Silanization as a strategy to design polyurethane-acrylic hybrid pressure-sensitive adhesives

Pressure-sensitive adhesives (PSAs) are a critical class of adhesives used in numerous applications. Acrylic copolymers and polyurethanes are two main categories of polymers that PSAs are made from. However, to take advantage of unique properties of both of them, polyurethane-acrylic hybrid PSAs have been proposed. To date, for synthesis of these hybrid PSAs, there should have been an acrylic comonomer containing a specific functional group to be able to react with the isocyanate group. This research was conducted to eliminate the need for such an acrylic comonomer with a specific functional group through silanization. For this purpose, firstly, a silanized polyurethane (SPU) was synthesized through silanization of a polyol. Subsequently, copolymerization of two acrylic comonomers was performed in the absence or presence of SPU. In the next step, prior to adding the acrylic comonomers to the SPU, silane was added to SPU to enable higher grafting. The PSA containing 0.04 wt % of silane showed a peel force, static shear strength, and tack of 1.6, 1.4, and 2.9 times those of the acrylic PSA on stainless steel, respectively. With this proposed silanization strategy, it is possible to design a wide variety of polyurethane-acrylic hybrid polymers.