) solution were milled in ball miller. The effect of PAA modification on the CB particles was researched by Raman, IR, and UV-Vis. TEM observation was used to check dispersion quality and the results showed that PAA modified CB particles dispersed uniformly in the composite under a certain amount (10wt%) and the average size of the particles was about200nm. The molecular weight of PAA added in milling progress played an important role on the dispersion of CB. The dispersion uniformity of CB in PI matrix was greatly improved as the increase of PAA molecular weight.The preparation and properties of high-performance PI/CB composite films were studied."Impurity-free" dispersant PAA not only stabilizes the dispersion of CB particles effectively, improving the reproducibility of resistivity for resulted PI/CB films, but also enhances the interface strength of CB and PI matrix, improving the mechanical performance greatly, which is far better than in the general commercial dispersants. The spontaneous coagulation behavior of CB in PAA/NMP solution was researched. A physical gel would formed when CB particles and PAA co-exist in the solvent, in which carbon black particles acts as the crosslink points and PAA molecular chains acts as network cable. The gel was reversible after destroyed.