bluuebunny/crossref_metadata_2025 huggingface dataset:
XPS studies on radiation‐induced structural changes in the copolymer of tetrafluoroethylene and ethylene
Authors: Zhong Xiaoguang , Yu Li , Sun Jiazhen , Zhang Yuefang
Published: April 2003

In this work, the radiation‐induced structural changes in the copolymer of tetrafluoro‐ethylene and ethylene (F‐40) were studied by X‐ray photoelectron spectroscopy (XPS). During irradiation, some CF2 groups in the polymer were found to have been converted into carbon structures that bonded indirectly with fluorine atoms. © 1993 John Wiley & Sons, Inc.
Effect of injection‐molding conditions on the crystallinity, orientation gradients, and mechanical properties of poly(aryl ether ketone). II. Large dumbbell parts
Authors: Hsiung C. M. , Cakmak M.
Published: April 2003

High‐temperature thermoplastics such as poly(arylene ether ketone) form multilayer structures when they are molded at low mold temperatures. The cavity geometry, particularly the cavity thickness, plays an important role in forming these structural gradients. In this paper, we present our results on relatively thick large dumbbell specimens. Unlike the thin specimens (reported in Part I of this series of papers) that show structural gradients composed of amorphous skin‐crystalline intermediate zone and amorphous core, thicker dumbbell specimens exhibit structural gradients with increasing crystallinity from skin to core at low mold temperatures. Optical profiling on thin‐sliced specimens indicate the presence of six layers from skin to core at low mold temperatures, and the number of layers decrease with the increase of mold temperature. As the mold temperature increases, the regions near the surface increase in crystallinity while the core crystallinities remain high and unaffected by the changes in the process variables. At very high mold temperatures where thermally activated crystallization is dominant, the crystallinities become uniform throughout the thickness of the specimens. Wide‐angle X‐ray pole figure investigations indicate that the skin layers possess high preferential orientation with uniplanar axial (200) [001] texture and the core regions possessing lower orientation levels exhibit simple uniaxial texture with the chain axes oriented primarily along the flow direction. Elongation to break, tensile strength, and impact strength increase with the decrease of injection speed. The implications of these structural gradients on the mechanical properties are discussed. © 1993 John Wiley & Sons, Inc.
Young's modulus variation within polystyrene injection moldings
Authors: O'Donnell B. , White J. R.
Published: April 2003

Young's modulus distributions in the depth direction within injection moldings made from polystyrene have been investigated by empolying two independent techniques. Both methods show that the material close to the surface exhibits relatively high stiffness, whereas at all other depths a lower uniform stiffness exists. The depth dependency of other material characteristics, such as tan δ peaks in the dynamic mechanical thermal analysis spectra and molecular orientation, have been investigated in an attempt to correlate them with the stiffness distributions. It appears that the thermomechanical history of the different regions within the moldings, particularly the stresses acting during flow and the temperature gradients set up during cooling, are primarily responsible for the Young's modulus distributions presented here. © 1993 John Wiley & Sons, Inc.
Natural and accelerated photoaging of linear low‐density polyethylene: Changes of the elongation at break
Authors: Tidjani Adams , Arnaud René , Dasilva Anicet
Published: April 2003

The photoaging of different linear low‐density polyethylenes (LLDPEs), namely, ethylene–butene (EB) and ethylene–hexene (EH), has been studied. Experiments have been carried out under natural and accelerated UV exposure. We focused our investigation on the changes of elongation at break and the modifications in the chemical structure (measured by the IR technique) occurring over the photoaging process. Our results showed that the changes of elongation at break were different under the two modes of irradiation from the very beginning of UV exposure; in contrast, the comparison of stoichiometry displayed a small difference in the later stage of UV irradiation. That pointed out the difficulty of establishing a relationship between the buildup of carbonyl groups and the mechanical changes due to UV irradiation, which has been usually attempted. In addition, it appeared that the density, oxygen permeability, and the type of α‐olefin of the polymer might have an effect upon the elongation‐at‐break changes. From our data, it can be suggested that the prediction of weathering resistance of polymers can be based on both mechanical changes and modifications in chemical structure to minimize erroneous prediction. © 1993 John Wiley & Sons, Inc.
Novel low refractive index self‐cross‐linking fluoroterpolymers with very low surface tension and good adhesion to substrates
Authors: Aharoni Shaul M. , Martin Mary F. , O'Brien Kennedy P.
Published: April 2003

A novel family of fluoroterpolymers was prepared, containing perfluoroalkylethyl methacrylate (PFAEM), methacrylic acid (MAA), and 2‐hydroxyethyl methacrylate (2‐HEM) residues. The refractive index of the fluoroterpolymers is in the range of 1.3675 ≤ n ≤ 1.4275. The surface tension of cured thin films falls in the interval from 15 mN/m to as low as 8 mN/m. Upon heating, these polymers undergo thermally initiated self‐crosslinking and develop tenacious bonding to substrates. The associated chemical reactions and products were identified by IR spectroscopy and some thermogravimetric scans. The spectra indicate that the reaction products are ester and anhydride groups. In general, the formation of esters occurs more rapidly and requires lower temperatures (≥ 110°C) than does the formation of anhydrides. Prolonged heating, especially at higher temperatures (≤ 150°C), favors the formation of anhydrides. When the molar ratio of MAA to 2‐HEM is substantially larger than 1.0, the formation of anhydride is favored; when the ratio is 1 : 1, the formation of ester is favored; and when the molar ratio is much smaller than 1.0, the rate of formation of both esters and anhydrides is greatly reduced. In the case of the fluoroterpolymers, the formed esters and anhydrides essentially originate exclusively from the MAA and 2‐HEM and seem not to involve any attack on the PFAEM residues. Only after very long heating at the higher temperatures employed, some loss of CF band intensity was noted. In a copolymer of PFAEM and MAA, a substantial and rapid attack by the acid on the ester group in the PFAEM residues takes place under relatively mild conditions. Such and more drastic conditions appear not to affect at all a homopolymer of PFAEM alone. This suggests that in the fluoroterpolymers the more polar MAA and 2‐HEM tend to aggregate close together, so that, when heated, they preferentially react with each other, forming both esters and anhydrides. In the absence of 2‐HEM, the MAA may react with itself or with PFAEM, producing only anhydride groups. Both esters and anhydrides may be intermolecular and/or intramolecular, resulting in a cross‐linked system in which the cross‐link concentration is directly related to the combined amount of ester and anhydride groups. © 1993 John Wiley & Sons, Inc.
Miscible and immiscible blends of ABS with PMMA. I. Morphology and rheology
Authors: Kim Young Jin , Shin Gui Sook , Lee In Tae , Kim Byung Kyu
Published: April 2003

Melt blends of ABS and PMMA were prepared using three types of ABS having different acrylonitrile (AN) content, and PMMAs with different MW. From TEM micrographs, it was found that ABSs containing 24 and 27 wt % AN were miscible, and the one containing 35 wt % AN was immiscible with PMMA. Morphologically miscible blends showed welldefined semicircles in Cole—Cole plots, whereas immiscible ones showed immiscible drifts from the semicircle. In addition, as the compounding temperature increases, the dispersed PMMA phase became stratified, and more rubber particles, especially larger ones, migrated toward the PMMA phase. Miscible blends gave viscosities lower than additivity would predict, whereas immiscible ones gave positive (ABS‐rich phase) and negative (PMMA‐rich phase) deviations from the additivity. © 1993 John Wiley & Sons, Inc.
Effect of phase transitions on the volatility of UV absorbers from polypropylene
Authors: Lustoñ J. , Pastus̆áková V. , Vaśś F.
Published: April 2003

The volatility of 2‐hydroxy‐4‐methoxybenzophenone and 2‐(2′‐hydroxy‐5′‐methylphenyl) benzotriazole from isotactic polypropylene was studied by thermal methods in the temperature range that included the melting point of one of the stabilizers and the fusion of the polymer. The process proceeds according to the first order of kinetics. The rate constants of the stabilizers' volatility were calculated and the Arrhenius plots were constructed. The observed discontinuities in the Arrhenius dependences are interpreted as the result of the phase transitions of the polymer (melting) and the stabilizer. The activation energies for all zones were calculated. © 1993 John Wiley & Sons, Inc.
Permanently electrostatic dissipative (ESD) property via polymer blending: Rheology and ESD property of blends of PETG/ESD polymer
Authors: Lee Biing‐Lin
Published: April 2003

Rheological and electrical properties were studied on blends of a PETG polyester (cyclohexanedimethanol‐modified polyethylene terephthalate) and an inherently static dissipative high molecular weight polyether based copolymer, hereafter referred to as ESD polymer. Several important electrical properties and flow phenomena have been observed. First of all, the PETG blends could result in ESD protected material with excellent performance and a minimal effect on physical properties and melt processability. The rheological characterization reveals that the ESD polymer has a high melt viscosity even at a temperature more than 150 degrees above its melting temperature and that it exhibits pseudoplastic behavior. The PETG melt shows a near constant dynamic viscosity at a low frequency region. The viscosity of the ESD polymer and PETG melt exhibits a cross over at the temperature range from 200–220°C; the PETG melt is the lower viscosity component at low shear rate and the ESD polymer is the lower viscosity component at high shear rate. This appears to result in the existence of a small composition difference in the thickness direction of an injection‐molded ESD polymer/PETG part, with a greater fraction of the ESD polymer component in the skin section. This, in turn, could enhance the surface conductivity of the skin region of an injection‐molded part. © 1993 John Wiley & Sons, Inc.
Shear yield and crazing stresses in selected glassy polymers
Authors: Ikeda Richard M.
Published: April 2003

The plane strain shear yield stress and the triaxial crazing stress were determined for several commercial glassy polymers as a function of temperature. The polymers considered were: polycarbonate (Lexan®), polysulfone (Udel®), polyetherimide (Ultem®), polyarylate (Arylon®), and an amorphous nylon (Zytel® 330). When normalized to Tg the data for the various polymers were similar but not identical. An exception may be the triaxial crazing strains. In the temperature region between [T–Tg] = −300° and −50°C the crazing strains were all small (<1.5%), showed little temperature dependence, and appeared identical within the precision of our measurements. For temperatures below Tg and above any major secondary relaxation, Poisson's ratio was found to be constant for all of the polymers examined, 0.42 (±5%). © 1993 John Wiley & Sons, Inc.
Structure–property relationships of polyurethane‐based materials (PUPA) for applications in biomedicine
Authors: Cimmino S. , Martuscelli E. , Silvestre C. , Barbucci R. , Magnani A. , Tempesti F.
Published: April 2003

Polyurethane poly(amido–amine) (PUPA) is a modified polyurethane whose chains are crosslinked with those of a tertiary aminic polymer [poly(amido–amine) (N2LL)] by the bifunctional agent hexamethylenediisocyanate (HMDI). PUPA is capable of complexing heparin; a behavior that is related to the presence of poly(amido‐amine). The effect of the chemical composition of the starting mixture and/or the reaction time on the morphology and physical properties was studied by using differential scanning calorimetry, dynamic mechanical experiments, x‐ray, scanning electron microscopy, and Fourier transform infrared attenuated total reflection analyses. © 1993 John Wiley & Sons, Inc.
Study of anionic and nonionic silicone lattices by 29Si NMR spectroscopy
Authors: Stein Judith , Leonard Tracey M. , Smith Joann F.
Published: April 2003

The curing of silicone lattices has been studied using 29Si NMR spectroscopy. It has been found that cross‐linking occurs prior to removal of the water. Stabilizers prevent gelation by slowing down the rate of condensation, particularly of higher functionality cross‐linkers. © 1993 John Wiley & Sons, Inc.
Surface structure and inert surface characteristics of perfluorodecanoic acid‐grafted polyurethane
Authors: Han Dong Keun , Jeong Seo Young , Kim Young Ha , Min Byoung Goo
Published: April 2003

The surface compositions and characteristics of perfluorodecanoic acid (PFDA)‐grafted polyurethane (PU) were investigated to understand its enhanced blood compatibility. The grafting of PFDA was identified by attenuated total reflectance–Fourier transform infrared (ATR–FTIR). The results from angular‐dependent electron spectroscopy for chemical analysis (ADESCA) demonstrated the fluorocarbon enrichment at the outermost layer in PFDA‐grafted PU. Static secondary ion mass spectroscopy (SIMS) experiments supported the results drawn from ATR–FTIR and ADESCA data about the surface compositions. Energy‐dispersive X‐ray analysis (EDXA) data by fluorine mapping also indicated a considerable coverage with fluoroalkyl groups on the PU–PFDA surface. The critical surface tension, γc, of the highly hydrophobic PU–PFDA surface revealed an extremely low value of 6.9 dyn/cm due to the optimal orientation of CF3 groups to the uppermost surface. Therefore, such an inert low‐energy surface may contribute to improve blood compatibility of PFDA‐grafted PU. © 1993 John Wiley & Sons, Inc.
The effect of radiation‐induced cross‐linking on the relaxation of taut tie molecules during annealing of drawn LDPE
Authors: Yan Rong Jiang , Luo Yunxia , Jiang Bingzheng
Published: April 2003

Shrinkage, retractive stress, and infrared dichroism of the drawn low‐density polyethylene (LDPE) as‐drawn and irradiated by 60Co‐ray have been measured under different annealing conditions. The shrinkage and the disorientation of the irradiated sample was undergone more rapidly than that of unirradiated one as the temperature was continuously increased, surpassing a certain value, and a higher degree of shrinkage and disorientation was achieved finally for the irradiated sample when the samples were annealed with free ends. For the samples heated isothermally with fixed ends, the retractive stress went through a maximum and then attenuated to a limited value, and the degree of such a stress attenuation for the unirradiated sample was much more than that for the irradiated sample. These results show that the taut tie molecules (TTMs) in drawn PE can relax by the pulling of chain segments out of crystal blocks that they anchored in at elevated temperatures higher than the α transition and also by the displacing of microfibrils if the samples were annealed with free ends. The cross‐links produced by irradiation prohibit the former process. It was further observed that the dependence of the average extinction coefficient of the band at 2016 cm−1 on that of the band at 1894 cm−1 is related to irradiation and annealing conditions, which has also been explained by the relaxation of TTMs and the function of irradiation‐induced cross‐linking on the relaxation. © 1993 John Wiley & Sons, Inc.
Laminating resol varnishes made with crude multivalent phenol
Authors: Sridhar S. , Gadlinge Pavitra , Ratra M. C.
Published: April 2003

During the carbonization process of a lignite source available in the southern part of India, a very cheap byproduct, crude multivalent phenol, was obtained. This crude consisting of substituted phenols and carbonaceous pitch was distilled to get a pitchfree distillate of about 60% yield. The distillate mixture was used along with other phenols for synthesis of resol varnish using a base catalyst. The properties of the resols were evaluated and found to be similar to that of pure phenol (C6H5OH) resins. The resol varnishes prepared were used for making cotton paper phenolic laminates by hand impregnation and the compression‐molding technique. The paper laminates have been evaluated for physical, chemical, mechanical, and electrical properties. The experimental investigations indicate that the distillate of multivalent phenol is a useful inexpensive substitute for conventionally used phenols in the manufacture of P3 grade laminates. © 1993 John Wiley & Sons, Inc.
Preparation and properties of macromolecular complexes consisting of [2‐(diethylamino)ethyl]dextran hydrochloride and potassium metaphosphate
Authors: Kubota Naoji , Kikuchi Yasuo
Published: April 2003

In aqueous solution [2‐(diethylamino)ethyl]dextran hydrochloride (EA) was reacted with potassium metaphosphate (MPK) to form a series of water‐insoluble macromolecular complexes (MC) at different hydrogen‐ion concentrations (EA–MPK system). EA was also reacted with MPK in the presence of CaCl2 (EA–MPK–CaCl2 system). The structure and properties of MC obtained were compared with each other; elemental analysis, IR spectroscopy, solubilities, thermogravimetric analysis, and scanning electron microscopy were used to characterize these complexes. The molecular structure and properties of each MC were dependent on the hydrogen‐ion concentration and whether the Ca2+ ion coexisted. It was suggested that MC prepared at acidic pH were composed of a relatively loose network including a small quantity of MPK, whereas those prepared at neutral and alkaline pH were composed of a relatively tight network including a large quantity of MPK. This seemed to be due to changes in the degree of dissociation and the conformation of EA and MPK with the hydrogen‐ion concentration. MC in the EA–MPK–CaCl2 system were supposed to have a rather tightly bound network structure due to the Ca2+ ion as compared with those in the EA–MPK system. © 1993 John Wiley & Sons, Inc.
Development of dynamic mechanical methods to characterize the cure state of phenolic resole resins
Authors: Follensbee R. A. , Koutsky J. A. , Christiansen A. W. , Myers G. E. , Geimer R. L.
Published: April 2003

We are interested in using dynamic mechanical analysis (DMA) to measure the degree of cure achieved by aqueous phenol‐formaldehyde (PF) resole resins as a result of previous exposures to various temperature‐humidity‐time regimes. We developed procedures that permit the obtaining of data that properly characterize and quantify the DMA behavior of these aqueous systems. Particularly important factors are substrate selection, sample clamping geometry, and sample humidification prior to analysis. In this report, we illustrate the problems encountered and the steps that we adopted to resolve them. We also present preliminary DMA data that illustrate some approaches for measuring the degree of cure achieved during previous resin exposures. One especially promising approach employs the area under the tan delta curve during isothermal scanning as an inverse measure of precure. © 1993 John Wiley & Sons, Inc.
Polyaminocarboxylic acids–Ce(IV) redox systems as an initiator in acrylamide polymerization
Authors: Erbil Candan , Cin Canan , Soydan A. Bahattin , Sarac A. Sezai
Published: April 2003

Acrylamide polymerization by Ce(IV)‐polyaminocarboxylic acids, i.e., EDTA, DTPA, EGTA, and NTA, which have strong chelating properties, have been studied at different [H+], initiator concentration, and reaction time. Initiation of polymerization proceeds through the formation of the free radical after decarboxylation of the carboxyl group of polyaminocarboxylic acid. Results also indicate that the termination of the polymerization reaction is mainly mutual termination. Decrease of the rate of disappearance of the cerium(IV) is in the order of DTPA ≥ EDTA > NTA > EGTA. © 1993 John Wiley & Sons, Inc.
The thermooxidative stability of cured epoxy resins. I
Authors: Burton Bruce L.
Published: April 2003

Prior studies have shown that for many epoxy resin systems significant oxidative degradation occurs in air at temperatures as low as 100°C and that thin oxidized surface layers serve as crack initiators in flexural samples at low strains and can reduce flexural strengths to less than 25% of the original values. This study was undertaken in an attempt to identify predominant degradation pathways and cured resin systems that are thermooxidatively stable in 125°C air. Based on flexural property retention and IR spectral data, the thermooxidative resistance ranking of D.E.R.*332 epoxy resin polymerized with the following is p‐toluenesulfonamide > 4,4′‐diaminodiphenyl sulfone or sulfanilamide > methylene dianiline ≫ triethylenetetraamine > 2,5‐dimethyl‐2,5‐diaminohexane. Oxidation of aliphatic amine‐cured D.E.R. 332 epoxy resin is initiated by electrophilic attack of oxygen on the lone‐pair electrons of the nitrogen to form an amine oxide. Polymer chain cleavage then occurs via Cope reactions. A newly proposed oxidative degradation pathway is described wherein the hydroxylamine products of Cope reactions are further oxidized to nitrones, which then decompose to amides via oxaziridine intermediates. Commercial antioxidants added to an aliphatic amine‐cured epoxy resin were ineffective, supporting the conclusion that the predominant degradation mechanism is not free radical in nature. © 1993 John Wiley & Sons, Inc.
Studies on macromolecular entanglement. II. Modification of macromolecular entanglements by heat treatment
Authors: Qian Baojun , Wu Zongquan , Hu Panpan , Qin Jian , Wu Chengxun , Zhao Jiongxin
Published: April 2003

The modifications of macromolecular entanglements in polyacrylonitrile copolymer fibers by heat setting in different mediums such as steam, hot air, and inert liquid are reported. The effects of applied tension, frozen internal stress, temperature, time, medium, crystallization, etc., during heat setting on the modification of entanglements are investigated in detail. These experimental results elucidate clearly the mechanism of entanglement and disentanglement and confirm fully the DSC method of swelling polymers for studying entanglement in solid polymer, as was previously published in Part I of this paper. © 1993 John Wiley & Sons, Inc.
Reactive ion etching of selected polymers in O2 and in CF4/O2
Authors: Hand B. , Long T. , Dems B. C. , Rodriguez F.
Published: April 2003

A series of 17 polymers was etched in the reactive ion‐etching (RIE) mode. The etch rates were monitored using a laser interferometer. The gases used were oxygen alone and a mixture of carbon tetrafluoride with oxygen (8% O2). The polymers fell into three groups: the aromatics (polystyrene and derivatives), the aliphatics (methacrylates and vinyl acetate), and the cellulosics (methyl ether and nitrate). In oxygen with a power density of 0.25 W/cm2, the etch rates for the three groups fell in the range of 200–300 nm/min, 350–450 nm/min, and 500–850 nm/min, respectively. The etch rates were also measured at a power density of 0.50 W/cm2. The etch rates at the higher‐power density were about 75–80% higher than those at the lower‐power density. The etch rate in the fluoride mixture was about half that in the oxygen, all other parameters being the same. Plasticizers that lower the glass transition temperature of polymers based on vinyl chloride, methyl methacrylate, or styrene do not change the etch rate of the polymers very much. There is a slight increase in the rate for polystyrene and a slight decrease in the rate for poly(methyl methacrylate). All the effects of composition on etching rate can be correlated to a first approximation with the molar fractions of carbon and oxygen in the resist. © 1993 John Wiley & Sons, Inc.
Curing of unsaturated polyester resins—effects of comonomer composition. III. Medium‐temperature reactions
Authors: Huang Yan‐Jyi , Chen Chaur‐Jeng
Published: April 2003

The effects of comonomer composition on the curing kinetics of unsaturated polyester (UP) resins at 70–90°C were studied by differential scanning calorimetry (DSC) and infrared (IR) spectroscopy over the whole conversion range. One commercial UP resin, UP2660PF2, with cobalt promoter added and with 8.85 unsaturated CC bonds per polyester molecule, was used. It was found that a marked shoulder in the initial DSC rate profile, rather than that reported after the peak of rate profile for low‐temperature and high‐temperature reactions, appeared when the molar ratio of styrene to polyester CC bonds was greater than 1. With the initiator system accelerated by cobalt promoter, the formation rate of microgel particles would be enhanced at the early stage of reaction, as supported by the much higher conversion of polyester CC bonds than that of styrene by IR spectroscopy. Those relatively greater number of microgel particles tended to facilitate the intramicrogel crosslinking reactions, which would be independently identified from the initial DSC rate profile as a shoulder. Consequently, the reaction mechanism was elucidated by decomposing the reaction rate profile into two individual profiles accounting for the intramicrogel dominated and the intermicrogel dominated crosslinking reactions, respectively. © 1993 John Wiley & Sons, Inc.
Photochemically modified thin‐film composite membranes. I. Acid and ester membranes
Authors: Trushinski B. J. , Dickson J. M. , Childs R. F. , McCarry B. E.
Published: April 2003

A photochemically active membrane was made by the interfacial copolymerization of 3‐diazo‐4‐oxo‐3,4‐dihydro‐1,6‐naphthalene disulfonylchloride and naphthalene‐1,3,6‐trisulfonylchloride with 1,6‐hexanediamine. The chemical functionality of the membrane surface was modified on irradiation of the surface of the membrane in the presence of various nucleophiles. Surface analysis techniques of attenuated total reflectance‐Fourier transform infrared and scanning electron microscopy have been used to monitor the changes in the chemistry of the thin‐film composite membranes. The surface functionality of the membrane was shown to affect the reverse osmosis flux and separation of various solutes. Results for membranes which have been converted to acid, and ester forms are presented. © 1993 John Wiley & Sons, Inc.
Studies on the swelling of cotton fibers in alkali metal hydroxides. III. Structure‐property relations in fibers swollen at 0°C
Authors: Sreenivasan S. , Iyer P. Bhama , Patel G. S.
Published: April 2003

Cotton fibers were subjected to swelling in various concentrations of LiOH, NaOH, and KOH at 0°C. Swollen fibers were characterized by measurements of physical, mechanical, and fine structural properties. Slack swelling in LiOH and NaOH produced tremendous changes in fiber properties. Clear‐cut swelling maxima, disorientation, and subsequent deterioration in tensile properties at and near the swelling maxima were evident in both LiOH and NaOH. On the other hand, KOH swelling did not produce any clear swelling maximum. Fibers swollen in this reagent showed better retention of tensile properties due to conducive changes in the structural parameters resulting from a lower but more uniform swelling. © 1993 John Wiley & Sons, Inc.
The short‐ and long‐term mechanical properties of filled and unfilled thermotropic liquid crystalline polymer injection moldings
Authors: Plummer C. J. G. , Wu Y. , Davies P. , Zülle B. , Demarmels A. , Kausch H.‐H.
Published: April 2003

The basic mechanical properties of a series of injection moldings of the thermotropic liquid crystalline polymer Vectra have been investigated to determine the effect of fillers on the short‐ and long‐term mechanical properties of these materials. Mineral‐filler addition results in a slight decrease in strength and an increase in stiffness in the flow direction, but has relatively little effect on the anisotropy. Glass fiber addition, on the other hand, may substantially lower the anisotropy depending on the degree of fiber orientation transverse to the flow direction. The glass fiber‐filled grade investigated also showed improved creep properties at high temperature compared with both the unfilled and mineral‐filled grades. © 1993 John Wiley & Sons, Inc.
The preparation and morphology of PPO–epoxy blends
Authors: Pearson Raymond A. , Yee Albert F.
Published: April 2003

Poly(phenylene oxide) (PPO) was found to be miscible in diglycidyl ether of bisphenol A (DGEBA) based epoxy. The PPO–DGEBA system exhibited upper critical solution temperature (UCST) behavior. The cloud point temperatures were measured and found to be sensitive to the mol wt of the epoxy resin. A series of PPO‐modified epoxies were cured with piperidine at 160°C, which is above the cloud point temperature. Upon cure, two phase solids were formed, which contained discrete PPO particles. However, the two‐phase particulate morphology was not uniform and numerous large, occluded PPO particles were observed. In order to improve the uniformity, several styrene‐maleic anhydride copolymers were evaluated as potential surfactants for PPO‐DGEBA bends. The formation of a uniform, particulate morphology was facilitated by the addition of a styrene–maleic anhydride copolymer, containing a 10:1 ratio of styrene to maleic anhydride. To our knowledge, this is the first time that an emulsifying agent has been added to improve the morphology of thermoplastic modified epoxies. © 1993 John Wiley & Sons, Inc.
The preparation of poly[N(n‐butoxymethyl) methacrylamide] grafted silk fibers by polymerization using a low pH system
Authors: Tsukada Masuhiro , Shiozaki Hideki , Crighton John S.
Published: April 2003

The graft polymerizations of the N(n‐butoxymethyl) methacrylamide (BMA) monomer onto silk fibers were effected after reducing the pH of the grafting system to 2.5 by the addition of a formic acid solution. We compared the grafting efficiencies, surface characteristics, and thermal behaviors, as well as the whiteness levels and the extent of reduction of the rate of yellowing following UV irradiation, with the equivalent features of poly(BMA)‐grafted silk fibers, prepared under normal (pH 6) conditions. The grafting efficiency [as poly(BMA) weight gain] onto silk fiber that was attained was almost 100% through optimization of the pH environment in the polymerization system by the addition of formic acid. The stiffness of the silk fabrics observed, following the conventional grafting, was markedly higher than that of equivalent silks after the polymerization at pH 2.5. The rates of yellowness index increase, for these latter silk fabrics following UV irradiation were also reduced, specifically in the initial irradiation period (up to 60 h).

The SEM of the grafted silk fabrics reveal the absence of granules on the surface of the grafted silk fiber, when the silk was grafted with poly(BMA), after reducing the pH of the grafting system to 2.5. These findings suggest that the BMA monomer was polymerized specifically within the silk fiber and not on the surface. It is suggested that the increase in the polymer weight gain, and the reduced adverse effect on the fabric handle, arise because of the modified polymer location. © 1993 John Wiley & Sons, Inc.
Aromatic polyimides: Synthesis, characterization, and evaluation of electric strength
Authors: Bjellheim Peter , Helgee Bertil
Published: April 2003

Aromatic polyimides have been synthesized via the formation of polyamic acids in solution. This solution was cast into films that were thermally imidized. The imidization process was monitored using FTIR. The degree of imidization was also determined with thermo‐gravimetric analysis. The electric breakdown field strength was tested under ac and dc conditions. Ac electric breakdown field strength measured in transformer oil was shown to follow a power‐law dependence on film thickness. This dependence was not affected by the molecular mass of the polymer but changed with the degree of imidization and the electron‐accepting properties of the diamine. High ac breakdown field values of polymides were obtained in dibutyl phthalate medium due to the suppression of partial discharges that occurs under these conditions. Measurements on films with thicknesses up to 60 μ showed no thickness dependence. No significant influence of the chemical structure on the break‐down field strength was observed under these conditions. Breakdown field measurements under dc conditions showed high values, which were in good agreement with the peak values of the ac measurements in dibutyl phthalate. This indicates similarities in the intrinsic ac and dc breakdown processes. © 1993 John Wiley & Sons, Inc.
Surface and interfacial FT–IR spectroscopic studies of latexes. VI. Orientation and spatial distribution of acid functionalities at the film–substrate interface
Authors: Thorstenson Timothy A. , Tebelius Lara K. , Urban Marek W.
Published: April 2003

Formation of dimeric carboxylic acid functional groups observed at the film‐substrate interface of ethyl acrylate/methacrylic acid (EA/MAA) and butyl acrylate / methyl meth‐acrylate / methacrylic acid (BA/MMA/MAA) latex films prepared on a high surface tension substrate, such as liquid mercury, is observed when sodium dioctyl sulfosuccinate (SDOSS) is employed as the synthetic emulsifier. To address the acid species assembled at this interface due to the inability of SDOSS to effectively alleviate interfacial tension and to assess the orientation and spatial configuration of acid groups species at the interface, polarized attenuated total reflectance, Fourier‐transform infrared spectroscopy (ATR FT–IR) is employed. It is found that the acid dimer rings adopt an average “on‐edge” configuration at the interface with the hydrogen‐bonded rings perpendicular to the film‐mercury interface. This configuration serves to provide not only the necessary interfacial acid‐dimer layer, but also facilitates favorable ring–ring interactions between groups of opposite polarity on adjacent rings. This study indicates that the on‐edge configuration may also serve to reduce unfavorable interactions between the polar acid functionality and the less polar components present in the bulk of the coalesced latexes. © 1993 John Wiley & Sons, Inc.
Measurement of thermophysical properties of polyester cured with styrene in the range 300–450 K
Authors: Hilal A. S. , Abousehly A. M. , Dessouky M. T. , Abd El‐Hakim A. A.
Published: April 2003

A pulse method for the simultaneous determination of thermal diffusivity, α, specific heat capacity, Cp, and thermal conductivity, λ, are measured for a series of curing of polyester and styrene in the presence of 10, 20, and 30% carbon black in the temperature range 300–450 K. The results show a dependence of the above‐mentioned properties on temperature and composition. The mechanism of heat transfer through the specimens is also discussed. © 1993 John Wiley & Sons, Inc.
Dissolution and crystallization behavior of poly(ethylene terephthalate)–diluent mixtures
Authors: Vane L. M. , Rodriguez F.
Published: April 2003

The solution crystallization kinetics and crystal dissolution behavior of three grades of poly (ethylene terephthalate) in N‐methyl–2‐pyrrolidinone were studied were using turbidimetric and calorimetric methods. The influence of concentration on the equilibrium dissolution temperature was described using Flory's melting point‐composition relationship. The effect of the solvent alkyl group was also investigated. N‐ethyl‐2‐pyrrolidinone was found to be a better solvent than N‐ethyl–2‐pyrrolidinone or N‐cyclohexyl–2‐pyrrolidinone for poly (ethylene terephthalate). From the calorimetric experiments, it was determined that two crystallization processes (primary and secondary crystallization) were responsible for the total crystallinity. The primary process dominated the early stages of the crystallization process and accounted for the majority of the final crystallinity for lower polymer concentrations. Based on coherent secondary nucleation theory, the effect of the crystallization temperature on the primary crystallization rate constant was quantified in terms of a temperature coefficient. This temperature coefficient was found to be relatively insensitive to PET concentration, PET structural impurities, and solvent alkyl group. © 1993 John Wiley & Sons, Inc.
Acrylonitrile–acrylic acids copolymers. I. Synthesis and characterization
Authors: Bajaj P. , Paliwal D. K. , Gupta A. K.
Published: April 2003

Acrylonitrile (AN) was copolymerized with acrylic acid (AA), methacrylic acid (MAA), and itaconic acid (IA) by the aqueous suspension method at 40°C with ammonium persulfate and sodium metabisulfite as the redox initiator. The reactivity ratios for the AN–AA and AN–IA systems were also calculated by the Finemann–Ross and the Kelen–Tüdõs methods. Higher r2 (AA) for the AN–AA system in comparison to r2 (IA) for the AN–IA system indicates greater reactivity of AA toward the propagating species. The influence of co‐monomers on intrinsic viscosity, tacticity, and number‐average sequence lengths was studied. 13C‐NMR spectra revealed that AN copolymers having approximately 2 mol % of AA have a greater percentage (>30%) of isotactic content than of homopolyacrylonitrile. Tacticity has also been calculated from infrared spectra of the polymers using stereospecific absorption bands at 1250 and 1230 cm−1. © 1993 John Wiley & Sons, Inc.
Preparation and properties of Si‐containing copolymer for near‐UV resist. III. Maleimide/silylstyrene copolymer
Authors: Chiang Wen‐Yen , Lu Jin‐Yuh
Published: April 2003

Poly(maleimide‐alt‐p‐trimethylsilyl‐α‐methylstyrene) (α‐PMTMMS) and poly(male‐imide‐alt‐p‐trimethylsilylstyrene) (PMTMSS) were synthesized for positive/negative near‐UV resists in the containing of diazonaphthoquinone sulfonate (DNS). The electron‐rich styrenic monomers tend to undergo alternating copolymerization with an electron‐poor maleimide monomer. The chain‐stiffening effects of the maleimide and α‐methylstyrene group were responsible for high thermal stabilities. A higher glass transition temperature of 226°C was found in α‐PMTMMS. Lithographic positive/negative images were obtained that were stable to temperatures higher than 200°C. Excellent solubility in aqueous base was observed with PMTMSS at 10.3 wt % silicon content and an oxygen‐plasma etching rate of 1:12 compared to hard‐baked HPR–204. © 1993 John Wiley & Sons, Inc.
Characterization of fluoroelastomer networks. I. Infrared analysis
Authors: Theodore A. N. , Carter R. O.
Published: April 2003

Fluorocarbon compounds based on vinylidene fluoride copolymers and dihydroxy nucleophiles were prepared to determine the network forming structures of the cured materials. Previous attempts to achieve this goal consisted of model compound reactions, of prevulcanization events, and of materials cured under conditions only approaching industrial vulcanization conditions. The proposed structures derived from these studies could be different from the entities that will come in contact with alternate fuels such as methanol/gasoline blends when used in automotive applications. The evolution of the solid‐state chemistry during cure and the final network structure needed to be defined. Thus, infrared vibrational spectra for 25‐μm thick sections from key stages of processing were recorded. These spectra established directly, for the first time, that bisphenol‐AF (BPAF) serves as the crosslinker during cure. Additionally, persistent unsaturation is formed on the elastomer backbone after crosslinking. Curing for extended periods of time produces no observable effect on the network. Furthermore, postcuring reduces residual hydrofluoric acid in the compound and results in two new absorptions at 2851 and 2920 cm−1, indicative of amorphous regions of polyvinylidene fluoride (PVF2). Although these findings help define the final network structure, there remain uncertainties about the pathway leading to the final structure. The data serve as input to understanding the fracture behavior and long term performance of this class of materials. It also could serve as a starting point for studies dealing with the enhancement of certain fluorocarbon properties such as low temperature behavior. © 1993 John Wiley & Sons, Inc.
Epoxidized linseed oil‐free fatty acids modified with substituted anilines as antioxidants and antirads for SBR vulcanizates
Authors: Younan A. F. , Al‐Kobtan A. F. , Badran B. M.
Published: April 2003

Epoxidized linseed oil‐free fatty acids were reacted with aniline and three isomers of toluidine, anisidine, and chloroaniline in such a manner that the carboxylic groups remained free. The prepared adducts were evaluated as antioxidants and antirads for styrene butadiene rubber (SBR) vulcanizates. It was found that 2 phr of orthotoluidine, paraanisidine, orthochloroaniline, and aniline adducts were the best antioxidants and/or antirads. © 1993 John Wiley & Sons, Inc.
Thermal analyses of graft copolymers of poly (methyl methacrylate) main chain with poly (propylene oxide‐b‐ethylene oxide) graft chain
Authors: Lucas Elizabete F. , Porter Roger S.
Published: April 2003

Poly(methyl methacrylate‐g‐(propylene oxide‐b‐ethylene oxide)) and poly (methyl methacrylate‐g‐(ethylene oxide‐b‐propylene oxide)), comprising chemically dissimilar sequences, exhibit intramolecular phase separation. These compositions have applications in coatings and as surface‐tension modifiers. This paper presents the thermal behavior of these graft copolymers: separate samples of the homopolymer and of the grafts were also analyzed to provide comparisons. The phase behavior has been analyzed by differential scanning calorimetry and by dynamic‐mechanical thermal measurements. Two glass transitions (Tg) are observed, caused by the partial incompatibility within the copolymers. The activation energy of the Tg relaxation process of the main chain is decreased by the graft chain. The influence of poly(propylene oxide‐b‐ethylene oxide) grafts on the thermal degradation of the poly(methyl methacrylate) (PMMA) main chain was studied by using thermogravimetric analysis. Prolysis of the graft copolymers occurs in three stages and begins on the graft chain and at a lower temperature than the pyrolysis of pure PMMA. Both the phase behavior and the thermal stability are found to depend sensitively on the composition of the copolymer. © 1993 John Wiley & Sons, Inc.
The influence of implantation conditions on the surface structure of polypropylene
Authors: S̆vorc̆ík V. , Rybka V. , Hnatowicz V. , Kvítek J.
Published: April 2003

The influence of the fluence and the energy of implanted F+ ions on the surface structure of polypropylene was studied by measuring the contact angle and UV‐visible spectra. With increasing ion fluence and energy, the polar component of the surface energy increases. At the same time, the number and the length of double‐conjugated bindings in the polymer also increase. With higher ion energy, an increasing number of conjugations are observed but their length remains unchanged. © 1993 John Wiley & Sons, Inc.
Evaluation of light‐scattering detectors for size exclusion chromatography. II. Light‐scattering equation selection
Authors: Jeng L. , Balke S. T.
Published: April 2003

A new multiangle laser light‐scattering (MALLS) detector for size exclusion chromatography promises simultaneous measurement of both weight‐average molecular weight (Mw) and radius of gyration (rg) at each retention volume across the chromatogram. However, there are a variety of ways of interpreting the raw data to provide these results. This study examines variations of three different rearrangements of the basic light‐scattering equation. Data from a room temperature analysis of polystyrene and a high‐temperature analysis of polyethylene were used. The degree of fit of each equation to the data and the precision of the Mw and rg values are evaluated. To define precision, joint confidence regions (JCRs) were calculated and compared to simple confidence intervals based upon standard deviations in order to see the effect of interdependence of Mw and rg. Results showed that the Debye equation was superior to the inverse Debye equation (similar to the Zimm plot) for the interpretation of MALLS data. The effect of the quantity of data included in the regression model was also assessed. Use of only the most precise four detector angles was compared to use of a full set of 15 angles. Precision of weight‐average molecular weight values was found to be improved as the detector angle decreased because of the shortened extrapolation to zero angle. Precision at room temperature was much superior to that at high temperature. Use of simple confidence intervals was shown to provide only a fair approximation to the more accurate JCR. The “natural scatter” of data shown by the JCR generally shows the same trend as do plots in the literature of Mw vs. rg. Thus, it is concluded that JCRs should be more often calculated in light‐scattering studies in order to distinguish random scatter from meaningful correlations of these values. © 1993 John Wiley & Sons, Inc.
Synthesis of 3‐substituted‐2‐cyanoacrylates: Their evaluation as cross‐linkers in cyanoacrylate adhesive compositions
Authors: Vijayalakshmi V. , Rupavani J. N. , Krishnamurti N.
Published: April 2003

Alkyl 2‐cyano‐2,4‐pentadienoates and alkyl 2‐cyano‐2,4‐hexadienoates were synthesized and characterized by spectroscopic methods. These were then evaluated as cross‐linkers in 2‐cyanoacrylate adhesive compositions to improve the heat stability of their adhesive bonds between various metal surfaces. © 1993 John Wiley & Sons, Inc.
The effect of different ammonium structure of quaternary ammonium resin on the electrochemical properties
Authors: Yang Chin‐Ping , Ting Chih‐Yang
Published: April 2003

The quaternary ammonium resin is synthesized by the ring‐opening reaction of an epoxy resin with a tertiary amine in the presence of a proton donor in the solution. This kind of resin can be dispersed in the water phase to form a conductible milky dispersion. In this study, different kinds of tertiary amines including the full‐alkyl group and the ester group‐containing or urethane group containing tertiary amine are reacted with DGEBA‐type epoxy resin to synthesize the quaternary ammonium resins. The resin characteristics and the electrochemical properties of its emulsion are investigated. In addition, properties of the emulsion prepared from tertiary amine salt resin are also measured for comparison. It is found that if the substituted groups of the ammonium structure of the quaternary ammonium resin are all alkyl groups, rupture voltage of the emulsion is very low. But when one of the substituted group contains an ester group or an urethane group, rupture voltage increases remarkably and the resin can be used for electrodeposition. Meanwhile, the electrodeposition theory of quaternary ammonium resin and its thermal cross‐linking reaction and the electrochemical properties of coemulsion prepared by mixing the quaternary ammonium resin and the tertiary amine salt resin are also discussed. © 1993 John Wiley & Sons, Inc.
Preparation of poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE)/epoxy laminate with functionalized PPE resin
Authors: Chao Herbert S.‐I. , Whalen Jana M.
Published: April 2003

Thermal expansion property at 288°C and methylene chloride resistance of poly(2,6‐dimethyl‐1,4‐phenylene ether (PPE)/epoxy laminate were found to be affected by the functionality on PPE resin. Nonlofting PPE/epoxy laminates were prepared with the PPE grafted with fumaric acid or the PPE having (di‐n‐butylamino) methyl substituent on the polymer backbone. Employing vacuum‐vented PPE extrudate or phenol‐redistributed PPE was also effective in improving the PPE/epoxy laminate properties. Attempts to preparing a real PPE/epoxy interpenetrating network as the matrix material for the laminate were also made by incorporating both PPE crosslinker and epoxy curing catalysts in the same formulation. © 1993 John Wiley & Sons, Inc.