bluuebunny/crossref_metadata_2025_split huggingface dataset:
Double melting phenomena of polyphenylene sulfide and its blends
Authors: Mai Kancheng , Zhang Mingqiu , Zeng Hanmin , Qi Shicheng 
Published: April 2003

AbstractThe melting behavior of PPS (polyphenylene sulfide) and its blends with PSF (bisphenol A polysulfone) and PEK‐C (polyetherketone with phthalidylidene groups) are investigated with DSC technique. It is found that, with a rise in melt temperature Tmelt and melt time tmelt, the intensities of the lower melting peaks of PPS increase while those of the upper ones decrease or disappear in some cases, which can be attributed to the obstructive effect of branching or crosslinking of PPS macromolecules on the crystallization of PPS at higher temperature. As the annealing crystallization temperature increases, both the peak temperatures and intensities of the lower melting peaks of PPS increase. PSF and PEK‐C have no influence on the lower melting peaks of PPS but are unfavorable to the crystallization of the higher melting species. The double melting behavior of the PPS component in the blends is much more susceptible to the changes in Tmelt and tmelt than that of neat PPS. © 1994 John Wiley & Sons, Inc.
Kinetic study of acrylic monomer grafting in the presence of a polyfunctional monomer onto radioperoxided poly(ethylene–tetrafluoroethylene) copolymer
Authors: Gineste Jean‐Luc , Largueze Christophe , Pourcelly Gerald 
Published: April 2003

AbstractAcrylic acid (AA), methacrylic acid (MA) and diethyleneglycol dimethacrylate (DEGDM) are grafted onto 100 μm radioperoxided poly(ethylene–tetrafluroethylene) copolymer (ETFE). The influences of the homopolymerization inhibitor, the solvent, the grafting temperature, and the monomer content on the grafting kinetics are studied. For the grafting of acrylic monomers, the limitation of the grafting yield is more important for AA grafting whatever the nature of the metallic salt; the difference between the two homopolymerization inhibitors is their respective concentration to obtain a given grafting yield. For the AA + DEGDM cografting, the grafting yield increases with the DEGDM content of the grafting solution. In both cases, the overall activation energy has been calculated, and its variation as a function of the composition of the grafting solution is discussed. © 1994 John Wiley & Sons, Inc.
Heat sealing of semicrystalline polymer films. I. Calculation and measurement of interfacial temperatures: Effect of process variables on seal properties
Authors: Meka Prasadarao , Stehling Ferdinand C. 
Published: April 2003

AbstractA finite element analysis (FEA) modeling technique was used to predict the interfacial temperature as a function of time during the sealing of semicrystalline polymer films. An experimental technique using micro‐thermocouples to measure rapidly changing interfacial temperatures during sealing was also developed. Agreement between predicted interfacial temperature profiles and measured values for polyethylene films was good except at temperatures substantially above the final melting point of the polymer. This deviation is caused by film‐thickness changes occurring during sealing that are not taken into account in the calculations. The effect of heat‐sealing process variables (seal bar temperature, dwell time, and pressure) on seal properties (seal strength, seal elongation, and seal energy) of polyethylene films has also been quantitatively determined. Seal properties are determined primarily by the maximum temperature achieved at the interface during heat sealing. Dwell time must be sufficiently long to bring the interfacial temperature to a desired level, but longer times at a given interfacial temperature do not improve seal properties at the conditions of our experiments. A slight pressure is helpful in bringing two microscopically uneven film surfaces into intimate contact, but higher pressure has no beneficial influence on seal properties. However, increased pressures and dwell times at temperatures above the final melting point of the polymer are detrimental to seal appearance due to material deformation in the sealing area. © 1994 John Wiley & Sons, Inc.
Heat sealing of semicrystalline polymer films. III. Effect of corona discharge treatment of LLDPE
Authors: Farley James M. , Meka Prasadarao 
Published: April 2003

AbstractThe effects of corona‐discharge treatment (CDT) of commercial polyethylene (PE) Linear low‐density PE (LLDPE) were studied with special emphasis on the heat‐seal behavior of treated films. A range of treat levels, representative of those used in industry, was obtained by varying the applied power to a commercial, on‐line treater. Film surfaces were characterized by XPS and wetting‐tension measurements. The primary effect of CDT on the heat‐sealing behavior of LLDPE films is a transition in the failure mode of heat seals from a normal tearing or inseparable bond to a peelable seal. In addition, CDT increases the seal initiation temperature 5–17°C and decreases the plateau seal strength 5–20% as the treat level, or wetting tension, increases from 31 to 56 dynes/cm. These effects are attributed to cross‐linking during corona treatment, which restricts polymer mobility near the surface and limits the extent of interdiffusion and entaglements across the seal interface. Results of heat‐sealing studies with electron‐beam‐irradiated PE, chemically oxidized PE, and CDT polypropylene (PP) provide indirect evidence for the proposed surface cross‐linking mechanism. The effect of commercial levels of slip additives on the heat‐seal behavior was also investigated. © 1994 John Wiley & Sons, Inc.
A kinetic study of the effect of three catalytic systems on the curing of an unsaturated polyester resin
Authors: Salla J. M. , Ramis X. 
Published: April 2003

AbstractWe studied by differential scanning calorimetry (DSC) the influence of three tertiary amines used as promoters on the curing kinetics of unsaturated polyester resins catalyzed with an organic peroxide. The kinetic study was made by means of the analysis of isothermal experiments and we used a kinetic model that does not presuppose knowledge of the experimental rate equation f(α), which relates the reaction rate dα/dt at constant temperature with the degree of conversion α through a rate constant k according to dα/dt = kf(α). It is thus possible to predict the time, temperature, and degree of curing without needing to know f(α). This model makes a linear relation between the logarithm of time needed to reach a given degree of conversion with the inverse of the inverse of the curing temperature according to the expression ln t = A+E/RT for a constant α, where A is a constant, R is the universal gas constant, and E the activation energy. The proposed model has been used to calculate the activation energies for each degree of conversion according to the type and amount of promoter used. From the relation between the time and the curing temperature for a given conversion, it is possible to predict values of curing time for different temperatures. We thus simulated curing kinetics by using the proposed model and compared them with those obtained experimentally by DSC. © 1994 John Wiley & Sons, Inc.
Preparation and characterization of polymers with pending UV‐absorber groups. I. Polymers based on polydimethylsiloxane
Authors: Riedel Jan‐H. , Höcker H. 
Published: April 2003

AbstractThe hydrosilylation reaction using dichloro(dicyclopentadiene) platinium (II) as catalyst is carried out to synthesize polymeric UV absorbers with polysiloxane backbone. An almost quantitative addition of vinyl groups of the UV absorber (benzophenone) to silane groups is observed. The IR spectra indicate the qualitative results of the reaction, whereas the 1H‐NMR spectra allow the following of the reaction quantitatively. Low glass transition temperatures are observed by DSC. UV spectroscopy shows that the extinction coefficient and spectra of the UV absorbers are hardly affected by the polymer analogous reaction. © 1994 John Wiley & Sons, Inc.
Structure and properties of poly(vinyl alcohol)–iodine complex formed in the crystal phase of poly(vinyl alcohol) films
Authors: Choi Yoon‐So , Miyasaka Keizo 
Published: April 2003

AbstractThe structure and optical properties of the complex formed in the crystal phase of PVA that is caused by soaking at very high iodine concentration are investigated. In the resonance Raman spectra of lightly and heavily iodinated specimens, two Raman shifts appeared at 109 and 161 cm−1. The 109 cm−1 peak due to the I mode was much stronger than the 161 cm−1 peak in a heavily iodinated specimen, whereas the peak was comparable with the 161 cm−1 peak in a lightly iodinated specimen. The complex formed in the crystal phase is identified as the I mode complex. It has an averaged iodine–iodine distance of 3.2 Å, which is different from the 3.08 Å of the I mode complex formed in the amorphous phase. The effect of KI concentration in the soaking solution on the formation of the complex is also examined. The increased KI concentration in the soaking solutions at a fixed iodine concentration increases the amount of the complex formed in the crystal phase. The change in the hydrogen‐bonding state in the crystal phase with the complex formation can be evidenced by IR and NMR. © 1994 John Wiley & Sons, Inc.
Effect of chain microstructure on modulus of ethylene–α‐olefin copolymers
Authors: Sehanobish K. , Patel R. M. , Croft B. A. , Chum S. P. , Kao C. I. 
Published: April 2003

AbstractA family of copolymers of ethylene and α‐olefin resins with homogeneous branching distribution, which behaves as elastomers at high short‐chain branching levels and acts as typical thermoplastics at low short‐chain branching levels, is now available. Control of this broad range of properties stems from the ability to control the molecular architecture more effectively using Dow's INSITETrademark of The Dow Chemical Co.
technology than in the past. Due to the unique combination of narrow short‐chain branching distribution (SCBD) and narrow molecular weight distribution (MWD), these resins provide a unique opportunity to model structure/property relationships in branched ethylene‐α‐olefin copolymers. The modulus in branched ethylene‐α‐olefin copolymers with aliphatic branches is shown to be primarily dictated by crystallinity. It is shown that the branch distribution and the branch type have an insignificant effect on the modulus of ethylene copolymers containing aliphatic branches at a given crystallinity. Modulus data have been successfully modeled in such systems using a lamellar fiber‐reinforced amorphous matrix composite model. Switching from aliphatic branches to cyclic branches significantly affected the modulus at similar crystallinities. © 1994 John Wiley & Sons, Inc.
Metallization of polyimide film by wet process
Authors: Ho Syh‐Ming , Wang Tsung‐Hsiung , Chen Han‐Lung , Chen Ker‐Ming , Lian Syh‐Ming , Hung Aina 
Published: April 2003

AbstractThe interfacial adhesion strength of metallized polyimide (BPDA/ODA/PDA) has been studied with respect to polyimide surface molecular structure, reactions during electroless nickel deposition, baking, copper electroplating, and thickness of polyimide film. Each factor is discussed in terms of its influence on the peel strength. For practical application, operation at optimized conditions for each step of the metallization process is essential for sustaining the mechanical integrity of the copper/polyimide laminate. © 1994 John Wiley & Sons, Inc.
Low dielectric, fluorinated polyimide copolymers
Authors: Stoakley Diane M. , St. Clair Anne K. , Croall Catharine I. 
Published: April 2003

AbstractCopolymers of fluorinated polyimides and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) have been prepared as films and composite laminates. The addition of BPDA was used as a means to achieve insolubility, making the polymers suitable as aircraft matrix resins. Glass transition temperatures, thermooxidative stabilities, and tensile strengths were increased with increasing BPDA content in the copolymers. Although the addition of BPDA did increase the UV cutoff and decrease the percent transmission slightly, the optical transparency of the polymers was still excellent. Dielectric constants of the copolyimide films ranged from 2.6 to 2.9. Astroquartz II laminates made with these resins had dielectric constant of 3.3–3.4. Flexural strength on unidirectional specimens were in the 1.24–1.41 GPa range and flexural moduli were 41 GPa. © 1994 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.
Monosize polystyrene latices carrying functional groups on their surfaces
Authors: Tuncel Ali , Kahraman Ridvan , Piskin Erhan 
Published: April 2003

AbstractIn this study, monosized polystyrene (PS) latices were prepared by dispersion polymerization of styrene in isopropanol‐water media using poly(acrylic acid) (PAA) as a steric stabilizer and 2,2′‐azobisizobutyronitrile (AIBN) as an initiator. The effects of initiator and stabilizer concentrations, alcohol/water and monomer/dispersion medium ratio on the polymerization kinetics, and the size and monodispersity of PS latices were experimented with in a stirred reactor system. Monosize PS beads in the size range of 1.0–3.0 μm were obtained. The PS latex obtained in the first step having a diameter of 2.3 μm were used as the seed latex, and styrene/acrylate monomers, acrylic acid (AA), 2‐hydroxyethyl methacrylate (HEMA), and dimethylaminoethyl methacrylate (DMAEMA) were copolymerized onto the PS latex particles. The incorporation of functional groups to the surface and bulk structure of PS was confirmed by IR, FTIR, XPS, and zeta potential measurements. © 1994 John Wiley & Sons, Inc.
Studies on the thermal and curing behavior of polyimide blends
Authors: Choudhary Veena , Pearce E. M. 
Published: April 2003

AbstractBlends of thermosetting (Thermid MC‐600 and Thermid FA‐700) and thermoplastic (UL‐TEM 1000) polyimide resins with different compositions were prepared. Curing and thermal behavior of the blends were investigated using differential scanning calorimetry and dynamic thermogravimetry in a nitrogen atmosphere. The peak exotherm temperature increased with increasing amount of thermoplastic resin, whereas the heat of polymerization decreased. The electrical characteristics of the blends were also investigated using a dielectric analyzer. Dynamic as well as isothermal scans were recorded. Ionic conductivity, permittivity, and the loss factor were measured as a function of temperature at various frequencies. These results showed the complete curing of the resins having 50% Ultem at 225°C in 1 h, whereas Thermid MC‐600 required a postcuring step to observe fully cured resins. A marginal decrease in thermal stability was observed on blending. © 1994 John Wiley & Sons, Inc.
Determination of filler content in rice husk ash and wood‐based composites by thermogravimetric analysis
Authors: Fuad M. Y. Ahmad , Zaini M. J. , Jamaludin Mustafah , Ishak Z. A. Mohd , Omar A. K. Mohd 
Published: April 2003

AbstractThree new types of fillers for polypropylene are investigated. The first two were derived from burnt rice husk ash (RHA), whereas the third, a wood‐based filler, was processed from oil palm trunk. One important characterization of the composites involves the checking for the actual filler content and filler distribution within the matrix. An analytical technique is described here for computation of the filler content in the composites based on a simple expression derives from thermogravimetric analyses. For filler with volatiles such as the black RHA, the derived expression was pf = 106(rb/mc), and for easily burnt fillers (wood‐based), the expression was pf = 156(md/mc). The technique has shown good agreement and consistency between analyzed and actual filler contents and a uniform filler distribution within the polypropylene matrix. © 1994 John Wiley & Sons, Inc.
Synthesis, characterization, and properties of reactive liquid rubbers based on butadiene–acrylonitrile copolymers
Authors: Chen D. , Pascault J. P. , Bertsch R. J. , Drake R. S. , Siebert A. R. 
Published: April 2003

AbstractReactive liquid polymers (RLP), carboxyl‐terminated butadiene–acrylonitrile copolymers (CTBN), epoxy‐terminated butadiene–acrylonitrile copolymers (ETBN), amine‐terminated butadiene–acrylonitrile copolymers (ATBN) of different molecular weights (from 2200 to 6500 g/mol), and a nonfunctional butadiene–acrylonitrile copolymer were synthesized and characterized. Selection of end groups of RLPs and the synthesis were discussed. Phase behaviors of CTBN, ETBN, and NFBN in the RLP/DGEBA system were investigated regarding to the molecular weight, molecular weight distribution, chain composition, and end groups with a light transmission method. These experimentally determined phase behaviors will be related to those of the RLPs in the systems to be modified. The effect of molecular weight of RLP on the viscosity was also studied. © 1994 John Wiley & Sons, Inc.
Preparation of PVA membranes containing β‐cyclodextrin oligomer (PVA/CD membrane) and their pervaporation characteristics for ethanol/water mixtures
Authors: Yamasaki Akihiro , Mizoguchi Kensaku 
Published: April 2003

AbstractPoly(vinyl alcohol) (PVA) membranes were modified by introducing β‐cyclodextrin (β‐CD) oligomer, which has an inclusion ability sensitive to size, structure, and hydrophilicity of the guest molecule. The modified membranes (PVA/CD membrane) were prepared by casting of the aqueous solutions of PVA and β‐CD oligomer. The CD oligomer was immobilized in the membranes by cross‐linking with glutaraldehyde. The cross‐linking times were 1 and 8 h. The content of CD in the membranes was 33 wt %. The effects of CD on the pervaporation characteristics for water/ethanol were investigated by comparisons with those of the cross‐linked PVA membranes. For the 1 h cross‐linked membranes, CD increased both the water permeation rate and selectivity at lower ethanol concentrations in the feed. At higher ethanol concentrations, CD increased the water selectivity, but it decreased the water permeation rate. For the 8 h cross‐linked membranes, at lower ethanol concentrations, CD increased the water permeation rate, but the water selectivity through the PVA/CD membrane was almost equal to that of the PVA membrane. At higher ethanol concentrations, CD increased the water selectivity and decreased the water permeation rate. These effects of CD can be interpreted in terms of the inclusion strength in the cavity and the reduction of the cross‐linking density of the PVA phase in the membranes. © 1994 John Wiley & Sons, Inc.
Dynamic mechanical properties of poly(vinyl chloride) and polyurethane carboxylate blends
Authors: Kim Sang June , Kim Byung Kyu , Jeong Han Mo 
Published: April 2003

AbstractThe miscibility of thermoplastic polyurethane elastomers (TPUs) with poly(vinyl chloride) (PVC) was studied. PVC blends with TPUs, prepared from 4,4‐diphenylmethane diisocyanate as diisocyanate, hydroxy‐terminated poly(butylene adipate) (PBA) as the soft segment, and dimethylolpropionic acid as the chain extender carrying a latent anionic site for neutralization by triethylamine, showed a single glass transition temperature (Tg), irrespective of neutralization of latent anionic sites of TPU. But in neutralized TPU/PVC blends, limited intimate segmental mixing was perceived from the mechanical properties observed. When hydroxy‐terminated poly(propylene glycol) was used as the soft segment instead of hydroxy‐terminated PBA, PVC/TPU blends showed two separate Tg's of PVC and TPU, irrespective of neutralization. © 1994 John Wiley & Sons, Inc.
Synthesis and studies of egyptian bagasse pith phenol formaldehyde cationic exchangers
Authors: Metwally M. S. , Metwally N. E. , Samy T. M. 
Published: April 2003

AbstractThe article is concerned with a simple method for preparing cationic resins from polycondensation of Egyptian bagasse pith (as a source of cheap and renewable material) with phenol and paraformaldehyde as a cross‐linking agent. Optimum principal reaction conditions of the preparation and properties are determined and compared with resin without bagasse pith content. The Synthesized resins are stable in water, organic solvents, thermal treatment, and mineral acids (1M). The sample having a cation exchange capacity up to 3.92 meq g−1 of dry resins are being introduced as new cationic exchangers. The synthesized resins are used in the study of the possible separation of univalent cations. The rational thermodynamic equilibrium constants (In K) are calculated for Li+ −Na+ exchanges on the resins having a various amount of bagasse pith. The thermodynamic parameters are computed and suitable explanations are described. © 1994 John Wiley & Sons, Inc.
Deswelling characteristics of poly(N‐isopropylacrylamide) hydrogel
Authors: Park Tae Gwan , Hoffman Allan S. 
Published: April 2003

AbstractPoly(N‐isopropylacrylamide) gels exhibit a lower critical solution temperature (LCST) behavior in aqueous solution. At temperatures below the LCST, the gel is more hydrated than at temperatures above the LCST. At the LCST, the volume change is sharp. It is shown here that the water content of the gel above the LCST depends upon previous states of the gel (e.g., dry or wet), the heating rate, and the gel thickness. Deswelling kinetics are also affected by the gel thickness. Caffeine release experiments indicate that microscopic water pockets are formed within the matrix during the rapid gel collapse procedure. © 1994 John Wiley & Sons, Inc.
Interdiffusion in microlayered polymer composites of polycarbonate and a copolyester
Authors: Pollock G. , Nazarenko S. , Hiltner A. , Baer E. 
Published: April 2003

AbstractThe interdiffusion of two miscible polymers, polycarbonate (PC) and a copolyester (KODAR), was studied at temperatures from 200 to 230°C. The two polymers were coextruded as microlayer composites with up to 3713 alternating layers. The microlayer structure provided a large area of intimate contact between the two polymers with minimal mixing. Initially, two glass transition temperatures were observed by DSC that were intermediate between the glass transition temperatures of the pure components. Upon annealing, the glass transition temperatures shifted closer together, reflecting the extent to which inter‐diffusion had occurred. After no more than 2 h of annealing, a single glass transition temperature was observed. A model was formulated based on Fick's law of diffusion that related the mutual diffusion coefficient, D, to the change in the glass transition temperatures. The model also incorporated an “equivalent” residence time to account for diffusion that occurred during the coextrusion process. It was not necessary to consider the concentration dependence of D to satisfactorily describe the data with this model. For the temperature range from 200 to 230°C, the value of D varied from 4.0 × 10−16 to 1.6 × 10−15 m2/s. The activation energy of interdiffusion was determined to be 95 kJ/mol. © 1994 John Wiley & Sons, Inc.