Influence of bentonite type in waterborne polyurethane nanocomposite mechanical properties

Aqueous dispersion of polyurethane ionomer (PUD), based on poly (propylene glycol) (PPG) as soft segment, isophorone diisocyanate (IPDI) as diisocyanate, dimethylol propionic acid (DMPA) as ionic center, hydrazine (HZ) as crosslinker and triethyl amine (TEA) as neutralizer, was reinforced with 1 to 5 wt % of clay to obtain nanocomposites. Substitution of Na+-montmorillonite for bentonite was made by using three types of bentonite. The tensile strength and elongation at break decreased for all nanocomposites having 5% clay in comparison to pristine polyurethane. The enhancement of mechanical properties over pristine polyurethane was achieved only by using 1% of clay. The structure of layered silicates in polyurethane was found to be maintained in some extent as evidenced from wide-angle X-ray diffraction analysis. Nevertheless, the rather weak and broad diffraction peaks appearing in the curves of bentonite clays nanocomposites indicated that a nanostructure of silicate in waterborne PU system has been formed using a low cost raw material and an environmental friendly aqueous polymer precursor.