Polyurethane foam is created through two primary reactions that compete for isocyanate monomer. In the first, isocyanate reacts with polyol to produce polymer, eventually creating a rigid solid. In the second, isocyanate reacts with water to produce CO2 gas that drives foam expansion. The kinetics of the resin polymerization were evaluated using a IR spectrophotometry on a dry polyurethane precursor, in order to separate the curing and blowing reactions. The kinetics of the gas generating reaction were measured by tracking volume evolution with time in the curing system while simultaneously measuring the system pressure. As the material polymerizes, it becomes both more viscous and viscoelastic, hindering expansion; hence, gas bubbles become pressurized, since there is no change in volume though more gas has been created. For this reason, we monitored the system pressure to help elucidate bubble pressurization and more accurately measure gas formation. Results show that the foaming reaction continues even after foam expansion is stopped. However, the curing reaction continues for some time after the gas generating reaction is complete. Understanding bubble pressurization can also help us understand dimensional stability of the solid foam as it ages, since diffusion of the CO2 out of the bubbles can change the solid properties over time. We have determined that the competing reactions can be treated as separable primary reactions, as the isocyanate is in excess during the expansion stages of the foam formation. A condensation-chemistry form of the curing reaction is shown to work well when compared to the IR data. A Michaelis-Menten kinetic approach is used to represent the foaming reaction. Both reactions show Arrhenius-type temperature dependence. Data are used to populate the model, which will be discussed in a companion presentation. Other experiments will provide model validation in complex geometries, including an idealized structural foam mold.