Preparation and properties of PTFE/PAI nanocomposites

Polytetrafluoroethylene/poly(amide-imide) PTFE/PAI nanocomposites were prepared by precipitation of TORLON® 4000TF (PAI) into a PTFE latex containing nanoparticles with average diameters of 41 nm and spherical shape. Several samples were obtained by varying the relative ratio between PAI and PTFE. SEM and PCS analysis indicates that the precipitation of PAI in the presence of PTFE leads mainly, if not exclusively, to bimodal mixtures of the two homoparticles. The PTFE crystallization process was quite complex and, depending on the sample composition, single or multiple crystallization exotherms were observed. This behavior, discussed within the fractionated crystallization frame, was revealing of the PTFE dispersion degree within the PAI matrix. When the PTFE amount is lower than 20%, a perfect PTFE nanoparticle dispersion is obtained. Partial aggregation is observed for PTFE amounts ranging from 20 to 40% whereas extensive aggregation is found for PTFE amount higher that 40%. The dynamic-mechanical behavior indicates that the interactions at nanoparticle/polymer interface are rather weak. A greater increase in the relative modulus (Ec/Em) in the rubbery state region with respect to the glassy region is observed and was explained in terms of the particle aggregation state.