Swelling and diffusion characteristics of polar and nonpolar polymers in asphalt

The swelling and diffusion characteristics of a polar polymer [ethylene vinyl acetate (EVA)] and a nonpolar polymer [low-density polyethylene (LDPE)] were studied with swelling experiments of the polymers in asphalt at different temperatures. The study showed that the diffusion mechanisms for LDPE and EVA were different and temperature-dependent. In the case of LDPE, the observed diffusion was anomalous at both swelling temperatures (70 and 90°C). LDPE at 90°C showed sigmoidal solvent-uptake behavior during the initial period of swelling and a sorption overshoot in a later period. EVA showed Fickian transport at 60°C and anomalous diffusion at a higher swelling temperature (70°C) with sigmoidal uptake behavior. An analysis of the diffusion coefficients and the Fourier transform infrared results showed that the diffusing molecules were different in the case of LDPE and EVA, and there were possible polymer–asphalt interactions. Differential scanning calorimetry and swelling studies showed that penetrant-induced crystallization affected the diffusion process in the case of LDPE. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phenomenological modeling of anomalous diffusion in polymers

Both normal and anomalous diffusion kinetics are considered in this article. Models of the relaxation, convection, and wetting–drying‐cycle kinetics and some other kinds of diffusion kinetics are evaluated. Analytically tractable solutions (when available) are presented. All calculations have been performed with the new nonlinear regression software Fitter (Moscow, Russia). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1102–1114, 2005     

Hindered diffusion of flexible polymers through polyimide ultrafiltration membranes

The hindered diffusion of polystyrene in dilute solutions of ethyl acetate through polyimide ultrafiltration membranes has been investigated. The present system did not show specific membrane‐solute interactions; furthermore, polystyrene can be considered as a flexible polymer coil. It is shown that the hindered diffusive permeability for monodisperse dilute solutions for a series of molecular weights can be compared well with the diffusive permeability curve of one polydisperse dilute polystyrene solution. In the case of very dilute solutions, the polymer coils have no interaction with each other, and the whole range of molecular‐weight‐dependent permeabilities can be determined from only one measurement. The diffusion behavior of polydisperse solutions through various polyimide membranes has been investigated as well. It was found that the diffusive permeability curve is strongly dependent on the type of membrane, that is, on the pore size distribution. It was not possible to calculate a pore size distribution from diffusion experiments due to mathematical limitations. Nevertheless, it was shown that hindered diffusion measurements are useful to estimate a maximum pore size for each membrane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1180–1193, 2000     

Diffusion of two associated solvents in various compositions through a swelling polymer material,EVAc

The particular sorption by a swelling polymer with the transfer of hydrocarbons was studied in order to evaluate some barrier properties of this material. The transfer of two types of solvents through two varieties of ethylene vinyl acetate was investigated: absorption of pure toluene and pure n‐hexane and absorption of a toluene/hexane mixture in various compositions. A comparison between the two processes showed that these transfers were very different and depended on two factors: vinyl acetate content and composition of the mixture. The kinetics of absorption were calculated for various compositions. The profiles of concentration as well as the kinetics of swelling were evaluated using a numerical model deduced from the general theory of radial diffusion of a substance with change in dimensions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2099–2106, 2007     

The effects of the pH value of the swelling medium on the kinetics of the swelling of a poly(acrylic acid) hydrogel

The isothermal kinetics curves of the swelling of a poly(acrylic acid) hydrogel in buffer solutions of different pH values (5, 7, and 9) at temperatures ranging from 30 to 40°C were determined. The possibilities of applying the Fick kinetics model and the Peppas equation were examined. It was found that the applicability of these models were limited. The kinetics model of a first‐order chemical reaction was found to describe the swelling kinetics of the PAA hydrogel in all the investigated buffer solution at all the investigated temperatures. Swelling kinetics is determined by the rate of expansion of the network. The kinetic parameters (E_a, ln A) of the swelling of the PAA hydrogel in buffer solutions of different pH values were determined. The activation energy and the pre‐exponential factor of the swelling of the PAA hydrogel in buffer medium decreased with increasing pH value of the swelling medium. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effect of high-intensity ultrasound on solid polymers

Powders of polyethylene, polypropylene, poly(vinyl chloride) and poly(methyl methacrylate) have been subjected to irradiation with high-intensity ultrasound while suspended in water. Changes in the particle sizes and the surface morphology were noted and the pattern of the results was correlated with the physical properties of the materials. In anticipation of sonochemically enhanced reactions at polymer surfaces, the effect on a polyethylene sheet was also examined. The implications of the results for preparative methods as well as surface reactions are discussed.     

Cyclic viscoplasticity of solid polymers: The effects of strain rate and amplitude of deformation

Observations are reported on polypropylene random copolymer in uniaxial cyclic tensile tests with various strain rates (ranging from 1.7 × 10⁻⁴ to 8.3 × 10⁻³ s⁻¹). Each cycle of deformation involves tension up to the maximal strain ε_max (from 0.05 to 0.20) and retraction down to the zero stress. The study focuses on deformation programs with 10-50 cycles in each test. A constitutive model is derived for the viscoplastic behavior of a solid polymer at three-dimensional cyclic deformations with small strains. Material constants in the stress-strain relations are found by fitting the experimental data. Good agreement is demonstrated between the observations and the results of numerical simulation.     

油田堵水调剖用吸水膨胀聚合物的研究

采用丙烯酰胺(AM)、丙烯酸(AA)、丙烯腈(AN)三元共聚法合成了两种分别适于淡水和盐水的吸水膨胀聚合物。在该种聚合物合成中掺入了30％粉煤灰颗粒作骨架,N,N-二甲基丙烯酰胺(MBIN)作交联剂,这种聚合物适于油田注水井及油井堵水调剖用。采用正交实验法对最佳吸水膨胀配方进行了优选。     

Mathematical modeling of water uptake through diffusion in 3D inhomogeneous swelling substrates

Diffusion‐driven water uptake in a substrate (imbibition) is a subject of great interest in the field of food technology. This is a particular challenge for rice grains that are preprocessed to accelerate the water uptake, i.e., to reduce the cooking time. Rice preprocessing disrupts the mesostructural order of starch and induces a microporous structure in the grains. The meso‐ and microstructural length scales have not been considered in joint approach until now. The (re)hydration of rice grains can be modeled by free (concentration‐driven) diffusion or by water demand‐driven diffusion. The latter is driven by the ceiling moisture content related to the extent of gelatinization of the rice substrate network. This network can be regarded as a fractal structure. As the spatial resolution of our models is limited, we choose to model the apparent water transport by a set of coupled partial differential equations (PDEs). Current models of water uptake are often limited to a single dimension, and the swelling of the substrate is not taken into account. In this article, we derive a set of PDEs to model water uptake in a three‐dimensional (3D) inhomogeneous substrate for different types of water diffusion as well as the swelling of the substrate during water uptake. We will present simulation results for different 3D (macroscopic) structures and diffusion models and compare these results, qualitatively, with the experimental results acquired from magnetic resonance imaging. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

The phase structure,chain diffusion motion and local reorientation motion: C Solid-state NMR study on the highly-crystalline solid polymer electrolytes

In our previous paper, we investigated the influence of the phase structure on the polymeric chain diffusion in the complexed crystals of solid polymer electrolytes of PEO:LiAsF₆ and PEO:LiCF₃SO₃. We observed that with the increase of the crystallinity, the chain diffusion rate decreases dramatically. In this work, by employing the ¹³C CODEX NMR spectroscopy, we demonstrate that opposite to the behavior of the chain diffusion motion, the local reorientation motion of polymeric chains within the complexed crystals are greatly increased with the increase of the crystallinity, which is accompanied by the change of the phase structure. The relationship between the different molecular motions within the complexed crystals and the phase structure are discussed therefore.     

Water diffusion in a soft contact lens polymer and its tolerance to UV radiation studied by positron lifetime technique

The kinetics of water sorption, the topology or the free‐volume changes due to the presence of sorbed water in a soft contact lens polymer, poly(2‐hydroxyethyl methacrylate), were investigated by using the positron lifetime technique. It was found that the ortho‐positronium lifetime increases in the beginning of sorption because of microstructural swelling of the polymer matrix. After reaching a maximum, the lifetime decreases and becomes constant, maybe because of the filling of the free‐volume holes with water molecules. The diffusion process is found to be non‐Fickian. By using the dual‐mode sorption model, the Fickian‐controlled part and the relaxation‐controlled part of diffusion were separated. Further, the positron results seem to indicate the existence of water clusters in the sorbed lens material. The tolerance or stability of the soft lens material to UV radiation seems to be satisfactory as revealed by positron results. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1355–1366, 2004     

Determination of the kinetics of diffusion in coals by solvent swelling techniques

A simple technique has been developed for measuring the kinetics of solvent diffusion in coals at various temperatures. The technique is based on a well-known method for measuring the volumetric swelling of coals by solvents. Several coals have been examined in both pyridine and tetrahydrofuran, at temperatures between 298 and 332 K. The diffusion follows the well-established case II rate law at ambient temperatures, implying that the processes are controlled by relaxation in the coal network structure. As temperatures are increased, the process becomes more Fickian in nature. The activation energies for the diffusion-relaxation processes are in the range 31 to 82 kJ mol⁻¹.     

Experimental and modeling study of the solid state polymerization of poly(ethylene terephthalate) over a wide range of temperatures and particle sizes

The solid state polymerization (SSP) of poly(ethylene terephthalate) was studied experimentally over a wide range of pellet sizes and temperatures. A comprehensive model was developed. It considered polycondensation, degradation and polycondensation of vinyl end groups together with diffusion. The reaction rate constants, diffusivities and the corresponding activation energies were obtained through parameter identification using experimental data. The effects of the reaction temperature and pellet size on the SSP time were also investigated. A decrease in the particle size decreases the concentration of the vinyl end groups and narrows the concentration distribution of end groups inside poly(ethylene terephthalate) particles. A decrease in the size of pellets also favors diffusion. Nevertheless it is preferable that the size of pellets be between 1 and 2 mm because too small pellets bring about difficulties with preparation and handling. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Swelling kinetics of linseed oil‐based polymers

Kinetics of swelling and sorption behavior of copolymers (based on linseed oil, styrene, divinylbenzene, and acrylic acid via cationic and thermal polymerization) is studied in tetrahydrofuran (THF) at different temperatures. The values of n in the transport equation are found to be below 0.4, showing non‐Fickian or pseudo‐Fickian transport in the polymers. The dependence of diffusion coefficient on the composition and temperature has also been studied for the linseed oil‐based polymers. The diffusion coefficient in cationic samples decreases with an increase in the oil contents in the samples. In case of thermal samples, the diffusion coefficient first increases up to 30% oil contents and then decreases. The diffusion coefficient decreases with an increase in temperature for all of the linseed oil polymer samples. The sorption coefficient increases with an increase in the oil contents for all samples. The crosslink density (calculated from the THF swelling) ranges from 20.16 to 92.34 × 10⁶ mol/cm³ for cationic samples and 20.62 to 86.01 × 10⁶ mol/cm³ for thermal samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effect of hydrogen bonding on vapor diffusion in water-soluble polymers

Water-vapor transport in poly(acrylic acid) (PAA), poly(N-vinyl-2-pyrrolidone) (PVPo), and their 2 : 1 interpolymer complex was measured between 30 and 50°C. It was found that the formation of interpolymer hydrogen bonding not only caused the T_g of the complex to be higher than those of the individual components, but also affected vapor-sorption behaviors. In the high vapor pressure region (P_r > 0.5), sorption isotherms in pure PAA and PVPo follow the Flory–Huggins solution theory and the sorbed water molecules may form clusters around the COOH groups in PAA and C=O groups in PVPo. However, sorption in the complex is almost linear for the entire range of water activities. The binary polymer—polymer interaction parameter between PAA and PVPo in the complex, ξ_PAA–PVPo, is less than zero, which is indicative of favorable interaction between PAA and PVPo. At lower water activities, sorption behaviors for water in the three polymers can be approximated by Henry's law and vapor-diffusion coefficients can be ranked as PVPo > complex > PAA. The water vapor diffusion coefficients in each system decrease with increasing P_r, in the region of P_r > 0.5 because the proportion of immobilized water molecules increases with vapor concentration. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 279–291, 1997     

Calculating hansen solubility parameters of polymers with genetic algorithms

In materials engineering, it is often essential to know what are the best solvents to process any polymer, and employing methods based on Hansen solubility parameters are an effective way to find them. In this work the Hansen solubility parameters of polyether sulfone, lignin, and bitumen have been calculated by an alternative optimization procedure. It has been shown that, by applying an evolutionary strategy to Hansen's correlation method, it is possible to improve the fitting of solubility spheres. Compared with previous calculations, most quality‐of‐fit parameters are optimized. As a result, the sphere radii are reduced and, except for lignin, at least one of the solubility parameters is considerably changed (by 0.9–1.5 MPa^1/2). Shortcomings of the correlation method are also pointed out, such as lack of data quality evaluation on set of solvents and uncertain character for partially solving solvents. At least the former could be handled by a proposed parameter called fill factor. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39696.     

Swelling behavior and diffusion studies of high‐water‐retaining acrylamide/potassium methacrylate hydrogels

Poly(acrylamide‐co‐potassium methacrylate) hydrogels were prepared by free‐radical simultaneous polymerization with aqueous solutions of acrylamide (AAm) and potassium methacrylate (KMA) with a redox initiator. The copolymerization was performed with eight different compositions of KMA at a fixed concentration of oil‐soluble crosslinkers, including 1,4‐butanediol diacrylate and ethylene glycol dimethacrylate (EGDMA). For every composition of AAm/KMA copolymer, the percentage swelling, swelling equilibrium, and diffusion characteristics were investigated. The copolymers were further studied for deswelling properties. The power law relationships of the hydrogels were evaluated for variation in terms of saline concentration. The AAm/KMA copolymers were confirmed by IR spectroscopy. Thermal studies of hydrogels were performed with differential scanning calorimetry and thermogravimetric analysis. EGDMA was found to be a better crosslinker for obtaining higher swelling and deswelling properties for the AAm/KMA hydrogels. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1153–1164, 2005     

吸水树脂PAA／AM的合成研究

以N，N-亚甲基双丙烯酰胺（Bis）为交联剂，过硫酸钾（KPS）做引发剂，以丙烯酸（AA），丙烯酰胺（AM）为反应单体水溶液聚合法合成了适用于淡水和盐水的吸水膨胀聚合物。采用正交实验法对最佳吸水膨胀配方进行了优选：单体浓度[M]=30％；单体中和度N=75％；引发剂浓度[I]=0．15％；交联剂浓度[C]=0.011％；反应温度为75℃及反应时间3h。对PAA的吸液速率进行了测定，并讨论了它的反复吸液能力。     

Effect of gelatin on the swelling behavior of organic hybrid gels based on N‐isopropylacrylamide and gelatin

Organic hybrid gels based on poly(N‐isopropylacrylamide) and a natural polymer, gelatin, were prepared through two‐step crosslinking with genipin or glutaraldehyde. The effects of the gelatin content on the swelling behaviors and physical properties of these hybrid gels were investigated. The results indicated that the swelling ratio decreased with an increase in the content of gelatin in these hybrid gels. The swelling ratio for the gel crosslinked by genipin was significantly smaller than that for the gel crosslinked by glutaraldehyde. The results also showed that the gel crosslinked with genipin had a higher crosslinking density and a higher gel strength. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1092–1099, 2005     

Controllable shape‐memory recovery regions in polymers through mechanical programming

A temperature memory effect means a shape‐memory material can remember its deformation temperature. In general, a higher deformation temperature requires a higher activation temperature for shape recovery. In this work, we demonstrate that the unloading temperature can also significantly influence the shape‐memory performance. A series of shape‐memory tests are performed on Nafion while varying the loading and unloading temperatures. The results show that the loading temperature determines the final shape‐recovery region, while the unloading temperature influences the onset recovery region. We also develop a finite‐deformation viscoelastic model to investigate the above findings. The simulation results show good agreement with the experimental data, though the model predicts the recovery region occurring at a lower temperature. The model is further used to study the effects of the loading rate, unloading rate, and the holding time on the shape‐memory behaviors. The results suggest that a smaller loading rate and unloading rate and a longer holding time can shift the recovery region to a higher temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45909.