The effects of pressure on reaction rates and final mechanical properties were studied for an unsaturated polyester (UP) and epoxy resin. A pressure chamber where reactions can be monitored by use of Raman spectroscopy has been built for these purposes. The chamber allows for pressures up to 13.8 MPa at 200 degrees C. An advanced temperature control system has been adapted to the vessel to precisely control and monitor sample temperature variations and overshoots. It is described how for an accelerated UP reaction increasing pressure will result in a competing effect on the reaction rate where the rate will initially lower, but with increased pressures it may accelerate due to acceleration of the reaction rate constants. The final mechanical properties exhibit a similar behavior slightly increasing with pressure but lowering as pressure is raised further. For epoxy, it was shown that the reaction kinetics were accelerated by pressure although no mechanical property differences could be noted for the pressure ranges tested. POLYM. ENG. SCI., 49:2099-2108, 2009. (C) 2009 Society of Plastics Engineers