Mass transport of low molecular weight compounds in polymers

Abstract Understanding mass transport of low molecular weight compounds in rubbery and glassy polymers is another factor of great relevance to interpret the physics and dynamics of polymer foaming and for the technological implementation of foaming processes. This chapter is dedicated to the illustration of the phenomenology of mass transport in polymers and of the approaches adopted to provide a theoretical basis for its interpretation. In particular, the relevant balance equations involved are discussed, evidencing the different behavior of rubbery polymers as compared to glassy polymers. Free volume approaches to model diffusion coefficients are presented, with a short description also of molecular models. Several kinds of experimental approaches devoted to the characterization of mass transport in polymers are described with a detailed discussion of gravimetric and vibrational spectroscopy (FTIR, Raman) methods.