Correlating mechanical properties of polyurethane-organoclay nanocomposite coatings with processing

In this study, mechanical properties were computed for polyurethane (PU)/ Cloisite20A (C20A) coatings. These coatings material were synthesized by three processing methods at variable clay weight percentages (0-3 wt%). Dispersion of C20A platelets in pre-polymer suspension were assessed by the transmission electron microscopy (TEM). In order to scrutinize the conformational changes in the functional groups at the molecular level, deconvolution of Fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR) spectrum was employed. An enhancement in elongation at break with the reduction in stiffness for the nanocomposites was quantified from dynamic tensile testing. For instance, 3 wt% C20A PU nanocomposites processed by sonication and subsequent homogenization showed a decrease of Young's modulus by 53% but exhibits an increase in both elongation at break and toughness by 97% and 93% respectively. The amount of shear force exerted during the processing protocols played a crucial role w.r.t dispersion of C20A. Even at low wt% (1-2) nanocomposite samples exhibit better mechanical properties in simultaneous processing using sonication and homogenization. To quantify the relationship between theoretical and experimental observations, three conventional mathematical models have been applied. Deviations in model behavior was observed, due to the high sensitivity of the nanocomposites to processing schemes, even with same chemical formulations.

Automated summary

This study synthesized PU/C20A coatings material using different processing methods at varying clay weight percentages, investigated the dispersion of C20A platelets in pre-polymer suspension, and quantified the mechanical properties and structural changes of the nanocomposites.