bluuebunny/crossref_metadata_2025 huggingface dataset:
The molecular basis of fracture in polystyrene films: Role of molecular weight
Authors: Sambasivam M. , Klein A. , Sperling L. H.
Published: April 2003

The molecular basis for fracture was examined using a custom‐built Dental Burr Grinding Instrument, which cuts at a depth of 500 nm per pass. A direct miniemulsification method was used to form uniform‐sized latex particles from narrow molecular weight distribution, anionically synthesized polystyrenes. Several polystyrenes were examined as a function of molecular weight, and blends were made of high and low molecular weight polystyrenes. In addition, a broad molecular weight polystyrene was included for comparison. These latexes were dried and cleaned, and molded under mild conditions, followed by annealing for various lengths of time at 144°C. The Dental Burr Grinding Instrument measures the total energy required to fracture the sample. The total number of chains undergoing scission per unit volume was determined via GPC before and after the fracture process. Using an energy balance approach, the total number of chains undergoing pullout (from either side of the fracture surfaces) was estimated. In order to obtain a broader picture of the process, data collected by Mohammadi et al., and by Sambasivam et al., were integrated into the analysis. Basically, at very low molecular weights, ca. 32,000 g/mol, substantially 100% pullout occurs. At the midmolecular weight range, about 150,000 to 180,000 g/mol, chain scission and chain pullout contributions to the total energy are approximately equal. For very high molecular weights, the chain scission contribution is about 90%. A scaling relationship is proposed between the molecular weight of the polymer and the fraction of chains undergoing scission. © 1995 John Wiley & Sons, Inc.
Core‐shell structured latex particles. I. Copolymerization of styrene/benzyl methacrylate as a choice for shell material and characterization of poly(n‐butyl acrylate) core latex particles
Authors: Segall I. , Dimonie V. L. , El‐Aasser M. S. , Soskey P. R. , Mylonakis S. G.
Published: April 2003

Composition, molecular weight, and microstructure of the “shell” polymer in core‐shell structured latex particles, designed for toughening polycarbonate matrix, should be controlled for enhanced miscibility between the shell polymer and the matrix. Various “shell polymer” systems based on styrene (St) and benzyl methacrylate (BM) were synthesized. Reactivity ratios were determined for (St) and (BM). Chain transfer efficiency studies revealed the susceptibility of styrene to transfer to a chain transfer agent. Benzyl methacrylate was found to have steric and stability factors hindering its tendency to chain transfer with various chain transfer agent. Miscibility tests between P(St/BM) and polycarbonate (PC) indicated different degrees of miscibility, depending upon polymerization conditions. Factors other than molecular weight, such as branching and crosslinking, were found to play a role in the miscibility. Monodisperse poly(n‐butyl acrylate) (PBA) seed latex particles of variable degree of crosslinking and particle size were successfully synthesized by batch emulsion polymerization. © 1995 John Wiley & Sons, Inc.
Rheo‐optical FTIR spectroscopy of epoxy resins
Authors: Scherzer Tom
Published: April 2003

This article presents the results of the first application of rheooptical Fourier transform infrared (FTIR) spectroscopy to monitor orientation phenomena in highly crosslinked epoxy/amine networks during the uniaxial deformation above their glass transition temperature. The resins were prepared from the diglycidyl ether of bisphenol‐A (DGEBA) and various polyether di‐and triamines in order to influence the structure of the network formed. The molecular orientation is discussea with respect to network density and structure. The orientation behavior is mainly determined by the flexibility of the polyether chain and the homogeneity of the network structure. Additionally, the epoxy resins were subjected to successive loading‐unloading cycles. The investigations show that the orientation of epoxy networks in their rubbery state is completely reversible, and that no significant fatigue due to gradual chain rupture occurs until sample failure. © 1995 John Wiley & Sons, Inc.
Effect of ethylene‐propylene copolymer with residual PE crystallinity on mechanical properties and morphology of PP/HDPE blends
Authors: Zhu Wei , Zhang Xuequan , Feng Zhiliu , Huang Baotong
Published: April 2003

Morphology and mechanical properties of polypropylene (PP)/high density polyethylene (HDPE) blends modified by ethylene‐propylene copolymers (EPC) with residual PE crystallinity were investigated. The EPC showed different interfacial behavior in PP/HDPE blends of different compositions. A 25/75 blend of PP/HDPE (weight ratio) showed improved tensile strength and elongation at break at low EPC content (5 wt %). For the PP/HDPE = 50/50 blend, the presence of the EPC component tended to make the PP dispresed phase structure transform into a cocontinuous one, probably caused by improved viscosity matching of the two components. Both tensile strength and elongation at break were improved at EPC content of 5 wt %. For PP/HDPE 75/25 blends, the much smaller dispersed HDPE phase and significantly improved elongation at break resulted from compatibilization by EPC copolymers. © 1995 John Wiley & Sons, Inc.
1H‐NMR study of reaction of melamine with oxiranes
Authors: Lubczak Jacek
Published: April 2003

This work describes results of investigations relative to composition and structure of the initial products of the addition of oxiranes to melamine analyzed by1H‐NMR spectrometry. The work Algebraic equations are shown that describe changes of contents in the functional groups of intermediate products in the function of the number of moles of oxirane that were attached. Reactivity of individual function groups of intermediate products are also discussed. The structure of polyetherols with ans‐triazine ring that forms in the reaction of melamine with oxiranes is proposed on the basis of these investigations. © 1995 John Wiley & Sons, Inc.
Acoustic absorption performance of polyacrylic composite latex
Authors: Yao Kangde , Cheng Guoxiang , Lu Tao , Zhu Wengsheng , Shun Qingchi , Wang Tiyong , Zhang Dawei
Published: April 2003

In this work, copolymers and a multilayer core/shell P(BA/BA‐MMA/MMA) composite latex of methyl methacrylate (MMA), butyl acrylate (BA), and ethyl acrylate (EA) were prepared by emulsion polymerization. The thermal and the mechanical properties of their films were characterized by differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA), while the acoustic absorption performance of dried films were estimated using the standing wave pipe method. The results show that a multilayer core/shell polymer of P(BA/BA‐MMA/MMA) has many glass transitions in a broad temperature region, and in the frequency range of sound, this core/shell polymer has better acoustic absorption properties than the random copolymer of P(BA‐MMA). © 1995 John Wiley & Sons, Inc.
Swelling of hydrophilic polymers. IV
Authors: Ogawa Ikuko , Yamano Hideki , Miyagawa Kinjiro
Published: April 2003

The swelling of five types of spherical crosslinked dextrans (Sephadex) that are either nonionic (G) or ionic [carboxymethyl (CM), sulphopropyl (SP), diethylaminoethyl (DEAE), and diethyl‐(2‐hydroxypropyl)aminoethyl (QAE)] in the same skeleton has been studied in water at different dissolved oxygen concentrations by microscopic observation and by dilatometry. The maximum specific volume, Vmax/V0 obtained by microscopic observation increased with the lowered dissolved oxygen concentration for each Sephadex. The change of the maximum specific volume was closely related to the changes of the dissolved oxygen concentrations. The maximum changes of the total volume took the larger negative values at the lower dissolved oxygen concentration. The effect of the difference in the dissolved oxygen on the change of the total volume with swelling was closely related to the viscosity B coefficient of the Jones‐Dole equation. From these results, we conclude that the structure of water on the inside of the gel differs from that on the outside of the gel. © 1995 John Wiley & Sons, Inc.
Plasma surface modification of propylene‐based polymers by silicon and tin‐containing compounds
Authors: Akovali Güneri , Rzaev Zakir M. O. , Mamedov D. H.
Published: April 2003

Plasma surface modifications of homo‐, co‐, and terpolymers of propylene films in the presence of selected organosilicon and organotin compounds were investigated. For this, organosilan(stannan)e type compounds (such as vinyltriethoxysilane, 3‐aminopropyltriethoxysilane, and tetraethylstannane) as well as organosiloxan (stannoxan)e type compounds (such as hexamethyldisiloxane and hexabutyldistannoxane) were exployed in plasma. Plasma surface modification of polyolefin films with organosilicon plasma has led to increase of the hydrophobicity, while the presence of organotin compounds in plasma produced less hydrophobic surfaces. Reaction of plasma‐activated polyolefin films further with vinyltriethoxysilane‐maleic anhydride oligomer also led to an increase in the hydrophobicity of polypropylene surfaces. It is observed that the degrees of swelling of (virgin, plasma‐treated, and plasma‐modified) polypropylene films in cyclohexanone strongly depend on the nature of the organoelement compounds used, organosilicon plasma causing lower degrees of swelling. The changes of surface properties observed are explained by different surface structures produced in plasma: in the case of organosilicon compounds, it is believed that poly(organosiloxane) and for organotin compounds poly(organotincarboxylate) fragments are formed primarily. © 1995 John Wiley & Sons, Inc.
Photooxidative degradation of polyethylene containing flame retardants by monochromatic light
Authors: Torikai Ayako , Chigita Ko‐Ichi , Okisaki Fumio , Nagata Masatoshi
Published: April 2003

Photodegradation of incombustible polymer materials [high‐density (HD) and low‐density (LD) polyethylene (PE) containing 0.5 to 2.0 phr of decabromodiphenyl ether (DBDE) or tetrabromobisphenol A (TBA) as a flame retardant] were studied using an Okazaki Large Spectrograph (OLS). Samples were irradiated in air at 23°C with monochromatic light of wavelengths at 260, 280, 300, 320, 340, and 360 nm. Ultraviolet and Fourier transform infrared (FTIR) spectra were taken to estimate the chemical changes caused by photoirradiation. Molecular weight change was followed by gel permeation chromatography (GPC) measurements. It was found that the photostability of PE samples was reduced by the addition of flame retardants. The threshold wavelengths of photodegradation are 320 nm and 360 nm for PE–TBA samples and PE–DBDE samples, respectively. Main‐chain scission is favored when the irradiation was carried out with the light of wavelength 300 nm for HDPE–DBDE and HDPE–TBA samples. The most effective irradiation wavelengths for crosslinking are found to be 300 nm and 280 nm for LDPE–DBDE and LDPE–TBA samples, respectively. 1995 John Wiley & Sons, Inc.
Studies on antioxidants. III. 2[(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)methylene]hydrazine carbothioamide as a melt stabilizer for unstabilized polypropylene
Authors: Raja A. R. , Pendyala V. N. S. , Xavier S. F. , Shah A. C. , Nair K. B.
Published: April 2003

Polypropylene's high processing temperatures initiate thermal oxidative degradation and loss of physical properties. Antioxidants protect polymers through the severe conditions of processing and fabrication and also through end use. Small amounts of antioxidants like 2,6‐di‐tert‐butyl‐4‐methylphenol and 2[(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)methylenel]‐hydrazine carbothioamide are shown to be effective in protecting isotactic polypropylene (IPP) against thermooxidative degradation. 2[3,5‐Di‐tert‐butyl‐4‐hydroxyphenyl)‐methylene]hydrazine carbothioamide was melt compounded with IPP using a twin screw extruder. The melt flow index of the extruded sample was measured. The extruded granules were injection molded to get specimens suitable for testing mechanical properties, such as heat deflection temperature, Izod impact strength, tensile strength, tensile modulus, flexural strength, and flexural modulus. 2[(3,5‐Di‐tert‐butyl‐4‐hydroxyphenyl)methylene]hydrazine carbothioamide was found to be an effective melt stabilizer for unstabilized polypropylene. © 1995 John Wiley & Sons, Inc.
Surface analysis of PP/EVA blends modified with amino acids for biomedical applications
Authors: Schroeder K. , Klee D. , Höcker H. , Leute A. , Benninghoven A. , Mittermayer C.
Published: April 2003

The copolymers poly(propylene‐co‐ethylene) (PP/E) and poly(ethylene‐co‐vinyl acetate) (EVA) and blends of these were modified to develop an artificial matrix which promotes the growth of endothelial cells. Covalent immobilization of amino acids or sequences of adhesion glycoproteins should trigger the formation of an endothelial cell monolayer onto the polymeric surface. Reactive functional groups were generated by saponifying the ester groups of the EVA component. Esterification with oxalylic or malonic dichlorides in the gas phase yielded the required monoesters and gave the best results for further immobilization of amino acids, while reaction with α,ω‐dicarboxylic acid dichlorides in solution led to diester formation. Subsequently, various protected amino acids were immobilized via the carbodiimide method. Surface analytical methods like infrared spectroscopy using at tenuated total reflection (IR‐ATR), X‐ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS) were used to prove the modification steps. The analytical results confirmed covalent side‐chain generation in the upper surface region. © 1995 John Wiley & Sons, Inc.
Basic kinetic model for the reaction yielding linear polyurethanes. II
Authors: Król Piotr , Gawdzik Andrzej
Published: April 2003

On the basis of the gradual polyaddition kinetic model developed earlier, an attempt was made to provide a generalized mathematical model for the set of reactions yielding linear polyurethanes. The model is a system of first‐order ordinary differential equations. It was assumed at the present stage of this model that the rate constants for the reaction considered do not change. The model developed was then solved numerically. Average molecular weight of the polymer and composition data for oligomers were calculated for a constant volume batch reactor and varied process parameters. The GPC method, which was tested for model urethane oligomers, was employed to verify the model developed. The reaction of 2,4‐TDI with 1,4‐butanediol proceeding in a solution was investigated. It was concluded that the model was applicable to a limited degree in describing the linear polyurethane manufacturing process which is more complex. However, it was suggested that the algorithms adopted could be utilized in developing further models which could assume changing rate constants for the polymer chain growth reactions. © 1995 John Wiley & Sons, Inc.
Viscometric and conductometric studies of poly(vinyl alcohol)‐g‐polyacrylamide composites
Authors: Kaur Inderjeet , Maheshwari Savita , Gupta Anita , Misra B. N.
Published: April 2003

Poly(vinyl alcohol)‐g‐polyacrylamide composites have been prepared by γ‐radiation‐initiated polymerization of acrylamide (AAm) in the presence of poly(vinyl alcohol) (PVA) in aqueous medium by the mutual method in air. Percentage conversion of AAm has been studied as a function of total dose, monomer concentration, and amount of water. Optimum conditions leading to maximum percent conversion of the monomer to give the composite have been evaluated. The products of polymerization of AAm in the presence of PVA consisted of unreacted PVA, the graft copolymer, PVA‐g‐PAAm, and the homopolymer polyacrylamide, PAAm, and this mixture is referred to as PVA‐g‐PAAm composite. AAm was also polymerized in the absence of PVA under similar conditions, and optimum conditions leading to maximum conversion of AAm to PAAm have been evaluated. A comparative study of the polyelectrolytic behavior of PVA, PAAm, and the composite has been made by viscometric and conductometric methods. © 1995 John Wiley & Sons, Inc.
Synthesis of highly crosslinked porous copolymers of methacrylic ester of p,p′‐dihydroxydiphenylpropane diglicydyl ether and divinylbenzene
Authors: Matynia Tadeusz , Gawdzik Barbara
Published: April 2003

Narrow disperse porous particles were formed by emulsion polymerization of two tetrafunctional monomers in the presence of the diluent mixture: n‐decanol and toluene. One monomer was divinylbenzene while the second was synthesized by the reaction between methacrylic acid and p,p′‐dihydroxydiphenylpropane diglicydyl ether. In order to obtain chromatographic packings of different polarities copolymers of the following molar ratio of monomers, 0.2 : 0.8, 0.5, 0.5, and 0.8 : 0.2, were synthesized. Porous structures of the obtained copolymers were studied by BET and EC methods. © 1995 John Wiley & Sons, Inc.
Low‐speed tack measurements of fluids and inks
Authors: Phillips J. C. , Chiang A. C.
Published: April 2003

Low‐speed tack measurements (≈ 0.1–6.0 rad/s or ≈ 1–57 RPM) have been determined for polymeric‐based solution inks and oil‐based dispersion inks, tripropylene glycol (TPG), Igepal (I‐530), and N‐350 (viscosity calibration standard) fluids using a metal roller/incline method. The inks and fluids were tested under “unaged” or reference conditions at 25°C. The inks were “aged” at 70°C and, subsequently, tack measurements were made at 25°C. The tack (Ti) and angular speed (Wi) for the inks were empirically fitted as functions of incline angle (α) and “aged” time, tcd. A correlation was also made for tack and percent weight change, ΔWi. Other factors, such as viscosity, surface tension, humidity, and “aging” temperature, Tcd, were also found to affect the magnitude and variation of tack. Additionally, the results suggest that low‐speed tack measurements are quite useful for selecting solution inks containing polymeric substances that possess the desirable spreading, mixing, and pressing properties in high‐speed/high‐volume printing and the component compatibility necessary for long‐term performance. © 1995 John Wiley & Sons, Inc.
A study on the tribological behavior of polyethylene. II. Effects of operating conditions on the friction behavior of polyethylene
Authors: Wang Qi , Kong Xiangan , Zhu Lushan , Zhe Ji , Fan Ying
Published: April 2003

In this article, the effects of the operating conditions, i.e., load, oscillation speed, temperature, and contact modes on the friction behavior of polyethylene were studied through the SRV vibration friction test machine, the MHK‐500 friction and wear test machine, as well as an on‐line temperature testing device. The experimental results showed that the friction coefficient μ of polyethylene increases with increase of the oscillation frequency and amplitude, the speed, and PV value, while load has a quite complex impact on μ; suitable choice of load could reduce μ and smoothen the friction process. Contact modes of friction pairs have considerable effects on μ, because all the real contact area of the friction assembly, the pressure, the indentation of surface asperities, as well as the temperature rise and distribution in the contact region are related to contact modes. Temperature is a key factor determining the viscoelastic properties of polyethylene, and therefore has great effect on μ. On‐line temperature testing offers a way to reveal the relations between temperature and the friction behavior of polyethylene. All the results obtained provide the basic data for establishing mathematical models and computational simulation methods to describe and study the tribological behavior of some polymer materials. © 1995 John Wiley & Sons, Inc.
NMR characterization of styrene–divinylbenzene gel beads in swollen state using chloroform as probe
Authors: Ogino Kenji , Sato Hisaya
Published: April 2003

Styrene—divinylbenzene copolymer gel beads in a swollen state were characterized with a proton nuclear magnetic resonance spectroscopy (1H‐NMR) using chloroform as a probe. The signal of chloroform was observed as doublet peaks and the peak at higher magnetic field was assigned to chloroform inside the gel beads and the other at lower magnetic field to one outside the gel beads. NMR parameters such as signal chemical shift, intensity, line width, and shape were investigated in relation to the characteristics of gel beads such as the swelling ratio, the diameter, pore size, and crosslinking density. The relative intensity of the signal due to chloroform inside the gel beads increased with the amount of diluent used in preparation of the beads. With the decrease of the diameter of the beads, two signals became closer, because the rate of exchange between the solvent molecules inside and outside increased. The pore size also influenced the shape of the doublet peaks. As the pore size increased, the two peaks overlapped due to the decrease of the portion of chloroform that interacts with the polymer matrix. The crosslinking density did not influence the peak shape although the dynamics of chloroform were affected by the crosslinking density. © 1995 John Wiley & Sons, Inc.
Studies of rigid poly(vinyl chloride) (PVC) compounds. II. Determination of the fusion level
Authors: Chen C. H. , Wesson R. D. , Collier J. R. , Lo Y. W.
Published: April 2003

Rigid poly(vinyl chloride) (PVC) compounds were prepared in a Haake torque rheometer using various blending conditions. The fusion levels of processed compounds were evaluated by a capillary rheometer and differential scanning calorimetry (DSC), based on the entrance pressure drop and the heat of fusion, respectively. S‐shaped fusion curves were obtained. Starting temperature of the mixer, rotor speed, and totalized torque are the three major factors that affect the fusion level of PVC compounds blended in the Haake torque rheometer. All three parameters have a significant effect; however, totalized torque has the greatest effect and this can be characterized using a torque rheometer. Both capillary rheological and DSC thermal analysis can be applied to determine the fusion level of a PVC compound. The morphological changes of the various fusion processes were characterized by scanning electron microscopy (SEM). © 1995 John Wiley & Sons, Inc.
Studies of rigid poly(vinyl chloride) (PVC) compounds. III. Correlation of compounding energy with fusion level
Authors: Chen C. H. , Wesson R. D. , Collier J. R. , Lo Y. W.
Published: April 2003

The major contributors to the compounding energy of a poly(vinyl chloride) (PVC) sample in the Haake torque rheometer are starting temperature, rotor speed, and totalized torque. In this study, the compounding energy was calculated by using an energy balance in the internal mixer reported by Pedersen. The fusion levels of the PVC samples, which were prepared in the Haake torque rheometer at various blending conditions (starting temperature = variable, rotor speed = 60 rpm, and totalized torque = 10 kg‐m‐min), were determined by DSC and a capillary rheometer. The compounding energy was then correlated with the fusion level. The simple total energy balance can be applied to correlate the compounding energy with the fusion level of the PVC compound prepared in the Haake torque rheometer. © 1995 John Wiley & Sons, Inc.
Synthesis, structure, and properties of poly(dimethylsiloxane) networks reinforced by in situ‐precipitated silica–titania, silica–zirconia, and silica–alumina mixed oxides
Authors: Wen Jianye , Mark James E.
Published: April 2003

Several novel fillers, specifically silica–titania, silica–zirconia, and silica–alumina mixed oxides, have been successfully precipitated into poly(dimethylsiloxane) (PDMS) networks using a sol‐gel approach. The resulting filled networks were found to have very good mechanical properties. In comparison with networks filled only with silica, these materials had good extensibilities as well as high strengths. Filler particle diameters were generally several hundred angstroms, but were found to decrease with increase in crosslink density of the networks. The distributions of particle size were relatively narrow, and there was very little particle aggregation. The presence of in situ silica–titania and silica–zirconia mixed oxides can also increase the onset temperature for degradation of the PDMS. © 1995 John Wiley & Sons, Inc.
Modeling and design of an industrial dryer with convective and radiant heating
Authors: Cairncross R. A. , Jeyadev S. , Dunham R. F. , Evans K. , Francis L. F. , Scriven L. E.
Published: April 2003

Industrial equipment for drying polymeric coatings normally consists of a series of zones, each with a controlled temperature and airflow. Drying of a polymer–solvent solution is strongly affected by the variation of diffusivity, solvent vapor pressure, and solvent activity with temperature and composition. The equations of mass transfer by diffusion and of heat transfer by conduction and radiation describe changes in composition and temperature within the shrinking coating. This system of equations is solved by Galerkin's method with finite element basis functions. The boundary conditions on dryer airflow and temperature change at the entrance to each zone. In a few test cases, the predictions show how evaporative cooling can slow drying in early zones where the coating temperature drops below the dryer temperature, whereas in later zones the coating temperature rapidly approaches the dryer temperature. Infrared heating can be used to reduce the extent of evaporative cooling. In the test cases and experiments, “blistering” occurs in later zones where high oven temperature causes the solvent partial pressure to rise; dryer parameters can be chosen to maintain solvent partial pressure just below ambient pressure in order to avoid “blistering” with least sacrifice of process speed. © 1995 John Wiley & Sons, Inc.
Preparation and properties of phenolated wood/phenol/formaldehyde cocondensed resin
Authors: Lin Lianzhen , Yoshioka Mariko , Yao Yaoguang , Shiraishi Nobuo
Published: April 2003

A phenolated wood/phenol/formaldehyde cocondensed novolac‐type resin was prepared with a two‐stage procedure. Wood was first liquefied in the presence of phenol by using an acid catalyst to produce a phenolated wood, and after the liquefaction, formalin (i.e., formaldehyde aqueous solution) was added to conduct a cocondensation reaction for converting the remaining nonreacted phenol into resin components. It was found that this procedure can convert almost all the phenol remained after liquefaction into resin, and therefore significantly upgrades the practical value of the liquefaction technique. In addition, it can also greatly improve the thermofluidities of the phenolated wood resins and the mechanical properties of their molded products. As a result, the flow temperatures and melt viscosities of the cocondensed resins were much lower than those of the phenolated wood resins. However, these two properties were more or less similar to those of the conventional novolac resin, resulting in an excellent processability. The flexural properties of the molded products made from the cocondensed resins were much higher than those of the phenolated wood and also somewhat superior to those of the conventional novolac resin. Therefore, this preparation procedure is a prospective technique for preparing wood‐based novolac resins. © 1995 John Wiley & Sons, Inc.
Polymerization and thermal behaviors of poly[dimethyl(acrylamidopropyl)ammonium propane sulfonate] poly (DMAAPS)
Authors: Lee Wen‐Fu , Tsai Chan‐Chang
Published: April 2003

The conversion in the free radical polymerization of zwitterionic sulfobetaine monomer [dimethyl(acrylamidopropyl)ammonium propanesulfonate] (DMAAPS) was investigated under various conditions, such as, monomer concentration, reaction time and temperature, and various salts. The high conversion of DMAAPS monomer could be achieved under lower temperature. The conversion of DMAAPS is enhanced in the presence of various salts in aqueous solution, but is not very significant because the reactivity of DMAAPS is very rapid even at lower temperature and lower concentration of the monomer. The thermal behavior of poly(DMAAPS) was also studied under nitrogen and air atmosphere at various heating rates. The kinetic parameters such as activation energy, preexponential factor, and reaction order were determined by Ozawa's method. Thermal degradation of such a polymer occurs in two and three stages in nitrogen and air atmospheres, respectively. © 1995 John Wiley & Sons, Inc.
Epoxy resins based on bisphenol S. II. HPLC analysis
Authors: Podzimek Š. , Sýkora V. , Horálek J. , Švestka Š.
Published: April 2003

Three types of bisphenol S (BS) based epoxy resins prepared by reaction of BS or a mixture of BS and bisphenol A (BA) with an excess of epichlorohydrin in alkaline medium or by thermal treatment of BS with diglycidyl ether of bisphenol A (DGEBA) were analyzed by reversed‐phase high‐performance liquid chromatography (HPLC). Some components present in the reaction products were identified by analogy with BA based epoxies, combination of semipreparative HPLC with IR and NMR spectroscopy, and derivatization of resins with HCl or NaOH. © 1995 John Wiley & Sons, Inc.
Liquid crystalline aromatic polyesters formed with terephthalic acid, phenyl hydroquinone, and napthalene or anthracene diols
Authors: Khan Nazir , Bashir Zahir , Price Duncan M.
Published: April 2003

The synthesis and characterization of aromatic copolyesters containing terephthalic acid and phenyl hydroquinone as the major constituents and either 1,4‐napthalene diol or 1,4‐anthracene diol as the minority comonomer is described. Both polymers melted in the vicinity of 300°C, giving birefringent fluids. Optical microscopy showed Schlieren textures consisting predominantly of inversion walls characteristic of the nematic phase. The clearing temperature was in the vicinity of 460°C, but was accompanied by charring. DSC experiments showed a high glass transition temperature of 130–160°C for both polymers. Crystalnematic and nematic‐isotropic endotherms were observed on heating; however, degradation took place near the isotropization temperature. Thus, on cooling, the sequence was reversible only if the previous heating was beyond the crystal‐nematic but below the isotropization temperature. The polymers were stable in terms of gross weight loss until about 450°C, though there were indications that crosslinking occurred above about 400°C over a short period of time. The polymers formed low‐viscosity injection‐molding compounds, but to use them effectively, it would require mold‐gate designs that reduce the “jetting” tendency for liquid crystal polymer melts, which result in weld lines. © 1995 John Wiley & Sons, Inc.
Synthesis and evaluation of positive‐acting photosensitive polyimides with phenol moiety
Authors: Oba Masayuki , Kawamonzen Yoshiaki
Published: April 2003

Novel positive‐acting photosensitive polyimide resists (1) developable with an alkaline aqueous solution were prepared. The resists consisted of a naphthoquinone diazide (NQ) and a polyamic acid bearing hydroxyphenyl groups (PA). The hydroxyphenyl moieties are newly incorporated by adding 2‐N,N‐dimethylaminoethyl‐3‐hydroxybenzoate (m‐PEA) or 2‐N,N‐dimethylaminoethyl‐4‐hydroxybenzoate (p‐PEA) to the polyamic acid, through ionic interaction between the carboxylic acid and the amine. The NQ acts as a solution inhibitor for the PA by the interaction with the hydroxyphenyl moiety. This system is similar to that of phenol‐novolac resin/NQ resists currently conducted in the fabrication of the Large Scale Integrated circuit (LSI). The resist (1) is exposed to a G‐line and is developed with tetramethylammonium hydroxide aqueous solution to provide fine patterns, proving that the (1) is compatible with LSI‐production lines currently applied. A novel polyamic acid‐curing mechanism found in the course of this study is also reported. © 1995 John Wiley & Sons, Inc.
ESR studies of chemically modified and photocrosslinked poly(vinyl alcohol) gels
Authors: Uhlich Thomas , Ulbricht Mathias , Tomaschewski Georg , Stösser Reinhard
Published: April 2003

The hydrophilicity of poly(vinyl alcohol) (PVA) was lowered by acetalization with propionic aldehyde. After UV irradiation of pendent styrylpyridinium groups, these prepolymers form networks of different hydrophobicity depending on the degree of acetaization. PVA films containing different amounts of propionic acetals were doped with 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl. Then, the ESR spectra of the spin probe entrapped in the polymeric network were monitored while allowing different solvents to diffuse into the polymer. The rate of spin probe mobilization depends on the hydrophilicity/hydrophobicity of both the polymer network and the solvent. However, the modified polymers, even the more hydrophobic ones, are hydrophilic in comparison to “really” hydrophobic polymers. This is probably caused by the character of the parent polymer (PVA), unreacted hydroxy groups. S++uiations of the ESR spectra have shown that in polymers with a higher degree of acetalization domains of different hydrophobicity are built in which the spin probes have a different mobility. © 1995 John Wiley & Sons, Inc.
Nonuniform cooling in multifilament melt spinning of polypropylene fibers: Cooling air speed limits and fiber‐to‐fiber variations
Authors: Andreassen Erik , Myhre Ole Jan , Oldervoll Frøydis , Hinrichsen Einar L. , Grøstad Kristin , Braathen Marianne D.
Published: April 2003

The cooling of the spinning stage in a commercial compact‐spinning line has been studied. A rectangular fiber bundle is extruded from the spinneret and cooled by air entering from one side. The speed of the cooling air is considerably reduced through the fiber bundle. There are practical lower and upper limits for the cooling air entrance speed, corresponding to filament breakage at the leeward and windward sides, respectively. These limits are functions of the material and processing parameters. Due to the nonuniform cooling, fibers sampled at the windward side generally have higher molecular orientation, lower amorphous fraction, higher density, and higher tensile modulus and strength. For most combinations of spinning and material parameters, the structure is either bimodally oriented α‐crystalline or uniaxially oriented mesomorphic at all spinneret positions. Fibers with different structure types show opposite windward/leeward side trends with regard to local order and melting behavior. The structure may be mesomorphic at the leeward side and α‐crystalline at the windward side, if the average spin‐line stress is close to a critical value for orientation‐induced crystallization, and the air speed difference across the spinneret is large. The cooling air speed affects the spin‐line stress. Hence, the fiber‐to‐fiber variations due to nonuniform cooling are discussed in terms of the molecular orientation in the melt and the effective time available for arranging molecules into ordered structures. © 1995 John Wiley & Sons, Inc.
Properties of fatty‐acid esters of starch
Authors: Sagar Ambuj D. , Merrill Edward W.
Published: April 2003

This work examines the properties of starch esters for their possible application as environmentally degradable thermoplastics. The rheological, thermal, and mechanical properties of a series of fatty‐acid esters of high‐amylose starch (as well as the effects of adding plasticizer on some selected properties) were evaluated. The ester group acts like an internal plasticizer, with an increase in the size of the fatty‐acid chain, resulting in greater internal plasticization. This is reflected in the rheological and thermal measurements as well as in the mechanical properties. Overall, larger ester groups and the addition of external plasticizer make these starch‐based materials more processable and more ductile. However, comparing their properties and cost to commodity thermoplastics leads us to believe that their commercial applications are likely to be limited, at least in the near future. © 1995 John Wiley & Sons, Inc.
Specialty polymeric membranes. V. Selective permeation of carbon dioxide through synthetic polymeric membranes having 2‐(N,N‐dimethyl)aminoethoxycarbonyl moiety
Authors: Yoshikawa Masakazu , Fujimoto Kiyoshi , Kinugawa Hirokazu , Kitao Toshio , Kamiya Yoshinori , Ogata Naoya
Published: April 2003

Permeation of CO2 was investigated by using synthetic polymeric membranes having a tertiary amine moiety, 2‐(N,N‐dimethyl)aminoethoxycarbonyl moiety. Permselectivity of the present membranes towards CO2 was achieved. Through poly{2‐(N,N‐dimethyl)aminoethyl methacrylate‐co‐acrylonitrile} (DMAEMA/AN‐199) membrane, where DMAEMA mol fraction was 0.199, the separation factor towards CO2 for CO2/N2 separation ranged from 60 to 90, ranging in the CO2 partial pressure in the feed gas from 61 to 3.6 cmHg. © 1995 John Wiley & Sons, Inc.
Maleated polyisobutylene: A novel toughener for unsaturated polyester resins
Authors: Abbate M. , Martuscelli E. , Musto P. , Ragosta G. , Scarinzi G.
Published: April 2003

A polyisobutene rubber was modified by grafting succinic anhydride onto its end groups and has been used as a toughening agent for an unsaturated polyester resin. Both the functionalization and the successive reaction between the modified rubber and the polyester was investigated by Fourier transform infrared spectroscopy (FTIR). The yield behavior of the cured resins was studied by compression measurements, while the fracture properties were determined at low and high strain rate. A morphological analysis of the investigated blends has been carried out by scanning electron microscopy (SEM). A considerable enhancement of tougheness has been achieved when the modified rubber was used in place of the plain polyisobutene. The effect was found to depend on the grafting degree of the rubber and on the time period during which the two‐component mixture was allowed to react prior to the curing process. © 1995 John Wiley & Sons, Inc.
Estimation by mechanical analysis of the molecular parameters of SBR vulcanizates at different cure conditions
Authors: Marzocca Angel José
Published: April 2003

The changes in the network structure of SBR‐1712 during vulcanization were analyzed by means of a study of the stress–strain behavior at uniaxial extension at room temperature. In order to obtain different degrees of crosslinking, samples were cured at 414 K and 433 K at several times and were characterized by a rheometer. The conformational tube model was applied for the treatment of the stress–strain measurements of vulcanized samples. This theory allows the separation of crosslink and constraint contributions to the stress–strain behavior and relevant network parameters can be estimated. In this article the change with the temperature and time of cure of the average molecular mass of the mobile network chains, the crosslink density, the microscopic lateral tube dimension, and the root‐mean‐square end‐to‐end distance of the network chain are evaluated. © 1995 John Wiley & Sons, Inc.
Gas permeability of crosslinked HTPB–H12MDI‐based polyurethane membrane
Authors: Huang Shih‐Liang , Lai Juin‐Yih
Published: April 2003

Crosslinked membranes were prepared by the addition of a crosslinking agent of benzoyl peroxide (BPO) to the hydroxyl‐terminated polybutadiene (HTPB) and 4,4′‐dicyclohexylmethane diisocyanate (H12MDI)‐based polyurethane (PU) solutions. The stress–strain properties of segmented HTP‐B based PUs were changed by the crosslinking between soft–soft segments. The gas permeabilities of HTPB‐based PU membranes with a suitable amount of crosslinking agent were higher than those of uncrosslinked membranes, which is due to the stretched and extended soft‐segment molecular chains. The reproducibility of gas permeability was improved by the crosslinked membranes. Thermal stability conducted by TGA was increased with increasing crosslinking agent content. FTIR was utilized to identify the segregation between hard and soft segments and structure change, which affects the gas‐transport properties. The change of glass transition temperature was detected by DSC, which can be used to manifest the degree of crosslinking of these membranes. The results of TGA, FTIR, and DSC measurements explain the crosslinking degree with different BPO content and, hence, the gas permeabilities as well. © 1995 John Wiley & Sons, Inc.
Mixed initiator approach to the surfactant‐free semicontinuous emulsion polymerization of large MMA/BA particles
Authors: O'Callaghan K. J. , Paine A. J. , Rudin A.
Published: April 2003

The emulsion polymerization of large monodisperse MMA/BA copolymer particles by surfactant‐free means at high solids content is described. A series of sequential seeded growth reactions were used to obtain monodisperse particles with diameters of at least 3 microns. A combination of an oil‐soluble initiator, AIBN, and a water‐soluble initiator, ammonium persulfate (AP), was used. The AIBN initiated the bulk of the polymerization and the AP provided the stabilization for the polymer particles through its charged endgroups. The amount of AP initiator to be used in each growth step was calculated empirically using a criterion of a constant ratio of moles of sulfate groups to the polymer particle surface area. © 1995 John Wiley & Sons, Inc.
Modeling high‐viscosity, melt‐phase, condensation polymer reactors with a time‐scales analysis
Authors: Sampson Kendree J. , Neogi Swati
Published: April 2003

Mathematical models for simultaneous reaction and mass transfer occurring in the manufacture of high‐viscosity, condensation polymers are considered. The specific example of polycondensation of polyethylene terephthalate is examined. Reactor performance is estimated by using a kinetic expression modified by an effectiveness factor. The effectiveness factor is correlated against a ratio of two characteristic times, one identified as the time scale of mixing and the other identified as the time scale of reaction. The time scale of mixing is estimated from experimental mixing data, thereby avoiding the use of potentially inaccurate mixing assumptions. In place of reaction experiments, overall reaction rates are generated using a more detailed mixing‐cell model. The effectiveness factor correlation is compared against previous models. Because the correlation is based on predicted reaction rates rather than experimentally measured reaction rates, the value of the present work lies in the demonstration of the time scales modeling technique. © 1995 John Wiley & Sons, Inc.
Structural characteristics of biodegradable thermoplastic starch/poly(ethylene–vinyl alcohol) blends
Authors: Simmons Stephanie , Thomas Edwin L.
Published: April 2003

To establish relationships among the blend composition, processing history, and the resultant properties of starch‐based thermoplastics, three varieties of corn starch: (1) Waxy Maize, (2) Native Corn, and (3) high‐amylose Hylon VII were extrusion‐blended with poly(ethylene‐vinyl alcohol) (EVOH) containing 56 mol % VOH. Wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to examine the structural characteristics of the blends. All starches were destructurized upon compounding and a fine dispersion was achieved with EVOH. The Native Corn and Hylon VII blends were phase‐separated and exhibited some miscibility between the polymer components as evident in EVOH melting‐point depression, smaller domain sizes, lower contrast between phases in TEM, and increased resistance to moisture and enzyme‐etching treatments. Starches containing amylose exhibited complexation and crystallinity in the starch fraction, although most of the crystallinity in the blends was due to the EVOH component. Waxy Maize blends were well phase‐separated with larger domain sizes and underwent phase coarsening as a function of time in the melt. When subjecting the blends to capillary flow, orientation of both starch‐rich and EVOH‐rich domains was observed at various compositions, with the EVOH component undergoing significantly more orientation relative to starch as evident by the presence of EVOH‐rich fibrils. Finally, EVOH was found to coat the surfaces of filaments produced from the blends even at rather high levels of starch (70%), which is expected to improve moisture sensitivity and slow down the initial rate of biodegradation. © 1995 John Wiley & Sons, Inc.
Viscoelastic and shrinkage behavior of ultrathin polymeric films
Authors: Weick Brian L. , Bhushan Bharat
Published: April 2003

Viscoelastic and shrinkage characteristics of five ultrathin polymeric films are presented. These films include poly(ethylene terephthalate) or PET, poly(ethylene naphthalate) or PEN, an aromatic polyamide (ARAMID), a polyimide (PI), and poly(benzoxazole) or PBO. PET film is currently the standard substrate used for magnetic tapes, and the other four films represent alternative substrates with improved material properties. Thicknesses of the films range from 14.4 μm for PET to 4.4 μm for ARAMID. A creep apparatus is used to measure the viscoelastic and shrinkage characteristics of the films. The largest amount of creep compliance was measured for PET followed by PI, PEN, ARAMID, and PBO. Creep velocity was highest for PET and PI, followed by ARAMID, PEN, and PI. Shrinkage measurements at 50°C for 100 h show that PEN shrinks more than all the other substrates. Time–temperature superposition is used to predict long‐term creep behavior, and relationships between polymeric structure and viscoelastic behavior are also discussed. Based on their relative cost and creep behavior, PEN and ARAMID substrates appear to be suitable alternatives to PET. © 1995 John Wiley & Sons, Inc.
Reactive processing of LLDPES in corotating intermeshing twin‐screw extruder. II. Effect of peroxide treatment on processability
Authors: Lachtermacher Marly G. , Rudin Alfred
Published: April 2003

Commercial ethylene–octene linear low‐density polyethylenes (LLDPEs) were reactively extruded with low levels of a peroxide [2,5‐dimethyl‐2,5‐di(t‐butylperoxy)hexane] to modify polymer molecular structure and processing properties. Peroxide levels were kept low to avoid crosslinking. This article reports the effects of this reactive extrusion on viscoelastic properties. Rheological properties are more sensitive than are molecular structure characteristics to the changes produced by reactions of very low peroxide concentrations. Complex viscosity increases are seen, especially at low frequencies. Shear‐thining behavior is also accentuated. The crossover between G′ and G″ moves to lower frequencies. A modified Cole–Cole presentation of these data shows that the elastic component is more predominant for extrusion‐reacted materials. Peroxide‐modified materials all have higher Bagley end correction values than those of barefoot resins. The former exhibit lower power indices (more shear thinning). All these properties indicate more long‐chain branching and higher melt elasticity. However, die swell decreased as a function of peroxide concentration. Peroxide treatment results in an enhancement of elongational viscosity, both under isothermal and cooling conditions, along with a decrease in drawdown ability. The rheological changes parallel those reported earlier in molecular characteristics but are more sensitive and suitable to evaluate the effects of reactive processing. The effectiveness of the reactive extrusion process for improving processability of LLDPEs depends critically on the extrusion conditions. © 1995 John Wiley & Sons, Inc.