bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and application of low molecular weight poly(vinyl chloride). I. Preparation and thermal stability
Authors: Yamamoto Kikuo , Maehara Takashi , Mitani Katsuo , Mizutani Yukio
Published: April 2003

Poly(vinyl chloride) with relatively low molecular weight (LMW‐PVC) was prepared by suspension polymerization in the presence of some chain‐transfer agents, such as mercapto compounds. It is elucidated by means of thermogravimetry, dehydrochlorination, color difference, and discoloration that the resultant LMW‐PVC has good thermal stability. The degree of dehydrochlorination of the LMW‐PVC obtained by using n‐dodecylmercaptan increases with increasing the content of component from the chain‐transfer agent. It is found that the LMW‐PVC obtained by using mercapto compounds shows better thermal stability (discoloration property) than does the one obtained without using these agents, at the same weight‐average polymerization degree. © 1994 John Wiley & Sons, Inc.
An FTIR solid‐state analysis of the diffusion of hindered phenols in low‐density polyethylene (LDPE): The effect of molecular size on the diffusion coefficient
Authors: Möller Kenneth , Gevert Thomas
Published: April 2003

Low‐density polyethylene (LDPE) has been investigated with respect to the diffusion of hindered phenol antioxidants added to the polymer matrix. In the study, a simple method was used to measure the diffusion coeficient, with the aid of FTIR spectroscopy without any extraction or refining steps in the analysis. The diffusion coefficient, D, of five phenols containing the same 3(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) structure but with different lengths of the hydrocarbon tail were obtained in the temperature range 30–60°C. The number of carbon atoms in the tail varied between 1 and 18. It was found that the logarithm of D decreased linearly with increasing molecular size. The temperature‐dependence of the phenols could be described by an Arrhenius‐type relationship. It was found that the activation energy, Ed, incresed linearly with increasing molecular size. © 1994 John Wiley & Sons, Inc.
Thermal degradation of segmented polyurethanes
Authors: Petrović Zoran S. , Zavargo Zoltan , Flyn Joseph H. , Macknight William J.
Published: April 2003

Thermal degradation of polyurethane samples was studied by a thermogravimetric method. The effect of soft‐segment length and soft‐segment concentration on activation energy of the degradation process was measured. Three methods of calculation gave activation energies at different stages of the very complex weight loss process. It was shown that at initial stages of the weight loss the process was dominated by hard‐segment degradation. Activation energy of the whole process calculated by the Ozawa–Flynn method did not offer clear insight into the structure–stability relationship of polyurethanes. The second method showed that activation energy of the initial stage of degradation increased with decrease in hard‐segment length. The Flynn method of calculating activation energy produced fairly constant activation energy of the first 40% degradation, at around 150 kJ/mol, for polymers in the C series. Generally, calculation of kinetic parameters of a complex degradation process as in polyurethanes gives results that are not easy to interpret. It has been shown qualitatively that polymers with higher soft‐segment concentration display lower initial weight loss and higher onset temperatures of degradation. © 1994 John Wiley & Sons, Inc.
Degradation of enhanced environmentally degradable polyethylene in biological aqueous media: Mechanisms during the first stages
Authors: Albertsson Ann‐Christine , Barenstedt Camilla , Karlsson Sigbritt
Published: April 2003

Degradation of LDPE films containing a biodegradable starch filler and a pro‐oxidant formulation was performed in aqueous media inoculated with bacteria or fungi at ambient temperatures for 1 year. The samples were characterized with the aim of elucidating the mechanisms that occur during the first stages and that are responsible for initiating the degradation of the LDPE matrix. Two interactive mechanisms were observed: The basal salt medium (water containing trace elements) triggered autoxidation of the pro‐oxidant through decomposition of trace hydroperoxides, which, in synergistic combination with biodegradation of the starch, eventually initiated autoxidation of the LDPE matrix as monitored by chemiluminescence (CL), differential scanning calorimetry (DSC), and confocal scanning laser microscopy (CSLM). The length of the induction period was dependent on the sample thickness and on the activity of the microbiological system. Up to 48% of the starch was consumed during the first year as revealed by polarized‐light microscopy. © 1994 John Wiley & Sons, Inc.
Relationship between superficial response to environmental changes and adhesive property of polyurethane cross‐linked polyacrylate network
Authors: Xu Mei Xuan , Gao Wei , Zhang Wen Hua , Peng Tao , Yao Kang De , Chen Hui Yin , Lu Yin Xian
Published: April 2003

A polyacrylic network containing carboxyl groups was cross‐linked with polyurethane. The dynamic contact angles (DCA) on specimens were estimated in water. The effect of ingredient ratio and average molecular M̄n of poly(oxypropylene glycol) (PPG) on DCA were investigated. Data obtained are correlated with 180° peel strength by using the polymer network as an adhesive to adhere both poly(vinyl chloride) (PVC) and polyethylene (PE) film. Results reveal that there is correlation of the surface response to bilateral adhesion of polar and nonpolar substrates. © 1994 John Wiley & Sons, Inc.
Studies on the sulfonation of poly(phenylene oxide) (PPO) and permeation behavior of gases and water vapor through sulfonated PPO membranes. II. Permeation behavior of gases and water vapor through sulfonated PPO membranes
Authors: Fu Hongyong , Jia Lianda , Xu Jiping
Published: April 2003

The permeation behaviors of water vapor and gases were studied for both PPO and SPPO of different sulfonation degree. It was found that the permeability of water vapor increased, and those of oxygen and nitrogen decreased; thus the selectivity for water vapor over gases increased remarkably with the increase of sulfonation degree. The possibility of using SPPO as a gas dehumidification membrane material is discussed. © 1994 John Wiley & Sons, Inc.
Studies on co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyester (IV) thermal history by differential scanning calorimetry
Authors: Shinn Ted‐Hong , Lin Chen‐Chong
Published: April 2003

A series of co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyesters with various compositions were prepared by the copolymerization of either poly(ethylene terephthalate) polymer (PET) or its oligomer (OET) as moiety (II) and p‐acetoxy‐benzoic acid (POB) as moiety (I). The polymeric products obtained were then subjected to solid‐state polymerization. The glass and melting transitions of the copolyesters obtained have been studied by differential scanning calorimetry (DSC). Effects of composition and solid‐state polymerization on DSC are discussed. The melting point of copolyesters possesses a higher value if the PET polymer is used as PET moiety in the copolyesters. In the DSC scan of the POB rich composition, the endothermic peak shows obscurely and enthalpy of fusion becomes small due to the change in the crystalline morphology from isotropic to anisotropic. In general, the melting point of copolyesters is increased by the solid‐state polymerization reaction. It is also found that both the melting temperature and enthalpy of fusion of the copolyesters can be increased simultaneously by the solid‐state polymerization reaction only when the composition of POB/PET is 80/20. This phenomenum at this composition may be attributed to the annealing effect caused by the randomness of two moiety units on the backbone chain of copolyesters and the increased molecular weight as well. © 1994 John Wiley & Sons, Inc.
Conversion–temperature–property diagram for a liquid dicyanate ester/high‐Tg polycyanurate thermosetting system
Authors: Simon S. L. , Gillham J. K.
Published: April 2003

The effects of conversion and temperature on the dynamic mechanical properties (at ≈ 1 Hz) of a dicyanate ester/polycyanurate thermosetting system are investigated after cure using torsional braid analysis (TBA). Extent of conversion is measured by Tg. The isothermal glassy‐state modulus at measurement temperatures below the glass transition temperature of the monomer (Tg0) decreases with increasing conversion. The isothermal modulus at temperatures above Tg0 passes through a maximum due to competition between increase in the isothermal glassy‐state modulus at the measurement temperature due to the vitrification process during cooling and the aforementioned decrease in the modulus with increasing conversion, which is considered to be due primarily to steric constraints in the developing network. The maximum in the isothermal modulus is associated with the boundary between the glass and glass transition regions. The experimental results are summarized in a conversion (Tg)–temperature–property diagram, the TgTP diagram, which is a framework for understanding relationships between transitions and material properties for thermosetting systems. © 1994 John Wiley & Sons, Inc.
Effect of matrix SAN in ABS/PMMA blends
Authors: Lee S. M. , Choi C. H. , Kim B. K.
Published: April 2003

The effect of the molecular weight and acrylonitrile (AN) content of the styrene–acrylonitrile copolymer (SAN) on the morphology, mechanical properties, and rheological properties of acrylonitrile–butadiene–styrene terpolymer/poly(methyl methacrylate) (ABS)/PMMA (60/40 by weight) blends were studied. When the AN content of matrix SAN (32%) was close to that of graft SAN (30%) AN, rubber particles existed separately. However, with matrix SAN having 35% AN, rubber particles showed tendency to agglomerate each other. With increasing molecular weight of matrix SAN, impact strength, ultimate elongation, and abrasion resistance of the blend generally increased. Yield strength increased with molecular weight at a constant AN content of matrix SAN, and it decreased with the decrease of AN content in spite of the increasing molecular weight of SAN. Melt properties, rather than the morphological and mechanical properties, were more sensitive to the AN content, rather than the molecular weight of matrix SAN. © 1994 John Wiley & Sons, Inc.
Thermoacoustical parameters of polymers at low temperatures
Authors: Kumar M. Ravi , Reddy R. R. , Rao T. V. R. , Sharma B. K.
Published: April 2003

The Moelwyn‐Hughes parameter has been utilized to evaluate a number of thermoacoustical parameters, viz., the Beyer nonlinear parameter; the isothermal, isobaric, and isochoric Grüneisen parameters; the repulsive exponent of intermolecular potential; the molecular constant; the fractional available volume; the Sharma thermoacoustical parameter So; and the Anderson–Grüneisen parameter for a wide variety of polymers at different low temperatures. A relationship among the isobaric, isothermal, and isochoric microscopic (lattice) Grüneisen parameters has been examined and analyzed in the case of several polymers. The results have been used to develop understanding of the significance of microscopic factors such as molecular order and intermolecular forces upon macroscopi thermoacoustic properties. The parameter S0 remains invariant with temperature over a wide range and retains, on average, a constant value of 1.10 for several polymers at low temperatures, similar to a wide variety of substances. The present treatment has the distinct advantage that several thermoacoustic parameters can be evaluated form the knowledge of volume expansivity data alone. © 1994 John Wiley & Sons, Inc.
Positive photosensitive polyimides using polyamic acid esters with phenol moieties
Authors: Hayase Rumiko , Kihara Naoko , Oyasato Naohiko , Matake Shigeru , Oba Masayuki
Published: April 2003

Polyimide resists developable with basic aqueous solutions were realized by polyamic acid esters with phenol moieties (PPh's) and naphthoquinone diazides. The polyimide precursors (PPh's) were synthesized from diamines and dicarboxylic acids that have phenol moieties through ester linkage. A selective reaction of alcohol groups with acid dianhydride groups made the synthesis of the PPh's possible, even if the phenol groups were in the reaction mixtures. The PPh's were soluble in basic aqueous developer, but their dissolution rates were too low for use as resists. To increase the resist dissolution rate, polyamic acids were added to the PPh's. By adjusting the dissolution rates in basic aqueous developers, fine patterns could be realized. The polyimide resists had high thermal stability and reliable adhesive property to silicon substrate. © 1994 John Wiley & Sons, Inc.
Thermotropic behavior of hydroxyethyl cellulose acetate
Authors: Huang Y.
Published: April 2003

Thermotropic behavior of hydroxyethyl celloulose acetate (HECA) was studied by polarizing microscopy, DSC, and X‐ray diffraction. It was found that HECA was an anisotropic liquid between the temperature from 130 to 185°C on heating, and when the temperature was over 185°C, it became isotropic. In cooling, however, mesophase began to form at about 165°C. The transformation temperature decreased with decreasing molecular weight and the temperature region of transformation decreased with decreasing the distribution of the molecular weight for HECA. The kinetic ability of tranformation appeared the maximum with molecular weight. The HECA liquid crystal is cholesteric and the distance between layers of ordered molecular chains was enlarged when HECA was transformed from liquid crystalline glass to the liquid crystalline state. © 1994 John Wiley & Sons, Inc.
Melt viscosity of poly(diethylene glycol‐co‐succinic acid): Molar mass dependence in the nonentangled regime
Authors: Liu G. , Vancso G. J.
Published: April 2003

Experimental and theoretical results are reported on the dependence of melt viscosity on the molar mass of poly(diethylene glycol‐co‐succinic acid) (DEG‐SA) in the nonentangled regime. A power law described the behavior with an exponent of 2.09 ± 0.10 at 30°C and of 2.59 ± 0.09 at 90°C. The modified Rouse theory was used to describe the relationship between melt viscosity and molar mass. The parameters related to the modified Rouse theory were determined by the WLF equation and the free‐volume theory. The WLF parameters of various samples were checked at their Tg, which is the reference temperature. Results confirmed that the free volume and the monomeric friction coefficient (ξ0) dominate the behavior of the melt. The agreement between the calculated and experimental melt viscosity is satisfactory. © 1994 John Wiley & Sons, Inc.
Release of tritium‐labeled estradiol steroids from fully swollen hydrogels of polyurethane networks
Authors: Zulfiqar M. , Quddos A. , Zulfiqar S.
Published: April 2003

Diffusion of uniformly dispersed tritium‐labeled estradiol in water‐swollen poly(ethylene oxide) ‐based hydrogels was studied by assaying the release of solute from cylindrical hydrogels into a finite volume of solution at 37°C. Fractional release followed a t0.5 relationship for a range of radil between 0.20 and 0.35 cm and different polymer compositions with equilibrium water uptake of 220–750 parts per hundred dry polymer. Values of the diffusion coefficient were calculated from the fully swollen hydrogels, which represents the swelling and release profile quite accurately. © 1994 John Wiley & Sons, Inc.
Low‐stress encapsulants by vinylsiloxane modification
Authors: Ho Tzong‐Hann , Wang Chun‐Shan
Published: April 2003

Dispersed silicone rubbers were used to reduce the stress of cresol–formaldehyde novolac epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The effects of structure, molecular weight, and contents of the vinylsiloxane oligomer on reducing the stress of the encapsulant were investigated. Morphology and dynamic mechanical behavior of rubber‐modified epoxy resins were also studied. The dispersed silicone rubbers effectively reduce the stress of cured epoxy resins by reducing flexural modulus and the coefficient of thermal expansion (CTE), whereas the glass transition temperature (Tg) was hardly depressed. Electronic devices encapsulated with the dispersed silicone rubber modified epoxy molding compounds have exhibited excellent resistance to the thermal shock cycling test and have resulted in an extended device use life. © 1994 John Wiley & Sons, Inc.
Hygrothermal aging studies of short carbon fiber reinforced nylon 6.6
Authors: Ishak Z. A. Mohd , Berry J. P.
Published: April 2003

A study of hygrothermal aging, in terms of the kinetics of moisture absorption by nylon 6.6 and its carbon fiber‐reinforced composites, has been undertaken. The diffusion of water into the various materials was investigated at 100% relative humidity, by immersion of specimens in water at temperatures of between 25 and 100°C. A mathematical treatment used in analyzing the data was that of a single free phase model of diffusion, which assumed Fickian diffusion and utilized Fick's second law of diffusion. Good agreement was observed between the experimental and theoretical values. The equilibrium moisture content and the apparent diffusion coefficient of the various composites were evaluated. Hygrothermal aging has reduced the tensile properties of both unreinforced and reinforced nylon 6.6, albeit a better recoverability of the properties was achieved by the former after drying. This behavior is explained in terms of the combined action of moisture‐induced plasticization and interfacial degradation. © 1994 John Wiley & Sons, Inc.
Crazing phenomena in PC/SAN microlayer composites
Authors: Haderski D. , Sung K. , Im J. , Hiltner A. , Baer E.
Published: April 2003

The crazing behavior of coextruded microlayer sheets consisting of alternating layers of polycarbonate (PC) and styrene–acrylonitrile copolymer (SAN) was investigated as a function of PC and SAN layer thicknesses. In this study, the total sheet thickness remained essentially constant and the PC and SAN layer thicknesses were changed by varying both the total number of layers from 49 to 1857 and the PC/SAN volume ratio. Photographs of the deformation processes were obtained when microspecimens were deformed under an optical microscope. Three different types of crazing behavior were identified: single crazes randomly distributed in the SAN layers, doublets consisting of two aligned crazes in neighboring SAN layers, and craze arrays with many aligned crazes in neighboring SAN layers. The transition from single crazes to doublets was observed when the PC layer thickness was decreased to 6 microns. Craze array development was prevalent in composites with PC layer thickness less than 1.3 microns. It was concluded that SAN layer thickness was not a factor in formation of arrays and doublets; formation of craze doublets and craze arrays was dependent only upon PC layer thickness. © 1994 John Wiley & Sons, Inc.
Effects of cast film fabrication variables on structure development and key stretch film properties
Authors: Degroot J. A. , Doughty A. T. , Stewart K. B. , Patel R. M.
Published: April 2003

The properties of films produced by the cast or blown film processes can be altered by varying the fabrication parameters. An experimental design is used to determine the effect of cast film fabrication variables on the performance of LLDPE stretch films. A three‐variable Box–Behnken designed experiment was conducted to study the effects of air gap, melt temperature, and line speed on the key cast stretch film properties. In addition, the differences in molecular orientation in the films were studied using optical birefringence and shrinkage methods. The key film properties are correlated with the fabrication conditions using a statistical analysis program. The results of this study are explained in terms of web tensile stresses before solidification and the degree of molecular orientation developed in the film due to the stresses. © 1994 John Wiley & Sons, Inc.
Thermal analysis of silver coatings used for tantalum capacitors
Authors: Ulrich M. , Sarraf L. , Loucheux C.
Published: April 2003

Silver‐filled polymer coatings are used to ensure the cathodic junction of tantalum capacitors. To polimerize new materials able to resist to the RTSH industrial test, we studied first the physical chemistry of the main commercial coatings used at the present time. Four commercial silver coatings (epoxy, polyester, polyimid, and polyacrylate binders) and one conductive epoxy adhesive were tested. We separated the silver flakes from the polymer binder by centrifugation and filtration. We analyzed the thermal degradation and stability of the two kinds of sample (with the without silver flakes) using DSC and TGA. The influence of fillers mixing is discussed. This article reports, also, the main chemical structures of the binder components, determined using 1H‐ and 13C‐NMR and elemental analysis, after HPLC or GPC fractionation. © 1994 John Wiley & Sons, Inc.
The thermo‐oxidative stability of fluorinated polyimides and polyimide/graphite composites at 371°C
Authors: Scola Daniel A. , Wai Martin
Published: April 2003

Increasing demands to decrease engine weight and improve engine performance has led to an investigation to develop polymer composites capable of being used at 371°C and above in 4 atmospheres of air. The results of an investigation to determine the thermo‐oxidative stability (TOS) of various fluorinated polyimides, 3F‐PDA, 36F‐PDA, Avimid‐N, AFR700B, and other PMR‐type resins and graphite composites containing these polyimides at 371°C in air at 1 and 4 atmospheres are presented. Weight losses due to aging under these conditions are presented as the criteria for measuring the TOS. The data show that 3F‐PDA and Avimid‐N which have equivalent TOS, exhibit twice the TOS than that of AFR700B and other PMR‐type resins. 36F‐PDA exhibits even better TOS than 3F‐PDA or Avimid‐N. © 1994 John Wiley & Sons, Inc.
Spreading of a droplet on a solid surface
Authors: Seaver Albert E. , Berg John C.
Published: April 2003

The spontaneous spreading of small liquid droplets on solid surfaces is examined with the objective of developing closed‐form expressions for the spreading dynamics, both for the case in which there is complete equilibrium spreading, that is the equilibrium contact angle is 0°, and for the case in which equilibrium spreading is incomplete. Such solutions are obtained using a simple hydrodynamic model. The results are consistent with the format of the universal Hoffman–Voinov–Tanner law (for complete spreading) and the modified Hoffman–Voinov–Tanner law for incomplete spreading. In the latter case, concurrence is found only when the dynamic contact angle is close to the equilibrium angle throughout the spreading process. © 1994 John Wiley & Sons, Inc.
Polymeric phosphonium salts as a novel class of cationic biocides. VI. Antibacterial activity of fibers surface‐treated with phosphonium salts containing trimethoxysilane groups
Authors: Kanazawa Akihiko , Ikeda Tomiki , Endo Takeshi
Published: April 2003

Alkoxysilane with phosphonium biocides as coupling agents were covalently attached to cotton‐fiber surfaces, and the antibacterial activity of the surface‐treated fibers against Staphylococcus aureus and Escherichia coli was evaluated by the viable cell counting method in sterile distilled water. These fibers with phosphonium salts were found to exhibit high antibacterial activity against S. aureus and E. coli, particularly against S. aureus, and the activity increased as hydrophobicity of the substituents bonded directly to phosphonium ions increased. Furthermore, morphological changes of the cells of S. aureus and E. Coli in contact with the fibers were evaluated by scanning electron microscopy. It was found that the fiber with the phosphonium biocides exhibited bacteriostatic as well as bactericidal activity against both strains, which was evident from observation of normal and deformed cells of these species in contact with the fibers. © 1994 John Wiley & Sons, Inc.
Electrochromic behavior and stability of polyaniline composite films combined with prussian blue
Authors: Morita Mitsuyuki
Published: April 2003

The electrochromic behavior of polyaniline–poly(vinyl alcohol) composite films (CPAn–PVA) combined with electrochemically synthesized Prussian blue films (PB) was investigated in LiClO4CH3CN nonaqueous aprotic solution. The combination was achieved by chemical deposition of CPAn–PVA on PB. When the combined films (CPAn–PVA–PB) are prepared with the appropriately low quantity of PB, CPAn–PVA–PB showed various visible absorption spectra overlapped roughly with the absorption of the component materials at different applied potentials. CPAn–PVA–PB provided the color change from green to blue at much lower applied potential than did CPAn–PVA. However, the combined PB eliminates protons from the first oxidized polyaniline chains to decrease the electrochemical activity of polyaniline. Therefore, to construct multicolor electrochromic devices by the combination of polyaniline with the other electrochromic materials, it is necessary to select the materials containing no deprotonation activity. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of long‐chain fatty acid cellulose ester (FACE)
Authors: Wang Pinglang , Tao Bernard Y.
Published: April 2003

Long‐chain fatty acid cellulose esters (FACE) were synthesized by the acid chloride‐pyridine reaction with different degrees of substitution (DS). The hydrolyzed soybean oil was used as unsaturated fatty acids, its unsaturation degree, and composition were analyzed by 1H and 13C NMR methods. The chemical structures of FACE were confirmed by solid‐state 13C NMR, and substitution reaction of fatty acid chloride on cellulose were analyzed by IR spectroscopy. FACE(s) are insoluble in common organic solvents, such as benzene, toluene, THF, etc., at refluxing temperature. As the DS increased, the tensile strength of extruded FACE films decreased, but elongation increased. © 1994 John Wiley & Sons, Inc.
Development of a poly(methyl methacrylate‐co‐n‐butyl methacrylate) copolymer binder system
Authors: Vail N. K. , Barlow J. W. , Beaman J. J. , Marcus H. L. , Bourell D. L.
Published: April 2003

Low molecular weight poly(methylmethacrylate) and poly(methylmethacrylate‐co‐n‐butylmethacrylate) emulsion‐based polymers are developed for use as fugitive binders of high temperature powders to be used with the rapid prototyping method known as selective laser sintering. Kinetics of the homopolymerization of methylmethacrylate and n‐butyl‐methacrylate are found to deviate from Smith‐Ewart Type II predictions. Reactivity ratios for the monomer pair are determined and indicate the pair to yield random copolymers. Molecular weight was controlled by the addition of chain transfer agents. Several transfer agents were studied and one, iso‐octyl‐3‐mercaptopropionate, was selected for use with emulsion polymerizations. Glass transition temperatures of the homopolymers and copolymers were studied. © 1994 John Wiley & Sons, Inc.
Polyurethanes synthesized from polyester polyols derived from PET waste. II. Thermal properties
Authors: Lee Sen‐Chong , Sze You‐Wen , Lin Chen‐Chong
Published: April 2003

Polyurethanes were synthesized from polyester polyols, derived from PET Waste. The PET waste was first depolymerized by glycolysis. The glycolysized products were reacted with adipic acid to yield polyester polyols, and the polyester polyols were then reacted with either MDI or TDI to obtain polyurethanes. In this article, the thermal properties of the polyurethanes obtained are discussed in detail. © 1994 John Wiley & Sons, Inc.
Development and characterization of cellulose acetate benzoate flat osmotic membranes
Authors: Vyas M. D. , Mody R. C. , Mody I. C.
Published: April 2003

Different parameters of casting solutions and casting conditions were studied for the development of cellulose acetate benzoate flat osmotic membranes. Casting solutions were prepared with different concentrations of the polymer, the additive, and the solvent; viscosity of the casting solution; and the thickness of the membrane developed. The membranes were given different evaporation periods and annealing temperatures under different RH. Different annealing baths were also used. Based on these, conditions were optimized for the development of cellulose acetate benzoate flat osmotic membranes. These membranes were characterized with respect to bound water content, specific water content, transport properties by direct osmosis, salt intake by direct immersion, water permeability coefficient of the dense membrane, diffusion coefficient, salt permeability, and salt distribution by electrical conductivity. Also, cellulose acetate benzoate membranes were compared with conventionally used cellulose acetate membranes. © 1994 John Wiley & Sons, Inc.
Chemical structure and dynamic mechanical behavior of silk fibers modified with different kinds of epoxides
Authors: Shiozaki Hideki , Tsukada Masuhiro , Gotoh Yoko , Kasai Nobutami , Freddi Giuliano
Published: April 2003

The chemical reactivity of epoxide molecules toward silk fibroin was investigated by determining the rate of conversion of reactive amino acid residues. Significant differences were found between two different bifunctional epoxides, diglycidyl ethers of ethylene glycol (E) and resorcinol (R), the former reacting at a higher extent with arginine and tyrosine. The moisture regain decreased by reaction with epoxides, at a variable rate and extent, according to the hydrophobic/hydrophilic properties of epoxides. A two‐step behavior was observed when moisture regain values relating to the silk content in modified silk, fibers were plotted as a function of the weight gain. Dynamic mechanical data showed that the major loss peak became broader and its temperature shifted to lower values following the increase of weight gain. The loss peak temperatures showed a linear relationship with the amount of weight gain. The fine structural changes induced by reaction with eposides will be discussed in terms of chemical and steric factors of the epoxides, as well as of epoxide location within the different structural domains of silk fibers. © 1994 John Wiley & Sons, Inc.
Aqueous solution properties of poly(trimethyl acrylamido propyl ammonium iodide) [poly(TMAAI)]
Authors: Lee Wen‐Fu , Tsai Chan‐Chang
Published: April 2003

The aqueous solution properties of a cationic poly(trimethyl acrylamido propyl ammonium iodide) [poly(TMAAI)] were studied by measurements of reduced viscosity, intrinsic viscosity, and flocculation test. The reduced viscosity and intrinsic viscosity of this cationic polyelectrolyte were related to the types and concentration of added salt. “Soft” salt anions were more easily bound on the quaternary ammonium (R4N+) of poly(TMAAI) than those of “hard” salt anions. Halide anions are hard anions; consequently, hard cations were more easily attracted to halide anions for reducing the binding degree of halide anion on the quaternary ammonium group (R4N+). Some salt ions were observed to strongly attract the quaternary ammonium of the cationic polymeric side chain for coagulation of the polymers. This effect would make the polymeric aqueous solution become turbid. The intrinsic viscosity behavior for cationic polyelectrolyte resulting from the electrostatic repulsive force of the polymer chain is contrasted with polyampholyte. A comparison of various flocculants as to the effect of flocculation was also studied. © 1994 John Wiley & Sons, Inc.
Micellar effect on the kinetics of ceric ion‐initiated polymerization of acrylonitrile in the presence of organic substrate
Authors: Patra C. M. , Singh B. C.
Published: April 2003

The micellar effect on the kinetics of ceric ion‐initiated polymerization of acrylonitrile (AN) in the presence of N‐acetylglycine has been studied in the temperature range 30–50°C. The neutral emulsifier (Triton X‐100) has no effect on the Rp, whereas both anionic (NaLS) and cationic (NCTAB) emulsifiers accelerate the rate of polymerization appreciably. Comparison of the effect of different organic substrates on the rate of polymerization has been made. Various effects such as the concentration of metal ion, surfactant, monomer, sulfuric acid, organic solvents, and inorganic salts on Rp have also been investigated. The most remarkable feature of the investigation involves the enhancement of Rp in the presence of micelles. A suitable mechanism for the derivation of the rate expression for the above system is proposed along with the calculation of activation energy and prediction of optimum conditions. © 1994 John Wiley & Sons, Inc.
Effects of reactive functional groups in the compatibilizer on mechanical properties of compatibilized blends
Authors: Wu Chung‐Jen , Kuo Jen‐Feng , Chen Chuh‐Yung , Woo Eamor
Published: April 2003

The compatibility of blends of polyamide‐6/[styrene‐(ethylene‐butylene)‐styrene] triblock copolymer (SEBS) was enhanced with a compatibilizer, maleated SEBS, whose compositions were varied from 0 to 4 wt % of the blends. The maleated SEBS (MA‐g‐SEBS) was synthesized by reacting (grafting) maleic anhydride (MA) with SEBS in the laboratory at various maleic anhydride concentrations ranging from 8 to 13 wt % of the maleated compatibilizer. The effects of graft levels of the reactive MA functional group in the compatibilizer on the effectiveness in compatibilizing the blends were investigated. The morphology and the impact strengths of the compatibilized blends were determined. It was found that, depending on the maleated extents, the compatibilizer influenced significantly the properties of the blends. Although the maleated extents (graft ratios) of the compatibilizer is influential, the concentrations of the compatibilizer in the blends more sensitively affected the mechanical properties of the compatibilized blends. In summary, this study has shown that by increasing the MA contents (within the reported window) in the compatibilizer, the impact toughness could be more dramatically improved. © 1994 John Wiley & Sons, Inc.
Kinetics study of slurry‐phase propylene polymerization with highly active Mg(OEt)2/benzoyl chloride/TiCl4 catalyst
Authors: Kim Il , Choi Hong Ki , Kim Jae Ha , Woo Seong Ihl
Published: April 2003

Propylene was polymerized in a slurry phase over superactive and stereospecific catalyst prepared by the reaction of Mg(OEt)2 with benzoyl chloride and TiCl4 in the presence of AlEt3 with or without an external donor. A kinetic analysis of propylene polymerization was carried out. The polymerization rate was first order with respect to monomer concentration and the dependence of overall polymerization rate on the concentration of AlEt3 can be explained by the Langmuir adsorption mechanism. Maximum activity was observed around an Al/Ti mole ratio of 20. The average rate over 90 min of polymerization as a function of temperature showed a maximum around 42°C and the overall activation energy was 8.5 kcal/mol at T < 42°C and −4.0 kcal/mol at T > 42°C. The analysis of the phenomenon of an optimum temperature gave 2.2 kcal/mol for the activation energy of the rate‐determining step, and 6.3 kcal/mol, for the adsorption energy of AlEt3. The addition of small amount of p‐ethoxyethyl benzoate (PEEB) as an external donor increased the percentage of isotactic polymer to 98% and slightly increased activity in spite of the decrease in the concentration of active centers due to the stabilizing effect of the active centers by the external donor. The temperature showing maximum yield was shifted to the higher temperature when AlEt3 and PEEB ([AlEt3]/[PEEB] = 5) was used as a cocatalyst. © 1994 John Wiley & Sons, Inc.
A comparison of methods for the estimation of polymer/monomer interaction parameters: The polystyrene/n‐butyl methacrylate system methacrylate system
Authors: Durant Yvon G. , Sundberg Donald C. , Guillot J.
Published: April 2003

To measure the polymer/monomer interaction parameter as a function of composition, a set of partially cross‐linked synthetic latices has been produced by batch and semicontinuous emulsion polymerization. The degrees of cross‐linking have been measured by DMA and also predicted by computer simulation based on kinetic data. With equilibrium monomer swelling experiments achieved on films made from these polymers, two curves of the interaction parameter vs. the polymer fraction have been computed. These curves compare favorably with a theoretical model based on a Unifac procedure for the estimation of monomer activity. Two different data bases, liquid‐liquid and liquid‐vapor equilibria, have been used in the Unifac model. For the polystyrene/n‐butyl methacrylate system, a linear relationship found between the interaction parameter and composition is both predicted and measured experimentally. In all cases, this interaction parameter is found to increase with polymer concentration. © 1994 John Wiley & Sons, Inc.
Suspended emulsion, a new process for vinyl chloride polymerization: Morphology control through surface active additives
Authors: Vindevoghel Ph. , Nogues P. , Guyot A.
Published: April 2003

Suspended emulsion is a new polymerization process in which a water phase containing the initiator is suspended in an organic phase containing the monomer; the polymer formed is insoluble in both the organic and water phase. The final morphology of the polymer is a powder of grains (around 100–300 microns) formed with agglomerates of primary particles (around 1 micron). This article describes the effects of small amounts of either suspending agents (water‐soluble polymers) or surfactants. These effects concern mainly the morphology (grain and particle size), but also the polymerization kinetics. A rather homogeneous distribution of grains and particles inside the grain may be obtained by using a cellulosic polymer as the suspending agent and an anionic surfactant such as sodium dodecyl sulfate. © 1994 John Wiley & Sons, Inc.
Particle sizing of flocculated latex particles by physisorption of nitrogen
Authors: Janssen E. A. W. G. , Zirkzee H. F. , German A. L. , Maxwell I. A.
Published: April 2003

Physisorption of nitrogen at one specific pressure is used to determine the specific surface area of a flocculated polystyrene latex by applying BET theory. Assuming that a flocculated sample of Polymer latex is composed of distinct spherical latex particles (i.e., there is no coagulation of particles), the volume–surface‐average diameter can be calculated. The resulting diameters are compared to sizes obtained using a disc centrifuge sedimentometer, which fractionizes the particles by sedimentation. The diameters from both techniques were in good agreement, showing that physisorption of nitrogen, which is a simple technique, can be used to determine sizes of flocculated latex particles. This agreement also shows that the flocculation of the polystyrene latex produced separate nonporous spherical particles. When flocculation of a latex is done above its glass transition temperature, coagulation will occur. While other particle sizing techniques can produce particle size distributions, the physisorption of nitrogen only gives the volume–surface‐average diameter. However, one advantage of the physisorption of nitrogen is that it covers a broad range of particle sizes compared to most other techniques. © 1994 John Wiley & Sons, Inc.
Cyano‐substituted polyester, polyurethanes, and epoxy resin derived from 2,6‐bis(4‐hydroxybenzylidene)‐1‐dicyanomethylene–cyclohexane
Authors: Diakoumakos Constantions D. , Mikroyannidis John A.
Published: April 2003

The condensation of cyclohexanone with 4‐hydroxybenzaldehyde utilizing dry HCI as the catalyst afforded 2,6‐bis(4‐hydroxybenzylidene)cyclohexanone. The latter was condensed with malononitrile to yield 2,6‐bis(4‐hydroxybenzylidene)‐1‐dicyanomethylene–cyclohexane, which was used as the starting material for the preparation of a novel class of polyesters, polyurethanes, and epoxy resins. In addition, a model diester and diurethane were synthesized and their spectroscopic data were correlated with those of the corresponding polymers. It was shown that the introduction of the dicyanomethylene groups in the polymer backbone remarkably improved the polymer solubility as well as its thermal stability. The crosslinked polymers obtained upon curing the polyester and polyurethanes at 300°C for 40 h were stable up to 365–407°C in N2 or air and afforded anaerobic char yields of 64–70% at 800°C. © 1994 John Wiley & Sons, Inc.
Microgelation in the curing reaction of unsaturated polyester resins
Authors: Liu S. B. , Liu J. L. , Yu T. L.
Published: April 2003

A series of unsaturated polyesters were synthesized with various chemical structures and molecular weights. These unsaturated polyesters were used to study the curing reaction with styrene by using gel permeation chromatography and differential scanning calorimetry. The variation of the size of microgel particles during the curing reaction in unsaturated polyester–styrene resins was studied by using gel permeation chromatography. The size and structure of the microgels depend strongly on the polymer chain length and the number of vinyl groups on each unsaturated polyester chain. Using the differential scanning calorimetric method, the conversion of styrene and polyester vinyl groups during the reaction was measured. The experimental results of this study revealed that microgel formation has a great effect on the curing reaction of unsaturated polyester resins. © 1994 John Wiley & Sons, Inc.
Cyclotrimerization of isocyanate groups. II. Catalyzed reactions of phenyl isocyanate in the presence of 1‐butanol or butyl‐N‐phenylurethane
Authors: S̆pírková Milena , Kubín Miroslav , S̆pac̆ek Pavel , Krakovský Ivan , Dus̆ek Karel
Published: April 2003

Cyclotrimerization of phenyl isocyanate at 30–50°C in the presence of 1‐butanol or butyl‐N‐phenylurethane and catalysts of tertiary amine, quaternary ammonium salt, or carboxylate types in 1,4‐dioxane was studied by reverse‐phase liquid chromatography. Urethane, allophanate, urea, biuret, isocyanurate, and isocyanate model compounds were found in the system. Stability of all reaction products was also examined. The time dependence of evolution of various products depends on the catalyst type and temperature. The overall reaction scheme was proposed. © 1994 John Wiley & Sons, Inc.
Grafting mechanism in SBR–St–MMA core–shell emulsion copolymerization
Authors: Zhao Jianqing , Yuan Huigen , Pan Zuren
Published: April 2003

The graft copolymerization of styrene and methyl methacrylate on SBR latex particles in the core–shell emulsion process was conducted in a 600 mL glass stirred vessel with the BPOFe2+ redox initiator. The effects of the principal factors such as the polymerization temperature, monomer‐to‐polymer ratio, the frequency of monomer addition and conversion on the grafting degree, and the grafting efficiency were studied. The surface‐controlled process model was proposed to describe the grafting mechanism. © 1994 John Wiley & Sons, Inc.
Effect of extruder type on the properties and morphology of reactive blends based on polyamides
Authors: Majumdar B. , Keskkula H. , Paul D. R.
Published: April 2003

The morphology and mechanical properties of polyamide‐based blends prepared in single and corotating twin‐screw extruders were compared using transmission electron microscopy (TEM) techniques. Reactive polyamide blends with SEBS‐g‐MA (a maleated styrenic triblock copolymer with ethylene–butvlene midblocks), EPR‐g‐MA (a maleated ethylene/propylene rubber), and ABS were selected for the purpose of this investigation. For blends of SEBS‐g‐MA with difunctional (nylon x,y) polyamides (e.g., nylon 6,6; nylon 12,12), the twin‐screw extruder was more effective in producing a finer dispersion of the rubber phase, which resulted in a significant lowering of the ductile–brittle transition temperature in case of the nylon 6,6 blend. On the other hand, blends of SEBS‐g‐MA with the mono‐functional nylon 6 material led to rubber particles that were too small for toughening for both extruder types employed in this work. For nylon 6/EPR‐g‐MA blends, the single‐screw extruder led to blends with excellent low‐temperature impact properties for both single‐step and masterbatch mixing techniques, whereas nylon 6/EPR‐g‐MA blends prepared in a single‐step operation in the twin‐screw extruder were brittle under ambient conditions. For difunctional polyamide blends with ABS (compatibilized with an imidized acrylic polymer), the morphology and mechanical properties were found to be independent of the extruder type employed for processing. © 1994 John Wiley & Sons, Inc.
Physical, mechanical, and morphological behavior of sequential polybutadiene–poly(methyl methacrylate) interpenetrating polymer networks
Authors: Das Bibekananda , Gangopadhyay Tanmoy , Sinha Sudipta
Published: April 2003

Both full and semi‐interpenetrating polymer networks (IPNs) of polybutadiene and poly(methyl methacrylate) were synthesized by sequential polymerization. The effect of compositional variation and the cross‐linking agent of both elastomer and plastomer on the physical, mechanical, and morphological properties were investigated. Full‐IPNs exhibited improved tensile strength, modulus, tear strength, gel content, and density, whereas the corresponding semi‐IPNs exhibited better toughness and elongation at break. Phase morphology of full‐IPNs were characterized by compact, tight network structures compared to those of semi‐IPNs. © 1994 John Wiley & Sons, Inc.
J‐integral studies of crack initiation and crack tip‐blunting of phenolphthalein polyether ketone
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu
Published: April 2003

The J‐integral is applied to characterize the fracture initiation of phenolphthalein polyether ketone (PEK‐C) for which the concepts of linear elastic fracture mechanics (LEFM) are inapplicable at high temperatures for reasonably‐sized specimens due to extensive plasticity. The multiple‐specimen resistance curve technique recommended by the ASTM is the basic method employed. The values of JIC increase with increasing temperature. The crack tipblunting of PEK‐C is observed. The parameters, such as crack opening displacement (COD), δ0, and the stretching increment Δab1 are introduced to describe the blunting phenomenon. The δ0 increases with increasing temperature, as does Δab1. This indicates that the blunting occurs easily as the temperature increases; i.e., as the material's yield stress, σy steadily falls. The relationships between δ0, Δab1, and σy are also discussed. © 1994 John Wiley & Sons, Inc.
Synthesis and thermal characterization of chemically modified phenolic resins
Authors: Antony Rosy , Pillai C. K. S.
Published: April 2003

Phenolic resins with improved/altered thermal stability and flame retardancy were prepared by introducing flame retardant elements such as phosphorus and bromine at the monomer stage, followed by condensation with formaldehyde or hexamethylene tetramine (HMTA). Thus, monophenyl phosphoric acid (MPPA), monophenyl phosphoric acid–formaldehyde resin (MPPAF), brominated phenol–formaldehyde resin (BrPF) and 2,4,6‐tribromophenyl‐phosphoric acid–formaldehyde resin (BrMPPAF) were prepared and characterised. Thermal stability and flammability of these polymers were evaluated by TGA and LOI respectively and compared with those of phenol–formaldehyde resin (PF) and phosphorylated phenol–formaldehyde resin (PPF). The TGA (in air) of MPPAF showed enhanced thermal stability (char yield 66%) over that of PF (char yield 52%) and PPF (char yield 58%) indicating the role of phosphorus in imparting thermo‐oxidative resistance to PF. The enhancement is better when phosphorus is introduced at the monomer stage. The incorporation of bromine, however, brought about an unexpected reduction in the thermal stability of PF (char yield: BrPF, 2% and BrMPPAF, 26%). Both phosphorus and bromine are found to enhance the LOI values of PF (cured) from 35 to 50, 48, and 56, respectively, for MPPAF, BrPF, and BrMPAFF. A comparison of LOI values of these resins with their char yield suggests a condensed phase mechanism for phosphorus and vapor phase mechanism for bromine operating during thermal decomposition. © 1994 John Wiley & Sons, Inc.