Mathematical modeling and experimental study of conveyor belt continuous curing process

A mathematical model was developed to predict the temperature distribution within various layers of conveyor belts during the continuous curing process. The results predicted by the model are found to be in good agreement with the experimental results, hence justifying the capability of the model for simulation of the conveyor belt continuous process. This information was utilized to provide more insight into the curing process in terms of the state of cure (SOC) and/or the degree of conversion, which may, in turn, be utilized for the optimization of the curing process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2448–2454, 2000     

Morphology and thermal behavior of PP/EHDPET blend fibers by alkaline hydrolysis treatment

Polypropylene superfine fibers or cell porous fibers were prepared from the Bi‐component blend fibers of polypropylene/easy hydrolytic degradation polyester (PP/EHDPET) by alkaline hydrolysis process. EHDPET is a kind of copolyester that can be rapidly hydro‐degraded in the hot alkaline solution. This article discusses the kinetics of alkaline hydrolysis of EHDPET, and the effect of catalyst, bulk ratio, and the content of PP‐grafted maleic anhydride on the alkaline hydrolysis process. Meanwhile, the morphological change of the outer surface of blend fibers during this process was also investigated by the technology of scanning electron microscope. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3010–3014, 2000     

High‐speed photocrosslinking of thermoplastic styrene–butadiene elastomers

Photoinitiated thiol/ene polymerization was used to crosslink a triblock styrene/butadiene/styrene (SBS) polymer of low vinyl content (8%). The crosslinking process was followed by infrared spectroscopy (loss of unsaturation), insolubilization, swelling, and hardness measurements. The photogenerated thiyl radicals react with both the vinyl and the 2‐butene double bonds of the copolymer. Concentrations of less than 1 wt % in the trifunctional thiol crosslinker and in the acylphosphine oxide photoinitiator proved to be sufficient to create, within 0.5 s, a permanent chemical network in the elastomeric phase. This UV‐curing technology was successfully applied to crosslink rapidly commercial SBS–Kraton® thermoplastic elastomers. It proved also effective in the case of the much less reactive triblock styrene/isoprene/styrene (SIS) polymer which contains no vinyl double bonds. The thiol/ene polymerization was shown to be a much more efficient process to crosslink SBS and SIS thermoplastic elastomers than was the copolymerization of the rubber double bonds with a diacrylate monomer. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1902–1912, 2000     

Reactions of hydroxymethyl derivatives of uric acid with oxiranes. I. Synthesis of polyetherols with purine rings

Preliminary results on the utilization of uric acid in the synthesis of a new group of polyetherols with purine rings are presented. The polyetherols were prepared in a two‐stage process. First, hydroxymethyl derivatives of uric acid were obtained from an uric acid and formaldehyde solution. This intermediate was then reacted with ethylene oxide or propylene oxide without any additional solvent. The structure of the intermediates and polyetherols and some of their physical properties were determined, and the possibilities of application of the polyetherols in manufacturing thermostable polyurethane foams were tested. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2667–2677, 2000     

Process monitoring and kinetics of rigid poly(urethane–isocyanurate) foams

Process temperature profiles of a two‐component rigid poly(urethane–isocyanurate) foam system were studied and compared with the predictions of a one‐dimensional numerical simulation. This model is based on experimentally determined thermophysical properties including thermal diffusivity, enthalpy of reaction, and rate of reaction. Temperature profiles were measured at three positions within the foam and at the foam surface for mold temperatures of 25°C and 55°C. A high rate of reaction and heat of reaction, along with low thermal diffusivity, cause temperatures near the foam center to be insensitive to mold temperatures for thick samples. Thermal analysis was used for determination of thermophysical properties. Temperature‐dependent heat capacity, reaction kinetics, and heat of reaction were evaluated using temperature‐scanning DSC. Thermal conductivity was analyzed from steady‐state heat profiles. The system reaction kinetics indicated much faster kinetics than reflected by process cure temperature profiles made using thermocouples. The simulations accurately predict experimental results, allowing determination of demold time dependence on process conditions, including feed temperature, mold temperature programming, and sample thickness. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 374–380, 2000     

Use of enzyme tests to monitor the biomass activity of a trickling biofilter treating domestic wastewaters

Easy enzyme tests were used to monitor the biomass activity of a trickling biological aerated filter processing a domestic influent. Biofilter wash‐waters were used as biomass source. Enzyme tests (hydrolases and dehydrogenases) carried out on wash‐waters showed relationships with the process active biomass (estimated by volatile suspended solids). Differences in dehydrogenase (DHA) specific activities were observed in two sampling campaigns and were linked to process performance. The DHA activity evaluated using glucose or acetate was also related to the substrate mass applied on the biological aerated filter (kg CODt m⁻³ biolite). These results indicated that, under normal operation, DHA activity is related to quantity of substrate applied to the biofilter. Similar relationships were obtained for hydrolases. However, β‐glucuronidase, Leu‐aminopeptidase and protease, expressed specifically, were more significantly inversely related to process removal performance. This reaction was probably caused by the biomass reacting with an influent that is difficult to biodegrade. Generally speaking, these tests can be easily applied to the regular monitoring of the active biomass from a process using biological filters or simply as an indicator of the active biomass content in the process. © 2000 Society of Chemical Industry     

Solid‐state polymerization and bulk crystallization behavior of poly(ethylene terephthalate) (PET)

The main variables involved in solid‐state polymerization of PET homopolymers, originally with molecular weight within the commercial range, were sequentially studied to determine their influence in polymerized products. These variables were precursor crystallinity, catalyst, and time and reaction temperature. An increasing molecular weight sequence was then used to study the bulk crystallization behavior with Avrami analyses. It was determined that thermal conditions at dissolution affect the prereaction morphology. This was important in the polymerization process because it was found that high crystallinity levels in precursors result in higher molecular weights. In agreement with other reports, typical catalysts used in melt polymerizations enhance postpolycondensation processes in the solid state. High reaction times and temperatures were also required to obtain high molecular weights. As the molecular weight increased, there was a decrease in nucleation density and Avrami analyses, applied to the isothermal bulk crystallization, indicating that the nucleation process changed from instantaneous to spontaneous with the increase in molecular weight. The consequences and relative importance of the observed results is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 78–86, 2000     

Polyperoxide surfactants for interface modification and compatibilization of polymer colloidal systems. I. Synthesis and properties of polyperoxide surfactants

Anhydride‐containing polyperoxides were synthesized by copolymerization of 5−tert−butylperoxy−5−methyl−1−hexen−3−yne with either maleic anhydride or its blends with styrene. The integral composition of the polyperoxides was theoretically calculated as the copolymerization process proceeded and its direct experimental evidence was obtained. In macrochain‐formation behavior, the process was found to be consistent with the generally accepted regularities of binary and ternary copolymerization. By employing their polymerizational transformations, water‐soluble polyperoxides exhibiting surface activity and initiating properties were obtained. In aqueous solutions, such polyperoxide surfactants form micellelike colloidal structures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1217–1227, 2000     

Oxidation of gamma‐irradiated ultrahigh molecular weight polyethylene

Ultrahigh molecular weight polyethylene (UHMWPE), the current polymer of choice in orthopedic prosthetic devices, is typically sterilized by exposure to Co‐60 gamma irradiation prior to packaging for long‐term storage. However, the exposure to Co‐60 irradiation generates free radicals along the polymer chain that can participate in a series of reactions commencing with the oxidation of the free radicals to form reactive peroxy radicals. This study was undertaken to identify the role of hydroperoxide species in shelf‐aged and accelerated aged UHMWPE samples by using a nitric oxide derivatization technique. It is shown that the concentration of hydroperoxides did not change appreciably with shelf aging. However, during accelerated aging the hydroperoxide concentration increased to a plateau and then decreased, suggesting its role as an intermediate in the process. By contrast, the concentrations of carbonyl species continued to increase during shelf aging and accelerated aging. The effects of several packaging materials on the oxidation characteristics were also investigated. A vacuum foil package is shown to be effective in preventing oxidation to a significant extent during accelerated aging. However, accelerated aging after removal from the foil pack resulted in oxidative degradation. Extended vacuum to remove dissolved oxygen and a 5‐week room‐temperature healing process in the foil pack were shown to be ineffective in reducing oxidative degradation. It also was shown that increased moisture content in the aging environment did not affect the degradation process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2525–2542, 2000     

Wastewater treatment by adsorption with electrochemical regeneration using graphite-based adsorbents

An innovative technology for wastewater treatment using adsorption and electrochemical regeneration has been developed at the University of Manchester. The process uses a low capacity graphitic adsorbent material (a graphite intercalation compound, Nyex^TM 1000) which can be regenerated electrochemically. In this study, we investigate the characteristics of a new, partially porous adsorbent material, Nyex^TM 2000 which offers increased surface area in comparison with Nyex^TM 1000. Nyex^TM 2000 was found to have an adsorption capacity of almost three times that of Nyex^TM 1000. The electrical conductivity of a Nyex^TM 2000 was found to be double that of Nyex^TM 1000, enabling improvements in the electrochemical regeneration characteristics. The removal of an anionic azo dye, acid violet 17, from aqueous solution using Nyex^TM 1000 and 2000 was investigated under various operating conditions. The adsorption of acid violet 17 on Nyex^TM 2000 was found to be comparatively fast with 75 % of the equilibrium capacity being achieved within 5 min. The parameters affecting the regeneration efficiency including the charge passed, current density, treatment time, adsorbent bed thickness, and pH were investigated. An electrochemical regeneration efficiency of around 100 % was achieved for a fully loaded Nyex^TM 2000 in a sequential batch electrochemical cell with a regeneration time of 60 min and a charge passed of 100 C g⁻¹ at a current density of 14 mA cm⁻². The charge required for electrochemical regeneration was found to be approximately equal to theoretical charge required for complete oxidation of the adsorbed acid violet 17, making process design relatively simple. Nyex^TM 2000 was found to be an economic adsorbent with relatively small electrical energy consumption required (31 J mg⁻¹ of acid violet 17 treated, compared to 52 J mg⁻¹ of acid violet 17 for Nyex^TM 1000). Multiple adsorption/regeneration cycles presented no loss in adsorptive capacity and material loses over five adsorption/regeneration cycles.     

Features of vapor-grown cone-shaped graphitic whiskers deposited in the cavities of wood cells

Vapor-grown graphitic whiskers in wood charcoal formed during heat treatment above 2000 °C are discussed through electron microscope observations. The whiskers were composed of conical stacked hexagonal carbon layers, with a cone apex angle of 136°. This angle probably helps the successive helical growth of the whiskers. To grow these whiskers, pyrolyzed gas from the walls of wood cells could be used as the carbon source, and the wood cell cavities functioned as a reactor that can store the pyrolyzed gas and concentrated it to supersaturation levels. Whiskers were produced under various conditions, and their features were compared using electron microscopy to examine the growth mechanism. Samples were prepared by precarbonizing wood along with SiC via a secondary heating process at 2000-2700 °C. The precarbonizing temperature controlled the potential supply of pyrolysate gas. Whisker growth began when the gas concentration reached the supersaturation level, and this was regulated by the secondary heat treatment temperature. The gas concentration can determine the size, features, and yield of the resulting whiskers. Since the carbon source was internal, originating from the surrounding cell walls, the regulation of the gas concentration was due entirely to the heat treatment and the features of the cell tissue.     

Oxidation of phenol in a bioremediation medium using chlorine dioxide

BACKGROUND: High concentrations of phenol in wastewater are difficult to remove by purely biological methods. Chemical oxidation is one way to treat high concentrations of phenol but complete oxidation will make the treatment process uneconomical. For the purpose of integrating chemical and biological treatment, the oxidation of phenol using chlorine dioxide was investigated in a medium suitable for bioremediation. The effects of chlorine dioxide concentration (500 to 2000 mg L^?1), temperature (10 to 40 °C) and pH (3 to 7) on the oxidation of 2000 mg L^?1 of phenol were determined. RESULTS: Chlorine dioxide concentration was found to be the dominant parameter for the removal of phenol in the nutrient rich medium. The optimal concentration of chlorine dioxide to completely oxidize 2000 mg L^?1 of phenol was 2000 mg L^?1. Compared with Fenton's reagent, half as much chlorine dioxide was needed to oxidize 2000 mg L^?1 phenol. The reaction of chlorine dioxide with phenol was very fast and reached equilibrium within 10 min. The main oxidation products were identified as 1,4‐benzoquinone and 2‐chloro‐1,4‐benzoquinone. CONCLUSION: Compared with Fenton's reagent, chlorine dioxide is a superior oxidant for removal of phenol from both pure water and bioremediation medium. Copyright © 2010 Society of Chemical Industry     

Kinetics of acrylic films photopolymerization through analysis of the thermal curve

Kinetic curves of polymerization were obtained through a photocalorimetric device that allows thermal measurements on flat films of controlled thickness of oligomers based on bis‐phenol‐A‐diglycidyl‐ether diacrylate. The temperature of the film was monitored during the ultraviolet irradiation under controlled conditions and the resulting thermal curve was processed by a suitable thermokinetic model based on the balance between the internal energy generation and the heat flow at the surfaces. The kinetic behavior of the acrylic group polymerization agrees with the kinetics followed by Fourier transform infrared analysis and fulfills the kinetic behavior expected for a photopolymerization process under steady state conditions. The proposed technique should be a suitable method to study in real time the reactivity of ultraviolet crosslinkable films in different condition of process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 458–463, 2000     

Acoustic characteristics of PMMA in the steady stress–strain state investigated by coherent Brillouin scattering method

The acoustic properties of PMMA poly(methyl methacrylate) deformed by tensile stress were investigated by the coherent Brillouin scattering method. The ultrasonic velocities of PMMA in steady stress–strain states were measured in the frequency range of 100 MHz to 1 GHz. The ultrasonic velocities decreased with increasing strain, and the ratio of the decrease increased with increasing strain rate. This result indicates that the crazing residues still remain in the steady stress–strain states, and the amount of the residues depends upon the strain rate. The velocity dispersion was observed around 400 MHz for virgin and deformed PMMA and reproduced with a single relaxation process. The relaxation process is assigned to the γ‐relaxation according to the dispersion map for methyl group relaxation in PMMA. The relaxation frequency and strength were independent of the applied stress and strain. The viscoelastic and plastic deformations have little effect on the γ‐relaxation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 978–986, 2000     

In situ photon transmission technique for monitoring phase separation in real time during gelation

Summary In situ, real time photon transmission technique was used to monitor the formation of heterogeneities during the free-radical crosslinking polymerization of acrylamide in the presence of N,N'-methylenebis(acrylamide) (BAAm) as a crosslinker. Two different gelation experiments were performed with various BAAm and water contents separately at room temperature. It was observed that the transmitted photon intensity, I _tr decreases dramatically at a certain time, in both type of experiments during the gel formation process from interconnected microgels. Decrease in I _tr was interpreted in terms of phase separation during gelation. The extent of phase separation was measured depending on the crosslinker content and on the degree of monomer dilution during the gel formation process. Received: 12 April 2000/Revised version: 15 August 2000/Accepted: 5 September 2000     

Morphology,thermal behavior,and mechanical properties of PA6/UHMWPE blends with HDPE‐g‐MAH as a compatibilizing agent

A functionalized high‐density polyethylene (HDPE) with maleic anhydride (MAH) was prepared using a reactive extruding method. This copolymer was used as a compatibilizer of blends of polyamide 6 (PA6) and ultrahigh molecular weight polyethylene (UHMWPE). Morphologies were examined by a scanning electron microscope. It was found that the dimension of UHMWPE and HDPE domains in the PA6 matrix decreased dramatically, compared with that of the uncompatibilized blending system. The size of the UHMWPE domains was reduced from 35 μm (PA6/UHMWPE, 80/20) to less than 4 μm (PA6/UHMWPE/HDPE‐g‐MAH, 80/20/20). The tensile strength and Izod impact strength of PA6/UHMWPE/HDPE‐g‐MAH (80/20/20) were 1.5 and 1.6 times as high as those of PA6/UHMWPE (80/20), respectively. This behavior could be attributed to chemical reactions between the anhydride groups of HDPE‐g‐MAH and the terminal amino groups of PA6 in PA6/UHMWPE/HDPE‐g‐MAH blends. Thermal analysis was performed to confirm that the above chemical reactions took place during the blending process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 232–238, 2000     

Aspects of interactions in complex polymer coating formulations

Acid–base interaction parameters have been measured by inverse gas chromatography for mixed stationary phases of film‐forming polymers and pigments. The quantities of adsorbed polymer required fully to coat the pigment surfaces were established, and rheological measurements were used to evaluate the thickness of polymer barriers generated by the adsorption process. Both the barrier thickness and the critical amount of polymer needed to overcoat the pigments were found to be dependent on acid–base interactions. Acid–base considerations also determined the rate of material redistribution when a third component was added to premixtures of two‐component polymer/pigment combinations. Time‐dependent variations in the surface energies of polymer films were attributed to the component redistribution process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1378–1386, 2000     

Craze morphology and molecular orientation in the slow crack growth failure of polyethylene

An optical microscopy study and a micro‐Raman spectroscopy study were carried out on polyethylene samples subjected to an environmental stress crack resistance (ESCR) test. The aim was to elucidate the molecular deformation mechanisms associated with the failure process. It has been shown that in the early stages of the ESCR test, in a regime of low local stress, failure in the craze occurs via a brittle process with limited ductility and with molecular orientation being detected. As the experiment progresses, however, extensive fibrillation takes place. The molecular orientation in these fibrils was found to be comparable to that measured in cold‐drawn samples. Moreover, the fibril molecular orientation decreased from the crack to craze tip and was found to be higher in the midrib part of the fibril (fibril failure point). As a consequence, fibril creep is the most likely mechanism of failure in the craze. Microscopy and Raman measurements showed that the extent of the brittle process is molecular weight‐dependent, that is, the brittle process seems to operate longer at higher molecular weights. These observations are in agreement with a previous work which showed that the molecular stress per macroscopic strain/stress decreases with increasing molecular weight, therefore holding the high molecular weight craze in a regime of low local stress for longer testing times. Fibrils spanning the craze are envisaged as the anchor points that hold the structure during the process of failure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 283–296, 2000     

Development of new dyeing photoinitiators for free radical polymerization based on 1H-pyrazolo[3,4-b]quinoline skeleton. IV.

Summary Several dyes containing 1H-pyrazolo[3,4-b]quinoline skeleton have been synthesized and evaluated as the novel photoinitiators for free radical polymerization induced in the UV region with the argon-ion laser. The kinetic study of photoinitiated polymerization, performed for viscous monomeric formulation with the use of thiophenoxyacetic acid has shown that the tested dyes are good dyeing photoinitiators. The results have shown that there is a linear relationship between the rate of polymerization and the square root of efficiency of the singlet oxygen formation. This finding clearly indicates that the electron transfer process between the tested dyes and electron donors occurs via triplet state. In the paper, it is also shown that the structure of the dye has a strong effect on its polymerization photoinitiation ability. The dyes tested were prepared in a way that allows, firstly, the elimination of the rotational freedom of selected parts of molecule and secondly, to increase the quantum yield of the triplet state formation. The latest was achieved by introducing to the molecule a heavy atom. The tested dyes absorb at the boundary of UV and visible region, therefore they might be considered as the potential photoinitiators for dental application. Received: 30 June 2000/Revised version: 30 September 2000/Accepted: 10 October 2000     

Molecularly imprinted nanoparticles prepared by core‐shell emulsion polymerization

Submicron core‐shell polymer particles, with molecularly imprinted shells, were prepared by a two‐stage polymerization process. Particles of this type, prepared with a cholesterol‐imprinted ethyleneglycol dimethacrylate shell and in the absence of porogen, were found to be 76 nm in diameter with a surface area of 82 m² g⁻¹. Cholesterol uptake from a 1 mM solution in isohexane was measured at both 10 and 30 mg mL⁻¹, with the imprinted polymer showing considerable binding (up to 57%). Imprinted but not hydrolyzed and hydrolyzed nonimprinted polymers showed very low uptakes (≤4.5%) and a phenol‐imprinted polymer showed reduced binding (36%) under the same conditions. Imprinted shells were also prepared over superparamagnetic polymer cores and over magnetite ferrocolloid alone. The cholesterol binding to magnetic particles was very similar to that of equivalent nonmagnetic materials. Magnetic particles could be sedimented in as little as 30 s in a magnetic field. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1851–1859, 2000