To study the interstellar chemical composition and interpret molecular observations, astrochemists have built chemical models over the years. Those models compute the composition of the gas and the icy mantles of interstellar grains taking in account a large number of processes, such as chemical reactions in the gas-phase, interactions with grain surfaces (sticking and evaporation) and chemical reactions at the surface of the grains. Those models rely on a number of parameters (physical parameters of the medium and intrinsic chemical parameters such as rate coefficients), which are estimated with an associated uncertainty. From a chemical point of view, those uncertainties are mainly due to an incomplete knowledge of the efficiency of the processes in the interstellar conditions. Many studies in the recent and past years have been undertaken to improve this knowledge, either using experimental or theoretical results in physico-chemistry.