Study On Preparation And Properties Of Polyimides/Attapulgite (PI/AT) Composites

Polyimide composites have been studied widely due to obtain improved comprehensive properties. Among these composites, polyimide/inorganic composites have gradually deep studied and achieved great research funding. However, the inorganic materials presently used in composites most focus on high purity nano materials, such as SiO2, TiO2, carbon nanotube et al which on one hand they improve the performance of polyimides, but on the other hand, they limit the multi-produce and application of composites because of the economic factor. In this thesis, we choose the cheap inorganic clay——attapulgite (AT) that has a wide array of sources and conduct modification on it, then prepare a series of polyimide/AT composites and study their properties.First, we adopt common used silane coupling agent APTES to modify AT, which enable the active-NH2group to graft on the AT surface and synthesize the dianhydride terminated co-polyimide ODA-ODPA-BPADA (co-PI), then AT is modified to co-PI via chemical bonding. The study results indicate that AT well disperses in the matrix except for a high loading, in which some aggregation occur in micro level. The thermal properties of composites are highly improved after adding1wt.%AT that the thermal decomposition temperature (Td) value increases from480℃to502℃, glass transition temperature (Tg) value also rises from222℃to239℃; the mechanical properties is strongly enhanced which show50%,80%,120%improvement in strength, modulus and breaking elongation, respectively, compared with pure polyimide. Moreover, all the composites film exhibit good optical property and have an effective ultraviolet shield property.Further, we adjust the proportion of compounds in co-PI, and study the effect of certain amount AT on properties of different PIs. Results show that all composites display better comprehensive properties than pure PIs and AT changes the molecular arrangement pile. When the ratio of BPADA and ODPA is1:3, the composite performs form brittle failure to tough failure in tension test, which indicates that AT has a positive effect on mechanical property of PI.Finally, we study the effect of AT on hyperbranched polyimides (HBPI) which show week mechanical properties because of lack of physics entanglement between inter molecules caused by globule structure. In the experiment, we modify the AT with isocyanate and prepare the amino terminated HBPI. Through the reaction between-NCO and-NH2, AT is grafted onto the HBPI and thus obtains the HBPI/AT composites. It is found that AT worked as chemical linkage and the whole composites form a network structure. Micro structure of HBPI is changed and thermal, mechanical properties are highly improved. What’s more, the surface property is transited from hydrophilic to hydrophobic.