These mixtures were melted and homogenized with stirring at 135☌ for 2 hrs under a nitrogen atmosphere to eliminate moisture. To determine chemical structure dependence, a test was initiated with a highly crystalline polyester (1, 6 hexane-diol adipate), to which 5% of each of several crystalline TPU grades were added. Tests were performed to understand the behavior of various crystalline TPU grades and their effects on RHM properties.

Consequently, there is an increase in molecular weight and a fully reacted polyurethane with urethane and urea groups alternately placed in the chemical structure, resulting in a strong and durable adhesive bond. The final bond strength and chemical crosslinking is attained when the isocyanate functional groups begin to react with ambient humidity or substrates. The initial bond strength and physical crosslinking are activated upon cooling by the solidification of the adhesive next to the crystallization of the soft segments from the polyols.

After the crosslinking reaction of the RHM, the joint shows great final strength high flexibility, both at low and high temperatures and great resistance to hydrolysis, heat, and chemicals.ĭepending on the external environmental (humidity and temperature) and the substrates, the strength of the joint gradually increases as a function of time. RHMs are moisture-curing adhesives that display a fast molecular weight increase when reacted with water from ambient humidity or from free electrons in the bonded substrates.

Melt viscosity test