Preparation And Properties Of Polymer/Rod-Like Silicate Nanocomposites

Recent advances in preparing polymer-inorganic nanocomposites with superior properties have stimulated great interest from both academy and industry. Among nanoparticles with various morphologies, fibrous or rod-like nanoparticles distinguished themselves as very promising enforcement materials in view of their large surface areas as well as high aspect ratios. Driven by the idea to explore cost economical fibrous nanoparticles, we described here the preparation and properties of polyimide/rod-like silicate nanocomposites and PMMA/rod-like silicate nanocomposites, by using attapulgite (ATT), a kind of natural rod-like clay, as the inorganic component.So far, several modification approaches including cation exchange and silylation have been proposed to turn the surface of ATT more hydrophobic. However, there are few reports on modification of ATT directly using agents that are structurally and property-wise identical to the matrix polymer, which is among the most desirable ways to optimize the properties of polymeric nanocomposites. Two novel methods of surface modification of ATT were developed here and characterized carefully. The corresponding polymeric nanocomposites were prepared and their morphologies and properties were studied as mentioned below.Firstly, Rod-like silicate/polyimide nanocomposites were successfully prepared from solution of poly (amic acid) and attapulgite modified by 4,4'-oxydianiline(ODA). ODA-modified ATT was obtained using urea linking chemistry and characterized by FTIR and TGA. High efficiency of grafting made the surface of ATT more hydrophobic, resulting in dramatically improved colloidal stability and homogeneous dispersion of ATT nanorods in polyimide matrix, which was investigated by SEM and TEM. The effect of ATT content on mechanical and thermal properties of PI/ATT nanocomposites was studied. A 70% increase in the tensile modulus of PI/ATT nanocomposites was obtained compared to that of pure PI. Both the maximum stress and the elongation increased at relatively low ATT content. In addition, both the glass transition temperatures and decomposition temperatures of nanocomposites are higher than that of pure PI. Secondly, the AGE modified ATT was obtained through the reaction between the silanol group of ATT and the oxirane ring of AGE. The AGE modified ATT were then copolymerized with MMA to produce organo-ATT (OATT). OATT exhibits better compatibility with organic solvents as demonstrated by the improved colloidal stability. PMMA/OATT nanocomposites were prepared by melt blending. The characterization on structure and properties of PMMA/OATT nanocomposites indicate that ATT were homogeneously dispersed and the storage modulus and glass transition temperature increased slightly. Rheology tests showed a less increase in modulus and viscosity than expected. It probably besause the rod-like silicate entrapped in PMMA domain was difficult to contribute to the overall solid-like transition due to the insufficient fluidity of PMMA.