Poly (vinyl chloride)(PVC) has been often used to prepare plastisols that are widely utilized in sealing gaskets for wide-mouth glass jars. However, since there have been safety concerns surrounding these materials, safer alternative materials such as polyurethanes are considered. By varying the NCO/OH molar ratio, here referred to as the R-value, the sealing properties of the urethane gaskets prepared from an aliphatic diisocyanate adduct, polyols and various additives were investigated. The optimum range of the R-values was found to be from 1.00 to 1.15 based on the desired mechanical properties of the prepared materials as effective sealing gaskets. Any value beyond this range means an excess amount of NCO groups resulting in an increased crosslinking as well as producing unreacted NCO groups behaving as dangling points, both of these yield unfavorable mechanical properties for the gaskets.