bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of gas permeation in vinyl and vinylidene polymers
Authors: Mohr J. M. , Paul D. R.
Published: April 2003

The gas transport properties of several simple vinyl and vinylidene polymers are compared to examine the effect of pendant group type (H, CH3, F, Cl) and symmetry of placement. The literature contains extensive information about these polymers, which has been critically reviewed to obtain consistent data for interpretation of the effect of structure on gas permeability. The gas transport data available for many of these polymers are quite variable because of differences in additives, thermal history, and crystallinity. The values used here are from studies where the physical properties of the film were reported along with the transport data. The appropriate data were not available for poly(vinyl fluoride) or poly(vinylidene chloride). For poly(vinyl fluoride), permeability measurements and thermal analysis were done to supply this information. Results for poly(vinylidene chloride) were obtained by extrapolation of copolymer permeation properties. Estimates of the permeability of oxygen in the amorphous phase of each polymer are discussed in terms of the estimated fractional free volume of that phase. In this way, the intrinsic effects of molecular structure on gas permeation exclusive of crystallinity effects have been evaluated.
Synergistic effects in fluorocarbon elastomer seals produced by a combined temperature and radiation environment
Authors: Bartko John , Siemon John T.
Published: April 2003

Fluorocarbon elastomer seals were subjected to single stress radiation and temperature tests and combined stress tests with the seals immersed in silicone oil, to obtain a service life estimate. Their sealing capability was mechanically tested during the tests. In single environment tests the seals were resistant to temperature‐induced stresses and very hard to radiation, showing no failures up to 108rads. The combined tests, using three matched pairs of temperature and radiation dose rate, indicated a reduction in service life from 40 years at 145°C with no radiation to 21 years at 50°C with radiation, pointing to a significant synergism between radiation and temperature.
Temperature dependence of diffusion of a disperse dye in the multiple layers of nylon fabric
Authors: Sasaki Hiroaki , Honma Yoshio , Kidoh Hanpei , Karasawa Mikio
Published: April 2003

The apparent diffusion coefficients of a disperse dye in the multiple layers of nylon fabric at 45‐75°C are determined as the dyeing model of the textile assembly. The modified pore model is introduced to explain the diffusion behavior in the multiple fabric. The Arrhenius plot of the diffusion coefficient of dye in the spaces or pores of nylon fabric gave a straight line and the activation energy of diffusion was about 9.4 kcal/mol. The temperature dependence of the dye diffusivity in polymer matrix was quantitatively described by a WLF‐type relation,

where aT is a shift factor of diffusion and Ts is the reference temperature.
Induced crystallization of cellulose in never‐dried cotton fibers
Authors: Iyer P. Bhama , Sreenivasan S. , Chidambareswaran P. K. , Patil N. B. , Sundaram V.
Published: April 2003

In the present investigation, we have made a systematic study of the induced crystallization in never‐dried cotton fiber, by allowing it to desiccate under different conditions of humidity and temperature. The resulting structural changes have been followed using x‐ray diffraction and infrared absorption techniques. A slow rate of drying coupled with a high temperature was more conducive for maximum crystallization. Analysis of the effect of temperature on the induced crystallization showed possible existence of a thermal transition in cellulose around 30°C. The induced crystallization brought about by slow drying as well as those produced using intercrystalline swelling agents, have been shown to be resulting from a proper channelization of the interfibrillar mobility existing in the never‐dried fibers.
A comparative study of sorption of water vapor by oligomeric triblock copolymers of ethylene and propylene oxides
Authors: Petr̂ík S. , Bohdanecký M. , Hadobaŝ F. , Ŝimek L.
Published: April 2003

Equilibrium sorption of water vapor by oligomeric block copolymers (PEP) of ethylene and propylene oxides was measured at 23°C at five values of the relative vapor pressure, 0.32 ≦ p/p0 ≦ 0.90. Sorption isotherms were described by a simple empirical two‐parameter equation. The effect of the copolymer composition on the parameters was established. The Lundberg‐Zimm clustering function, the mean size of clusters of water molecules, and the Flory‐Huggins interaction parameters were estimated. Their dependencies on copolymer composition and water content in the system are discussed.
Solvent self‐diffusion in crosslinked polymers
Authors: Vrentas J. S. , Vrentas C. M.
Published: April 2003

A theory is developed for predicting the solvent self‐diffusion coefficient in a crosslinked, amorphous polymer. The theory is based on a modification of the free‐volume theory of transport for the presence of crosslinks in the polymer. The general predictions of the theory for the variations of the self‐diffusion coefficient with temperature, concentration, degree of crosslinking, and solvent size are compared with general experimental trends.
Temperature dependence of contact angles on elastomers
Authors: Budziak C. J. , Vargha‐Butler E. I. , Neumann A. W.
Published: April 2003

Contact angle measurements with three different liquids were performed on: (i) butyl rubber PB 101‐3 (Polysar Ltd.) and (ii) Dow Corning 236 dispersion. Contact angles were measured at different temperatures within the range from 23°C (room temperature) to 120°C. The surface tensions, γsv, of the polymeric coatings at each temperature were calculated from the contact angles. The temperature coefficients of the surface tensions, dγsv/dT, i.e., the surface entropies, were established for the temperature range covered.
Improvement of plybond strength of paperboard by corona treatment
Authors: Sakata Isao , Morita Mitsuhiro , Furuichi Hiroshi , Kawaguchi Yoshifumi
Published: April 2003

It was found that the treatment of the surfaces of wet pulp sheets (moisture content; up to 85%) in a corona discharge improved greatly the plybond strength of the paperboard obtained when the treated wet pulp sheets were laminated together, pressed, and then dried. Treatment was carried out by use of a corona apparatus which had variable driven roll electrodes for transporting the wet pulp sheets through a corona field and was attached to a high‐voltage generator (∼ max 500 W, ∼ 16 kV at 5 kHz). The plybond strengths of the paperboards were examined by means of Tappi RC‐273 and JIS P8139 methods. Some experiments regarding the chemical effects of the corona treatment on the surface modification of wet pulp sheets were made with the aid of dye adsorption methods. Both untreated and corona‐treated pulps adsorbed basic dyes, methylene blue, etc., with the same extent of dyeing. This indicates that no measurable acidic sites (carboxyl groups) increased on the surfaces of the pulp sheets during the corona treatment. To detect aldehyde groups, the dyeing examination of the pulps with Schiff's reagent was made, and the results showed a higher dyeing ability for the corona‐treated pulps compared to the untreated, indicating that aldehyde groups on the pulp surfaces increased with an increase in the degree of corona treatment. The corona treatment seems to produce on the surface layer lightly oxidized and fairly degraded polysaccharide chains, which will tend to swell in water and thus act as an adhesive in plybonding the pulp sheets.
The chemical and physical properties of electrochemically prepared polyaniline perchlorate (PAP)
Authors: Choi Kyung Moon , Lee Eun Ju , Park Joon Woo , Kim Keu Hong
Published: April 2003

Polyaniline perchlorate (PAP) was synthesized by electrochemical oxidation from 0.2 M aniline in acetonitrile solution containing 0.1 M tetraethylammonium perchlorate as supporting electrolyte. From polarographic and cyclic voltammetry results, the values of the half‐wave potential (E1/2), transfer coefficient (α), and number of electrons related to the electrode reaction (n) were calculated to be 825 mV, 0.894, and 1, respectively. The morphology of the PAP film was observed by using an SEM analyzer. From thermal analysis of the PAP sample, the reaction rate (R) for its thermal decomposition was obtained from the TGA result and a exothermic peak at 330°C was also observed in the DSC curve. The electrical conductivity of the PAP pellet was measured at temperatures from −170 to 25°C. From a plot of conductivity vs. 1/T, the activation energy (Ea) was obtained to be 0.14 eV. The conduction mechanism in a pressed pellet of PAP is suggested to be electronic hopping conduction. The values of the ESR parameters were calculated from an ESR curve for PAP at room temperature.
Studies on the preparation and properties of conductive polymers. IV. Novel method to prepare metallized plastics from metal chelates of polymides–imides
Authors: Huang Chueh‐Jung , Yen Chih‐Chao , Chang Teh‐Chou
Published: April 2003

A new type of polyamide–imides (PAI) was synthesized by direct polycondensation. A series of polyamide–imide metal chelate films was prepared by the transition‐metal salts (AgNO3, CuCl2, and CoCl2) mixed with the polyamide–imides in NMP solution. These polyamide–imide metal chelate films were reduced by various reducing agents, and the reduced films exhibited low surface resistivity around 100−101 Ω/cm2. The surfaces of these conductive films were proved to be metallized by means of X‐ray analysis. The metal adhered on the film was believed to be responsible for the improvement of electrical conductivity. The effects of kinds and concentrations of metal salts, kinds and concentrations of reducing agents, and reduction time on the conductivity of metallized films were investigated. The IR spectra and SEM observations of unreduced and reduced polymer chelate films were also studied.
Diffusion and sorption of organic liquids through polymer membranes. II. Neoprene, SBR, EPDM, NBR, and natural rubber versus n‐alkanes
Authors: Harogoppad S. B. , Aminabhavi T. M.
Published: April 2003

Diffusion and sorption of n‐alkanes (C6–C10) through commercial polymer membranes such as neoprene, styrene butadiene rubber, ethylene propylene diene terpolymer, nitrile butadiene rubber, and natural rubber have been studied from 25 to 60°C. The diffusion results have been explained in terms of the size of liquid molecules and the diffusion mechanism was found to follow the Fickian trend. Nitrile butadiene rubber and neoprene showed much smaller values of diffusivities and sorption constants than the other polymer membranes. Arrhenius parameters for the activated diffusion process and the thermodynamic quantities for the process of equilibrium sorption have been estimated.
Application of the dynamic SIMS technique to the study of silicone release coatings
Authors: Stein Judith , Leonard Tracey M. , Smith Gary A.
Published: April 2003

Secondary ion mass spectrometry (SIMS) depth profiling has been used to determine elemental compositions of cured silicone release coatings as well as the location of controlled release additives (CRAs) in the cured polymer matrix. The two CRAs examined were found to be uniformly distributed throughout the matrix with no apparent increase at either the air or adhesive interface. As CRAs are required for tight release, this suggests that a minimum concentration at the surface is necessary but this concentration is not greater than that found in the bulk.
Oxygen permeation through Teflon–PFA tubing into flowing helium
Authors: Giacobbe F. W.
Published: April 2003

The permeability coefficient for oxygen diffusing through a sample of Teflon‐PFA tubing has been determined experimentally. The source of the diffusing oxygen was ambient air surrounding a 1.835 m length of PFA tubing. Pressurized high purity helium was directed through the center of the PFA tubing. Oxygen permeating from the low pressure ambient air source, through the PFA tubing, and into the flowing pressurized helium was observed in the effluent gases as they passed through a trace oxygen analyzer. By this means, oxygen concentrations in the effluent helium were determined as a function of varying helium flow rates, at helium gas pressures of 1.92 and 4.40 atm (absolute), within the tubing bore. All measurements were carried out at ambient temperatures of 23.5 ± 1.3°C. In addition, a theoretically related graphical method of evaluating the experimental data was employed to actually determine the oxygen permeability coefficient for this system.
Hydrocarbon‐soluble alkylaniline/formaldehyde oligomers as corrosion inhibitors
Authors: Bacskai R. , Schroeder A. H. , Young D. C.
Published: April 2003

Hydrocarbon‐soluble oligomers were prepared by the acid‐catalyzed condensation of alkylanilines with formaldehyde. Highest molecular weight oligomers (MW ∼ 6000) were obtained from alkylanilines prepared by the Friedel‐Crafts alkylation of aniline with α‐olefins. By NMR, it was shown that the oligomers contain structures corresponding to methylene‐linked aromatic rings and methylene linked to both an aromatic ring and a nitrogen atom. The oligomers exhibit very good initial inhibition of metal corrosion in aqueous environment; and the inhibition is more persistent than that observed with monomeric analogs.
Sorption of CO2/CH4 mixtures in poly(phenylene oxide) and a carboxylated derivative
Authors: Story Brooks J. , Koros W. J.
Published: April 2003

The sorption of CO2 and CH4 and their binary mixtures in poly(phenlene oxide) (PPO) and its carboxylated derivative (CPPO) is reported. All mixed gas data are accurately described by the dual model sorption model, which predicts mixed gas sorption on the basis of pure gas sorption parameters. The present paper extends the mixed gas sorption data base to include polymers having a wide range of permeabilities and chemical structures. The confirmed accuracy of the model for these systems provides strong support for applying the mixed gas dual mode sorption model to any gas/polymer system. A numerical simulation of the mixed gas sorption experiment is also presented which greatly simplifies the experimental procedures used to maintain the partial pressure of one of the gas components at a constant value over the course of a sorption isotherm measurement. By establishing the appropriate amounts of each gas component which are added to the polymer sample chamber of the sorption cell, the mixed gas apparatus simulator (MIGAS) can be used to maintain the partial pressure of one of the components to within 1% of the desired value.
A DSC study of curative interactions. III. The interaction of TMTM with ZnO, sulfur, and stearic acid
Authors: Kruger F. W. H. , McGill W. J.
Published: April 2003

The interaction among various combinations of sulfur, tetramethylthiuram monosulphide (TMTM), ZnO, and stearic acid were studied by differential scanning calorimetry in the absence of rubber. Sulfur and TMTM reacted to form tetramethylthiuram disulphide, and the ternary eutectic mixture melted at about 80°C. The absence of the Sγ → Sμ transition in sulfur/TMTM mixes was related to a sulfur/TMTM interaction, wherein the eightmembered sulfur rings were opened at temperatures well below 170°C. The interaction of stearic acid with TMTM led to the decomposition of TMTM, but the reaction was largely suppressed when both ZnO and sulfur were present in the mixture. No evidence was found for the formation of a zinc‐accelerator complex of the type normally attributed a role in the accelerated sulfur vulcanization.
Structures and properties of injection moldings of crystallization nucleator‐added polypropylenes. II. Distribution of higher‐order structures
Authors: Fujiyama Mitsuyoshi , Wakino Tetsuo
Published: April 2003

Flexural test specimens were injection‐molded from polypropylenes added with 0.5 wt % calcium carbonate, talc, p‐tert‐dibutyl‐benzoic acid monohydroxy aluminum, or p‐dimethyl‐benzylidene sorbitol under cylinder temperatures of 200–320°C. Distributions in the flow direction of higher‐order structures such as a*‐axis‐oriented component fraction [A*] and crystalline orientation functions and distributions in the thickness direction of higher‐order structures such as crystallinity, β‐crystal content, the degree of b‐axis orientation to the thickness direction, [A*], and crystalline orientation functions were studied. These higher‐order structures are inhomogeneous in the flow and thickness directions, which strongly influences the product properties such as mechanical and thermal properties.
Synthesis of a copolymer of tetrafluoroethylene and 1‐fluorosulfonyl–difluoroacetylfluoride
Authors: Kostov G. K. , Ivanov G. D. , Kotov St. V.
Published: April 2003

Tetrafluoroethylene (TFE) was copolymerized with 1‐fluorosulfonyl‐difluoroacetylfluoride (FSDFAF) in both the bulk and solution by using a free radical initiator at temperature 50°C. The presence of sulfonyl fluoride (SO2F) functional groups in the copolymers was proved by infrared (IR) spectroscopy. The copolymers were subjected to alkaline hydrolysis followed by an acid treatment and the SO2F groups content was found not to exceed 0.40–0.50 meq/g with polymer yield ranging between 1 and 36%. Copolymerization in solution of 1,1,2‐trichloro‐1,2,2‐trifluoroethane (Freon 113) under TFE pressure about 1.0 MPa and TFE/FSDFAF mole ratio 1.5–2.0 was proposed for further investigations. A random distribution of single FSDFAF units along the polymeric chain consisting mainly of TFE fragments was considered to exist. The copolymers had melting temperatures within 10–15°C lower than polytetrafluoroethylene and their thermal stability was 360–380°C.
Sign reversal of piezoelectric polarization of hydrated native collagenous and cellulosic fibers by addition of ions
Authors: Maeda Hideatsu
Published: April 2003

Complex piezoelectric constants of native collagenous and cellulosic fibers, which take highly oriented and ordered microfibrilar structures, have been measured at 10 Hz between −150 and 50°C. We have found that piezoelectric polarization of both hydrated fibers, which contain many ions, steeply decrease around −60°C and subsequently exhibit the sign reversal around −40°C. These temperatures are found to agree with that at which bound water between the microfibrils begin to get mobile. The steep decrease and sign reversal of the piezoelectric polarization may be explained by actions of ions that reside in piezoelectric and nonpiezoelectric regions of such ordered structures.
The effect of the side chain of acrylate comonomers on the orientation, pore‐size distribution, and properties of polyacrylonitrile precursor and resulting carbon fiber
Authors: Tsai Jin‐Shy , Lin Chung‐Hua
Published: April 2003

The side‐chain size of acrylate comonomer in polyacrylonitrile (PAN) precursor markedly influences the microstructure of PAN fiber and its resulting carbon fiber. In this paper, we propose that the model of the crystal orientation of PAN precursor and its resulting carbon fiber can explain the effect of the side‐chain size of acrylate comonomer on the orientation of PAN fiber and carbon fiber. When PAN precursor contains a larger side chain of comonomer, PAN precursor has the preferred crystal orientation and higher crystallinity and the orientation of its resulting carbon fiber unexpectedly decreases. This is because the larger the side chain is, the lower is the orientation of the amorphous region of PAN fiber; as a result, the average orientation after carbonization decreases. In the same mole fraction of comonomer, the carbon fiber based on PAN precursor with a smaller side chain of acrylate comonomer has better mechanical properties and higher yield.
Novel polyurethane hydrogels for biomedical applications
Authors: Lai Yu‐Chin , Baccei Louis J.
Published: April 2003

Polyurethane hydrogels derived from UV‐curable urethane prepolymer and hydrophilic monomers were prepared and their properties were evaluated. The urethane prepolymer used in this study contained well‐defined hard segments centered with a polyether‐based soft segment and end‐capped with methacrylate groups. The hydrophilic monomers studied were 2‐hydroxyethyl methacrylate (HEMA), N‐vinyl pyrrolidone, and glycerol methacrylate. Methacryloxypropyl tris (trimethysiloxy) silane (TRIS) was also used in some cases to modify properties. All composition were UV‐cured and formed hydrogels after hydration. The oxygen permeabilities of the hydrogels decreased as the water contents increased and increased as the TRIS content was increased. The tear strengths and moduli decreased as the water contents of the hydrogels increased. Most compositions studied have higher oxygen permeability and tear strength than poly(HEMA) because of the presence of urethane prepolymer in the composition.
The forming properties of high molecular weight polyethylene
Authors: Lee Y. W.
Published: April 2003

The formabilities of cold‐rolled high molecular weight polyethylene (HMWPE) sheets have been studied by measuring their plastic anisotropy ratio (R value), strain‐hardening exponent (n value), strain distribution, and the forming limit diagram (FLD). The deep drawability of the polymer is improved by rolling. After 40% or more reduction in thickness by cold rolling, the HMWPE sheet could be deep‐drawn into a cylindrical cup. The results of R value measurement indicate that the R value is responsible for improved drawability. Cold rolling also increases the n value but decreases the strain gradient. Stretch forming tests have also been carried out, and the results show that cold working could also improve the stretchability of this polymer. The results of the FLD are in agreement with the other properties studied. The mechanical properties, environmental stress cracking resistance, and shape, size, and property stability of the deep‐drawn HMWPE cups have also been investigated.
Analysis of filling, packing, and cooling stages in injection molding of disk cavities
Authors: Chiu Wen‐Yen , Chen Leo‐Wang , Wang Chi , Wang Ding‐Chang
Published: April 2003

This research tried to simulate three stages of injection molding cycles (filling, packing, and cooling) for polypropylene. The cavity used was a center‐grated disk‐shaped mold. During the filling stage, we assumed the polymer fluid obeyed the CEF equation and flowed nonisothermally. The packing stage was represented by isothermal flow of Newtonian fluid, and, during cooling stage, we took into account the effect of pressure drop on the energy balance. By finite difference method, we could solve the partial differential equations numerically. The results showed. (1) Elastic effect was not significant at the filling stage. (2) Pressure buildup in the cavity was very quick at the packing stage. (3) At the cooling stage, temperatures predicted by taking into account pressure drop were lower than those without considering pressure drop. In addition, the influences of mold temperature, flow rate, and inlet melt temperature on the three stages of injection molding process were discussed.
Effect of water absorption and temperature gradients on polycarbonate injection moldings
Authors: Qayyum M. M. , White J. R.
Published: April 2003

Polycarbonate injection moldings have been conditioned for various times in (i) hot water (40, 60, 80, and 100°C) or (ii) in a temperature gradient (with hot surface/cold surface temperatures 80/25, 100/25, 120/35, and 140/60°C). Water absorption occurred in hot water and caused the formation of disc‐shaped flaws, which were located at all depths within the bars and at all orientations. The presence of the flaws caused severe embrittlement and cracks were nucleated by them during uniaxial tensile testing. Residual stress levels were found to be diminished by hot water conditioning more than those in bars conditioned at the same temperatures in air. The sense of the residual stresses reversed in a bar that was allowed to cool slowly in the water bath, an observation attributed to desorption. It was generally found that the flaws near the surface healed on allowing the bars to stand in air at room temperature. Temperature gradient conditioning caused reversal of the sense of the residual stresses near to the hot surface at the two higher temperatures used and significant reduction in magnitude at the lower temperatures. Fracture nucleated at this surface during uniaxial tensile testing.
Property stabilization in filled, drawn polyethylene
Authors: Malik T. M. , Carreau P. J. , Schreiber H. P. , Rudin A. , Kale L. , Tchir W.
Published: April 2003

Mechanical properties of high density polyethylene (HDPE) extended to draw ratios in the 20–40 range have been determined and compared with corresponding properties of the polymers containing particulates including rutile, carbon black, iron oxide, and mica. Shrinkage of drawn structures was studied to temperatures near the fusion of the polymer host. The degree of interaction at polymer/additive interfaces was varied by surface coating certain of the solids with standard coupling agents. Solids were found to increase tensile moduli and to decrease shrinkage, particularly at higher exposure temperatures. The magnitude of changes due to the presence of solids was shown to depend on the apparent interaction at contacts between host and additive. In a dispersion–force matrix, like HDPE, benefits were optimized when the particulates were amphoteric or neutral, rather than having pronounced acid or base interaction potentials.
Structural characteristics of silk fibers treated with epoxides
Authors: Tsukada Masuhiro , Nagura Masanobu , Ishikawa Hiroshi , Shiozaki Hideki
Published: April 2003

Structural characteristics of the silk fibroin fiber‐modified with epoxide treatment were elucidated by refractive index measurement, differential scanning calorimetry, and thermomechanical analysis and on the basis of strength–elongation measurements. The four epoxides used were glycidol (G), ethylene glycol diglycidyl ether (E), tolyl glycidyl ether (T), and resorcinol diglycidyl ether (R). The values of the isotropic refractive index of the silk fiber increased by the action of T or R. The position of the endothermic peak attributed to the thermal decomposition and the position of the onset of the contraction of each of the samples treated with epoxides shifted to higher temperature, suggesting the more thermal stability. However, the values of the molecular orientation and the crystallinity of the specimen evaluated from X‐ray diffraction analysis remained unchanged regardless of the epoxide treatment. These experimental results have been interpreted in terms of the cross‐links between the adjacent silk fibroin molecules and of the hydrogen bonds between the hydroxyl groups of the epoxide molecules attached to the side chains of the silk fibroin.
Mathematical modeling of weather‐induced degradation of polymer properties
Authors: Hamid S. H. , Prichard W. H.
Published: April 2003

Weather‐induced degradation of polymer properties is caused by all the factors of weather, which include solar radiation, temperature, humidity, wind, rain, environmental pollutants, thermal cycling (cold night and hot days), and sand abrasion. Linear low‐density polyethylene (LLDPE) is exposed to natural weather, and degradation is monitored by the mechanical properties testing system, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). Three mathematical models were developed with weather parameters as independent parameters and mechanical property (tensile strength), chemical change (carbonyl growth), and thermal property (percent crystallinity) as dependent parameters. The mechanical property was found to be more dependent on the ultraviolet (UV) portion of the total solar radiation, chemical change was found to be synergestically effected by UV and total solar radiation, and change in thermal property was because of UV, total solar radiation, and temperature. Humidity and other weather parameters were found to play a less significant role in the weather‐induced degradation of LLDPE properties.
Effect of structure on the thermal stability of photocurable urethane acrylate formulations
Authors: Shama Sami A. , Tortorello Anthony J.
Published: April 2003

The effect of structural segments on the thermal stability of photocurable urethane acrylates was studied. A series of model compounds, where one segment of the molecular structure was varied at a time while keeping the remainder of the molecule unchanged, was tested for thermal stability. The results from this study indicate a prominent equivalent weight effect: Increasing the equivalent weight decreases the thermal stability within a given series of model compounds. Polyol‐based urethanes were found to be more stable than their amine counterparts. Of the hydroxy‐terminated starting materials, polycaprolactones were found to produce the greatest thermal stability, whereas polyethers resulted in the least stable photocurable materials. The diisocyanate segment exhibits a marked effect on the thermal stability of the cured material also. Surprisingly, the dicycloaliphatic diisocyanates resulted in greater stability than the aromatic diisocyanates, while the monocycloaliphatic diisocyanates yielded the least stable materials in the model compound series tested.
Modified avrami expression for polymer crystallization kinetics
Authors: Pérez‐Ćardenas Fernando C. , Castillo L. Felipe Del , Vera‐Graziano Ricardo
Published: April 2003

The Avrami equation has been widely used to describe polymer crystallization kinetics. However, the equation accurately fits experimental data only during the early stages of the crystallization process, and is unsuccessful in describing the entire process because it does not take into account secondary crystallization. Here we present a modified Avrami expression that describes polymer crystallization kinetics that takes into account both primary and secondary processes. The expression uses a new parameter introduced to indicate the fraction of material that has completed crystallization when the primary crystallization process has terminated. The theoretical results are in good agreement with experimental data.
Kinetics and mechanisms of water sorption in hydrophobic, ionizable copolymer gels
Authors: Firestone B. A. , Siegel R. A.
Published: April 2003

The aqueous kinetic swelling properties of a class of cross‐linked hydrophobic polyamine copolymer gels based on n‐alkyl esters of methacrylic acid (nAMA) and N,N‐dimethylaminoethyl methacrylate (DMA) have been studied as a function of solution ionic composition (pH, ionic strength, and buffer content), gel composition, and temperature. Water uptake and swelling in these gels are driven by ionization of the DMA amine groups, which overcomes the hydrophobic tendency of these gels to exclude water in the unionized state. Sorption kinetics in initially glassy gel disks are generally biphasic, characterized by an initial phase of relatively slow water uptake followed by an accelerated phase during which significant volume expansion of the gel occurs. This sorption/swelling behavior strongly suggests a moving penetrant front mechanism. The initial rate of water sorption increases markedly as (1) solution pH decreases, (2) gel nAMA comonomer content decreases, (3) gel nAMA side‐chain length decreases, and (4) temperature increases. Furthermore, the initial phase of sorption in initially glassy gels is generally non‐Fickian and approaches zero‐order behavior as (1) pH increases, (2) nAMA content increases, and (3) temperature decreases. In direct contrast, sorption in initially dry, rubbery gels is monophasic, but non‐Fickian, and approaches zero‐order behavior as temperature increases. This behavior is contrary to the Fickian sorption behavior normally observed in polymers above their glass transition temperatures. Finally, sorption kinetics critically depend upon the nature of the ions in solution: Kinetics are significantly faster in the presence of weak electrolytes than that of strong electrolytes. We discuss the importance of the rate of ion transport in determining the overall sorption kinetics and how sorption kinetics can be non‐Fickian in rubbery gels. Also, we propose a mechanism for the observed enhanced kinetics in the presence of weak electrolytes.
Selective plasticization of the ionic domains in a segmented thermoplastic ionene cationomer
Authors: Venkateshwaran L. N. , Leir C. E. , Wilkes G. L.
Published: April 2003

The use of zinc stearate as an ionic plasticizer has been demonstrated to function effectively in a segmented ionene cationomer thereby permitting its melt processability. The ionene polymer is prepared by reacting dimethylamino‐terminated polytetramethylene oxide (PTMO) oligomers with various benzyl dihalide compounds, leading to a segmented cationomer. Since the unplasticized ionene polymer undergoes degradation near the softening temperature (ca. 180°C), an ionic plasticizer was incorporated as a means of lowering the softening temperature to prevent degradation and permit melt processability. Zinc stearate was utilized in this study as it has been demonstrated to function well in other ionomers (essentially anionomers) in this capacity. Through the utilization of melt rheological and solid‐state morphological investigations, it has been clearly shown that zinc stearate will function effectively as an ionic plasticizer in these quite different ionomer materials by lowering the softening temperature to ca. 120°C, thereby permitting melt processability. In addition, due to the crystallization of the zinc stearate following cooling, this same species also serves to enhance the mechanical properties in the solid state.
Study on cure behavior of epoxy resin–BF3–MEA system by dynamic torsional vibration method
Authors: Pingsheng He , Chune Li
Published: April 2003

A dynamic torsional vibration method has been developed and used to investigate the isothermal cure processes of resin system of epoxy resin–boron trifluoride monoethylamine complexSiO2, optimizing its cure conditions and estimating the apparent dynamic parameters including gel time and rate of cure reaction and discussing the effect of filler on cure. The cure behavior of resin system has been predicted by the nonequilibrium thermodynamic theory. The theoretical prediction is in good agreement with the experimental results obtained by dynamic torsional vibration method.
Formation of polymeric microspheres using electron beam radiation
Authors: Mcherron Dale C. , Wilkes Garth L.
Published: April 2003

Polymeric particulates are currently being produced by a variety of different techniques. This new approach illustrates the formation of cross‐linked polymeric microspheres by incorporating trimethylolpropane propoxylate triacrylate (a radiation‐sensitive monomer) into a polyaphron system and exposing it to electron beam radiation. Polyaphrons are essentially a collection of droplets encapsulated in a very thin aqueous film dispersed in a aqueous matrix. This film gives extreme stability to the system, which allows for extremely high dispersed‐phase concentrations. The formation of polyaphrons requires the presence of a surfactant in both the dispersed (monomer) and continuous (aqueous) phases. The effects of monomer‐phase concentration, monomer‐ and acqueous‐phase surfactant concentration, aqueous‐phase surfactant type, and preparation temperature were studied to gain an understanding of the conditions that promote the formation of polymeric microspheres with a narrow size distribution. Polymeric microspheres ranging from 2 to 40 microns in diameter were formed with monomer concentrations as high as 67 vol % without any aphron bridging occurring or need for agitation to keep the monomer‐phase dispersed in the aqueous matrix. In addition, the ability to reduce the wettability of the microspheres is demonstrated through incorporation of a polymerizable fluorinated acrylate in the dispersed phase.
Effects of voids on the response of a rubber poker chip sample. III
Authors: Kakavas P. A. , Blatz P. J.
Published: April 2003

The effects of voids on the response of a rubber poker chip sample are examined. A theoretical estimation of the diametral contraction of the sample was performed, using the linear theory of stress analysis. Experimental measurements of the lateral contraction at the middle plane of the poker chip elastomer specimen have shown that the testing rubber is not incompressible. By comparing the experimental data with the theoretical predicted equation, the value of the Poisson's ratio veff was found to be 0.487, for a given aspect ratio a* of the sample. A theoretical equation for the volume dilatation of the poker chip rubber sample was developed. Using the given aspect ratio, the value of veff, and the experimental stress/strain curve of the sample, an estimation of the volume dilatation was formed. The effective Poisson's ratio was also found using the linear stress analysis, by comparing the developed mathematical equations for an incompressible rubber with voids with a compressible one.
Graft polymerization of some vinyl monomers onto alkali‐treated cellulose
Authors: Mansour O. Y. , Nagieb Z. A. , Basta A. H.
Published: April 2003

Treatment of cellulose by different concentrations of alkali, namely, 5–30% NaOH, changed its fine structure and transferred cellulose I into cellulose II. The decreased crystallinity due to alkali treatment and the transformation of cellulose I into cellulose II lowered the reactivity of cellulose toward the grafting polymerization reactions. Compactness of the structure as a result of the treatment of cellulose with 5% sodium hydroxide concentration decreased the rate of the grafting reaction and the grafting yield. On the other hand, such treatment of cellulose with different concentrations of alkali increased the rate of ceric consumption, i.e., increased the rate of oxidation of cellulose. Thus, the termination reaction of the grafting polymerization process may occur as a result of such oxidation and because of the increase of the active sites onto cellulose, leading to a decrease of the grafting yields and rate of grafting polymerization reaction by using the free‐radical grafting process. The use of the ionic‐xanthate method of grafting polyvinyl‐ and polyallyl‐on alkali‐treated cellulose shows an increase of grafting efficiency and grafting yields. Maximum grafting efficiency and yields were achieved when cellulose was treated with sodium hydroxide concentration below 15%, and maximum crystallinity indices were obtained. Using 15–25% sodium hydroxide lowered the indices of crystallinity, and lower grafting yields and grafting efficiency were achieved. Thus, transformation of cellulose I into cellulose II decreased the reactivity of these treated celluloses toward graft polymerization reactions by the use of the ionic‐xanthate method. In our opinion, termination reactions may also occur and affect the results.
Mathematical analysis of transport properties of polymer films for food packaging. VII. Moisture transport through a polymer film with subsequent adsorption on and diffusion through food
Authors: Smith Jeffrey S. , Peppa Nikolaos A.
Published: April 2003

A system of partial differential equations was developed to describe the transient, three‐step transport of moisture through packaged food products. The steps included (i) Fickian diffusion through the polymer package film; (ii) Langmuirian adsorption upon the food surface; and (iii) Fickian diffusion through the food material. A set of finite difference equations was derived to approximate the continuous model. These equations were solved for standard boundary conditions in each section of the food packages. The results can be used for the determination of the food package shelf life.
Generation of spherical and monodisperse particles of poly(styrene) and poly(methyl methacrylate) by atomization of monomers and dissolved polymer precursors
Authors: Panagiotou Thomai , Levendis Yiannis A.
Published: April 2003

A technique to produce spherical and monodisperse particles of selected polymers is presented. Liquid precursors of either mixtures of organic monomers and initiator catalysts or polymers dissolved in organic solvents were sprayed inside a vertical thermal reactor. The temperature range in the reactor was 400–670 K and the experiments were conducted in a nitrogen atmosphere. Atomization was achieved by an acoustically excited aerosol generator. Batches of equal size particles of two thermoplastic materials, poly(styrene) and poly(methyl methacrylate), were obtained in the range of 30–60 μm in diameter. Elemental analysis showed that the C and H composition of the produced particles was very close to theoretically expected values. The thermal environment, atomization conditions, and residence times the particles experienced in the reactor were explored using numerical techniques; residence times in the order of 4–10 s were estimated.
Surface properties of commercial polymer films following various gas plasma treatments
Authors: Wade William L. , Mammone Robert J. , Binder Michael
Published: April 2003

Surface properties of a number of commercial thermoplastic polymer films were investigated before and after brief exposures to RF induced, low temperature gas plasmas. Water wettability and adhesion of vapor deposited aluminum to thin films (8–12 micron) of polyethylene, polypropylene, polyester, polysulfone, polycarbonate, and polyvinylidene fluoride films were studied before and after treatments with oxygen, 96% CF4/4% O2, and helium plasmas. Treatment with oxygen plasmas showed the greatest change in water wettability for polyvinylidene fluoride and polypropylene films, while treatment with 96% CF4/4% O2 showed dramatic changes in wettability of polycarbonate, polysulfone, and polystyrene. Excellent adhesion of aluminium was found for polymers that had been previously exposed to gas plasmas.
Infrared spectroscopic studies of the nonformaldehyde durable press finishing of cotton fabrics by use of polycarboxylic acids
Authors: Yang Charles Q. , Andrews B. A. Kottes
Published: April 2003

A number of polycarboxylic acids have been used successfully as new nonformaldehyde cross‐linking agents for cotton fabrics. In our previous research, Fourier transform infrared photoacoustic spectroscopy (FTIR/PAS) demonstrated the ability for characterizing ester cross‐linkages in the finished cotton fabrics. In this research, the effects of different acid concentrations, different catalyst concentrations, different curing temperatures, and different curing times on the ester cross‐linking of the cotton fabrics were determined by FTIR/PAS. The infrared spectroscopic data were also correlated to durable press (DP) ratings. FTIR appears to be useful for evaluating the effectiveness of polycarboxylic acids as cross‐linking agents for cotton fabrics. FTIR definitely complements the existing methods for evaluating finished textile fabrics.
Preparation and characterization of low‐halogen and nonhalgoen fire‐resistant low‐smoke (FRLS) cable sheathing compound from blends of functionalized polyolefins and PVC
Authors: Sen Achintya Kumar , Mukherjee Bibha , Bhattacharya A. S. , Sanghi L. K. , De P. P. , Bhowmick Anil K.
Published: April 2003

An attempt is made to develop a novel series of cable sheathing compounds with variation in chlorine content and sufficient fire retardance and unique low‐smoke characteristics. These are prepared by blending PVC and functionalized polyolefins in different compositions. PE and EPDM have been functionalized by grafting dibutyl maleate (DBM) using DCP as initiator. FRLS compounds made from PVC‐functionalized polyolefin blends possess the special characteristics of low‐smoke, low‐acid‐gas generation, increased fire retardance, and improved volume resistivity, which are much better in comparison with a typical PVC sheathing compound. Thermoplastic elastomer (TPE) based nonhalogen FRLS compounds are also reported. The mechanisms for grafting, polymer‐polymer and polymer‐filler interactions have been presented.
Thermal degradation of EVA and EBA—A comparison. I. Volatile decomposition products
Authors: Sultan Bernt‐Åke , Sörvik Erling
Published: April 2003

This is the first in a series of papers in which structural changes during thermal degradation of ethylene‐vinyl acetate (EVA) and ethylene‐butyl acrylate (EBA) copolymers are compared. EVA, containing 11.4 mol% vinyl acetate (VA) and EBA, containing 5.4 mol% butyl acrylate (BA), were pyrolyzed at 280°C in nitrogen for 30 min. In another series of pyrolysis, EVA containing 1.2, 2.2, and 11.4 mol% VA were treated at 150–190°C for 3 h. The volatile decomposition products were collected in cooled traps respectively gas bags and then analysed with GC‐MS and ion‐chromatography. EVA is rather labile. The main volatile decomposition product is acetic acid. A linear decomposition rate was found already at the lowest investigated pyrolysis temperature, 150°C. After 30 min at 280°C every 15th of the acetate side groups had been eliminated. EBA is much more stable to pyrolysis. Thirty minutes at 280°C resulted in a decomposition of one out of 1500 BA groups. Butene is the main volatile decomposition product. Ester pyrolysis is supposed to account for the degradation of both types of polymers. The big difference in reactivity is presumably due to conformational differences. The ester pyrolysis mechanism will result in random unsaturations in EVA and carboxylic groups in EBA. To a minor extent acetaldehyde is formed when EVA is degraded. According to the mechanisms suggested, carbonyl groups remain in the main chain. Contrary to what is reported for poly(butyl acrylate), no alcohol was formed when pyrolysing EBA. This indicates that adjacent acrylate groups are needed for alcohol formation. For both types of polymer, scissions of the main chain results in hydrocarbon fragments mainly. In addition, acrylate containing fragments are observed when EBA is degraded. EVA, however, does not give any acetate‐containing fragments.
Thermal degradation of EVA and EBA—A comparison. II. Changes in unsaturation and side group structure
Authors: Sultan Bernt‐Åke , Sörvik Erling
Published: April 2003

This is the second in a series of papers in which the thermal degradation of ethylene‐vinyl acetate (EVA) and ethylene‐butyl acrylate (EBA) copolymers are compared. The EBA samples contain 0.8, 1.6, and 5.4 mol % butyl acrylate (BA), respectively, and the EVA samples 1.2 and 6.7 mol % vinyl acetate (VA). The samples were heated in nitrogen in a tubular oven at 285, 333, 350, 370 and 390°C for 6–120 min. The samples were analyzed with IR, NMR, gravimetry, and titration of carboxylic groups. The EVA samples were rapidly degraded by deacetylation, which was complete after about 30 min at 333°C. A linear relation between the loss of acetate groups and the formation of trans double bonds was found. A small amount of keto groups and traces of lactones were also observed. The data confirm the previously proposed mechanisms for deacetylation and the formation of acetaldehyde. A mechanism for lactone formation is suggested. The deacetylation rate is increasing with the VA content, presumably because of an increased amount of block sequences and an enhanced acid catalytic effect. The acrylate sidegroups are much more stable than the acetate groups, and are similar in stability to the main hydrocarbon chain. The BA decomposition results in carboxylic and anhydride groups. Decarboxylation also occur and increases with the thermal treatment. In LDPE and EBA the increase in unsaturation is small and mainly due to vinyl end groups formed via β‐cleavage or disproportionation. In EVA the formation of vinyl end groups is suppressed.