bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface modification of ultrafiltration membranes by low temperature plasma. I. Treatment of polyacrylonitrile
Authors: Ulbricht Mathias , Belfort Georges
Published: April 2003

Excitation with low temperature helium or helium/water plasma and subsequent exposure to air of polyacrylonitrile (PAN) ultrafiltration membranes was used to hydrophilize the surface of these materials. We analyzed the effectiveness of this approach as a function of plasma operating variables including gas phase composition, plasma power, treatment time, and system pressure. Following the changes in physical and chemical composition of the PAN surface resulting from these modifications was a major aspect of this work. Techniques such as the captive bubble contact angle method, ellipsometry, ESCA, and FTIR‐ATR were all used. In addition, the formation and lifetime of peroxides during these processes were determined. At low powers (≤ 25 W) and short treatment periods (≤ 30 s), the main chemical conversion of PAN surfaces was simultaneous hydrophilization and stabilization via PAN cyclization. Relatively small water permeability changes were observed as a result of such treatment. © 1995 John Wiley & Sons, Inc.
Surface and interfacial FTIR spectroscopic studies of latexes. X. The effect of coalescence on surfactant exudation in polystyrene and poly(n‐butyl acrylate) latex films
Authors: Tebelius Lara K. , Urban Marek W.
Published: April 2003

In an effort to establish to what extent transient effects prior to coalescence may influence mobility, distribution, and orientation of surfactant molecules after coalescence, poly(n‐butyl acrylate) (n‐BA) and polystyrene (Sty) were polymerized independently and mixed in a 5 : 1 ratio. It appears that if a mixture of the n‐BA and Sty latex particles is allowed to stabilize prior to coalescence, the time of stabilization may have a significant effect not only on the distribution of SDOSS surfactant molecules across the coalesced film, but also on their orientation changes depending upon the stage of coalescence and the water front moving toward the surface. The coalescence of latex films was conducted under gaseous nitrogen and at 60% relative humidity. While the water front moves from the film‐substrate upward, during this process, various segments of the surfactant molecule change their orientation. Near the F–A interface, hydrophobic segments are being reoriented from parallel to perpendicular, whereas preferentially parallel orientation exhibit hydrophylic SO−3 Na+ segments. When water molecules, however, diffuse out of the film, the surfactant molecules have no preferred orientation. © 1995 John Wiley & Sons, Inc.
Solid‐state polycondensation of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. II
Authors: Karayannidis George P. , Kokkalas Demetris E. , Bikiaris Demetris N.
Published: April 2003

Poly(ethylene terephthalate) (PET) taken from postconsumer soft‐drink bottles was subjected to solid‐state polycondensation after cutting into small pieces or after dissolution in trifluoracetic acid, trifluoracetic acid/dichloromethane mixture (50/50%, v/v), or nitrobenzene, and coagulation in methanol. The effect of various reaction parameters such as time and temperature of reaction (180, 200, 220, and 230°C) on intrinsic viscosity [η] and carboxyl and hydroxyl end‐group content have been investigated. The highest number average molecular weight, M̄n = 61,400 was obtained from PET (M̄n = 20,300) dissolved in nitrobenzene and solid‐state polycondensated by heating under vacuum at 230°C for 8 h. The thermal behavior of solid‐state samples was studied by differential scanning calorimetry (DSC); all samples showed a characteristic double endothermal melting peak and no glass‐transition temperature. The PET samples taken from the bottles without dissolution were also studied by thermomechanical analysis. The heat distorsion temperatures obtained by this analysis were in very good agreement with the two endothermal melting peaks taken by DSC. This finding indicates that in these samples the crystallites form a coherent matrix and the amorphous phase is dispersed in the voids. © 1995 John Wiley & Sons, Inc.
Nonlinear stress properties of poly(styrene‐block‐butadiene‐block‐styrene) melt under elongational and shear deformation
Authors: Takahashi Tatsuhiro , Toda Hideyuki , Minagawa Keiji , Takimoto Jun‐Ichi , Iwakura Kenji , Koyama Kiyohito
Published: April 2003

Effects of block copolymerized structure on nonlinear stress properties under elongational and shear deformation were investigated. Samples used in this study were poly(styrene‐block‐butadiene‐block‐styrene) (SBS, weight rate of S/B = 40/60) and polystyrene (PS) as a reference. Tensile stress–strain and shear stress relaxation properties were measured at the molten state. SBS showed high elasticity after reaching the yield point under elongational deformation at room temperature. PS melt showed substantial tensile stress increase after the yield point as strain rates increased. However, SBS melt did not exhibit noticeable tensile stress rise at higher elongation, and this property was almost independent of strain rates. Stress relaxation experiments revealed that the damping function of SBS melt was more strain‐softening than that of PS melt. The results suggested that the block copolymerized structure decreases melt elasticity under elongational and shear deformation. A transmission electron micrograph indicated that the lack of melt elasticity in SBS melt is caused by orientation of the lamellar structure toward the stretched direction during deformation. © 1995 John Wiley & Sons, Inc.
Tensile and compressive behavior of poly(p‐phenylene benzobisthiazole) fibers
Authors: Sahafeyan Mohsen , Kumar Satish
Published: April 2003

Heat treated poly(p‐phenylene benzobisthiazole) (PBZT) fibers tested in tension result in two types of failure modes. In failure mode I, the fiber exhibits a relatively sharp break; mode II is characterized by significant axial fiber splitting. Approximately 20% of the fibers failed in mode II when tested at 2.54, 7.62, and 12.7 cm gage lengths. At 1.25 cm gage length all the fibers failed in mode I. Tensile strength decreased from the 1.25 to 7.62 cm gage length, but tensile strength of the fibers tested at 7.62 and 12.7 cm gage lengths were similar. The two failure mode observation is supported by the Weibull statistical distribution. Fiber tensile properties were also measured at 150°C. Axial compressive strength of the PBZT fibers as determined from the recoil test is also reported and is found to be independent of fiber tensile modulus and fiber diameter. As‐received heat‐treated fibers were post heat treated between 700 and 775°C. Structural changes in the fiber were studied using infrared spectroscopy, small and wide angle x‐ray scattering, and swelling studies. © 1995 John Wiley & Sons, Inc.
Fluorinated copolyimides prepared by one‐shot and stepwise monomer addition method
Authors: Chun Byong‐Wa
Published: April 2003

Copolyimides containing a hexafluoropropylidene group are prepared by the stepwise monomer addition method as well as the conventional one shot method. The stepwise addition method goes through an oligomeric imide prepolymer. The molecular weight distribution of the prepolymers approximately follows the Flory's statistical distribution in the fluorinated imide prepolymer. Except for the final molecular weight, the conventional one‐shot method does not give a significant difference in the copolymer character from the stepwise method, indicating that the segmental distribution in the copolyimides is practically statistical in the present monomer combination. The observed difference in the molecular weight by the preparation method may be related to the reactivity difference of the two monomer pairs. © 1995 John Wiley & Sons, Inc.
Quantification of the functional groups present at the surface of plasma polymers deposited from propylamine, allylamine, and propargylamine
Authors: Fally F. , Doneux C. , Riga J. , Verbist J. J.
Published: April 2003

The surface chemistry of plasma‐deposited films created from amine‐functionalized saturated (propylamine) and unsaturated (allylamine and propargylamine) precursors has been investigated by high‐energy resolution XPS, chemical derivatization, elemental analysis, and HREELS.XPS results show that nitrogen‐rich deposits are obtained from unsaturated precursors at low power or at high power in the postdischarge region. Quantitative information on the chemical groups in the polymers is obtained by simulating the XPS C1s and N1s core levels and by performing derivatization reactions. The proportion of primary amine functions deduced from tagging reactions with pentafluorobenzaldehyde in the liquid phase and with 4‐trifluoromethylbenzaldehyde in the vapor phase varies between 10 and 33%. These groups are converted into imine (more than 50%) in polypropylamine and polyallylamine, while imine and nitrile functions were found in polypropargylamine. HREELS has allowed us to distinguish between different nitrogen‐containing functionalities present at the extreme surface of the polymers. The comparison of the HREELS and TIR spectra shows that the chemical composition at the extreme surface of the samples is representative of that of the bulk. To explain the conversion of the chemical groups in the plasma, polymerization mechanisms are proposed for each of the monomers. © 1995 John Wiley & Sons, Inc.
Effect of MAA/MAM pregrafting on DMEU finishing of cotton fabrics
Authors: Min Rong‐Rong , Hwang Kuo‐Shien
Published: April 2003

Cotton fabrics were pregrafted with mixed monomer of methacrylic acid (MAA) and N‐methylolacrylamide (MAM) before undergoing finishing with 1,3‐dimethylolethylene urea. Experiments show that when the molar ratio of MAA and MAM is 4 : 6 the finished fabric has the maximum nitrogen content (N%) and crosslinking density. The pregrafting can improve the wet crease recovery angle and the moisture regain, can reduce the tensile strength retention, and has little effect on the dry crease recovery angle. In addition, at a pregrafting ratio of 4 : 6, the finished fabric has the highest crease recovery angle and moisture regain. © 1995 John Wiley & Sons, Inc.
Pervaporation separation of alcohol–water mixture through 4‐vinylpyridine chemical modified poly(4‐methyl‐1‐pentene) membrane
Authors: Lai J. Y. , Yin Yih‐Lang , Lee Kueir‐Rarn
Published: April 2003

For dehydrating separation aqueous alcohol solution by the pervaporation technique, a chemical modified poly(4‐methyl‐1‐pentene) (TPX) membrane was synthesized with 4‐vinylpyridine (4‐VP). The morphology, crystallinity, and thermodegradation properties were investigated by scanning electron microscopy, X‐ray, and thermogravimetric analysis, respectively. The modified TPX membrane possessed higher stability than that of the unmodified TPX membrane. The effects of feed temperature and poly(4‐VP) (P4‐VP) content of the modified TPX membranes on the performances of pervaporation were studied. A separation factor of 133 and a permeation rate of 115 g/mh can be obtained for the TPX/P4‐VP membrane with 3.0 wt % P4‐VP content. © 1995 John Wiley & Sons, Inc.
Grafting reactions onto poly(organophosphazenes). IV. Light‐induced graft copolymerization of organic polymers containing free acid or basic functionalities onto poly[bis(4‐benzylphenoxy)phosphazene]
Authors: Minto Francesco , Gleria Mario , Bortolus Pietro , Fambri Luca , Pegoretti Alessandro
Published: April 2003

The light‐induced graft copolymerization of acrylic acid, methacrylic acid, and 4‐vinylpyridine onto poly[bis(4‐benzylphenoxy)phosphazene] films to prepare new grafted phosphazene copolymers containing acid and basic functionalities is reported. The process was carried out in monomer/methanol mixtures in the presence of benzophenone or benzoin ethyl ether as photosensitizers by selective excitation of these last species. The yield of the grafting processes was evaluated as a function of the monomer concentration in the reaction medium, type of photoinitiator, and characteristics of the grafted organic monomers. The acid functions inserted in poly[bis(4‐benzylphenoxy)phosphazene]‐g‐poly(meth)acrylic acid grafted copolymers, and the basic groups of the poly[bis(4‐benzylphenoxy)phosphazene]‐g‐poly‐4‐vinylpyridine substrates were allowed to interact with basic and acid dyes, respectively, to form permanently colored polymeric films. The photoactivity of these films as substrates for the photosensitized production of singlet oxygen was tested. © 1995 John Wiley & Sons, Inc.
Diffusion of organic solvents in rubber membranes measured via a new permeation cell
Authors: Guo C. J. , De Kee D. , Harrison B.
Published: April 2003

An experimental method based on a gravimetric permeation cell was designed and successfully used in measuring the diffusivities, permeabilities, and the breakthrough times of several rubber–solvent systems. The experimental results for four organic solvents: benzene, o‐xylene, ethylbenzene, and chloroform in silicone, natural, and bromobutyl rubbers, respectively, are reported along with a description of the experimental method. The relations between the diffusivities measured by a permeation method and a sorption uptake method are discussed. This permeation cell provides a simple and reliable mean to determine the diffusional transport properties of a polymer–solvent system. © 1995 John Wiley & Sons, Inc.
Processing characteristics and structure development in solid‐state extrusion of a new semicrystalline polyimide (BTDA–DMDA)
Authors: Wang Y. D. , Cakmak M. , Harris F. W.
Published: April 2003

In this article, we present detailed processing characteristics and structure development in a thermoplastic polyimide BTDA–DMDA in the solid‐state extrusion process. This fully imidized polyimide polymer is known to crosslink at fast rates when it is brought to a molten phase even for short periods of time. This characteristic makes it difficult to process it in the molten phase and attempts at melt processing result in melt fracture and highly distorted extrudates. However, this polymer can be shaped into high‐quality extrudates when it is processed below its melting temperature directly from its postpolymerization powdered state. The solid‐state extrusion of precompacted BTDA–DMDA powder was studied in the temperature range from 250 to 320°C. At the temperatures from 290 to 320°C, high‐quality extrudates were obtained. Below 290°C, solid‐state extrusion was not possible due to the limitation of the load cell capacity of the capillary rheometer used in this research. Above 320°C, the extrudates were found to be of poor quality as a result of degradation and crosslinking in the molten phase. Structural characteristics of the samples produced by solid‐state extrusion was investigated by the microbeam X‐ray diffraction technique. The thermal behavior of the extrudates was also characterized by differential scanning calorimetry (DSC). The DSC results show that at low extrusion temperatures the samples exhibit dual endothermic peaks and are highly crystalline in an extruded state. The higher melting peak located at about 350°C is due to the melting of the new crystalline phase that has developed partially during the solid‐state extrusion process and partially during the recrystallization process that takes place at temperatures at and slightly above the primary melting process during the DSC heating scan. This has been confirmed by DSC, depolarized light hot‐stage video microscopy, and wide‐angle X‐ray diffraction studies. The long spacing of the higher melting crystals was found to be much larger than that of the lower melting crystals, as evidenced by the small angle X‐ray scattering studies. © 1995 John Wiley & Sons, Inc.
In situ reactive compatibilized noryl/LCP blends
Authors: Chang Dor‐Yaw , Chang Feng‐Chih
Published: April 2003

This article reveals that the already known improved properties of the thermoplastic–liquid crystalline polymer (LCP) blends can be further improved substantially over the corresponding noncompatibilized counterparts by using a reactive in situ type compatibilizer, the styrene–glycidyl methacrylate (SG) copolymer. This SG copolymer has been demonstrated in this article to be an effective reactive compatibilizer to improve the processability, heat deflection temperature, and mechanical properties of Noryl/LCP blends. The epoxy functional groups of the SG copolymer can react with the end groups of PPO (in Noryl) and LCP. The in situ‐formed SG–g–LCP copolymer tends to reside along the interface of Noryl–LCP and reduces the interfacial tension during melt processing. The resultant LCP fibers in the Noryl matrix of the compatibilized blends have a higher aspect ratio because the fibers become finer, longer, and tend to form lamellate domains with a greater interphase contact area than those from the noncompatibilized blends. The compatibilized blends also improve the interphase adhesion between Noryl and LCP. The presence of ethyl triphenylphosphonium bromide catalyst promotes the grafting reaction to improve blend compatibilization. © 1995 John Wiley & Sons, Inc.
Free volume after cure vs. fractional conversion for a high‐Tg epoxy/amine thermosetting system
Authors: Venditti R. A. , Gillham J. K. , Jean Y. C. , Lou Y.
Published: April 2003

Isothermal glassy‐state properties of cured thermosetting materials pass through maximum and minimum values with increasing fractional chemical conversion. In this work, a diglycidyl ether of bisphenol A (a diepoxide) and trimethylene glycol di‐p‐aminobenzoate (a tetrafunctional aromatic diamine) system was investigated for the purpose of analyzing the complex behavior after cure of the isothermal properties of the glassy state with increasing conversion. The glass transition temperature (Tg) is used as a direct measure of conversion. Dilatometric, differential scanning calorimetry, torsional braid analysis, and positron annihilation spectroscopy techniques were used to monitor the density, Tg, modulus, and free volume of the material after cure with increasing conversion. The specific volume at 25°C after cure passes through a minimum and the modulus passes through a maximum with increasing conversion. The fractional free volume and the average radius of free volume at 25°C after cure pass through minimum values with respect to conversion. The specific volume, modulus, and fractional free volume at 25°C vs. conversion data qualitatively correlate. The anomaly of the increasing specific volume in the glassy state with increasing conversion is thus considered to arise from changes in free volume on a length scale corresponding to angstroms. The increasing free volume with increasing conversion is related to the phenomenon of antiplasticization. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of biodegradable poly(1,4‐butanediol succinate)
Authors: Song Dae Kyung , Sung Yong Kiel
Published: April 2003

Biodegradable poly(1,4‐butanediol succinate) was synthesized from 1,4‐butanediol and succinic anhydride. The synthesized polymer was identified by 1H‐NMR spectrometer and FT‐IR spectrophotometer. The weight average molecular weights were between 4,600 and 29,000, and molecular weight distributions were in the range of 1.7 and 1.9. The glass transition temperature of poly(1,4‐butanediol succinate) was revealed at 73°C. The crystallization and cold crystallization of the polymers were investigated as a function of heating rate, cooling rate, reheating rate, and molecular weight. The biodegradation behavior of poly(1,4‐butanediol succinate) in micro‐organisms such as fungi, actinomycetes, and bacteria was studied by using modified ASTM method. Based upon visual observation, the crystalline structure of films composed of larger molecular weight polymers retained their crystallinity longer than similar structures in low molecular weight samples. © 1995 John Wiley & Sons, Inc.
Silk fibroin/cellulose blend films: Preparation, structure, and physical properties
Authors: Freddi Giuliano , Romanò Maria , Massafra Maria Rosaria , Tsukada Masuhiro
Published: April 2003

This article deals with the preparation and characterization of silk fibroin (Bombyx mori)/cellulose blend films. Following dissolution with a metal complex solution, the average molecular weight of silk fibroin slightly decreased. While cellulose was almost unaffected. After coagulation and washing, transparent films were obtained by blending fibroin and cellulose in all proportions. The crystalline structures of regenerated fibroin and cellulose were β‐form and cellulose II, respectively, as shown by the characteristic x‐ray diffraction profiles. Density values increased with cellulose content, though less than expected from a pure additive behavior. Moisture regain increased following the addition of a small amount of cellulose to silk fibroin. The mechanical properties showed that both strength and elongation at break of silk fibroin films were improved by blending with cellulose. IR spectra exhibited changes in the skeletal frequences of silk fibroin, suggesting the occurrence of intermolecular interactions between fibroin and cellulose through hydrogen bond formation. © 1995 John Wiley & Sons, Inc.
Polymer‐dispersed liquid crystal materials prepared by electron‐beam‐initiated polymerization
Authors: Maschke Ulrich , Coqueret Xavier , Loucheux Claude
Published: April 2003

Polymer‐dispersed liquid crystal (PDLC) films were prepared using electron beam radiation by a polymerization‐induced phase separation process. The composite material was obtained from a blend including a polyester acrylate and the nematic liquid crystal mixture E7. The electro‐optic properties of the PDLC films were investigated as a function of film thickness. The obtained transmission vs. voltage curves exhibit a good reproducibility, low threshold voltages, and a high transmission in the on state. © 1995 John Wiley & Sons, Inc.
Structural characterization of polyester resins by electrospray mass spectrometry
Authors: Hunt S. M. , Binns M. R. , Sheil M. M.
Published: April 2003

Sixteen different polyester paint resins have been examined by electrospray ionization mass spectrometry (ESI‐MS) in a novel application of the technique for structural analysis of polyesters. Synthetic resins typically contain a range of polymeric structures comprised of various ratios of the monomeric components. When polyesters are analyzed by ESI‐MS, singly and doubly charged ions are produced and oligomeric species of the polyesters can be clearly identified. The addition of alkali metal salts to the polyester samples and modification of the solvent system was also found to dramatically enhance the ESI‐MS efficiency of polyesters. The ESI mass spectra enabled identification of the range and relative abundance of chemical structures present in each sample. Using this information, average molecular weights, polydispersity, the distribution of acid versus alcohol end groups, overall monomer proportions, average functionality per molecule, and average frequency of branching per molecule have been calculated. The identities of peaks in the ESI‐MS spectra have been confirmed by tandem mass spectrometry. © 1995 John Wiley & Sons, Inc.
Influence of molecular weight distribution on the structure and properties of melt‐spun polypropylene filaments
Authors: Misra S. , Lu F.‐M. , Spruiell J. E. , Richeson G. C.
Published: April 2003

The role of molecular weight distribution on the spinnability, structure, and properties of melt‐spun isotactic polypropylene filaments was studied with the aim of clearly distinguishing the effect of the breadth of the distribution from the effect of the average molecular weight and resin melt flow rate (MFR). Nine resins were chosen for this purpose, ranging in MFR from 16 to 78 and in polydispersity from 2.6 to 5.4. It was observed that the spinnability, structure, and properties of the spun filaments were all strong functions of the breadth of the distribution. Spinnability decreased with increasing breadth. At given spinning conditions and polydispersity, an increase in the weight‐average molecular weight (decrease in MFR) produces an increase in crystallinity, birefringence, tensile strength, and tensile modulus. But at given spinning conditions and resin MFR, broadening the molecular weight distribution (increasing the polydispersity) produces an increase in crystallinity, tensile modulus, and elongation‐to‐break while birefringence and tensile strength decrease. The major influence of the polydispersity on the structure and properties developed was attributed to its effect on both the elongational viscosity of the resin and the ability of high molecular weight tails in the distribution to influence the stress‐induced crystallization that occurs in the spinline. © 1995 John Wiley & Sons, Inc.
Soluble aromatic polyimides and polyamides based on 4,4′‐diaminotriphenylmethane
Authors: Likhatchev D. , Alexandrova L. , Tlenkopatchev M. , Vilar R. , Vera‐Graziano R.
Published: April 2003

Aromatic polyamides and polyimides were synthesized from 4,4′‐diaminotriphenylmethane (DA‐TPM) for studying their solubility, thermal, and mechanical properties. The polymers were found to be soluble in amide solvents and pyridine, and this could be attributed to the practically free rotation of the polymer chain segments around the bridging group within the DA‐TPM and the effect of its pendant phenyl ring. The polyimides and polyamides exhibited well‐distinguished glass transition in the range of temperatures, which is typical for flexible‐chain polymers. For the polyimides, significant differences in solubility and mechanical properties were observed between the samples prepared by chemical and thermal imidization of poly(amic acids). Thermal imidization brought about remarkably less soluble brittle films. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of melt‐polymerizable aminophthalocyanine monomers
Authors: Boyle Michael E. , Adkins James D. , Snow Arthur W. , Cozzens Robert F. , Brady Robert F.
Published: April 2003

The strategy, synthesis, and characterization of a soluble amine‐functionalized phthalocyanine monomer and two examples of its polymerization into optically transparent glasses are reported. A simple, fast, and versatile method for incorporating metal ions into the metal‐free phthalocyanine is demonstrated. Measurements of the nonlinear optical properties associated with a lead‐substituted phthalocyanine/urethane copolymer are also reported. © 1995 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Effect of antioxidant on peroxide modification of LLDPE
Authors: Bremner Tim , Rudin Alfred
Published: April 2003

A commercial linear low density polyethylene (1‐hexene comonomer) was reacted with dicumyl peroxide at appropriate levels to initiate chain extension without crosslinking. The peroxide modification was carried out both in the presence and absence of a common hindered phenolic antioxidant. Thermal treatment of the resin was also completed with and without antioxidant present to evaluate the contribution of classical thermooxidative degradation to the peroxide modification process. In terms of pure thermal degradation, the phenolic antioxidant was found to be effective in prevention of reduction of molecular weights at the high end of the molecular weight distribution, as reflected in changes in Mz. At the low end of the distribution, the opposite effect is seen, where the removal of the antioxidant actually allows an increase in the value of Mn, through chain coupling reactions. Processing of the resin with addition of the organic peroxide significantly increases the molecular weights of both antioxidant containing and antioxidant free resins. Increasing the reaction temperature increases the rate of degradative chain scission and nonenlarging disproportionation reactions. At low temperatures, the presence of the antioxidant acts negatively with respect to chain enlargement reactions, and an overall reduction is seen in the efficiency of the peroxide in its role of increasing molecular weights. As the reaction temperature is increased, chain scission reactions become more predominant, and the antioxidant free resin shows very substantial decreases in molecular weight. Retention of the antioxidant at higher reaction temperatures is beneficial to maintaining high molecular weights, both with and without peroxide present. As in the peroxide free case, branching is essentially unchanged by the absence of antioxidant in peroxide modification. © 1995 John Wiley & Sons, Inc.
Correction for interdetector volume in size exclusion chromatography (SEC)
Authors: Pigeon Michael G. , Rudin Alfred
Published: April 2003

In a multidetector SEC system it is necessary to match the outputs of the detectors that sense eluant concentration with that are molecular weight dependent. There are several methods to accomplish this. The most common is to determine the interdetector volume or time difference between detectors. The difficulty with this technique is that with detector systems where the column eluent is split, the interdetector time difference varies with solution viscosity. Two new techniques were implemented on a high temperature SEC/DRI/LALLS/VISC system which take into account changes in solution viscosity due to high molecular weight polymers. Both techniques use calibration curves of hydrodynamic volume versus elution volume for the different detectors to determine the “instantaneous” time difference between the detectors as it varies with solution viscosity. Either method provides the correct interdetector time lag information. We note also that in multidetector systems the configuration of the detectors should be such as to maximize solvent flow rates through each detector and hence to minimize band broadening effects. © 1995 John Wiley & Sons, Inc.
Thermal dehydrochlorination of poly(vinyl chloride) in the presence of Jatropha seed oil
Authors: Okieimen F. E. , Sogbaike Clara E.
Published: April 2003

Thermal degradation of poly(vinyl chloride) was studied in a nitrogen atmosphere in the presence of Jatropha seed oil, epoxidized Jatropha seed oil, and soaps (barium and cadmium) of Jatropha seed oil at various temperatures. The rate of dehydrochlorination measurement at 1% degradation, RDH, and the time required for dehydrochlorination to attain 1% conversion were used to assess the effect of the additives on the susceptibility of the polymer to dehydrochlorination. It was found from the kinetic studies and the results from viscosity measurements on degraded polymer samples that the Jatropha seed oil derivatives suppressed the initial loss of HCl from the polymer and the extent of polymer chain scission accompanying the dehydrochlorination process. Thermal degradation studies of poly(vinyl chloride) in the presence of mixtures of barium and cadmium soaps of Jatropha seed oil were also carried out. It was found that soap mixtures containing less than 80 wt% cadmium soap exerted a deleterious (antagonistic) effect on the degradation of poly(vinyl chloride) while in the presence of soaps containing more than 80 wt% cadmium soap, considerably lower values of RDH and higher values of tDH were observed. The soap mixture containing 90 wt% cadmium soap was found to exhibit a remarkedly improved stabilizing effect on the dehydrochlorination of poly(vinyl chloride). © 1995 John Wiley & Sons, Inc.
Orientation in uniaxially drawn polystyrene plasticized by CO2 sorption
Authors: Kajitani Takahiro , Uosaki Yasuhiro , Moriyoshi Takashi
Published: April 2003

Uniaxial drawing experiments of the polystyrene films plasticized by a sorption of compressed CO2 gas at pressures up to about 18 MPa were carried out with strain rates ε of 0.0290 and 0.0079 s−1. The drawing was performed successfully with draw ratio λ up to 4 at the temperatures of 308.15, 318.15, 328.15, and 338.15 K. The Hermans orientation function f of the drawn samples was determined from the dichroic ratio measured by an infrared spectrophotmeter. While f value increases with increasing ε or λ, it decreases with increasing CO2 pressure or temperature. © 1995 John Wiley & Sons, Inc.
Estimation of critical micellar concentration through ultrasonic velocity measurements
Authors: Durackova S. , Apostolo M. , Canegallo S. , Morbidelli M.
Published: April 2003

A technique based on ultrasound propagation velocity measurements has been developed to investigate surfactant's behavior in aqueous solutions. Applications to the estimation of the critical micellar concentration of two emulsifiers, sodium dodecyl sulfate and dodecylbenzene sulfonic acid sodium salt, and a mixture of them are discussed. A simple model was developed to interpret the experimental ultrasound propagation velocity measurements. The model provides a theoretical foundation to the experimental results as well as a valuable tool for smoothing out the disturbances affecting the experimental data. © 1995 John Wiley & Sons, Inc.
Mechanical and microstructural properties of pectin/starch films
Authors: Coffin David R. , Fishman Marshall L. , Cooke Peter H.
Published: April 2003

Films were made from blends of high methoxy pectin and high amylose starch gelatinized in a microwave oven in the presence and absence of glycerol at times ranging from 10 to 105 s. Three thermodynamic transitions were observed when storage modulus, loss modulus, and loss tangent were plotted against temperature. All three transitions gave minima when the transition temperature was plotted against time of gelatinization. Overall, there were only modest changes in these moduli over the range of gelatinization times studied, with little difference between films made with the starch gelatinized in either the presence or absence of glycerol. Starch granules were found to disappear at gelatinization times between 20 and 30 s, although much smaller starch particles seemed to recur at gelatinization times of 75 s and above. The minima found in the transition temperature and modulus plots were believed to result from a minimum in the amount of intermolecular interactions between the starch molecules. © 1995 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Studies of the effect of fiber surface and matrix rheological properties on nonwoven reinforced elastomer composites
Authors: Epstein Mikael , Shishoo R. L.
Published: April 2003

The influence of fiber type and fiber‐surface properties on matrix flow behavior was investigated using structural reaction injection‐molding (SRIM). The influence of fiber type, fiber‐surface properties, and matrix type on strength properties in elastomeric composites reinforced with nonwoven fibrous structures was investigated using tensile tests on elastomer composite samples from SRIM and latex coagulation (LC) fabrication methods and the microbond strength method on individual fibers. The fibers used were PET, LLDPE, and p‐aramid. Fibers were treated with epoxy, styrene, and isocyanate derivatives, which make the surface chemically reactive. Treatments were also made with NaOH and a copolymer of polyester and polyol ether, causing a change in the fiber surface energy. The matrix types were polyurethane elastomer and natural rubber. The results show that the surface treatments which produced a change in the surface energy influenced the flow rate of the matrix polymer during the composite fabrication process. The treatments resulted in chemically reactive fiber surfaces which improved the fiber‐matrix bond strength without affecting the Young's modulus of the composite material. Good correlation was found between bond strength and surface energy including the dispersive component of surface energy in the case of polyurethane elastomer and surface‐modified PET fibers. The age of the polyurethane matrix has a marked influence on the bond strength. The fiber volume fraction in composites has a strong influence on the Young's modulus of the elastomer composite. © 1995 John Wiley & Sons, Inc.
Physicomechanical properties of poly(methyl methacrylate‐co‐N‐arylmaleimides)
Authors: Bharel Renu , Choudhary Veena , Varma I. K.
Published: April 2003

The article describes the effect of incorporating low mol fractions of N‐o‐tolymaleimide (MO)/N‐p‐tolymaleimide (MP) in poly(methyl methacrylate) (PMMA) on Tg, thermal behavior, mechanical, and optical properties. The glass transition temperature (Tg) of PMMA increased by 10–12°C upon incorporation of an ∼ 0.026 mol fraction of N‐arylmaleimides. A further increase of N‐arylmaleimide content up to 0.1 mol fraction in the copolymers resulted in a further ∼ 10°C increase in Tg. The tensile strength and % elongation decreased, whereas modulus increased with increasing maieimide content. The solar transmittance and % transmittance at higher wavelengths of the copolymer sheets having a low mol fraction of N‐arylmalemides (i.e., 0.026–0.05) were comparable to PMMA. © 1995 John Wiley & Sons, Inc.
Preparation of macroporous carbons from phase‐inversion membranes
Authors: Hatori H. , Yamada Y. , Shiraishi M.
Published: April 2003

Preparation of porous carbons from phase‐inversion membranes was investigated as a control method of pore structure in carbon materials. The structure in carbon films was estimated by means of electron microscopy, mercury porosimetry, and gas‐adsorption methods. When phase‐inversion membranes of Kapton‐type polyimide were carbonized, they maintained the film form and gave macroporous carbon films having high porosity. However, micro‐ and mesopore structures in the carbon films were not influenced by phase inversion in the polymer stage, and, thus, the macroporous carbons had a molecular sieve property similar to that of carbons prepared from nonporous polyimide films. A macroporous structure in cellulose membranes was similarly maintained through the carbonization step, but some of these were fractured or deformed owing to the large shrinkage. Polymer membranes have a capability as porous carbon precursors if they satisfy two requirements: solid‐state carbonization and relatively high carbon yield. A composite membrane of a macroporous carbon with a dense carbon having an impervious ability was readily produced by shaping at the precursor stage. © 1995 John Wiley & Sons, Inc.
Transition points of polymers
Authors: Furukawa Junju
Published: April 2003

As a model for polymers, the pseudocrosslink of various sizes is proposed. The size of links, lengths of connected chains, and the times τ's for their translation or relaxation are derived. According to the size, four transition temperatures (T's) are proposed such as the linking for the smallest size A (TA), that for the largest one B (TB), the melting point (Tm), and the glass transition point (Tg). The equation for Tg is derived with an assumption that the cooling time t is equal to the relaxation time of the segment at Tg and Tg is found to be about 50°C higher than TA. Tg decreases with t. TB is twice as much as TA. Tg/TB is 2/3 in the general case and 1/2 for hindered polymers. Tm is very close to TB, but somewhat lower than it when the cohesion heat is large. Related problems are discussed: The thermal expansion coefficient above Tg is about 1/10 Tg. The rebound resilience of rubber at temperature T is given by a ratio of (T – Tg)/(T – TA). The sound velocities in glassy plastics and rubber are 2000 and 50–100 m/s, respectively, depending on the elasticity. The temperature‐shift factor for the stress‐relaxation spectrum is derived directly from the equation for the relaxation time without use of the thermal expansion coefficient. © 1995 John Wiley & Sons, Inc.
Surface modification of polypropylene by a combination of photooxidation and photosubstitution reactions
Authors: Pasternak Mordechai
Published: April 2003

An efficient photoprocess has been developed to increase polypropylene surface wettability by insertion of acid, ester, and amide functionalities. A systematic study of polypropylene surface irradiations indicates that photoxidations always precede the photosubstitution reactions that occur at the carbonyl site to form carboxyl, ester, and amide groups. Irradiations with amines to form amide groups always achieved the highest level of wettability improvement without changing bulk morphology. This process may be very beneficial in facilitating the fabrication of composite membranes with hydrophilic barriers on top of a hydrophobic polymeric support such as polypropylene. The high chemical resistance of polypropylene matrix to various solvents makes the partially hydrophilized polypropylene an ideal membrane support when hydrophilic membrane barriers made by interfacial polymerization/crosslinking are needed for a variety of separation application. © 1995 John Wiley & Sons, Inc.
Water‐soluble sulfonated phenolic resins. I. Synthesis
Authors: Hsu K. C. , Lee Y. F.
Published: April 2003

A new water‐soluble sulfonated phenolic resin as a water reducer in concrete was prepared in this study. It was synthesized from formaldehyde, phenol, and NaHSO3through a four step reaction procedure. The structure of resin was determined through analyses of IR and NMR spectra. The influence of reaction conditions on the properties of synthesized products was also examined and discussed. © 1995 John Wiley & Sons, Inc.
Biocidal polymers active by contact. IV. Polyurethanes based on polysiloxanes with pendant primary alcohols and quaternary ammonium groups
Authors: Hazziza‐Laskar J. , Helary G. , Sauvet G.
Published: April 2003

Functional polysiloxanes bearing both primary alcohols and quaternary ammonium salts (QAS) as lateral substituents were prepared. The synthesis involves a cohydrosilylation of allylic derivatives (N,N‐dimethylallylamine and allyloxytrimethylsilane) with various poly(dimethylsiloxane‐co‐hydrogenomethylsiloxane)s. During the quaternization of the tertiary amino groups the alcohol functions are also deprotected. The hydroxyl groups allow the polysiloxane to be incorporated in polyurethane films whereas the QAS impart biocidal properties to the coating. In the case of a QAS bearing a hexadecy substituent, a very high activity was found against Escherichia coli without any observable diffusion. The mode of action by contact between the solid polymer and the microorganisms was confirmed by the excellent durability of the biocidal power after 1 month of immersion in water. © 1995 John Wiley & Sons, Inc.
Use of EVA‐containing mercapto groups in natural rubber–EVA blends. I. Mechanical, thermal, and morphological properties
Authors: Jansen P. , Amorim M. , Gomes A. S. , Soares B. G.
Published: April 2003

The effect of ethylene–vinyl acetate (EVA) modified with mercaptoacetic acid on mechanical, thermal, and morphological properties of blends of natural rubber (NR) and EVA copolymers has been investigated. The introduction of EVASH promotes a crosslinking of natural rubber phase as indicated by extraction experiments and microscopy analysis. This crosslinking may be attributed to bonding between sulfhydryl groups along the EVASH backbone and double bonds in rubber phase and may be responsible for the hardness improvement of most of the studied blends. Better results on hardness and ultimate tensile strength with EVASH addition were achieved for NR–EVA (60 : 40) ratio, probably due to cocontinuous morphology of this composition. The influence of EVASH on crystallinity degree of NR–EVA blends was also studied by differential scanning calorimetry. The morphology of the blends was studied through scanning electronic microscopy. © 1995 John Wiley & Sons, Inc.
Degradability and antigen‐release characteristics of polyester microspheres prepared from polymer blends
Authors: Sah Hongkee , Chien Yie W.
Published: April 2003

Biodegradable microspheres were prepared to function as a depot system for the controlled release of a model protein antigen bovine serum albumin (BSA). As an approach to achieve its controlled release, microspheres were fabricated blending a high‐molecular‐weight poly‐d,l‐lactide‐co‐glycolide (Mw = 61,000) with a low‐molecular‐weight poly‐d,l‐lactic acid (Mw = 2000, PLA2000). The effects of PLA2000 on microsphere degradability and release characteristics of BSA from microspheres were investigated. On the basis of the pH change in microsphere suspensions and water uptake of microspheres, the kinetics of microsphere degradation was derived to describe the rate of formation of hydrogen ions due to hydrolysis of ester linkages of polymers. It substantiated that PLA2000‐containing microspheres were subject to controlled degradation that was necessary to achieve continuous release profiles of the antigen. Immunization of rabbits by subcutaneous injection of BSA‐containing microspheres enhanced the antigenicity of BSA, and significantly increased the duration of humoral immune responses. © 1995 John Wiley & Sons, Inc.
Determination of the interfacial mass transfer coefficient of vinyl acetate monomer diffusion into poly(vinyl acetate) and polystyrene latex particles stabilized with different stabilization mechanisms using a vapor phase addition method
Authors: Kim Joong‐In , Vanderhoff John W. , Klein Andrew
Published: April 2003

A vapor phase monomer addition method was used to measure the monomer transfer rate into latex particles. The classical mathematical model for the diffusion process was used to calculate the overall mass transfer coefficients of monomer between the vapor and the water phases, and between the water and the polymer particle phases. At the initial stage of the monomer transfer into the glassy polystyrene latex particles at 60°C, the rate‐determining step was the monomer transfer inside the polymer. As more monomer transferred into the latex particles and the glass transition temperature of the swollen latex particles decreased below the experimental temperature, the rate‐determining step became the monomer transfer across the interfacial surfactant layer. This transition was not observed with poly(vinyl acetate) latex, which was rubbery at the experimental temperature. The diffusion coefficients calculated were in the order of 10−13 to 10‐14 cm2/s. These low values correspond to molecular diffusion of small molecules through a solid or glassy membrane. This was attributed to the resistance of the adsorbed surfactant layer. The mass transfer rates into latex particles stabilized with ionic, nonionic surfactants, and a water‐soluble polymer were compared. In the case of the ionic surfactant, sodium dodecyl sulfate, when a large amount of electrolyte was added, the mass transfer rate decreased compared to the electrolyte addition free case. This was attributed to the formation of a “condensed” layer of adsorbed surfactant. Adsorbed nonionic surfactant or water‐soluble polymer showed larger resistance to monomer transport compared to the ionic surfactant layer. © 1995 John Wiley & Sons, Inc.