Synthesis and characterization of interpenetrating polymer networks (IPNs) based on UV curable resin and blocked isocyanate/polyols

Interpenetrating polymer networks (IPNs) are a non-bonded combination of two or more cross-linked polymers and have superior mechanical properties. Herein we synthesized a series of IPNs by a sequential UV-thermal dual-curing method, which is consisted of UV curable resin network and polyurethanes (PU) network. Blocked isocyanate (BI), polyols, and UV curable resin solutions were mixing completely, the resulting mixture was exposed to UV light to obtain a single network. Then the double network was formed via thermally triggered reaction of deblocking-isocyanate and polyols. The effect of polyol hydroxyl number (from two to six) on properties of IPNs was systematically studied. The results exhibit that pentaerythritol as polyol can be dual-cured by UV and heating to give the highest tensile strength (17.5 MPa), of a 21% increase compared to unheated sample. Furthermore, a series of semi-interpenetrating networks (semi-IPNs) were obtained by using poly-tetramethylene ether glycol (PTMEG) instead of the polyols. The results showed that introducing inter-penetrating or semi-interpenetrating networks exhibit improved mechanical properties of the UV curable resin. Besides, the deblocking temperature of BI is just appropriate for the 3D-printing temperature.