High Shear Processing of Expanded Vermiculite Filled Polymer Composites: Particle Size Effect on Flexible Composites

Filler dispersion is an important issue for polymer-based composites. Fillers can be dispersed by melt or solution processing methods. Solution-based mixing offers various combinations including ultrasonication, mechanical stirring, or high shear mixing. Planetary high shear mixing is a simple method with high dispersion performance. Dispersion and wetting of the fillers are provided by not only planetary shear movement of the mixer but also by the decrease in viscosity of the polymer phase because of high shear. Although that is advantageous for the dispersion of nanofillers, it might be challenging for the particles that have morphology with loosely bonded layers. To observe the effects of high shear mixing on expanded vermiculite (VMT) filled styrene-[ethylene-(ethylene-propylene)]-styrene (SEEPS) flexible composites, two different VMTs were used with different particle sizes at various VMT ratios from 1 to 30 wt%. Morphological, structural, thermal, mechanical properties, flame spread character of the composites, and viscosity of the solutions were analyzed. From morphological analysis, high shear mixing was found to be effective in terms of decreasing particle size and filler dispersion. While mechanical properties showed decrease, thermal stability, and flame retardancy of the composites increased. KEYWORDS: expanded vermiculite (VMT); flexible composites; flame retardancy; Planetary high shear mixing; styrene-[ethylene-(ethylene-propylene)]-styrene (SEEPS); thermoplastic elastomer