The mass transport of ethyl acetate in syndiotactic polystyrene

The mass transport of ethyl acetate in syndiotactic polystyrene (sPS) has been studied. Two groups of specimens were prepared using press‐cooling and water‐quenching. The press‐cooled and water‐quenched specimens were identified as crystalline and amorphous structures, respectively, by X‐ray diffraction. The weight gain of ethyl acetate in sPS was monitored at temperatures from 50°C to 70°C. The crystallinity of a press‐cooled specimen prior to solvent sorption was greater than that after solvent sorption. However, solvent‐induced crystallization was observed in the water‐quenched specimen. The transport of ethyl acetate in both press‐cooled and water‐quenched specimens was anomalous and consisted of two stages. Each stage of the sorption curves was well fitted with Harmon's model. Both the diffusion coefficient and velocity component satisfy Arrhenius behavior. For the press‐cooled specimen, fluxes of Case I and Case II transport flow from the outer surface to the center, but for the water‐quenched specimen, the solvent is squeezed out. Pure Case II transport did not appear in the water‐quenched specimen.     

Effect of methanol on optical property of irradiated poly(methyl methacrylate)

The effect of methanol on optical property of irradiated poly(methyl methacrylate) (PMMA) has been investigated. The gamma irradiation enhances the methanol transport in PMMA. The activation energies of diffusivity for case I and velocity for case II decreases with increasing gamma ray dose. For the same wavelength, in the range 350–800 nm, the transmittance decreases with increasig gamma ray dose. The equation of transmittance I with gamma ray dose ? at the wavelength 405 nm is I = I₀ exp(?0.06?^1/2), where I₀ is the transmittance of virgin PMMA. When the irradiated PMMA is immersed into methanol bath, the yellow color fades out gradually. The recovery of transmittance increases with methanol content in irradiated PMMA. The boundary to separate the outer region (solvent affected zone) from the inner region (no solvent-affected zone) is also studied. The rate of boundary movement increases with gamma ray dose.     

The effect of calcium chloride dihydrate on the optical properties and mass transport of methanol in poly(methyl methacrylate)

The effect of calcium chloride dihydrate on optical properties and the mass transport of methanol in poly(methyl methacrylate) (PMMA) has been investigated. The solvent transport was analyzed based on the Harmon model accounting for Case I, Case II, and anomalous diffusions. Both Case I and Case II transports satisfy the Arrhenius equation. Calcium chloride dihydrate depresses Case I diffusion and enhances Case II diffusion. From the mass transport data, the equilibrium solvent content of methanol with various concentrations of calcium chloride dihydrate in PMMA is obtained and satisfies the van't Hoff plot. A comparison of movement of sharp front and mass transport is made. The increase of UV transmittance of specimens treated with a mixture of methanol and calcium chloride dihydrate is attributed to the reduction of the carbonyl group. The critical solvent content to change transmittance from a slow increase to a fast increase occurs when the sharp fronts meet at mid‐plane. The decrease of transmittance in UV range is due to void creation for a large amount of solvent. The visible light transmittance of the specimen with small solvent content is the same as that of the specimen without solvent treatment. The visible wavelength dependence of transmittance of specimens with large solvent content is attributed to the void of which the size is smaller than the wavelength of visible light. The void is enlarged during the mass uptake, then it is fully closed after desorption of a small solvent amount and shrinks to a small size after desorption for a large solvent content.     

Annihilation kinetics of color center in polycarbonate irradiated with gamma ray at elevated temperatures

Annihilation kinetics of color center in polycarbonate (PC), irradiated with gamma ray at elevated temperatures, was investigated. The transmission loss in the PC was monitored in the ultraviolet and visible wavelength range. The transmittance decreased with increasing gamma‐ray dose. The loss was attributed to the presence of annealable and permanent color centers. The absorbance in situ data were detected at the wavelength of 450 nm and found in good agreement with the theoretical model in which the annealable color center followed a first‐order kinetic process. The rate constant satisfies the Arrhenius equation, with the activation energy of the color centers decreasing with increase of the gamma‐ray dose. The results were compared with the early findings reported in the literature. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Radiation crosslinking and sorption properties of hydrogels based on 1‐vinyl‐2‐pyrrolidone,hydroxyethyl methacrylate,and their copolymers

This work has been concerned with the synthesis of the hydrogels of poly (vinyl pyrrolidone) (NVP), poly (hydroxy ethylmethacrylate) (HEMA), and their copolymer under the effect of gamma radiation in the presence of N,N‐methylenebisacryl‐amide (MBAm) as a crosslinking agent. The effect of the different factors that may affect the gelation and yield product, such as solvent composition and irradiation dose, was investigated. The formed hydrogels were characterized in terms of swelling in water and different organic solvents, X‐ray diffraction (XRD), and IR spectroscopic analysis. The sorption capability of these hydrogels towards some commercial basic and acid dyesstuffs was also studied. The results showed that a solvent mixture composed of equal contents of water and methanol is the most suitable to afford the minimum sol fraction and the highest yield product at a minimal irradiation dose of 10 kGy. It was observed that NVP hydrogel displayed the highest swelling in water, alcohols, and dimethyformamide of ～1300% and a lower tendency to swell in nonpolar solvents. The results showed that HEMA hydrogel has a high affinity to absorb basic dyes while NVP has a tendency for acid dyes. Also, the sorption of either the basic or acid dyes by the different hydrogels was found to greatly depend on the concentration of dye in solution and the mass of the used hydrogel. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3274–3280, 2004     

Network structure and methanol transport dynamics in poly(methyl methacrylate)

The effect of the polymer network structure on methanol transport dynamics in glassy polymers was investigated in both dry and plasticized disks of poly(methyl methacrylate) (PMMA) through gravimetric integral sorption studies. PMMA was synthesized by a controlled free radical polymerization mechanism, crosslinked in bulk with ethylene glycol dimethacrylate, and swollen in methanol under a variety of conditions. In the Case II transport regime, control over the transport rate was shown to depend on the glassy‐state properties of the polymer, and the Case II front velocity was found to be proportional to the square root of the crosslinking density. Similarities were observed in the penetrant transport behavior of both dry and plasticized samples at high degrees of crosslinking, and the activation energy of methanol transport at low degrees of crosslinking was found to be similar for both Fickian and Case II mechanisms. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Effect of compression and thickness on acetone transport in polycarbonate

We investigated the kinetics of acetone transport in polycarbonate (PC) under compression and with different thicknesses using the sorption experiment technique. A model combining Case I transport arising from concentration gradient and Case II transport driven by stress relaxation was employed to analyze the transport process. The sorption data are in good agreement with the theoretical prediction. Both the diffusion coefficient D of Case I and the velocity v of Case II transport satisfy the Arrhenius equation. The activation energies of D and v are higher in the stress‐free PC than in PC subjected to compression. The activation energies increase with decreasing specimen thickness. The calculated heat of mixing is ?5.1 kJ/mol for both the stress‐free sample and the sample subjected to compression at 196 MPa, and ?8.4 kJ/mol for the sample subjected to compression at 294 MPa. However, the calculated mixing heats are almost the same regardless of specimen thickness. FTIR spectra show no new absorbance peak when the PC is exposed to acetone. The solvent‐induced crystallization is confirmed using FTIR spectra. A periodical stripe pattern is observed on the surface when a sample of thickness less than 0.8 mm is exposed to acetone at temperatures greater than 20°C. POLYM. ENG. SCI., 45:687–693, 2005. © 2005 Society of Plastics Engineers     

The effect of 60Co γ‐rays on the crystal structure,melting and crystallization behavior of poly(butylene succinate)

The results obtained for poly(butylene succinate) (PBS) after ⁶⁰Co γ‐ray irradiation, studied by wide‐angle X‐ray diffraction (WAXD), differential scanning calorimeter (DSC) and polarizing optical microscopy (POM), revealed that the degree of crystallinity, melting temperature and enthalpy decreased with increasing irradiation dose, but that the crystal structure of PBS did not vary when compared to non‐irradiated PBS. By using Scherrer equation, small changes occurred in the crystal sizes of L₀₂₀, L₁₁₀ and L₁₁₁. The spherulitic morphology of PBS was strongly dependent on irradiation dose and changed significantly at higher irradiation dosages. The crystallization kinetics of PBS indicated that the Avrami exponent (n) for irradiated PBS was reduced to 2.3, when compared to non‐irradiated PBS (3.3). Copyright © 2004 Society of Chemical Industry     

Ultrasonic characterization of water sorption in poly(2-hydroxyethyl methacrylate) hydrogels

A complex mechanism characterizes the water uptake kinetics in hydrogels, as a consequence of the strong structural changes occurring in the material during the sorption process. The water sorption involves the transformation of a glassy, moderately crosslinked polymer in a rubbery material. In this study, the changes in the ultrasonic attenuation and velocity in crosslinked poly(2-hydroxyethyl methacrylate) [poly-(HEMA)] hydrogel films during water sorption are measured by scanning laser acoustic microscopy (SLAM) and a pulse–echo system. In particular, the pulse–echo technique provides additional valuable information, thanks to its capability for monitoring the position of the swollen/unswollen fronts during water sorption. The evolution of the attenuation observed by SLAM is analyzed in terms of reflections on macroscopic discontinuities and absorption mechanisms. Finally, the propagation of ultrasonic waves acts as a dynamic mechanical test of the material; and, therefore, the measured longitudinal velocity and ultrasonic attenuation are applied to the calculation of the storage bulk longitudinal modulus of the poly(HEMA) hydrogels during water sorption. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:823–831, 1998     

Radiation synthesis and characterization of 2‐hydroxyethyl‐methacrylate‐based hydrogels containing di‐ and tri‐protic acid and its application on wastewater treatment

Radiation‐crosslinked 2‐hydroxyethylmethacrylate/citric acid (HEMA/CAc), 2‐hydroxyethylmethacrylate/tartaric acid (HEMA/TA), and 2‐hydroxyethylmethacrylate/succinic acid (HEMA/Sc) copolymers were prepared by using ⁶⁰Co γ‐rays. The gel fraction yield and the swelling behavior of the prepared hydrogels were studied. It was shown that increasing irradiation doses was accompanied by an increase in yield of gel fraction and a decrease in swelling degree. The parameters of equilibrium swelling, maximum swelling, initial swelling rate, swelling exponent, and diffusion coefficient of the hydrogels were determined by studying the swelling behavior of the hydrogels prepared. It was seen that the equilibrium swelling degree increases as the content of acid increases, as a result of introducing more hydrophilic groups. When the hydrophilic polymer (acids) varies in the content range of 40–80 mg, swelling exponents (n) decreases, thereby indicating a shift in the water‐transport mechanism from the anomalous (non‐Fickian)‐type to the Fickian‐type. Characterization and some selected properties of the prepared hydrogels were studied, and accordingly the possibility of its practical use in the treatment of industrial wastes such as dyes and heavy metals (Fe, Ni, Co, and Cu) were also studied. The effect of treatment time, pH of feed solution, initial feed concentration, and temperature on the dye and heavy metals uptake was determined. The uptake order for a given metal was HEMA/TA hydrogel > HEMA/CAc > HEMA/Sc hydrogel. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of gamma irradiation on the interpenetrating networks of gelatin and polyacrylonitrile: Aspect of crosslinking using microhardness and crosslink density measurements

The present article reports the effect of gamma irradiation on the hardness behavior of the interpenetrating polymer networks (IPNs) of gelatin and polyacrylonitrile (PAN). Various compositions of gluteraldehyde‐crosslinked gelatin and N, N′‐methylene bis acrylamide (MBA)‐crosslinked PAN were prepared and investigated for microhardness studies. The pre‐ and post‐irradiated IPNs were characterized for their crosslinking density, determined with swelling ratio measurements. It was found that the crosslinked IPNs get further hardened because of radiational hardening at specific doses in the range from 2 to 250 kGy. The role of acrylonitrile and crosslinker (MBA) in the IPNs, as a consequence of irradiation, has also been explained. A fair consistency has been observed between the microhardness results and crosslinking density measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2581–2586, 2006     

Radiation Stability of Spark‐Plasma‐Sintered Lead Vanadate Iodoapatite

Spark‐plasma‐sintered lead vanadate iodoapatite Pb_9.85(VO₄)₆I_1.7, a promising nuclear waste form for the immobilization of I‐129, was irradiated with energetic ions, electrons, and gamma rays, to investigate its radiation stability. In situ TEM observation of the 1 MeV Kr²⁺ irradiation shows that lead vanadate iodoapatite generally exhibits higher tolerance against ion irradiation‐induced amorphization than lead vanadate fluorapatite, and the spark plasma sintering can further enhance its radiation stability attributed to the enhanced crystallinity, reduced defect concentration, and denser microstructure. The critical amorphization dose and critical temperature for the SPS‐densified iodoapatite at 700°C are determined to be 0.25 dpa at room temperature and 230°C, respectively. No significant phase transformation or microstructural damage occurred under energetic electron and gamma irradiations. Raman spectra of gamma‐ray‐irradiated iodoapatite indicate improved V–O bond order at 500 kGy dose. Generally, the spark‐plasma‐sintered iodoapatite exhibits excellent radiation stability for nuclear waste form applications. The significantly enhanced radiation stability of the SPS‐densified iodoapatite suggests that SPS holds great promise for fabricating iodoapatite waste form with minimum iodine loss and optimized radiation tolerance for effective management of highly volatile I‐129.     

Characterization and gas‐permeation properties of crosslinked diacetylene‐containing polymer membranes from ferulic acid

Thermally and UV crosslinked poly[propargyl(3‐methoxy‐4‐propargyloxy) cinnamate] (PPOF) were investigated in terms of their physical, thermal, optical, and gas‐permeation properties. The crosslinked membranes had high gel contents because of the formation of a diacetylene network. The wide‐angle X‐ray diffraction patterns showed that all of the membranes were amorphous in structure, regardless of the type of crosslinking reaction. The membrane density increased after the crosslinking reaction; this suggested that the free volume of the crosslinked membrane was lower than that of the untreated membranes. Drastic color changes in the membranes were also observed because of the highly conjugated crosslinked network of diacetylene. In addition, the conjugation caused by diacetylene crosslinking led to visible absorption within the range 400–600 nm. The gas permeation of the crosslinked membrane was reduced compared with that of the untreated membranes. In particular, the gas permeability of the thermally crosslinked membrane was lower than that of UV‐irradiated membrane. On the basis of this result, the degree of crosslinking by thermal treatment was higher than that of UV irradiation. Hence, the crosslinked PPOF membranes showed improved gas‐barrier properties due to the high conjugation of the crosslinked diacetylene network induced by thermal treatment and UV irradiation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of crosslinked structure on SO2 gas sorption properties in amino‐functional copolymers

SO₂ gas sorption properties were examined for poly(styrene‐co‐chloromethyl styrene) functionalized with N,N‐dimethyl‐1,3‐propanediamine (DMPDA). The DMPDA‐functional copolymers were prepared under various reaction conditions. Two types of SO₂ sorption behaviors were observed for these DMPDA‐functional copolymers: SO₂ sorption capacity was very high irrespective of slow sorption/desorption rates (type I), and the sorption/desorption rates were very fast while SO₂ sorption capacity was small (type II). Fourier transform infrared analysis and dielectric loss measurement revealed that the type II sorption behavior was obtained for the highly crosslinked DMPDA‐functional copolymers. The degree of crosslinking was affected by both the solvent used to react DMPDA with the copolymer and the percent conversion of the chloromethyl styrene group. It was confirmed that DMPDA‐functional copolymers having a highly crosslinked structure are suitable materials in quartz crystal microbalance (QCM)‐type polymeric SO₂ gas sensors. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2982–2987, 2003     

Preparation of crosslinked chitosan by electron beam irradiation in the presence of CCl4

In this article, we report the synthesis of crosslinked chitosan using 8 MeV electron beam (EB) irradiation in the presence of carbon tetrachloride. The crosslinked chitosan is characterized by dissolution, Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning colorimetry (DSC), and nanoindentation studies. The insolubility of irradiated films in acetic acid indicates that chitosan has undergone crosslinking reaction. FTIR analysis also confirms the crosslinked structure of chitosan. Mechanical properties such as elastic modulus and hardness are calculated from the nanoindentation data. Modulus and hardness of chitosan increase with increase in the irradiation dose due to the increase in the crosslinking. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of <Emphasis Type="Italic">α</Emphasis>-phenylcinnamylideneacetylated poly(2-hydroxyethyl methacrylate)

A photosensitive polymer, -phenylcinnamylideneacetylated poly(2-hydroxyethyl methacrylate) (poly(HEMA)), was synthesized and characterized. Light irradiation upon the photosensitive poly(HEMA) film induced gel formation via dimerization between the pendent -phenylcinnamylideneacetylates of the polymer. The gel content of the crosslinked polymer increased with increasing irradiation time and reached 60% when irradiated for 30 minutes. Correspondingly, the water content decreased from 27% to 18% with irradiation time increasing from 0 to 30 minutes. The solute permeability of the -phenylcinnamylideneacetylated poly(HEMA) without irradiation is about the same as that of the poly(HEMA) film. The crosslinked -phenylcinnamylideneacetylated poly(HEMA) film prepared by light irradiation had much lower permeability as compared with the non-crosslinked film. More specifically, the photocrosslinked film had the permeability of 5.37 × 10^–7 cm/s, 1.32 × 10^–7 cm/s and 0.53 × 10^–7 cm/s for p-nitrophenol, tryptophan and flurbiprofen, respectively. This photosensitive -phenylcinnamylideneacetylated poly(HEMA) provides a new base material for fabricating poly(HEMA) hydrogel.     

Viscoelastic properties of crosslinked LLDPE films biaxially oriented at temperatures below melting point

Creep and stress‐relaxation of linear low‐density polyethylene (LLDPE) crosslinked with β‐irradiation was studied as a function of irradiation dose. It was shown that both storage modulus and α‐relaxation are influenced by irradiation. An influence of relatively low gel content on stress relaxation was detected. However, the creep results showed an increase of the creep strain when the polymer is irradiated with a dose below 4 Megarad (MR) in comparison with a nonirradiated film. This increase corresponded to the disorientation in the amorphous phase, which takes place as a result of the film heating during irradiation. This disorientation was demonstrated by differential scanning calorimetry (DSC) and X‐ray analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3718–3723, 2007     

Anomalous transport of hydrocarbons in polystyrene

The transport kinetics and equilibrium concentrations of n-pentane at high penetrant activities in cast, annealed polystyrene were determined and compared with similar measurements in biaxially-oriented polystyrene. The rate of Case II (relaxation-controlled) sorption in biaxially-oriented polystyrene is three to four times faster than the sorption rate in cast, annealed polystyrene. The Case II sorption process in biaxially-oriented polystyrene is more highly temperature dependent than in cast, annealed film. The higher activation energies coupled with the larger relaxation-controlled sorption rates in biaxially-oriented polystyrene imply the involvement of larger polymer segments in the rate controlling polymer relaxations. The sorption in cast, annealed polystyrene was a position-dependent relaxation controlled transport process; in contrast the sorption in biaxially oriented polystyrene, albeit relaxation-controlled, was not position dependent. The position dependence of the Case II sorption appears to be a consequence of the presence of residual benzene in the film which accelerates the rate-determining relaxations. Desorption measurements at very low penetrant activities were quite similar for both biaxially oriented and cast, annealed polystyrene. The desorption kinetics were Fickian and were only a weak function of polymer orientation at these low activities.     

Mechanical improvement of concrete by irradiated polypropylene fibers

Fiber reinforced concrete (FRC) contains fibers physically mixed with gravel, sand, cement, and water. So far, adequate mechanical performance of FRC has been obtained at high cost and using complex technologies; important here is the geometry and surface characteristics of the polymers. We have modified polymeric‐fiber surfaces by using gamma radiation. Irradiated polypropylene (PP) fibers were submitted to 0, 5, 10, 50, and 100 kGy of gamma irradiation dosages. First, tensile strength of PP fibers was evaluated, and then fibers blended at 0, 1.0, 1.5, and 2.0% in volume with Portland cement, gravel, sand, and water. The highest values of compressive strength were obtained with irradiated‐fibers at 10 kGy and 1.5% in volume of fiber. The result is 101 MPa, as compared to 35 MPa for simple concrete without fibers. POLYM. ENG. SCI., 45:1426–1431, 2005. © 2005 Society of Plastics Engineers     

Surface treatment of phosphate glass fibers using 2‐hydroxyethyl methacrylate: Fabrication of poly(caprolactone)‐based composites

2‐Hydroxyethyl methacrylate (HEMA) solution (1–10 wt %) was prepared in methanol and phosphate glass fibers were immersed in that solution for 5 min before being cured (irradiation time: 30 min) under UV radiation. Maximum polymer loading (HEMA content) was found for the 5 wt % HEMA solution. Degradation tests of the fibers in aqueous medium at 37°C suggested that the degradation of the HEMA‐treated fibers was lower than that of the untreated fibers. X‐ray photoelectron spectroscopy revealed that HEMA was present on the surface of the fibers. Using 5 wt % HEMA‐treated fibers, poly(caprolactone) matrix unidirectional composites were fabricated by in situ polymerization and compression molding. For in situ polymerization, it was found that 5 wt % HEMA‐treated fiber‐based composites had higher bending strength (13.8% greater) and modulus (14.0% greater) than those of the control composites. For compression molded composites, the bending strength and modulus values for the HEMA‐treated samples were found to be 27.0 and 31.5% higher, respectively, than the control samples. The tensile strength, tensile modulus, and impact strength of the HEMA composites found significant improvement than that of the untreated composites. The composites were investigated by scanning electron microscopy after 6 weeks of degradation in water at 37°C. It was found that HEMA‐treated fibers inside the composite retained much of their original integrity while the control samples degraded significantly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009