Local Rigidity as a Criterion of Gas Permeation of Polymer and Composition Materials; PAL and TSL Experiments (original) (raw)
Related papers
Elementary prediction of gas permeability in glassy polymers
The transport model proposed by Minelli and Sarti for the representation of gas and vapor permeability in glassy polymers has been extensively applied to various systems, and the model results are thoroughly analyzed. The approach is based on fundamental theory for the diffusion of low penetrant species in polymers, in which the diffusivity is considered as the product of the molecular mobility, and a ther-modynamic coefficient, accounting for the concentration dependence of the chemical potential. The model relies on the thermodynamic description of the penetrant/polymer systems provided by the NonEquilibrium Thermodynamics for Glassy Polymers (NET-GP) approach. The penetrant mobility is assumed to depend exponentially on penetrant concentration, and the model contains two parameters only: mobility coefficient at infinite dilution and plasticization factor. The model parameters obtained from the analysis of the permeability behaviors of various systems have been examined and general correlations are derived. The mobility coefficient is indeed correlated to the properties of the pure penetrants (penetrant molecular size) and pure polymer (fractional free volume and characteristic energy). This allows the derivation of a simple and general expression for the prediction of the permeability of any penetrant species in glassy polymers in the range of low penetrant pressures, as well as the selectivity of any gas pair. Remarkably, the model predictions are able to represent quite accurately the experimental data available in the literature. Furthermore, the plasticization factor is correlated to the swelling produced by the penetrant into the glassy polymer matrix, obtaining thus a reliable tool for the estimation of the pressure dependence of gas permeability on upstream pressure.
Acta Physica Polonica A, 2017
Gas barrier properties of polymeric membranes with different rigidness of their matrix where studied by gas phase permeation measurements. Gas transport results in membranes made of epoxy resin with different cross linking densities and epoxy resin with dispersed few layer graphene fillers were discussed and compared in the framework of the free volume theory of diffusion. Transport in cellulose membranes was found to occur in the diffusion configurational regime. The physical description of the transport properties was based on positron annihilation lifetime spectroscopy measurements which allowed to evaluate experimentally the fractional free volume in epoxy resin membranes and the size of rigid elongated cavities in cellulose thin films.
Permeability of gas mixtures in glassy polymers with and without plasticization
In this research, the solubility, permeability and diffusivity of gas mixtures through glassy polymers were comprehensively studied. The diffusivity of the components in the mixture was assumed to be a function of the concentration of all components in the mixture. Then, the permeability of pure species was expanded to the gas mixtures and to check the validity, the model was fitted to the experimental data for permeation of CO 2 /CH 4 through different glassy membranes and the parameters of the model were calculated. Afterwards, the obtained parameters were used for predicting the permeability of CO 2 and CH 4 in the mixture. The results showed that the solubility, diffusivity, and the permeability of CO 2 in the glassy polymers are suppressed in the presence of CH 4 as well as plasticization. Moreover, the diffusivity (D) for pure CO 2 is significantly pressure dependent in the presence of plasticization whereas with the increase in the CH 4 fraction, this dependency decreases due to the reduction in the plasticization.
Gas permeameter for polymers and nanocomposites: a new equipment
SN Applied Sciences
Information on the gas transport coefficients in the permeation of homogeneous semipermeable materials such as semicrystalline polymers under extreme pressures and temperatures is rarely found in the literature. Therefore, the objective of this work is to showcase innovation regarding the accuracy and usability of the medium pressure and temperature gas permeameter suitable for polymeric and polymeric nanocomposite plates built by the authors, which was tested with nitrogen at 1 MPa and 69 °C (342.15 K) permeating pure high density polyethylene samples (HDPE) and HDPE samples with added nanoclay, redoing the tests published in a previous work on the subject. The results were compared against data obtained previously and information present in the literature, validating the permeameter presented in this work, which is capable of analyzing gas permeability under the described conditions with greater accuracy and ease of operation than the previous model for the values of the transport...
Gas Transport in Prepregs : Model and Permeability Experiments
2009
Controlling voids and porosity is important when processing composite structures [1] as they have a negative effect on mechanical and physical properties of a laminate [2,3]. In aerospace applications there is often an upper limit on the amount of porosity allowed to ensure that the laminate meets strength specifications. The amount of voids in a laminate is governed by the interaction of many factors including: type of prepreg (chemistry, tack, fibre architecture, morphology), ply orientation, ply terminations, layup method, debulking, laminate size and shape, detailed geometry (curvature and radii), tooling (male or female), bagging details, and process cycle (temperature, vacuum, and pressure). Although there are several theories in the literature about individual phenomena such void growth and dissolution, the subject is complex and not yet fully understood.