Polystyrenes with macro-intercalated organoclay. Part II. Rheology and mechanical performance

Polymeric nanocomposites (PNC) of polstyrene (PS) with organoclay were studied for their rheological and mechanical behavior. The organoclay (COPS) is a product of clay quaternization with a copolymer of styrene with vinyl benzyl tri-methyl ammonium chloride. PNC preparation and characterization was described in Part I of this paper. The clay platelets in COPS and its PNC's are well dispersed, i.e. with the interlayer spacings of d 001=7–8 nm. By contrast, d 001=3–4 nm for PNC with Cloisite ® 10A. However, the COPS in PS formed large, deformable domains. At concentration exceeding 5.8-wt% of COPS, the domains started to form a three-dimensional network with enhanced elasticity and progressive viscoelastic non-linearity. At temperatures of 160–180 °C the neat COPS did not flow; its behavior resembled that of a crosslinked elastomer. Application of the time–temperature superposition led to master curves of bending moduli vs. 19 decades of reduced frequency. The curves indicated a transition at ca. 180 °C, most likely associated with the disintegration of ammonium ion clusters. With the same amount of clay the mechanical properties of PNC with COPS were slightly worse than those with Cloisite ® 10A—the immiscibility of COPS, and the presence of extractable (by the matrix) low molecular weight compounds explain the behavior.