Mechanical properties and permeability of polypropylene and poly(ethylene terephthalate) mixtures

Abstract

AbstractThe synthetic membranes currently used for soil stabilization and road construction are mainly made of polypropylene and of polyesters. They are used separately for each application. The polymer used has an effect on the wettability and, the permeability of the membrane. The polypropylene membranes, for instance, have a zero wettability, whereas it is high for polyester membranes. This paper reports on the mechanical properties and the permeability of mixtures of polypropylene (PP) and poly(ethylene terephthalate) (PET). The elastic modulus of the mixture was at a minimum for a 50/50 mixture. For the other compositions, the moduli gave a positive deviation as compared with the additivity equation results. This is probably due to the fact that pure PET has a fragile behavior at the temperature at which the mechanical tests were run. This 50/50 composition corresponds to the domain where a phase inversion occurs. The permeability to water vapor gave an S‐shape curve that is typical of a “mixture” of immiscible polymers. The diffusion of the water molecules is controlled by the continuous phase. To compatibilize the two homopolymers, a 94/6 copolymer of PP and of polyacrylic acid was added, at various levels, to a 60/40 mixture of PET and PP: This did not affect markedly the elastic modulus. The yield stress increased, however, indicating that we had a better adhesion and that the copolymer seems to have a certain emulsifier effect, increasing the quality of the dispersion.