bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlled antibody release from a matrix of poly(ethylene‐co‐vinyl acetate) fractionated with a supercritical fluid
Authors: Mark Saltzman W. , Sheppard Norman F. , Mchugh Mark A. , Dause Richard B. , Alan Pratt J. , Dodrill Amy M.
Published: April 2003

A new method is presented for controlling the rate of antibody (Ab) release from an inert matrix composed of poly(ethylene‐co‐vinyl acetate) (EVAc), a biocompatible polymer that is frequently used to achieve controlled release. Using supercritical propane, a parent EVAc sample (Mn = 70 kDa, Mw/Mn = 2.4) was separated into narrow fractions with a range of molecular weights (8.7 < Mn < 165 kDa, 1.4 < Mw/Mn < 1.7). Solid particles of Ab were dispersed in matrices composed of different polymer fractions and the rate of Ab release into buffered saline was measured. The rate of Ab release from the EVAc matrix depended on molecular weight: > 90% of the incorporated Ab was released from low molecular weight fractions (Mn < 40 kDa) during the first 5 days of release, while < 10% was released from the high molecular weight fraction (Mn > 160 kDa) during 14 days of release. No significant differences in polymer composition, glass‐transition temperature, or crystallinity were identified in the different molecular weight fractions of EVAc. Mechanical properties of the polymer did depend on the molecular weight distribution, and correlated directly with Ab release rates. Because it permits rapid and reproducible fractionation of polymers, supercritical fluid extraction can be used to modify the performance of polymeric biomaterials. © 1993 John Wiley & Sons, Inc.
Preparation and characterization by thermal analysis of magnetic latex particles
Authors: Noguchi Hiromichi , Yanase Noriko , Uchida Yasuzo , Suzuta Tatsuo
Published: April 2003

Emulsion polymerization of styrene and methyl methacrylate in the presence of a ferrofluid was briefly studied. Thermal properties of the resulted latex particles were investigated by TG–DTA analysis. Determination of the residue weight after the thermal analysis that indicated complete decomposition of the organic components was found to be a facile and practical method to determine the magnetite content in the latex particles. The method was applied to magnetic polystyrene latex particles prepared in the presence of various amounts of the ferrofluid. Analysis of the results suggested that the magnetic content in the latex particles is primarily determined by the weight ratio of the ferrofluid to monomer. © 1993 John Wiley & Sons, Inc.
Functionalized polysulfone membranes by heterogeneous lithiation
Authors: Guiver Michael D. , Black Paul , Tam Chung M. , Deslandes Yves
Published: April 2003

Polysulfone membranes were modified heterogeneously by lithiation, using n‐butyllithium and low concentrations of tetrahydrofuran (THF). The effects of various conditions of reactant concentration, temperature, and time were determined quantitatively. The degree of substitution was measured by XPS and FTIR, using the carbonyl absorption band of lithium‐activated membranes that had been converted to ones containing acyl fluoride substituents. The optimum conditions for membrane functionalization were 0.2M n‐butyllithium in hexane at room temperature. The reaction rate increased substantially in the presence of 2% THF. The surface‐lithiated membranes can be derivatized, potentially with a wide variety of functional groups. © 1993 John Wiley & Sons, Inc.
The positive temperature coefficient phenomenon of vinyl polymer/CB composites
Authors: Tang Hao , Piao Jianhui , Chen Xinfang , Luo Yunxia , Li Shuhua
Published: April 2003

In this paper, the results of a systematic study of carbon black (CB)‐filled conducting polymer positive and negative temperature coefficient (PTC/NTC) effects are report. The conductivity of the composites jumps by several orders of magnitude at the critical value of carbon black. This critical value, øc, decreases with the increase of melt index and degree of crystallinity of the polymer. The crystalline lamellae just “modify” the distribution of carbon black and make the dispersion heterogeneous. Radiation cross‐linking enhances the PTC intensity and decreases the NTC effect of the materials. The electrical reproducibility of compounds is improved by the cross‐linking structure that reduces the freedom of carbon black movement at high temperature. The NTC phenomenon is related to the carbon black coagulation that facilitates electrical conduction at high temperature. The larger the melt index, the more easily carbon black coagulates. A new model was set up to explain the results successfully. © 1993 John Wiley & Sons, Inc.
Studies in the thermal degradation of poly(vinyl chloride)
Authors: Okieimen Felix E. , Ebhoaye Justus E.
Published: April 2003

Thermal degradation of poly(vinyl chloride) (PVC) was studied in nitrogen atmosphere in the presence of rubber seed oil and epoxidized rubber seed oil, barium and lead soaps of rubber seed oil, and epoxidized seed oil at various temperatures. The rate of dehydrochlorination at 1% degradation and the time required to attain 1% degradation were used to assess the effect of the thermal susceptibility of PVC to dehydrochlorination. It was found that epoxidized rubber seed oil, the metal soaps of rubber seed oil, and epoxidized rubber seed oil markedly enhance the thermal stability of PVC. The order of increasing stabilizing influence was metal soaps of epoxidized rubber seed oil > metal soaps of rubber seed oil > epoxidized rubber seed oil > rubber seed oil. © 1993 John Wiley & Sons, Inc.
COR‐eos and BH‐eos parameters for polymer melts with the error in the all‐variables method
Authors: Wohlfarth Christian
Published: April 2003

All the data for more than 100 polymer melts in a PVT data base were used to determine best‐fit characteristic parameters for two different theoretical equations‐of‐state (eos): the chain‐of‐rotators (COR) and the Bruce Hartmann (BH) eos. Fitting was performed by applying an error in all‐variables algorithm that was recently developed by Hartmann etal. Despite their very different theoretical basis, both equations‐of‐state led to close descriptions of the PVT surface with comparable average deviations. © 1993 John Wiley & Sons, Inc.
Nucleation and crystal growth of PEEK on carbon fiber
Authors: Zhang Zhiyi , Zeng Hanmin
Published: April 2003

The necleation and crystal growth of poly(ether ether ketone) (PEEK) on carbon fiber during isothermal crystallization were studied using optical microscopy. It was shown that the nucleation rate on the fiber is affected by the crystallization and melting temperatures. Transcrystallinity of PEEK was found to appear in the range 280–315°C after PEEK was melted at rather high temperature. Its linear growth rates at various temperatures were found to be similar to those of the spherulite in the bulk. Also, its thickness depends on the crystallization and melting temperatures. Variation of the molecular weight of PEEK within a small range has no obvious influence on its nucleation rate on the fiber, but affects the transcrystalline growth rate. © 1993 John Wiley & Sons, Inc.
Molecular mobility in styrene‐co‐methacrylic acid random copolymers from 100 to 450 K
Authors: Alberola N. , Bergeret A. , Battesti P. , Revillon A.
Published: April 2003

Molecular mobility of both the polystyrene homopolymer and a series of styrene‐co‐meth‐acrylic acid copolymers with various amounts of methacrylic acid is analyzed in the tem‐perature range from 100 to 450 K, by high‐resolution dynamic mechanical spectrometry, IR, and differential scanning calorimetry. Isochronal spectrometry exhibits for polystyrene homopolymer two relaxations, the β and α relaxations, with increasing temperature. Styrene‐co‐methacrylic acid copolymers exhibit three mechanical relaxations, the γ, β, and α re‐laxations, from 100 to 450 K. These relaxations could be related to the progressive occurring of motions of the side groups and of the backbone chains when increasing the temperature. This could be due to the progressive breakdown of hydrogen bonds, which could show a somewhat wide range of magnitude. Furthermore, The decreasing of the magnitude of the α relaxation with increasing methacrylic acid content could suggest the presence of a stable network of chemical cross‐links induced by the presence of anydride so that molecular mobility could be partially inhibited above Tg. The remaining of a fluctuation network of hydrogen bonds (labile contacts) above Tg could also emphasize the decrease in molecular mobility. © 1993 John Wiley & Sons, Inc.
Weathering of starch–polyethylene composite films in the marine environment
Authors: Breslin Vincent T. , Li Boen
Published: April 2003

Polyethylene and starch–polyethylene composite films were exposed outdoors in the straw‐line of a marsh and in sea water on flow‐through seatables in the laboratory. The deterioration of these films following exposure was measured by determining changes in tensile properties, weight loss, starch loss, and carbonyl content of the sheet plastic films. Low rates of deterioration were observed for control and starch–polyethylene composite films submerged in sea water. In contrast, both starch–polyethylene composite and control polyethylene films rapidly deteriorated during exposure in the strawline of a marsh. Differences in the observed rate of deterioration of the films placed in the exposure sites is attributed primarily to photodegradation of the films placed in the strawline of a marsh. © 1993 John Wiley & Sons, Inc.
Orientation distribution and layerlike morphology in extrusion‐molded sheets of a liquid crystalline copolyester amide
Authors: Kaito Akira , Kyotani Mutsumasa , Nakayama Kazuo
Published: April 2003

Fracture surface morphology and orientation distribution in the extrusion‐molded sheets of a thermotropic liquid crystalline copolyester amide were investigated by scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD), and polarized Fourier transform infrared (FTIR) microspectroscopy. The layerlike morphology consisting of two outer layers and a central layer between them was observed on the fracture surface. The microscopic orientation functions in the extrusion‐molded sheets were evaluated from the polarized FTIR microspectra that were measured in the microscopic domain 40 μm wide using a redundantly apertured infrared microscope. The microscopic orientation function in the outer layer was shown to be higher than that in the central layer. The effects of the draw‐down ratio and extrusion temperature on the orientation distribution and the layerlike morphology are discussed. © 1993 John Wiley & Sons, Inc.
Gas transport through integral‐asymmetric membranes: A comparison to isotropic film transport properties
Authors: Pfromm P. H. , Pinnau I. , Koros W. J.
Published: April 2003

Pressure‐normalized gas fluxes for defect‐free integral‐asymmetric membranes prepared according to a dry/wet phase inversion process were measured as a function of temperature and pressure and compared to measurements on thick isotropic films. Asymmetric membranes were prepared from polysulfone, polycarbonate, and poly(ester carbonate). The activation energies of permeation for O2 and N2 in the range of 25–55°C were higher for the asymmetric polysulfone membranes than for a thick isotropic film. O2/N2 selectivities of the asymmetric membranes are higher than those for isotropic films. The asymmetric membranes did not show the typical dualmode behavior for the CO2 flux as a function of pressure as determined for thick films. Differences in the free volume and its distribution in the ultrathin skin layer of the asymmetric membranes compared to isotropic films may be responsible for these results. © 1993 John Wiley & Sons, Inc.
Change of morphology in high molecular weight polyethylene during die drawing
Authors: Lee Y. W. , Li J. X.
Published: April 2003

Deformed high molecular weight polyethylene (HMWPE) rod, produced by die drawing at 115°C, was cleaved longitudinally at liquid nitrogen temperature and the cleaved surface was etched using a permanganic etching technique. A series of etched surfaces of HMWPE sections with different draw ratios (from 1 to 13) were analyzed employing scanning electron microscopy (SEM). The change of crystalline structure in HMWPE during die drawing was observed. In undrawn HMWPE. the spherulites were made up of sheaflike lamellae and scattered within the amorphous phase. During die drawing in the first instance, the microscopically inhomogeneous deformation occurred and the spherulites aligned along the drawing direction. At a draw ratio of about 7, local melting occurred, the spherulites disintegrated, and the sheaflike lamellae oriented, followed by straininduced recrystallization and the growth of the lamellae. Finally, at a draw ratio of about 12, the plastic deformation of the lamellae occurred and microfibrils were formed. © 1993 John Wiley & Sons, Inc.
Microporous polypropylene sheets containing CaCO3 filler
Authors: Nakamura Shunichi , Kaneko Shingo , Mizutani Yukio
Published: April 2003

Biaxial stretching of polypropylene sheets containing CaCO3 filler results in microporous sheets, that feel soft and dry. Their properties depend on filler content, particle size of the filler, and stretching degree etc. We have studied the dependency of some properties of the microporous polypropylene sheets on stretching degree. It is elucidated that mechanical properties are controllable by adjusting stretching degrees in machine and transverse directions. © 1993 John Wiley & Sons, Inc.
Kinetics of polyester fiber alkaline hydrolysis: Effect of temperature and cationic surfactants
Authors: Grancarić A. M. , Kallay N.
Published: April 2003

The surface kinetic model was applied to the interpretation of the dissolution of poly (ethylene terephthalate) fibers in alkaline medium. The model assumes first‐order kinetics with respect to surface area and concentration of OH−ions. The dependency of the rate constant of dissolution on temperature was treated by the Arrhenius equation. The addition of a cationic surfactant resulted in an increase in both activation energy and preexponential factor. © 1993 John Wiley & Sons, Inc.
Dynamic mechanical properties of short carbon fiber‐filled styrene–isoprene–styrene block copolymer
Authors: Roy D. , Bhowmick A. K. , De S. K.
Published: April 2003

The mechanical and dynamic mechanical properties of short carbon fiber‐filled styrene–isoprene–styrene (S–I–S) block thermoplastic elastomeric composite have been studied. Brabender mixing followed by milling of the fiber–rubber compositions caused about a 30‐fold decrease in the fiber aspect ratio and random fiber orientation. Although low‐strain moduli increased on fiber incorporation, tensile and tear properties dropped and anisotropy in mechanical properties was not observed. Tan δ values at the Tg region decreased on filler incorporation, but at room temperature, the tan δ values increased with filler loading. The variation of storage moduli and tan δ values with frequency followed a pattern similar to the variation of these properties with filler incorporation. © 1993 John Wiley & Sons, Inc.
Improved mechanical properties of NR/EPDM and NR/ butyl blends by precuring EPDM and butyl
Authors: Suma N. , Joseph Rani , George K. E.
Published: April 2003

Ethylene‐propylene‐diene rubber (EPDM) and isobutylene‐isoprene rubber (IIR) were compounded, precured to a low degree, and then were blended with natural rubber (NR). The compounding ingredients for NR were then added and the final curing was done. NR/EPDM and NR/IIR blends, prepared using this method, were found to possess much improved mechanical properties as compared to their conventional counterparts. The optimum precuring crosslink density that has to be given to the EPDM and IIR phases has been determined. © 1993 John Wiley & Sons, Inc.
The elastic modulus of filled polymer composites
Authors: He Dayong , Jiang Bingzheng
Published: April 2003

The elastic modulus of polyepichlorohydrin (PECH) filled with glass beads and wollastonite was studied. It was found that the elastic modulus of the composites depends not only on the volume fraction of the fillers but also on their size. Percolation theory was used to explain the experimental results. © 1993 John Wiley & Sons, Inc.
The chelating properties of chitosan fibers
Authors: Qin Yimin
Published: April 2003

Chitosan fibers were treated with aqueous solutions of CuSO4 and ZnSO4 for different periods of time to prepare samples containing different levels of metal‐ion contents. The effect of metal ions on the tensile properties of chitosan fibers was studied. It was found that after chelation of metal ions the chitosan fibers gained substantial increases in both dry and wet strengths. The metal ions were readily removed from the chitosan fibers by treatment with an aqueous EDTA solution. The effect of the degree of acetylation on the chelating ability of the chitosan fibers was also studied. It was found that after acetylation the chitosan fibers lost the chelating ability due to the conversion of primary amine groups to acetamide groups. © 1993 John Wiley & Sons, Inc.
Synthesis of phosphorus‐, zinc‐, and chlorine‐containing poly(ethylene terephthalate)
Authors: Troev K. , Kisiova Ts. , Grozeva At. , Borisov G.
Published: April 2003

Phosphorus‐, zinc‐, and chlorine‐containing oligomer was used as a comonomer including ionic bonds in its molecules in the synthesis of poly(ethylene terephthalate). Phosphorus‐, zinc‐, and chlorine‐containing poly(ethylene terephthalate) including ionic bonds in its main polymer chain was synthesized. With a content of 0.6% P and 1.25% Zn and 0.1% Cl, the resin has the following characteristics: ηrel= 1.407; COOH 39.90 mg equiv KOH/g 10−6; and mp 255.8°C. The modifier acts as a thermostabilizer. © 1993 John Wiley & Sons, Inc.
Effects of a polymeric additive in a biomedical poly(ether urethaneurea)
Authors: Freij‐Larsson Christina , Kober Maria , Wesslén Bengt , Willquist Eva , Tengvall Pentti
Published: April 2003

The biomedical poly(ether urethaneurea) Biomer has previously been shown to contain a standard antioxidant and a polymethacrylate additive with surface active properties. In the present communication, the latter additive has been shown to influence the morphology, mechanical properties, and surface chemistry of a poly(ether urethaneurea) with a composition similar to Biomer. It was shown that the in vitro blood compatibility of the poly(ether urethaneurea) was improved and that adsorption of fibrinogen from blood plasma decreased significantly due to the presence of the surface active polymethacrylate additive. © 1993 John Wiley & Sons, Inc.
Fibril formation in in situ composites of a thermotropic liquid crystalline polymer in a thermoplastic matrix
Authors: Crevecoeur G. , Groeninckx G.
Published: April 2003

Blends of a thermotropic liquid crystalline polymer, Vectra B950, and a matrix of poly (phenylene ether) and a polystyrene were extruded through a capillary designed to yield a converging flow with a constant elongational rate of strain. Fibril formation of the Vectra phase, initially dispersed as spherical droplets, was studied as a function of strain rate and blend composition. It was found that for blends with low Vectra contents, i.e., small Vectra particles, or below a minimum strain rate, no fibril formation takes place. These phenomena could be explained by the balance between interfacial tension and shear stress in the flow field. The critical conditions for fibril formation, estimated from these experiments, are comparable to the literature data. Furthermore, the elongational viscosity of the blends was calculated from the pressure gradient over the capillary. The elongational viscosity was found to decrease with Vectra content, to observe power‐law behavior, and to be three orders of magnitude larger than the shear viscosity of the blends. © 1993 John Wiley & Sons, Inc.
Statistical estimation of diffusion coefficients under finite bath, surface barrier conditions
Authors: Etters J. N.
Published: April 2003

When surface‐barrier effects are not taken into account, computation of diffusion coefficients from data obtained under finite bath conditions can lead to error. A technique is given by which the most probable diffusion coefficient and the most probable dimensionless surface barrier parameter simultaneously can be estimated for diffusant uptake by solid polymeric cylinders. © 1993 John Wiley & Sons, Inc.
Processing effects on optical anisotropy in spin‐coated polyimide films
Authors: Lin Linda , Bidstrup Sue Ann
Published: April 2003

The effects of spinning speed, substrate material, and thermal treatment on the optical anisotropy of spin‐coated polyimide films have been examined using the Metricon 2010 Prism Coupler to measure the birefringence. A decrease in the molecular orientation, as determined by birefringence, with increasing film thickness has been attributed to a stress gradient in the thickness of the film and the presence of air‐polymer‐substrate interfaces. The extent of the thickness dependence is a function of the polymer chain rigidity associated with the polyimide chemistry. The birefringence of the polymer film is also influenced by the substrate material due to the coefficient of thermal expansion mismatch between the film and the substrate. In addition, as a result of potential interdiffusion of solvent molecules and polymer segments between multiple layers of film, the birefringence in polyimide films obtained from multiple coatings of polyamic acid depends on the thermal treatment between the individual coatings. The birefringence of PMDA/ODA polyimide film derived from polyamic acid solution increases as the imidization temperature is increased to 400°C. For preimidized polyimide, the birefringence initially increases upon solvent removal, but decreases above 200°C, possibly indicating the occurrence of thermal cross‐linking. © 1993 John Wiley & Sons, Inc.
The effect of o‐phenyl phenol on the dyeing of an acrylic fiber with basic dyes
Authors: Kim J. P. , Burkinshaw S. M.
Published: April 2003

The equilibrium uptake of o‐phenyl phenol onto Courtelle S at 98°C was found to follow a Nernst adsorption mechanism, indicating that uptake arises by virtue of hydrophobic interaction as well as ion–dipole, dipole–dipole, and dipole‐induced dipole forces operating between the fiber and the nonionic carrier. Differential scanning calorimetry was used to demonstrate the plasticizing action of the carrier on Courtelle S yarn. A linear relationship was obtained between the extent of plasticization, as measured by reduction in Tg of the fiber, and concentration of carrier applied to the fiber with the maximum extent of plasticization, showing a close correspondence to the aqueous solubility of o‐phenyl phenol at 98°C, the temperature at which the fiber was treated with the carrier. The relationship between the extent of enhancement of uptake of C. I. Basic Green 4 and C. I. Basic Red 13 onto Courtelle S yarn at 98°C and concentration of the carrier in the dyebath was also examined: The concentration of o‐phenyl phenol that gave maximum enhancement of dye uptake coincided with the aqueous solubility of the carrier at 98°C. © 1993 John Wiley & Sons, Inc.
Novel cellulose derivatives. I. Liquid crystal phase formation in tri‐O‐α‐naphthylmethyl cellulose solutions
Authors: Davé Vipul , Frazier Charles E. , Glasser Wolfgang G.
Published: April 2003

Tri‐O‐α‐naphthylmethyl cellulose was prepared by homogeneous phase reaction using SO2–diethylamine (DEA)–dimethyl sulfoxide (DMSO) as the solvent system. Observations made by dynamic mechanical spectrometry and by cross‐polarized optical microscopy revealed liquid crystalline behavior for the concentrated solutions of tri‐O‐α‐naphthylmethyl cellulose in dimethylacetamide (DMAc). Experimental and calculated (predicted) critical volume fraction of the derivative, Vcp, did not show agreement. It is determined that Vcp is affected by bulky substituents on the cellulose backbone to some extent. © 1993 John Wiley & Sons, Inc.
Structure development during dynamic vulcanization of hydrogenated nitrile rubber/nylon blends
Authors: Bhowmick Anil K. , Inoue Takashi
Published: April 2003

The factors that influence the morphology and the interfacial parameters during dynamic vulcanization of hydrogenated nitrile rubber/nylon blends are examined. The particle size of the dispersed phase (R̄) and the correlation distance (ξ) of a 50 : 50 blend decreased with increasing mixing time at 250°C, attained a minimum value, and then increased. The increase in the number of particles with time (dn/dt) may be expressed as (dn/dt) = k'nm, where n is the number of dispersed particles at time t, and m and k' are constants. R̄ and ξ gradually increased as the mixing temperature was increased from 250 to 300°C at a constant mixing time of 10 min. The particle size increased also with the increasing gel fraction of the rubber. At a constant mixing time of 10 min at 250°C, the particles were larger when the addition of the cross‐linker was delayed. These observations can be explained with the help of a hypothetical model, similar to that proposed by Wu, considering the breaking down of rubber particles, coagulation and coalescence of droplets, and droplet rupture in a matrix of nylon. On vulcanization, the thickness of the interface (λ) reduced from 62 to 48 nm. The interaction parameter and interfacial tension, as estimated from λ, for a bilayer specimen vulcanized in situ, at 250°C were 2.8 × 10–3 and 0.24 mN/m, respectively. The high value of λ for the dissimilar polymer pair may be due to polymer‐polymer graft formation at high temperature. © 1993 John Wiley & Sons, Inc.
Semicontinuous emulsion copolymerization to obtain styrene–methyl acrylate copolymers with predetermined chemical composition distributions
Authors: Schoonbrood Harold A. S. , Thijssen Henk A. , Brouns Harry M. G. , Peters Matt , German Anton L.
Published: April 2003

Four types of emulsion copolymerization processes were applied to produce various styrene–methyl acrylate copolymer latices. (1) Batch emulsion copolymerization. (2) Monomer starved semicontinuous emulsion copolymerization, i.e., a monomer mixture of constant composition was fed to the reactor at a constant rate. Sufficiently low addition rates led to homogeneous copolymers. (3) Optimal addition rate profiles were used to produce homogeneous emulsion copolymers in relatively short times. The profiles were determined in a semiempirical way, and applied to three different copolymer compositions. (4) We made an attempt to determine an addition rate profile to produce a heterogeneous emulsion copolymer with predetermined heterogeneity, i.e., a copolymer of which the chemical composition distribution (CCD) did not consist of one narrow peak, as with homogeneous copolymers, but had a predetermined broadness profile. Strategies (2) and (3) were used to produce homogeneous emulsion copolymers with varying fractions of styrene. Strategy (3) was also used to demonstrate the influence of the monomer ratio on the kinetics. The advantage of this method is that the monomer ratio is constant over the whole conversion range in the latex particles. High performance liquid chromatography (HPLC) was used to determine the homogeneity/heterogeneity of the copolymers produced, and proved to be invaluable in determining the optimal addition rate profile. The final goal will be to study the influence of the chemical composition distribution (CCD) on mechanical properties of these copolymers, as both homopolymers used in this study have quite differentglass transition temperatures; the results will be published later. © 1993 John Wiley & Sons, Inc.
On the chemistry, behavior, and cure acceleration of phenol–formaldehyde resins under very alkaline conditions
Authors: Pizzi A. , Stephanou A.
Published: April 2003

The curing acceleration by organic esters of alkaline phenol‐formaldehyde (PF) resins can be explained by two different mechanisms. In the course of the work, the unexpected curing behavior of PF resins alone, under very alkaline conditions, was observed, which diverged from past assumptions. PF resins curing, which is supposed to be accelerated by the formation of phenate ions, is instead markedly slowed down by increasingly alkaline pHs and accelerates in the presence of esters. The mechanism of ester acceleration of PF resins curing was clarified and the effect of different esters was quantified and was related to the pKa and quantity of the acid forming the ester. A second mechanism, which appeared also to explain the peculiar slowing down at increasing pH of PF resin curing, could not be confirmed; some evidence appeared clearly to deny it. The impossibility of isolating an Na+ phenol ring complex, theorized by other authors and other evidence, indicates that this second mechanism is unlikely to occur. © 1993 John Wiley & Sons, Inc.
Membranes of semicrystalline aliphatic polyamide nylon 4,6: Formation by diffusion‐induced phase separation
Authors: Bulte A. M. W. , Folkers B. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

The preparation of membranes of nylon 4,6 by diffusion‐induced phase separation (DIPS) using formic acid as a solvent and water as a nonsolvent was studied. Nylon 4,6 is a semi‐crystalline polymer; phase separation from a solution can occur by solid–liquid (s–l) de‐mixing as well as by liquid–liquid (l–l) demixing. Upon quenching films of solutions with low polymer concentration (< 17 wt %) in a nonsolvent bath containing water, the morphology of the membranes show a foam‐like structure typical for l–l demixing. When phase separation is induced by water vapor a transition in structure occurs from the cellular type to a morphology typical for s–l phase separated films. At higher polymer concentrations membranes exhibit structures consisting of spheres or smaller crystal‐like units resulting from an s–l phase separation process. The addition of 2 wt % or more of water to polymer solutions with low concentration (up to 15 wt %) resulted in s–l demixing as well. In a DIPS process s–l demixing is kinetically competitive with l–l demixing if nuclei are already present in the starting solutions (heterogeneous nucleation), or if a relatively long time is available for crystal nuclei to be formed. The morphology resulting from s–l demixing is a result of spherulitic crystallization. A certain concentration of nuclei or of precursor particles already present results in a small nucleation density during precipitation and thus large spherulites can be grown; at higher polymer and/or water concentrations the nucleation density increases resulting in an axialitic morphology of the membranes. © 1993 John Wiley & Sons, Inc.
Crystallinity, particle size, and mechanical properties of fibers in some egyptian and american cotton cultivars
Authors: Abdel‐Rehim Salwa A. , Ahmed Naeima A. , Hammad S. M. , Askalany Zeinab M.
Published: April 2003

The main objective of this study was to measure the crystallinity, particle size, and mechanical properties of fibers and to assess their relationship in 18 Egyptian and American cotton cultivars. Remarkable variations in crystallinity were found, ranging between 49 and 90%, whereas the range of differences in particle size was somewhat narrow, and so its effect on mechanical properties was not detectable. The cotton cultivars that have higher values of crystallinity are characterized by higher values of tenacity at either \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{1}{8} $\end{document} in. or zero gauge and stiffness and by reduced elongation. © 1993 John Wiley & Sons, Inc.
The interfacial polycondensation of tetrabromobisphenol‐A polycarbonate. II. Reactivities and phase distribution of catalysts
Authors: Gu Jen‐Tau , Wang Chun‐Shan
Published: April 2003

Tetrabromobisphenol‐A (TBBPA), a sterically hindered bisphenol, is known to give only low molecular weight polymers using the interfacial process. The low reactivity is attributed to the bulkiness and electron‐withdrawing bromine substituents at the ortho positions. The optimum reaction conditions for the interfacial polymerization of TBBPA using pyridine derivatives as a catalyst have been developed. From the two‐phase concentration distribution constant (Ke) and pK's values of triethylamine, 4‐dimethylaminopyridine (DMAP), and TBBPA, the critical process parameters were obtained. Because of its high nucleophilicity and facile leaving character, the DMAP catalyst system produces a high molecular weight TBBPA–polycarbonate (PC) successfully. The profile of the process was followed to obtain a better understanding of the reaction mechanism. © 1993 John Wiley & Sons, Inc.
Plasma treatment of polypropylene surfaces: Characterization by contact‐angle measurements
Authors: Wittenbeck P. , Wokaun A.
Published: April 2003

Air plasma treatment has been used to introduce polar functional groups onto polypropylene surfaces to enhance the adhesion of coatings and paints. Plasma exposure times as well as the reaction medium (ambient, technical, and moistured technical air) have been varied. Time‐dependent changes subsequent to the plasma treatment are monitored by contact‐angle measurements. After short plasma exposures, the polar component of the surface energy is observed to decrease, to reach a minimum after ≈ 40 min. This behavior is interpreted in terms of a rotation of the introduced surface hydroperoxide groups into the interior of the polymer. This undesired loss in surface functionalization can be avoided by (a) increasing the treatment time in dry air, (b) use of moistured air as the reaction medium, or (c) posttreatment of the plasma‐treated parts by water immersion. A plasma exposure of 120 s in dry air, followed by posttreatment in an aqueous medium at room temperature for 2–5 min, results in reproducible values of the surface energy σ, with polarities (σpolar/σtotal) close to the desired value of ≈ 50%. © 1993 John Wiley & Sons, Inc.
Bound rubber theory and experiment
Authors: Meissner B.
Published: April 2003

Adsorption of polymer on filler from bulk is known to result in a partial loss of polymer solubility (“bound rubber”). The existing theories of this phenomenon were critically examined, and the random adsorption model suggested by the author was found to provide the most complete explanation of available experimental data. Theory based on this model and containing one adjustable parameter (filler surface area per adsorption site) correctly predicts the change of molar mass distribution with adsorption on filler and satisfactorily describes the experimental dependence of fraction B of the filler‐bound polymer on filler concentration and surface area and on Mw of the polymer, in both narrow and very broad molar mass distributions. No distinct effect on B of a moderate degree of branching of EPM, EPDM chains could be detected. It is concluded that the modification of the random adsorption model suggested by Shiga is not warranted, neither theoretically nor experimentally. © 1993 John Wiley & Sons, Inc.
Synthesis of N‐(aminoalkyl) chitosan for microcapsules
Authors: Dunn E. J. , Zhang X. , Sun D. , Goosen M. F. A.
Published: April 2003

Chitosan was chemically modified by alkylation with N‐(2‐bromoethyl) phthalimide, N‐(3‐bromopropyl) phthalimide, and N‐(4‐bromobutyl) phthalimide. The resulting N‐(phthalidimidoalkyl) chitosans were treated with hydrazine to remove the phthalidimido group resulting in the final N‐(aminoalkyl) chitosan products. For comparison purposes, poly(vinyl alcohol) (PVA) was alkylated with N‐(3‐bromopropyl) phthalimide, then treated with hydrazine to give the N‐(3‐aminopropyl) PVA product. All alkylation products were characterized by solution 1H‐ and 13C‐NMR and by solid‐state CP‐MAS 13C‐NMR. The above synthetic polymer derivatives, as well as chitosan, polyallyl amine, and polyethylen‐imine, were used to form membrane coatings around calcium alginate beads in which blue dextran of molecular weight 7.08×104 or 26.6×104 was entrapped. These microcapsules were prepared by extrusion of a solution of blue dextran in sodium alginate into a solution containing calcium chloride and the membrane polymer. Membrane integrity and permeability were assessed by measuring the elution of the blue dextran from the capsules, spectrophotometrically. © 1993 John Wiley & Sons, Inc.
Synthesis of water‐soluble polyamidoamines for biomedical applications. II. Polymers possessing intrachain‐type secondary amino groups suitable for side‐chain attachment
Authors: Caldwell Gregg , Neuse Eberhard W. , Stephanou Andreas
Published: April 2003

As part of a program to synthesize water‐soluble polymeric carriers suitable for drug binding, the polyaddition reaction of methylenebisacrylamide with comonomers containing two pri‐mary amino groups is investigated. The copolymerization of the bisacrylamide with equi‐molar quantities of primary diamines under properly controlled experimental conditions is found to proceed in a linear propagation, giving rise to the formation of polyamides comprising two or more secondary amino groups in the recurring unit. Selected diamine monomers include ethylenediamine, diethylenetriamine, triethylenetetramine, 1,2‐bis (3‐aminopropylamino) ethane, and three 0,0´‐bis‐(2‐aminopropyl) derivatives of poly(ethylene glycol) of different chain length, the last three monomers being chosen because of their outstanding hydrosolubilizing properties. Use of two different diamines in the proper stoi‐chiometry leads to corresponding copolymers. The reactions are conducted in aqueous phase over periods of 1–3 days at 65°C, and the polymeric products, possessing the linear polyamidoamine structures 1 and 2, are fractionated by dialysis in membrane tubing with 12000–14000 molecular‐mass cutoff and are isolated by freeze‐drying as solid or resinous materials possessing complete solubility in water. Inherent viscosities are in the range of 8– 40mLg‐1. Microanalytical and spectroscopic data confirm the proposed structures. The suitability of the intrachain secondary amine functions for side chain attachment and drug coupling is demonstrated in model reactions involving N‐substitution. © 1993 John Wiley & Sons, Inc.
Gas‐phase polymerization of ethylene using MgCl2/ethyl benzoate/TiCl4 + triethylaluminum catalyst: Effects of triethylaluminum and temperature
Authors: Dusseault John J. A. , Hsu Cheng C.
Published: April 2003

A gas‐phase reactor system was developed to polymerize ethylene using the MgCl2/ethyl benzoate (EB)/TiCl4+ triethylaluminum (TEA) catalyst. The reproducibility of the reactor was tested and found to be adequate for kinetic study. The effects of TEA and temperature were studied with the multisite model that assumes a multiplicity of active sites. It was found that the productivity increased with Al/Ti molar ratio while initial activity leveled off. The deactivation rate, after an initial increase, Al/Ti molar that assumes a multiplicity of active sites. It was found that the productivity increase, decreased with Al/Ti. This corresponded with a transition in deactivation order: below Al/Ti = 70, first‐order deactivation was predominant; above Al/Ti = 70, second‐order deactivation was predominant. The second‐order deactivation reactions were made less disperse at higher Al/Ti. Molecular weight of the polyethylene was very high (> 1,000,000) indicating negligible transfer reactions. For Al/Ti > 130 a monomer sorption limitation for polymerization was found. The effect of temperature was also studied with a maximum in productivity at 55°C for Al/Ti = 98.0 and no maximum when Al/Ti = 53.0. Apparent activation energies (Ea) for activity were found to be 19.5 ±3.3 kJ/mol at Al/Ti = 98.0 and 9.3±1.1 kJ/mol at Al/Ti = 53.0. for deactivation Ea was found to be 36.6±5.0 kJ/mol at Al/Ti = 98.0 and–15.5± 4.4 kJ/ mol at Al/Ti = 53.0. Temperature increased the dispersity of second‐order deactivation reactions. © 1993 John Wiley & Sons, Inc.
Pervaporation separation of binary organic‐aqueous liquid mixtures using crosslinked PVA membranes. I. Characterization of the reaction between PVA and PAA
Authors: Rhim Ji‐Won , Sohn Min‐Young , Joo Hyeok‐Jong , Lee Kew‐Ho
Published: April 2003

For the purposes of the water‐selective membrane material development for pervaporation separation, poly(vinyl alcohol) (PVA) was crosslinked with a low molecular weight of poly(acrylic acid) (PAA). The crosslinking reactions between PVA and PAA were characterized through IR spectroscopy, differential scanning calorimetry (DSC), and tensile tests when varying the reactions conditions, that is, time, temperature, amounts of cross‐linking agents, PAA. It was found that the crosslinking reaction was fast: in other words, that the reaction mainly occurred at the initial step of each reaction condition. The best reaction conditions for preparing the crosslinked PVA membranes were found to be: reaction time not over 1 h, reaction temperature in the range of 150–180°C. PAA contents of 15–20 wt % were found satisfactory with respect to the application areas. © 1993 John Wiley & Sons, Inc.
The molecular orientation and mechanical properties of poly(ethylene terephthalate) under uniaxial extension
Authors: Chang C. L. , Chiu W. Y. , Hsieh K. H. , Ma C.‐C. M.
Published: April 2003

The molecular orientation, induced crystallization, and mechanical properties of amorphous poly(ethylene terephthalate) (PET), stretched at different temperatures and strain rates, were studied. The results indicate that the orientation parameter [P2(cosθ)] of oriented PET varies strongly with both temperature and strain rate, but the strain‐induced crystallinity seems dependent on temperature only. It was also found that as draw ratio increased, the Young's modulus, yield stress, and necking ratio were greatly improved in the stretching direction, but slightly declined in the transverse direction. A rubber network model was used to make a quantitative description of the orientation development with draw ratio. © 1993 John Wiley & Sons, Inc.
Measurement of adhesion between fibers and fast curing elastomer resin
Authors: Epstein M. , Shishoo R. L.
Published: April 2003

A method was developed to measure the adhesion between fibers and fast curing elastomer, in droplet form, using the microbond pull‐out method. Samples were fabricated by arranging the fibers as a grid on which elastomer droplets were formed for testing. A droplet sliding test method was developed to investigate the nature of the sites of the droplets on the fiber after displacement of the droplets. Fibers of polyester, aramid, and HMW‐polyethylene were tested with resins of polyurethane and natural rubber latex. The fibers had been surface‐treated by corona, gamma radiation, or methanol extraction. The shape of the droplets was determined by microscopic measurement. The shear strength of the fiber/matrix bond was tested using a microvise grip in a tensile strength tester. © 1993 John Wiley & Sons, Inc.
Flexural strength, toughness, and fracture properties of polyester composites
Authors: Vipulanandan C. , Mebarkia S.
Published: April 2003

Flexural behavior of particle‐filled fiber‐reinforced polyester composite was investigated by varying the polymer and fiber contents. The polymer content was varied between 10% and 18% of the total weight of the polyester composite (PC) and the glass fiber content was varied up to 6% (by weight of PC). The chopped glass fibers were 13 mm long. The fine aggregates were well graded, with particle size varying from 0.1 to 5 mm, and were mainly composed of quartz. The fine aggregates and glass fibers were also pretreated with a coupling agent (γ‐methacryloxypropyltrimethoxysilane, γ‐MPS) to improve the mechanical and fracture properties of the polyester composites. In general, the addition of fibers increased the flexural strength, toughness, fracture properties, and failure strain (strain at peak stress), but the flexural modulus of polyester composites remained almost unchanged. The addition of 6% fiber content and silane treatment increased flexural strength of 18% PC by 95% to 41.6 MPa (6,040 psi). Crack resistance curves, based on the stress intensity factor (KR‐curve), have been developed for the fiber‐reinforced PC systems. A two‐parameter relationship was used to predict the complete flexural stress‐strain data. There is good agreement between the predicted and measured stress‐strain relationships. © 1993 John Wiley & Sons, Inc.
Development of a new advanced process for manufacturing polyacetal resins. Part II. Vapor‐liquid equilibrium of formaldehyde‐water system
Authors: Masamoto J. , Matsuzaki K. , Morishita H.
Published: April 2003

To develop a new technology for the purification of formaldehyde from formalin by a distillation method, the vapor‐liquid equilibrium of formaldehyde—water binary systems was investigated. Based on the studies of Thompson et al. and Iliceto et al., the vaporliquid equilibrium of formaldehyde and water are calculated and these calculations are in good agreement with the reported data. It was found that the vapor pressure of formaldehyde is determined by the free formaldehyde concentration (mol/L), whereas the vapor pressure of water is determined by the molar ratio of free water. The vapor‐liquid equilibrium of formaldehyde‐water in the presence of a diluent was also investigated. It was shown by calculation that in some cases, when the concentration of the diluent is high, the volatility of formaldehyde is always higher than that of water and these calculations are in good agreement with experimental data. Based on this principle, the purification of formaldehyde by an extraction distillation method was established. © 1993 John Wiley & Sons, Inc.
Chain extension of recycled poly(ethylene terephthalate) with 2,2′‐Bis(2‐oxazoline)
Authors: Cardi Nicoletta , Po Riccardo , Giannotta Giorgio , Occhiello Ernesto , Garbassi Fabio , Messina Giuseppe
Published: April 2003

2,2′‐Bis(2‐oxazoline) was used as a chain extender during processing in a twin‐screw extruder with the aim of counteracting degradation phenomena in recycled poly(ethylene terephthalate) (PET). The same experiments were performed on fiber‐grade PET for comparison purposes. Rheological characterization showed that while the melt viscosity of fiber‐grade PET at constant temperature and shear rate is quite constant with time, that of recycled PET decreases dramatically. By addition of oxazoline, an increase of melt viscosity occurs for fiber‐grade PET, whereas for recycled PET, thermal and hydrolitic degradation effects are partially compensated. Characterization was performed by solution viscosity measurements, gel permeation chromatography, and COOH end‐group titration on samples obtained at variable residence times at 280°C. Lower molecular weights accompanied by a higher amount of COOH were observed; the use of oxazoline resulted in higher molecular weights and lower COOH concentrations at equal residence times, while polydispersity did not vary. © 1993 John Wiley & Sons, Inc.
Removal and recovery of gallium ion from solution by insoluble amphoteric starches
Authors: Chan Wu‐Chung
Published: April 2003

The removal and recovery of gallium ion (Ga+3) from a solution with the high cross‐linked amphoteric starches containing the phosphate anionic group and the quaternary ammonium or tertiary amine cationic group was investigated. The adsorption capacity of tertiary amine phosphate starch (TAP) and quaternary ammonium phosphate starch (QAP) is 0.54 and 0.48 meq/g, respectively. The adsorption process has been found to be concentration dependent and endothermic, and follows the Langmuir isothermal adsorption. The heat of adsorption (ΔH) is equal to 7.65 kcal/mol for the QAP and equal to 7.65 kcal/mol for the TAP. The percentage of adsorbed Ga+3 ion decreases when HCl, H2SO4, NaCl, or Na2SO4 is added to the solution. The Ga+3 ion adsorbed on the adsorbents can be recovered by treating with an NaOH or HCl solution (1M and 3M); the maximum percentage of recovery is about 70% when 1M NaOH solution is used. © 1993 John Wiley & Sons, Inc.