Transport of gases in miscible polymer blends above and below the glass transition region

Abstract

The study of diffusion and permeation of methane, nitrogen, and helium in miscible blends of poly(styrene-stat-acrylonitrile) (PSAN) and poly(methy1 methacrylate) (PMMA) at 35-140°C shows that permeation coefficients (P) of helium followed the linear logarithmic mixing rule. Positive deviations from the linear logarithmic mixing rule were observed for permeation and diffusion coefficients (0) of methane and nitrogen below the glass transition temperature (Tg). The deviations decreased with increasing temperature and disappeared above Tr The experimental results were analyzed by free volume and activated state theories. The Arrhenius plots of log D or log P us. the reciprocal of temperature exhibited discontinuities in the glass transition region for all gases and blend compositions. The discontinuities are caused by large thermal expansion coefficient differences between the rubbery and glassy states of PSAN and PMMA. The sorption of methane in 50150 PSAN/ PMMA has dual-mode characteristics below Tr Experimental Studies MaterialsPoly(styrene-stat-acrylonitrile) (PSAN), containing 30 wt. 070 of acrylonitrile and poly(methy1 methacrylate) (PMMA) were obtained from Scientific Polymer Products. The weightaverage molecular weight of PSAN is 185,000 as supplied by the manufacturer. The weight-average molecular weight of PMMA is 93,000 and the number-average molecular weight 46,000.The glass transition temperatures ( T,) of the polymers were measured by the use of a Perkin Elmer 7 Series differential scanning calorimeter (DSC). DSC experiments were carried

Experimental and Simulation Studies on the Transport of Argon through Poly(pentaerythritoltribenzoate acrylate)

“…For some polymers, Arrhenius plots of the diffusion coefficient present discontinuities in the glass transition region which have been linked to high values of the Δα/α g ratio, where α g is the thermal expansion coefficient at the glassy state and Δα is the change of the thermal expansion coefficient at T g . − These discontinuities have not been observed for those polymers in which Δα/α g < 1. Accordingly, whether the values of D evolve smoothly with temperature in the transition from the glassy to the rubbery state depends on the Δα/α g ratio …”

“…Accordingly, whether the values of D evolve smoothly with temperature in the transition from the glassy to the rubbery state depends on the ∆R/R g ratio. 43…”

Oxygen permeability in blends of a vinyl alcohol/ethylene copolymer and a metallocenic ethylene/1‐octene copolymer

“…Hopfenberg and Paul5 reviewed the literature on gas transport in polymer blends and found that the following simple mixing rule for P was useful in the analysis of transport data in blends and copolymers: where ϕ x is the volume fraction of component x and P x is the permeation coefficient. The permeability of homogeneous blends21–23 consisting of miscible polymers approximately obeys the logarithmic rule of mixing, which is derived under the assumption of the additivity of the free volumes of the components. On the other hand, heterogeneous blends are known to show an S‐shape dependence of the logarithm of permeability on the blend composition.…”

Gas transport in vulcanized natural rubber-cellulose. II. Composites

“…The free volume of natural rubber–cellulose composites at a given temperature and pressure can be written as:42, 43 where υ fA , υ fB , and ϕ A , ϕ B are, respectively, the free volumes and volume fractions of components A (natural rubber) and B (cellulose), respectively, in the mixture, whereas Δυ f is the excess free volume resulting from the mixture of cellulose and natural rubber. By taking into account the mixing rule: where D A and D B are, respectively, the diffusion coefficients of the penetrant in the natural rubber and cellulose phases of the composite.…”