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The relaxation behaviour of coextruded linear low-density polyethylene (LLDPE) films, prepared from copolymers of ethylene-1-octene, is reported. The spectra, expressed in terms of loss tan δ, present a γ relaxation of lower intensity than that exhibited for conventional low density polyethylene of the same crystallinity, followed, with increasing temperature, by a β relaxation process that appears...
Solvent transport into Santoprene thermoplastic rubber samples exposed to n-alkanes (C 5 to C 16 ), 2,2,4-trimethylpentane, cyclohexane and 1,2,3,4-tetrahydronaphthalene in the temperature interval 25-70°C has been studied. For all liquids, equilibrium penetrant uptake and degree of penetrant overshoot have been influenced by factors such as penetrant size, shape, polymer morphology...
Molecular dynamics (MD) simulations have been used to study the diffusion of methane as a small molecule penetrant example in cis-1,4-polybutadiene (PBD). The non-bonded potential for an anisotropic united atom (AUA) representation of the -CH group was calibrated by adjusting the constants to fit experimental volume temperature data for the polymer melt. This potential was used along with...
In the first of two papers studying diffusion in bimodal and polydisperse polymer solutions, the self-diffusion coefficients of various protonated polymers in a series of bimodal solutions containing deuterated polymers have been measured. Utilizing the chemical specificity of the pulsed-field gradient nuclear magnetic resonance (p.f.g.n.m.r.) technique, it was possible to study the effects of both...
In the second of two papers studying diffusion in bimodal and polydisperse polymer solutions, the average self-diffusion coefficient of two polydisperse polystyrene samples has been measured as a function of concentration by the pulsed-field gradient nuclear magnetic resonance technique. Utilizing the concepts introduced in the previous paper, estimates of the molecular-weight distribution obtained...
Solvent uptake in thin, amorphous samples of poly(ether ether ketone), poly(ether imide) and a 50 blend has been measured as a function of temperature. Diffusion coefficients, percentage weight increase and apparent activation energies have been calculated. The 50 blend shows anomalous diffusion behaviour which may be attributed to specific interactions between the homopolymers and density changes...
The diffusion and transport of inhibitor-free styrene through crosslinked natural rubber (NR) have been studied at various temperatures. NR has been vulcanized by conventional, efficient, peroxide and mixed vulcanization techniques. The dependence of diffusion coefficient on the crosslinking system has been studied for all the systems. The influence of temperature on the sorption and the activation...
Permeation fluxes of water and acetic acid from water-acetic acid mixtures were independently monitored as a function of time in differential permeation with dual detection. Two successive permeation waves were detected for water permeation and only one for acetic acid permeation in the transient regime. The onset of the second permeation wave for water coincides with that of acetic acid permeate...
Ethylene-vinyl alcohol (EVAL) membranes with particles-bonded structure are prepared by phase inversion from DMSO solvent into the coagulation baths of water and isopropanol (IPA) mixture. It is based on controlling the relative diffusion rate of solvent to nonsolvent and the liquid-liquid demixing area. Using this analysis, it can explain the effects of adding IPA to the water bath on the formation...
Self-diffusion of the cation, the anion and the polymer chain in the low-molecular-weight polymer electrolyte systems Li(CF 3 SO 3 )PEG 10 and LiN(CF 3 SO 2 ) 2 PEG 10 has been studied as a function of temperature using nuclear magnetic resonance spectroscopy. The diffusion behaviour is very similar in the two systems, where the cation...
Experimental values for sorption, desorption, resorption and redesorption processes for a polymeric blend of ethylene-propylene random copolymer and isotactic polypropylene were obtained at 25, 40, 55 and 70°C with haloalkanes using a gravimetric method. Diffusion coefficients exhibited a dependence on the type and nature of solvent molecules. In view of an increase in diffusivity with temperature,...
Molecular dynamics (MD) simulations have been used to study bulk atactic polystyrene (aPS). A united-atom non-bonded potential is calibrated for the aromatic-ring carbons, which, along with previously determined non-bonded functions, results in a good representation of pressure-volume-temperature relations for aPS. Experimental X-ray scattering data for glassy aPS are well reproduced in simulation...
The sorption and diffusion of four aromatic hydrocarbons through vulcanized natural rubber filled with high-abrasion furnace black (HAF) and that filled with silica (Ultrasil VN3) at the same loading have been investigated in the temperature range of 28–70°C by conventional weight-gain experiments. The diffusion results have been analysed in terms of the Fickian diffusion equation. The transport behaviour...
The diffusion phenomena, including the molecular diffusion processes and the effect of diffusion on the cure kinetics and molecular size distribution, during the curing of a zinc-catalysed cyanate ester resin have been studied. The average diffusivity, which was estimated using the dielectric analysis-based approach, decreased by several orders of magnitude during the curing process. The molecular...
The two-stage integral sorption data for water vapour in a glassy poly(2-hydroxyethyl methacrylate) (PHEMA) membrane are analysed by the variable-surface concentration model, the diffusion-relaxation model, and the diffusion-reaction model. Satisfactory fitting of the data and similar kinetic and equilibrium parameters are obtained using these models. The diffusion coefficient for water is about...
The sorption and desorption of water vapour into and from a hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) membrane were examined with the gravimetric method in an integral manner at 37 o C. The sorption isotherm of water in PHEMA at 37 o C followed Henry's law at lower activities and Flory-Huggins type sorption at higher activities. The water content which leads to a glass-rubber...
Treatment of experimental dependence of the translational friction coefficient on molecular weight, f(M), obtained for semi-flexible macromolecules, is discussed. A draining effect is significant for these chains and must be taken into account to determine the correct values of unperturbed dimensions of the macromolecule. For this purpose a new relation between the Flory factor P and the scaling exponent...
The diffusion of methylene chloride and tetrahydrofuran in amorphous poly(ether ether ketone) (PEEK) films was studied by the following method. A specimen was immersed in the solvent, the reaction was stopped by immersing the specimen in liquid nitrogen, the dried specimen was finally fractured into two pieces, one for observation under scanning electron microscope and the other for thermal analysis...
Molecular transport of aromatic hydrocarbons through crosslinked SBR has been carried out in the temperature range 25-65°C. SBR has been vulcanized by four different vulcanizing techniques viz., conventional, efficient, dicumyl peroxide and a mixture consisting of sulfur and peroxide. SBR vulcanized with EV system showed highest solvent uptake tendency and that vulcanized with peroxide showed the...
This paper compares the kinetic behaviour of a given chemical reaction in homogeneous and heterogeneous polymer melts using a batch mixer as reactor. The underlying chemistry was the addition esterification of epoxy groups attached to a polymer backbone and a carboxylic acid. Specifically, the homogeneous polymer melt was composed of 1-naphthylacetic acid (NAA) and a random copolymer of ethylene,...
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