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The diffusion kinetics of water and acetone into dried PVOH polymer films have been measured simultaneously using the FTIR–ATR technique. The data have been fitted to a pseudo-Fickian model, along with allowance for a ‘lag’ time which lengthens considerably when the water mole fraction is low. It has been found that a case II model is viable at short times when the polymer is ‘glassy’ (<T g...
The dependence of the diffusion coefficient, D, of polymer systems on the Dynamically Accessible Volume (DAV) was calculated in the framework of the Bond Fluctuation Model. The quadratic relationship between dynamically accessible volume and diffusion coefficient, which has been observed for some other models, has been confirmed for high values of DAV, whereas smaller diffusion coefficients than those...
A novel application of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic imaging to study polymer interdiffusion and dissolution under high-pressure or supercritical carbon dioxide environments has been demonstrated. Miscible systems of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) of different molecular weights have been chosen for this investigation. These...
This paper addresses two important features of the diffusion of liquids into a molten polymer matrix: the dependence of the mutual diffusion coefficient on the liquid miscibility and molar mass of polymers. In addition, a rheological approach is chosen for its capacity to support modeling, and the mutual diffusion coefficient expressed with the free-volume theory, is estimated by an inverse method...
Penetrant diffusion in semicrystalline polyethylene was simulated by first generating model spherulitic systems, and then, in the same systems, generating penetrant trajectories. Spherulitic growth was mimicked with an algorithm able to generate structures comparable to those observed in polyethylene. Current limitations in the number of lattice points of the system restricted the minimum amorphous...
Nitrile rubber (NBR, 39:61wt% of acrylonitrile:butadiene) and styrene butadiene rubber (SBR, 50:50wt% of styrene:butadiene) matrices have been equilibrated by molecular dynamics (MD) simulations. Transition-state approach is used to calculate the diffusion and solubility coefficients of small penetrants in these matrices, indicating quite low values in NBR and reasonable agreement with experimental...
Sorption experiments are often conducted in gravimetric sorption columns where several deviations from ideal conditions could potentially occur. For example, heat effects due to solvent sorption, errors introduced due to concentration dependent diffusion coefficients and swelling are unavoidable. In this study, we develop a model to study the importance of the combination of these effects in obtaining...
Water transport in a densely crosslinked epoxy network, TGDDM–HHPA, was investigated by coupling time-resolved FTIR spectroscopy and gravimetric measurements. Vibrational analysis yielded information on the different water species present in the system and allowed a quantitative estimation of their population at sorption equilibrium.The transport of water molecules was found to follow a Fickian behaviour...
We reported a new preparation method in the previous paper, by which an excellent graded polymer blend was simply prepared. In this report, we propose a new model for the dissolution–diffusion process. The model was derived by obeying Fick's second law for diffusion and by assuming that the evaporation of the solvent in PMMA solution during the diffusion could be neglected. We then proved that this...
An algorithm able to mimic crystal lengthening, branching, widening and thickening was developed in order to build spherulites similar to those observed in polyethylene. The ranges of volume crystallinity and crystal width-to-thickness ratio attainable were ≤40% and 8–35, respectively. An on-lattice Monte Carlo-based algorithm was used to generate penetrant trajectories in the built spherulites. Diffusivity...
The geometry of the Dynamically Accessible Volume, DAV, in polymeric materials has been observed by means of the Bond Fluctuation Model. Simulations were conducted in conditions that yield varying amounts of accessible volume in the lattice, acting on the density of the system, and introducing geometrical restrictions to motion. A parameter has been defined to characterise the connectivity of holes...
Solvent diffusion into polymers is central to their performance, for example as controlled delivery pharmaceutical products. In this work, we present the novel application of terahertz (THz) time-domain reflectance spectroscopy to quantify the ingress of acetone into various polymer materials. Reflections from the top and bottom surfaces of the discs are temporally resolved, as is a reflection from...
A model reactive system was defined for studying experimentally and by simulation the competition between reaction and diffusion of two low molecular weight reactants, 2,3-epoxypropyl-phenylether (EPPE) and dipentylamine (DPA). Both reactants are miscible in a high-viscous molten polymer, poly(ethylene-co-vinyl acetate) (EVA). The comparison of the experimental rates of reaction for initially homogeneous...
Polystyrene-block-poly(4-vinylpyridine) (PS-b-PVP) forms hairy micelles with PVP and long PS block as the core and corona in toluene, respectively. Diffusion of the micelles in solution in the presence of poly(methyl methacrylate) (PMMA) or polystyrene homopolymer (h-PS), from dilute to semidilute, has been investigated by laser light scattering (LLS). Our results indicate the micelles only exhibit...
The capillary column inverse gas chromatography technique was used to determine diffusivity and solubility data for several solutes in a poly(styrene-co-acrylonitrile) random copolymer (SAN). Both infinite dilution and finite concentration experiments were conducted using an IGC-mass spectrometer (IGC-MS) technique that combines the performance of the gas chromatography technique with the resolution...
This paper reports the sorption and diffusion characteristics of methanol vapor in polyethylene terephthalate (PET). Amorphous PET, semicrystalline, biaxially oriented annealed and non-annealed samples have been studied for equilibrium sorption and kinetics of methanol. At activities of methanol less than 0.30, uptake shows Fickian kinetics and isotherm follows the Dual Mode model. Diffusion coefficients...
The diffusion coefficients of polystyrene (PS) in decahydronaphthalene (DHN) and in solutions of carbon dioxide (CO 2 ) and DHN were measured for dilute PS solutions over a range of temperatures and CO 2 –DHN ratios using high pressure dynamic light scattering. Infinite dilution diffusion coefficients (D 0 ) of PS and dynamic second virial coefficients (k D ) were determined...
Diffusion coefficients of small oligosaccharides within high strength poly(ethylene glycol)/poly(acrylic acid) interpenetrating network (PEG/PAA IPN) hydrogels were measured by diffusion through hydrogel slabs. The ability of hindered diffusion models previously presented in the literature to fit the experimental data is examined. A model based solely on effects due to hydrodynamics is compared to...
Star polymers with a hydrophobic cholane core and four poly(ethylene glycol) (PEG) arms, CA(EG n ) 4 , have been synthesized by anionic polymerization. Pulsed-gradient spin-echo NMR spectroscopy was used to study the diffusion behavior of the star polymers, ranging from 1000 to 10,000g/mol, in aqueous solutions and gels of poly(vinyl alcohol) (PVA) at 23°C. The star polymers have a...
Isotactic polypropylene (iPP) pellets were used to prepare isotactic polypropylene/polystyrene (iPP/PS) blends by diffusion and subsequent polymerization of styrene in water medium, with initiator benzoyl peroxide (BPO) added after diffusion of styrene. Two methods, differencing in whether the excess monomer was removed after diffusion, were used and parameters influencing PS contents were investigated...
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