bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture toughness of adhesive joints. I. Relationship between strain energy release rates in three different fracture modes and adhesive strengths
Authors: Lim Won Woo , Hatano Yasunori , Mizumachi Hiroshi
Published: April 2003

The three strain energy release rates, GIC, GIIC, and GIIIC, of adhesive joints can be attributed to their ability to resist crack propagation of solids in the adhesive layer. The dependencies of GIC, GIIC, and GIIIC on crack lengths for various adhesive joints were determined using the double‐cantilever beam specimen by a compliance method. The two types of adhesive strengths, i.e., adhesive tensile strength and adhesive shear strength, corresponding to GIC and GIIC, respectively, were carried out at room temperature and 65% RH with a crosshead speed of 10 mm/min. The GIC, GIIC, and GIIIC were dependent upon crack length and had constant values irrespective of geometric parameters of the specimen over the crack length of five times adherend thickness, 0.65 (= crack length over half a length of span) and eight times adherend thickness, respectively. In the region of the crack length, we determined the following increasing order of fracture toughness: GIC < GIIIC < GIIC. A positive correlation was found between adhesive tensile strength and GIC. A significant relation between adhesive shear strength and GIIC was not found in this work. Further studies are needed to clarify the relation between adhesive shear strength and GIIC with general adhesives. © 1994 John Wiley & Sons, Inc.
Polymer blend: A novel method for the preparation of a natural rubber–carboxylated nitrile rubber blend
Authors: Naskar Nityananda , Biswas Tapasi , Basu Dipak Kr.
Published: April 2003

Bis(diisopropyl)thiophosphoryl disfulfide (DIPDIS) can be successfully used to form a blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar NR through a chemical link between the two. It is revealed from the study that the physical properties of the vulcanizates obtained from the NR‐XNBR blend could be significantly improved by the judicious selection of the NR:XNBR ratio. These properties can further be improved by two‐stage vulcanization as described in the procedure. The SEM study reveals that it is possible to form a coherent blend of NR and XNBR in the presence of DIPDIS. © 1994 John Wiley & Sons, Inc.
Oxidative damage and recovery of silicone rubber surfaces. I. X‐ray photoelectron spectroscopic study
Authors: Tóth András , Bertóti Imre , Blazsó Marianne , Bánhegyi György , Bognar Alajos , Szaplonczay Pál
Published: April 2003

The oxidative degradation of silicone rubber surfaces in air plasmas obtained by RF or corona discharges and the subsequent recovery process were studied by X‐ray photoelectron spectroscopy (XPS or ESCA). Using relatively short treatment times (5 min), the surface oxygen content was found to increase and that of carbon to decrease. Within 1 day some recovery toward the original composition was observed, but it was far from being complete. Angle‐dependent measurements have shown an almost total recovery in the topmost layer. The degree of surface degradation of a solvent‐extracted sample was much higher while its recovery was much smaller than the corresponding features of the nonextracted sample. According to GC and GC–MS analyses the extract contained a mixture of cyclic, and, in a minor quantity, linear dimethylsiloxane oligomers. Based on the above results the following steps were proposed for the oxidative damage and the subsequent recovery processes on silicone rubber surfaces: first the majority of surface methyl groups is removed and an oxidized layer containing Si atoms bound to 3 or 4 oxygens appears. The surface is later covered by a very thin (2–3 nm thick) “silicone oil” layer due to migration of low‐molecular‐weight components from the bulk. This diffusion‐controlled migration step plays a more important role in the recovery process than the eventual reorientation of the newly formed polar groups from the surface toward the bulk. The proposed model is discussed in the light of published data. © 1994 John Wiley & Sons, Inc.
Morphological studies of bisphenol series thermotropic liquid crystalline wholly aromatic copolyesters
Authors: Zhao Zhouming , Wu Xuqin , Lin Yongwei , McLean John
Published: April 2003

A family of aromatic thermotropic liquid crystal (TLC) copolyesters are prepared based on terephthalic acid (TPA), isophthalic acid (IPA), p‐hydroxybenzoic acid (HBA), and a family of bisphenols. The morphological behaviors of the copolyesters are studied by using polarized optical microscopy, small‐angle light scattering (SALS), and depolarized light intensity (DLI) analysis. The copolyester melts exhibit nematic mesophase textures within wide temperature ranges without showing transitions to isotropic phases. The textures under different temperatures and deformation conditions are investigated. Scattering patterns of the mesophases change greatly during shear deformation and relaxation. The early formation of the mesophases is a one‐dimension heterogeneous nucleation based on isothermal condition. © 1994 John Wiley & Sons, Inc.
Surface modification of UHMWPE fibers
Authors: Silverstein M. S. , Breuer O. , Dodiuk H.
Published: April 2003

Ultrahigh molecular weight polyethylene (UHMWPE) fibers have a high specific strength, high specific modulus, and outstanding toughness, but their poor adhesive properties has limited their use for composite material applications. In this research, the effects of chemical etching on the surface chemistry and topography have been explored using chromic acid, potassium permanganate, and hydrogen peroxide etching. The smooth surface observed on the as‐received fiber was rich in ether and/or hydroxyl oxygen. This smooth surface resulted from the presence of an outer layer, a weak boundary layer, that was removed by all the etchants. A fibrillar structural hierarchy was revealed beneath this outer layer and the fiber was relatively unchanged by further etching. Chromic acid, the strongest etchant studied, produced a rough and oxidized UHMWPE surface with both ether and carbonyl oxygen. The combination of outer layer removal, roughness, and changes in oxygen bonding helps explain the improved adhesion on chromic acid etching in spite of the reduction in surface oxygen. Neither hydrogen peroxide nor potassium permanganate etching roughened or oxidized the surface to a great extent and neither yielded improved adhesion. © 1994 John Wiley & Sons, Inc.
Ductile tearing instability in phenolphthalein poly(ether ketone)
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu
Published: April 2003

Phenolphthalein poly(ether ketone) (PEK‐C)can fail by tearing instability when the elastic contraction is greater than the plastic extension due to crack growth. Tearing instability (TIS) theory developed by Paris and coworkers describes the effect of specimen geometry on the ductile fracture properties of polymers. The stability of crack growth in three‐point bend specimens depends on the specimen's dimensions. In this article, tearing instability theory is applied to describe the ductile tearing instability of PEK‐C at different temperatures. The temperature dependence of tearing modulusTm,dJ/dδa, and the relationship betweendJ/dδaand yield stress are discussed. © 1994 John Wiley & Sons, Inc.
Electrostriction of highly swollen polymer gel: Possible application for gel actuator
Authors: Hirai Toshihiro , Nemoto Hiroshi , Hirai Mitsuhiro , Hayashi Sadao
Published: April 2003

A gel of poly(vinyl alcohol) highly swollen with dimethyl sulfoxide was demonstrated to actuate at a much faster rate (more than 1000 times) than those reported on conventional gel actuators in air and to flap a wing of 12.5 cm at a rate of 2 Hz with a span of 10 cm by periodically applying electric field. The action (8% in length) induced by the electric field reached several hundreds times larger than those reported on the conventional ferroelectric solid materials. The electrostrictive gel was, thus, found to be a promising candidate material as a novel type of actuator or artificial muscle by having overcome some difficulties in responding time, electrochemical reactions on the electrodes, and magnitude of action in conventional methods or materials. © 1994 John Wiley & Sons, Inc.
Transient shear response of liquid crystal‐forming hydroxypropyl cellulose solution in dimethylacetamide. II. Correlation between band formation and stress relaxation
Authors: Suto Shinichi , Kohmoto Kenichi , Abe Atsushi
Published: April 2003

The simultaneous determination of band formation and stress relaxation behavior was carried out using a parallel glass plates apparatus for the liquid crystalline hydroxypropyl cellulose solutions. The effects of shear rate and concentration on both behavior were mainly determined. The dependence of band formation on shear rate was the same as that reported in the literature: the higher shear rate is, the more rapidly the band forms. The band formation depended on the concentration. The effect of concentration appeared to depend on the solution phase (biphase or fully liquid crystalline phase); for the biphasic solutions, the band formed rapidly with increasing concentration, whereas for the fully liquid crystalline solutions, the band formed rapidly with decreasing concentration. Qualitatively, the stress relaxation was divided into two regions; one was the first rapid relaxation process, and another was the secondary slow relaxation one. It was speculated that the band does not form in the first process, but begins to form around the beginning of the secondary process. © 1994 John Wiley & Sons, Inc.
Grafting of maleic anhydride onto polypropylene: Synthesis and characterization
Authors: Sathe Sachin N. , Rao G. S. Srinivasa , Devi Surekha
Published: April 2003

Isotactic polypropylene was grafted with maleic anhydride using benzoyl peroxide as an initiator and toluene as a solvent. Effects of various parameters such as monomer and initiator concentration, reaction time, and reaction temperature on percentage grafting were studied. Effect of various solvents on extent of grafting was also studied. The maximum extent of grafting achieved was 5.3%. The graft copolymers were characterized by i.r., thermal, viscometric, and contact angle studies. Improved thermal stability and decreased intrinsic viscosity and critical surface tension were observed for graft copolymers. © 1994 John Wiley & Sons, Inc.
Aqueous dispersion of polyurethane anionomers from H12MDI/IPDI, PCL, BD, and DMPA
Authors: Kim B. K. , Kim T. K. , Jeong H. M.
Published: April 2003

Polyurethane anionomer dispersions were prepared from hydrogenated diphenylmethane diisocyanate (H12MDI) or isophorone diisocyanate (JPDI), poly(caprolactone) (PCL) diol, 1,4‐butane diol (BD), and dimethylolpropionic acid (DMPA). Upon neutralization of the DMPA with triethylamine (TEA), the NCO‐terminated polyurethane (PU) ionomers were self‐emulsified by adding water, followed by chain extension using triethylenetetramine (TETA) in aqueous media. Polyurethanes from H12MDI showed coarser dispersion and better tensile properties over those from IPDI. Polyurethanes prepared by the one‐shot method had better dispersion and tensile properties over those by the two‐shot method. When some of the PCL diol was replaced by DMPA or BD, tensile strength increased and ductility decreased due mainly to the increased chain rigidity and intermolecular forces. © 1994 John Wiley & Sons, Inc.
Catalyzed hydrolysis of polyethylene terephthalate melts
Authors: Campanelli J. R. , Cooper D. G. , Kamal M. R.
Published: April 2003

The effect of zinc catalysts on the hydrolytic depolymerization of polyethylene terephthalate (PET) melts in excess water was studied using a 2‐L stirred pressure reactor at temperatures of 250, 265, and 280°C. The main products of the reaction were found to be terephthalic acid, ethylene glycol, and diethylene glycol. Rate constants were calculated from initial rate data at each temperature and found to be about 20% greater than the corresponding rate constants for uncatalyzed hydrolysis. The catalytic effect of zinc, as well as sodium, salts is attributed to the electrolytic destabilization of the polymer‐water interface during hydrolysis. The depolymerization rate data at 265°C were found to fit a kinetic model proposed earlier for the uncatalysed hydrolysis of PET. The effect of zinc and sodium salts on the activation energy of hydrolysis, or on the formation of ethylene glycol monomer is unclear. © 1994 John Wiley & Sons, Inc.
Cardanyl acrylate/methacrylate based cross‐linked copolymers as novel supports: Synthesis and characterization
Authors: John George , Thomas Shali K. , Pillai C. K. S.
Published: April 2003

Cardanyl acrylate/methacrylate on suspension polymerization with methyl methacrylate, styrene, and acrylonitrile yielded copolymer beads. The beads were almost uniform in size and cross‐linked in nature. The copolymers synthesized were characterized by infrared, thermogravimetric analysis, scanning electron and optical microscopy, and swelling studies. © 1994 John Wiley & Sons, Inc.
Interpenetrating polymer networks based on thermoplastic polyurethanes (TPUS) and cis‐1,4‐polyisoprene
Authors: Mishra V. , Murphy C. J. , Sperling L. H.
Published: April 2003

Semi‐interpenetrating polymer networks based on two elastomers, cis‐1,4‐polyisoprene (PI) and thermoplastic polyurethane elastomers (TPUs) were prepared in varying compositions. The PI component was cross‐linked using peroxide initiators. Modulus and mechanical properties were investigated as a function of composition and temperature. Slight synergisms were observed in mechanical properties, particularly for compositions containing 10% PI by weight. Little or no molecular mixing is shown by differential scanning calorimetry (DSC) for these two‐phase materials. © 1994 John Wiley & Sons, Inc.
The effect of interfacial microstructure on the interfacial strength of glass fiber/polypropylene resin composites
Authors: Moon Chang‐Kwon
Published: April 2003

In this study, a new method to form resin droplets on fibers has been developed, and samples for the single fiber pull‐out test were prepared using this method. The effects of microstructure of polypropylene (PP) resin and the microstructure of interface between the glass fiber and PP resin on the interfacial strength have been investigated. In addition, the influence of the microstructure of the interface on the interfacial strength of glass fiberreinforced PP composites have been discussed. It has been found that in the pull‐out test, the transcrystallinity formed at the interface between the glass fiber and PP resin improved the interfacial strength when no spherulites developed in the PP matrix. On the other hand, it has been found that when the spherulites were well developed in the PP matrix, the transcrystallinity formed at the interface reduced the interfacial strength. Finally, rapid cooling has been shown to improve the interfacial strength between the fiber and resin in the crystalline polymer matrix composites. © 1994 John Wiley & Sons, Inc.
The use of GPC coupled with a multiangle laser light scattering photometer for the characterization of polymers. On the determination of molecular weight, size and branching
Authors: Podzimek S.
Published: April 2003

The use of gel permeation chromatorgraphy (GPC) coupled with the multiangle laser light scattering (MALLS) detector for the determination of molecular weight and size distribution and for the identification of polymer branching is demonstrated on several examples of both organic and water souluble polymers. The influence of the second virial coefficient and the way of the light scattering data evaluation on the results obtained is shown. Measurements of the root mean square radius are presented for two series of polystyrene and polymethylmethacrylate standard, and the results are compared with the radii calculated from the Flory‐Fox equation. © 1994 John Wiley & Sons, Inc.
Phase behavior of blends of styrene/maleic anhydride copolymers
Authors: Gan P. P. , Paul D. R.
Published: April 2003

The phase behavior of blends of styrene/maleic anhydride copolymers (SMA) with styrene/methyl methacrylate copolymers (SMMA), styrene/acrylonitrile copolymers (SAN), tetramethyl bisphenol‐A polycarbonate (TMPC), and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) have been determined. Tentative binary interaction energies were evaluated from mapping the copolymer composition miscibility boundaries using the Flory–Huggins theory combined with the binary interaction model. Data on phase‐separation temperatures were too sparse for these systems to obtain refined estimates using the Sanchez–Lacombe theory. A negative interaction energy was obtained for the MA/AN pair; however, the MA unit showed strong repulsive interactions with all other monomer units examined here. © 1994 John Wiley & Sons, Inc.
Polymer swelling. XV. Swelling and deswelling studies of polystyrene–liquid systems in binary solutions
Authors: Errede L. A. , Hanson S. C.
Published: April 2003

The specific sorption capacities of poly(styrene‐co‐divinylbenzene) [i.e., (Sty)1−x (DVB)x samples for binary solutions of toluene (α = 1.98)] and a second solvent [i.e., heptane (α = <0.01), methanol (α = <0.06), acetone (α = 0.92) or chloroform (α = 3.00)] were correlated with the corresponding DVB mole fraction (x) in the sorbent polymer samples (0.01 < x < 0.11), with the volume fraction (z) of toluene in the sorbed binary liquid (which was cycled at least twice from z = 0 to z = 1 and back to z = 0 in increments of 0.1) and with the adsorption parameter (α) of the sorbed liquid. These correlations demonstrated that the sorption capacity during the initial transit from z = 0 to 1 reflects the molecular architecture in the original dry state. Once the samples have been swelled to saturation in toluene (z = 1), however, the “memory” of the former dry state is erased; thereafter the sorption capacity reflects only the architecture established in the fully swollen state, and the composition of the sorbed solution. The molecular nature of the solvent exchange processes is discussed in the text. © 1994 John Wiley & Sons, Inc.
Polysulfone membranes. V. Poly(phenyl sulfone) (Radel R)–poly(vinyl pyrrolidone) membranes
Authors: Dal‐Cin M. M. , Tam C. M. , Guiver M. D. , Tweddle T. A.
Published: April 2003

Ultrafiltration membranes were prepared from mixtures of poly(phenyl sulfone) (Radel R5000) and poly(vinyl pyrrolidone) (PVP) dissolved in 1‐methyl‐2‐pyrrolidinone (NMP). The effects of the casting solution composition on membrane performance and morphology are presented. Radel R5000 membranes showed higher productivity for a given pore size when compared to other polysulfone membranes. The biphenyl group in Radel R5000 makes it more rigid in comparison to other polysulfones. This may result in more ordered packing, which resulted in the higher productivities and smaller pore sizes observed in the membranes. © 1994 John Wiley & Sons, Inc.
Investigation on damping behavior and morphology of polyurethane/polymethacrylates and polyacrylates interpenetrating polymer networks
Authors: Chen Qingmin , Ge Hanhua , Chen Dongzhong , He Xiangdong , Yu Xuehai
Published: April 2003

Simultaneous Interpenetrating Networks (SINs) were synthesized based on polyepichlorohydrin glycol (PECG), toluene diiocyanate (TDI), and trihydroxymethyl propane (TMP) as network I; and methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), and ethyleneglycol dimethylacrylate (EGLM), respectively as network II. Damping behavior of the SINs was studied by a dynamic viscoelastometer. It was found that loss factor, tan δ, of PU/PEMA and PU/PEA is much higher than that of PU/PMMA and PU/PMA. The present authors consider that the length of pendant groups has an influence on the height of tan δ in the interpenetrating structure. Transmission electron microscopy (TEM) photos show that the SINs possess multiphase structures. These two networks are dispersed in a system microheterogeneously. © 1994 John Wiley & Sons, Inc.
Radiation vulcanization of hydrogenated acrylonitrile butadiene rubber (HNBR)
Authors: Zhao Wenwei , Yu Li , Zhong Xiaoguang , Zhang Yuefang , Sun Jiazhen
Published: April 2003

Raw polymer and compound of hydrogenated acrylonitrile butadiene rubber (HNBR) were subjected to γ‐ray irradiation. Crosslinking was found to be the main chemical reaction induced by irradiation; the ratio of chain scission to crosslinking as well as the does at which gelation occurred were determined from gel content measurements to be 0.41 and 3.8 Mrad, respectively. The excellent hot‐air and oil‐resistant properties should be retained because no formation of double bonds or changing of the nitrile groups were observed with in the optimum dose range. Desired mechanical properties of the vulcanizate may be conveniently obtained by controlling the radiation dose. © 1994 John Wiley & Sons, Inc.
A new technique for preparing monodisperse polymer particles. II. Phase separation mechanisms
Authors: Hou Wei‐Hsin , Lobuglio Thomas M.
Published: April 2003

Nylon 6 polymer particles with a narrow‐size distribution are made by phase separation of different concentrations of polymer solutions. At concentrations above 0.15 wt %, the diameter of the precipitated particles increases linearly with the increasing of polymer concentration. The experimental results suggest that coagulation plays an important role in particle growth during the propagation stage. A mechanism is proposed for the formation of monodisperse polymer particles during phase separation. The uniformity of the precipitated nylon 6 particles decreases when the cooling process is slowered. The surface morphologies of the nylon 6 particles are controlled by changing the drying conditions. © 1994 John Wiley & Sons, Inc.
Kinetic and catalytic aspects in melt transesterification of dimethyl terephthalate with ethylene glycol
Authors: Santacesaria E. , Trulli F. , Minervini L. , Di Serio M. , Tesser R. , Contessa S.
Published: April 2003

The kinetics of melt transesterification of dimethyl terephthalate with ethylene glycol in the presence of zinc acetate as catalyst has been studied in semibatch conditions. We observed that this reaction occurs with the formation of many oligomers characterized from the terminal groups of the chains that can be hydroxyl–hydroxyl, methyl–hydroxyl or methyl–methyl. Experimental runs have been performed at different temperatures, initial reagents ratios, and catalyst concentrations, following the amount of methanol released during the time as well as the concentration of any kind of oligomer. All the oligomers have been identified and determined by HPLC analysis. A classic Kinetic model based on a complex reaction scheme containing four or five reaction sequences has been developed.

The scheme with four sequences foresees 24 oligomeric species involved in 58 different reactions, while the scheme with five sequences has 48 oligomeric species involved in 228 reactions. Despite the large number of oligomers and occurring reactions, only two kinetic parameters and two equilibrium constants are necessary to simulate the kinetic behaviour of all the oligomers. A kinetic constant is related to the reaction of a methyl group with a hydroxyl of ethylene glycol, while the other corresponds to the reaction of a methyl group with a hydroxyl in a chain. Both kinetic constants show an activation energy of about 15 kcal/mol. We observed a nonlinear correlation between activity and catalyst concentration and interpreted this fact by assuming two different catalytic activity levels for a dissociated and an undissociated zinc ionic couple, respectively. © 1994 John Wiley & Sons, Inc.
Oxidation of poly(1‐trimethylsilyl‐1‐propyne)
Authors: Nagai Kazukiyo , Nakagawa Tsutomu
Published: April 2003

The oxidation of poly(1‐trimethylsilyl‐1‐propyne) (PMSP) proceeded normally in air at room temperature and under mild thermal conditions. Two different bands assigned to the carbonyl groups on a side chain and on a decomposed chain end were found in the IR spectra of the oxidized PMSP membrane. However, no band assigned to a hydroxyl group was observed. An allyl‐type methyl group of the PMSP was mainly autooxidized without a decrease in molecular weight at room temperature. Only the former band assigned to the carbonyl groups appeared and it had a shoulder peak. In the case of mild thermal oxidation, the decomposition started in the backbone chain and both bands appeared. When the thermal oxidation proceeded further, all bonds were broken and various carbonyl and siloxane bonds were then randomly produced. © 1994 John Wiley & Sons, Inc.
Effect of surface‐modifying macromolecules and solvent evaporation time on the performance of polyethersulfone membranes for the separation of chloroform/water mixtures by pervaporation
Authors: Fang Yi , Pham Vu Anh , Matsuura Takeshi , Santerre J. P. , Narbaitz Roberto M.
Published: April 2003

Polyethersulfone (PES) membranes using different evaporation periods were fabricated by the phase‐inversion method. Pervaporation experiments were conducted for chloroform/water mixtures to determine the selectivity of the PES membranes. It was found that chloroform could be concentrated in the permeate from chloroform/water binary feed mixtures by PES membranes prepared using longer evaporation periods, and that the selectivity of PES membranes in pervaporation could be reversed by shorter evaporation periods. This study also showed that by adding surface‐modifying macromolecules (SMM) up to 1 wt % into the casting solution, chloroform enrichment in the permeate could be increased by 50%. Chloroform enrichment increased with increasing SMM concentration until an optimal value, after which the enrichment decreased. © 1994 John Wiley & Sons, Inc.
Properties of highly water‐absorptive hydroxyethylcellulose graft copolymers: Viscoelasticity and moisture sorption
Authors: Miyata Namiko , Yokoyama Miyuki , Sakata Isao
Published: April 2003

The viscoelasticity of the hydrogels, the moisture sorption, and the characteristics of the sorbed water of highly water‐absorptive hydroxyethylcellulose (HEC) graft copolymers [e.g., HEC graft copolymers containing partially hydrolyzed polyacrylamide (HEC‐P‐Hyd‐PAM), etc.] were investigated in comparison with commercial absorbents. The viscosity (η) and the rigidity (G) of the dispersions of their hydrogels were, respectively, proportional to the second to the sixth powers and the fifth to the seventh powers of their concentrations (η = KC2–6 and G = K′C5–7). With respect to the characteristics of the sorbed water, the conductivity of 0.1 N KCI in the hydrogels of the HEC water, absorbents was about 11.8 mS/cm, which was almost the same as that of 0.1 N KCI in pure water, and the water absorbency of dry matter (soybean seeds) in their hydrogels was almost the same as that in pure water. These results suggest that most of the sorbed water in the HEC super water absorbents behaves like free water. The maximum volume of sorbed moisture in a monolayer fashion (Vm) of HEC‐P‐Hyd‐PAM analyzed using the Brunauer‐Emmett‐Teller equation was about 0.21 g/g (1.2 mol water/polymer repeat unit), and there was no cluster water at 92% relative humidity or below as a result of applying the cluster function concept. © 1995 John Wiley & Sons, Inc.
Carbodiimide catalysis in cross‐linking of cotton cellulose with 1,2,3,4‐butanetetracarboxylic acid
Authors: Choi Hyung‐Min , Mahmood Tariq , Li Jiang Dong , Schlup John
Published: April 2003

This study examined carbodiimde catalysis (cyanamide, dicyandiamide, disodium cyanamide) in the cross‐linking of cotton cellulose with 1,2,3,4‐butanetetracarboxylic acid (BTCA). Considerable improvement in the smooth drying appearance of the treated cotton substantiated the fact that cellulose cross‐linking has been achieved by BTCA in the presence of carbodiimide. Bath pH was a very important factor in determining the performance properties of the treated cotton. Two possible reaction mechanisms were proposed: direct esterification and anhydride intermediate formation. Both pathways involved the formation of urea. Semiquantitative analyses of the spectra obtained by Fourier transform infrared spectroscopy revealed that the cyanamide was somewhat less effective than were dicyandiamide and sodium hypophosphite in esterification efficiency. © 1995 John Wiley & Sons, Inc.
A DSC study of the crosslinking of polychloroprene with ZnO and MgO
Authors: Mallon P. E. , McGill W. J. , Shillington D. P.
Published: April 2003

Polychloroprene and compounds of polychloroprene with ZnO and MgO were crosslinked by heating in a DSC at a programmed rate. The reaction was stopped at points along the thermogram and the crosslink density of the compound determined. The amount of chlorine evolved during reaction was measured as ZnCl2 and/or MgCl2. Two crosslinking processes were identified, both involving reaction of the 1,2 units in the polymer chain; the first comprising a rapid crosslinking reaction that occurs prior to the isomerization of 1,2 units and the second, a much slower reaction of isomerized 1,2 units. ZnCl2, which forms during compounding and on crosslinking, catalyzes the first reaction, while ZnO promotes the allylic rearrangment of 1,2 units. MgO increases the scorch time by trapping HCl evolved during compounding, thus limiting the amount of the crosslinking catalyst (ZnCl2) formed. © 1995 John Wiley & Sons, Inc.
Lifetime prediction of polymers
Authors: Hamid S. H. , Amin M. B.
Published: April 2003

Natural and artificially accelerated weathering trials were carried out on low‐density polyethylene samples used for agricultural and disposable purposes. Modifications in polymer characteristics were studied using Fourier transform infrared (FTIR) spectroscopy, different scanning calorimetry (DSC), gel permeation chromatography (GPC), scanning electron microscopy (SEM), and mechanical properties testing. The natural exposure trials were conducted at five geographical locations representing varying ambient temperature and humidity conditions and receiving different doses of solar radiation. The artificially accelerated exposure trials were carried out in an Atlas weatherometer for 5,000 hours, whereas the natural exposure was for 24 months. Rates of photo‐oxidative and thermal degradation have been determined by measuring the formation of non‐volatile carbonyl oxidation products which absorb in the infrared region with a maximum absorbance level at 1710cm−1. Thermal characteristics were noticed to vary in terms of the shape and size of melting peak for both the natural and artificial weathering. This implies a change in crystallinity, which has indicated an increasing trend with exposure time. The crystalline melting temperature (Tm) remains almost steady for both exposure tests. The drop in mechanical properties and the modification in polymer chain length were also monitored. The GPC analysis indicated the change in molecular weight distribution (MWD), which shows the formation of lower molecular‐weight species. Surface modifications were revealed in terms of abrasion effects apparent from SEM micrographs. A correlation between natural and artificial weathering was considered for lifetime prediction in a short exposure time. It was found that the confidence level of predicting lifetime on the basis of artificially accelerated exposure trials is dependent on many parameters, which include time, material, equipment, etc. © 1995 John Wiley & Sons, Inc.
Surface area of aqueous sodium hydroxide hydrolyzed high‐speed spun poly(ethylene terephthalate) fibers
Authors: Holmes S. A. , Zeronian S. H.
Published: April 2003

The specific surface area (SSA) of delustered undrawn and drawn high‐speed spun PET fibers hydrolyzed in aqueous NaOH was measured using three methods: (1) geometric, based on fiber diameter; (2) gas adsorption using N2 and the BET equation; and (3) adsorption of a nonionic surfactant. Increasing the spinning speed had little effect on the SSA of the untreated fibers, while drawing resulted in considerably larger SSA. For the hydrolyzed fibers, both adsorption methods resulted in larger SSAs than that predicted geometrically due to surface pitting. After hydrolysis, the higher spinning speed resulted in a greater increase in SSA over the untreated sample, whereas the increase in SSA was less for the drawn fibers compared to the undrawn. The kinetics of hydrolysis are also discussed. © 1995 John Wiley & Sons, Inc.
Organic polymer‐surface modified precipitated silica
Authors: Waddell Walter H. , O'Haver John H. , Evans Larry R. , Harwell Jeffrey H.
Published: April 2003

To improve the performance of rubber compounds using precipitated silica as a reinforcing filler, the silica surface was directly modified by (1) adsorption of a surfactant, (2) adsolubilization of an organic monomer, (3) in situ polymerization of the monomer in the surfactant bilayer, and (4) partial surfactant removal. Silica was thus surface modified with polymerized styrene, isoprene, butadiene, and copolymers. Styrene–butadiene modification afforded the most promising candidate based on evaluation in a silica‐filled model tire compound. Compound physical testing showed that cure times were decreased, and break strength, tear energy, elongation to break, and cut growth resistance were increased. Thus, surface modification of silica by the in situ polymerization of organic monomers affords unique materials useful in improving rubber cure properties and cured compound physical properties. © 1995 John Wiley & Sons, Inc.
Biodegradation of nitrate esters. II. Degradation of nitrocellulose by a fungus isolated from a double‐base propellant
Authors: Sharma A. , Sundaram S. T. , Zhang Y.‐Z. , Brodman B. W.
Published: April 2003

An organism found to be growing on moist double‐base propellant, containing nitrocellulose (NC) and nitroglycerine aerobically degraded NC in submerged cultivation. This organism, which was subsequently identified as Penicillium corylophilum Dierckx, was able to degrade the NC (13.17%N) when it was present as the sole nitrogen source, in conjunction with either starch or xylan as a carbon source. It was found that 20% of the NC was utilized in a 3‐day period. Also, NC degradation was studied utilizing Fusarium solani IFO 31093, a denitrifying fungus, in combination with P. corylophilum; however, no increased utilization was observed. Evidence for the degradation includes a decrease in the NC weight, an increase in the biomass weight, the presence of celluloytic and denitrifying enzymes, and other appropriate growth parameters. © 1995 John Wiley & Sons, Inc.
Size‐exclusion chromatography with two‐angle laser light‐scattering (SEC‐TALLS) of high molecular weight and branched polymers
Authors: Mourey Thomas H. , Coll Hans
Published: April 2003

The accuracy and precision of results obtained from light‐scattering detection at two angles (TALLS) for size‐exclusion chromatography (SEC) are examined for linear narrow molecular weight distribution polystyrenes between 1,290,000 and 20,000,000 MW and for branched polyesters. The ratio of light‐scattering intensities at 15° and 90° is used to calculate weight‐average molecular weight, M̄w, and an average root‐mean‐square radius, r̄gu, equivalent to the z‐average radius. A shape for the polymer molecule is assumed and an analytical relationship for the particle‐scattering function is required. It is shown that analysis of the data using the particle‐scattering function for a random coil is valid for both high molecular weight, linear polystyrenes and long‐chain branched polyesters. The radius, r̄gu, is determined with high precision by using the ratio of light‐scattering signals, which is insensitive to errors in sample concentration and changes in the eluent flow rate. The correct average radius for the whole polymer is obtained despite using low‐efficiency, large‐particle diameter SEC columns; however, axial dispersion significantly affects molecular weights and radii calculated at each retention volume that can limit the utility of plots used to deduce polymer conformation. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of new flame‐retardant polyaryl phosphoramide esters containing furan and thiophene units
Authors: Kannan P. , Umamaheshwari N. , Kishore K.
Published: April 2003

Two series of new flame‐retardant polyaryl phosphoramide esters were synthesized by low‐temperature solution polycondensation from arylphosphorodichlorides with 3,4‐bis(4‐ami‐nophenyl)2,5‐diphenylfuran and 2,5‐bis(4‐aminopheny1)3,4‐diphenylthiophene. The polymers were characterized by IR, 1H, 13C, and 31P NMR spectroscopy and elemental analysis. The thermal stability and flammability were studied by thermogravimetry and limiting oxygen index, respectively. © 1995 John Wiley & Sons, Inc.
Plasma graft polymerization of vinylimidazole onto Kapton film surface for improvement of adhesion between Kapton film and copper
Authors: Inagaki N. , Tasaka S. , Masumoto M.
Published: April 2003

Kapton film was modified by means of the plasma graft polymerization of vinylimidazole for the improvement of the adhesion with copper metal. Argon plasma exposure generated hydroperoxides at the surface of the Kapton film. Hydroperoxides generated by the argon plasma exposure could initiate the graft polymerization of vinylimidazole. The graft polymerization was restricted at the surface of the Kapton film and never occurred on the inside of the Kapton film. The graft polymer layer was 150–200 nm thick. The surface modification by the plasma graft polymerization of vinylimidazole led to the improvement of adhesion between Kapton film and copper metal. A part of the copper metal made a complex with imino groups in the vinylimidazole chains graft‐polymerized onto Kapton film. The complex is considered to contribute to the improvement of the adhesion. © 1995 John Wiley & Sons, Inc.
Effects of chemical structure of hardener on curing evolution and on the dynamic mechanical behavior of epoxy resins
Authors: De Nograro F. F. , Guerrero P. , Corcuera M. A. , Mondragon I.
Published: April 2003

A diglycidyl ether of bisphenol‐A‐type difunctional epoxy resin was cured with different amine‐type curing agents at stoichiometric ratios. The crosslink process was followed by viscosimetry and differential scanning calorimetry. The gelation time and the apparent activation energy were found to be strongly dependent on the structure of the hardener. The heat of reaction did not vary significantly when the hardener was changed. An interpretation based on structural aspects such as amine reactivity, steric hindrance, and chain rigidity is proposed for the variations corresponding to the curing process. Master viscosity curves have been built up for all mixtures. The effect of the hardener on the glass transition temperatures of the different mixtures has been analyzed taking into account the crosslink density, measured by the rubber modulus obtained by dynamic mechanical studies, and the chemical structure of the hardener chains. © 1995 John Wiley & Sons, Inc.
Number‐average molecular weight and functionality of poly(tetramethylene glycol) by multidetector SEC
Authors: Harrison Catherine A. , Mourey Thomas H.
Published: April 2003

Multidetector size exclusion chromatography (SEC) is used to simultaneously determine molecular weight and number of reactive end groups per chain (functionality) of poly(tetramethylene glycol)s. Hydroxyl groups are first quantitatively derivatized with phenyl isocyanate, providing an end‐group‐selective UV‐absorbing tag. The number of end groups per chain is then determined from the SEC chromatogram using a UV detector. Molecular weight at each retention volume and the number‐average molecular weight of the whole polymer are calculated by four methods involving (1) a concentration detector and a narrow standard log M calibration curve, (2) the UV detector and a narrow standard log M calibration, (3) a viscometry detector and a universal calibration curve, and (4) combined differential viscometry and concentration detectors using a universal calibration curve. The multidetector experiment provides a unique opportunity to assess the accuracy and limitations of each approach on low‐molecular‐weight polymers. In particular, the effect of end groups on the concentration detector response and the application of universal calibration principles at small molecular sizes are important factors. It is shown that the concentration response can be corrected by a simple relationship between detector response and reciprocal molecular weight. Also, the quality of calibration curves is critical to the calculation of accurate molecular weight. In general, log M calibration curves provide superior results to universal calibration methods. © 1995 John Wiley & Sons, Inc.
Desorption of free radicals in semibatch emulsion polymerization of methyl acrylate
Authors: Chern C. S.
Published: April 2003

Desorption of free radicals from particles can cause an emulsion polymerization system to deviate from Smith–Ewart case II kinetics. A mechanistic model has been developed to predict the effect of desorption of radicals from particles on the kinetics of semibatch emulsion polymerization of methyl acrylate under the monomer‐starved condition. Experimental data available in the literature are used to assess the proposed kinetic model. The model predicts the experimental data reasonably well for a wide range of monomer feed rates. The rate of polymerization increases with an increase in the rate of monomer addition. The kinetic data are also useful in evaluating the desorption rate constant (K′d) for methyl acrylate. The best fitted value of K′d at 50°C is 4 × 10‐12 cm2/s, which is in good agreement with the theoretical values predicted by desorption theory. © 1995 John Wiley & Sons, Inc.
Novel polyurethane–silicone hydrogels
Authors: Lai Yu‐Chin
Published: April 2003

Polyurethane hydrogels derived from polysiloxane‐based ultraviolet‐curable polyurethane prepolymers and hydrophilic monomers were prepared and their properties were evaluated. The polyurethane prepolymers used in this study contained different arrangements of hard and soft segments and were derived from isophorone diisocyanate, neopentyl glycol, diethylene glycol, 1,4‐butanediol, hydroxy‐terminated polydimethylsiloxane, and 2‐hydroxyethyl methacrylates. The hydrophilic monomers used were 2‐hydroxyethyl methacrylate and N,N‐dimethyl acrylamide. All compositions can be cured under ultraviolet (UV) and form hydrogels after hydration. The oxygen permeabilities of the hydrogels are much higher than those of nonsilicone hydrogels and decreased as the water contents increased. The tear strengths and moduli decreased as the water contents of the hydrogels increased. All hydrogels prepared showed good hydrolytic stability and did not absorb lysozyme. © 1995 John Wiley & Sons, Inc.
Application of dielectric spectroscopy and DSC to the study of relaxations in some copolymeric hydrogels
Authors: Ahmad Mansor Bin , O'Mahony John P. , Huglin Malcolm B. , Davis Thomas P. , Ricciardone Adam G.
Published: April 2003

The nature of water in copolymeric N‐vinyl pyrrolidone/methyl methacrylate hydrogels has been investigated using dielectric thermal analysis (DETA) and differential scanning calorimetry (DSC). Dielectric tan δ measurements are reported over a frequency range 500 Hz‐20 kHz and a temperature range of −140 to +20°C. The observed complex relaxations were attributed to the mobility of water and the relaxation processes of the copolymer matrix. In addition DSC was used to measure the melting endotherm of water in gels partially swollen to a pseudoequilibrium. The resultant data were fitted to a two‐phase approximation model. © 1995 John Wiley & Sons, Inc.
Gel formation in free‐radical crosslinking copolymerization
Authors: Naghash Hamid J. , Okay Oǧuz , Yildirim Hüseyin
Published: April 2003

Polymer gels with varying amounts of crosslinker and solvent were prepared by solution free‐radical crosslinking copolymerization of methyl methacrylate/ethylene glycol dimethacrylate (MMA/EGDM) and styrene/p‐divinyl benzene (S/p‐DVB) comonomer systems. The structural characteristics of the gels were examined using equilibrium swelling in toluene and gel fraction measurements. Experimental results were compared with the predictions of a kinetic model developed recently for free‐radical crosslinking copolymerizations. Experimental data on S/EGDM networks reported by Hild, Okasha, and Rempp were also used to test this model. It was found that the model correctly predicts the development of the gel properties in free‐radical crosslinking copolymerization. © 1995 John Wiley & Sons, Inc.
Dissolving poly(tetrafluoroethylene) in low boiling halocarbons
Authors: Tuminello William H. , Brill Donald J. , Walsh David J. , Paulaitis Michael E.
Published: April 2003

An apparatus and methodology are described for dissolving poly(tetrafluoroethylene) in relatively low boiling perhalocarbons at temperatures as high as 330°C and up to about 20 MPa pressure. Cloud points are reported for these solutions with the following solvents: n‐perfluorohexane, perfluorodecalin, Freon® 113 (1,1,2‐trichloro‐1,2,2‐trifluoroethane) and Fluorinert® FC‐75 (a perfluorocarbon ether). Most of the solutions were studied above the critical temperatures of their solvents. © 1995 John Wiley & Sons, Inc.
Novel polymeric alcohols by controlled catalytic polymer functionalization
Authors: McGrath Martin P. , Sall Erik D. , Forster Denis , Tremont Samuel J. , Sendijarevic A. , Sendijarevic V. , Primer D. , Jiang J. , Iyer K. , Klempner D. , Frisch K. C.
Published: April 2003

Novel EPDM (ethylenepropylenediene monomer) and polybutadiene polyols can be synthesized by a two‐step process of controlled hydroformylation and then reduction of the formyl groups to place a desired amount of pendant alcohol groups along the polymer chain. The degree of functionalization can be controlled by measuring gas uptake from a calibrated reservoir during hydroformylation. Hydroformylation can be performed in solution or under simulated melt‐phase conditions using either HRh(CO)(PPh3)3 or Rh(acac) (CO)2 as catalysts. Reduction of the polyaldehyde by NaBH4 generates the polymeric alcohol without further reaction of the remaining double bonds. Polymer functionalization and further modifications were followed by H‐NMR and FTIR. These unique hydrophobic polyols can be reacted further to produce other polymer systems. As an example, urethanes have been made with these polyols by reaction with diisocyanates. © 1995 John Wiley & Sons, Inc.
Catalyst–accelerator method for the preparation of wood–polymer composites at ambient temperature
Authors: Elvy Shane B. , Dennis Gary R. , Ng Loo‐Teck
Published: April 2003

Wood–polymer composites (WPC) are materials which may be prepared by impregnating wood with a variety of monomers which are subsequently polymerized by either gamma irradiation or by conventional radical initiators. The inclusion of the polymer into the wood matrix improves the physical properties of the composite compared to plain wood. The catalyst–accelerator method allows in situ polymerization of vinyl monomers at ambient conditions and thus reduces the loss of the volatile monomer during curing, which is a major disadvantage of the heat–catalyst method. The combination of peroxide initiators with an aromatic amine accelerator was optimized for the methyl methacrylate system. Polymer loadings and mechanical properties of WPC prepared from Pinus radiata using the catalyst–accelerator method were compared with those obtained using the gammaradiation method. © 1995 John Wiley & Sons, Inc.