bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interdiffusion in a particle matrix system of two miscible polymers: An investigation by positron annihilation lifetime spectroscopy and differential scanning calorimetry
Authors: Dlubek G. , Taesler C. , Pompe G. , Pionteck J. , Petters K. , Redmann F. , Krause‐Rehberg R. 
Published: October 2004

AbstractPositron annihilation lifetime spectroscopy (PALS) and differential scanning calorimetry (DSC) were used to study the interdiffusion in a particle matrix system consisting of (styrene‐maleic anhydride) copolymer containing 24% maleic anhydride (SMA) and poly(methyl methacrylate) (50:50). Starting from the phase separated state of the miscible components, the transition to the mixed state due to interdiffusion during annealing at 160 and 180 °C was investigated. The diffused mass fractions of both components were estimated by DSC; they increase linearly with the logarithm of the annealing time. Both components show the same behavior, suggesting an average interphase composition of 50:50. For subsequent annealing, the kinetic behavior differs from the earlier behavior, probably because of the different diffusion coefficients of the two components. Experimental evidence is presented that the ortho‐positronium (o‐Ps) intensity correlates to the interdiffusion process. The response is due to the diffusion of inhibitors for Ps formation from one phase into the other. A semiquantitative model is developed that allows the estimation of the interphase volume fraction from the relative change of the annihilation parameters. The PALS results are discussed in relation to those obtained by DSC. The results show that PALS is a useful tool to study mixing and demixing processes in polymer blends with a three‐dimensional morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 654–664, 2002; DOI 10.1002/app.10362
Miscibility, melting, and crystallization of poly(trimethylene terephthalate)/poly(ether imide) blends
Authors: Huang Jieh‐Ming , Chang Feng‐Chih 
Published: October 2004

AbstractMiscibility, melting, and crystallization behaviors of solution‐blended poly(trimethylene terephthalate) (PTT)/poly(ether imide) (PEI) blends have been investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and polarized light microscopy (PLM). These blends show a single and composition‐dependent glass transition temperatures over the entire composition range, implying that these blends are fully miscible in the amorphous region. The enthalpy of the middle endotherm melting of the primary crystallization decreases with increasing PEI content in the blend. Recrystallization of PTT during heating scan in DSC is either retarded or fully inhibited by the presence of PEI. In nonisothermal crystallization, the depression of crystallization temperature of PTT also depends on the blend composition and cooling rate; the presence of PEI decreases the PTT segments migrating to the crystallite‐melt interface. The effects of temperature and PEI content on the spherulite growth rate of PTT were evaluated by PLM. The spherulite growth rate decreases with the increase of the PEI content, implying that it is a thermodynamically dominant process. Both thermodynamic and kinetic factors cause total inhibition of PTT crystallization at higher PEI content in the blend. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 850–856, 2002; DOI 10.1002/app.10367
Resolving lateral variations in the frequency dependence of adhesive properties at the surface of a model pressure sensitive adhesive
Authors: Jia Shijun , Foster Mark D. 
Published: October 2004

AbstractA commercial scanning probe microscope may be used to laterally resolve qualitative differences in the frequency dependence of material properties at the surface of a model pressure sensitive adhesive (PSA). In a heterogeneous PSA made from polyisoprene and a wood rosin derivative, both the polymer‐rich matrix and tackifier‐rich domains regions at the surface appear stiffer and show higher adhesive force when increasing the testing frequency from 0.01 to 1 Hz at room temperature. The limited frequency range of the instrument and piezo creep constrain the applicability of the approach. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 400–404, 2002; DOI 10.1002/app.10369
Semiempirical rate equation for solid state polymerization of poly(ethylene terephthalate)
Authors: Duh Ben 
Published: October 2004

AbstractSolid‐state polymerization (SSP) of poly(ethylene terephthalate) (PET) is characterized by two distinct features. First, there exists an ultimate or limiting intrinsic viscosity (IV). Second, the SSP rate varies with the prepolymer IV. Although there are several existing empirical rate equations and numerous published models for the SSP of PET, none can adequately describe these features. In this article, a simple semiempirical rate equation that aptly describes the behaviors of the SSP of PET is proposed. It is based on the assumptions that there are two categories of functional end groups, active and inactive end groups, and that the overall SSP follows a second order kinetics. Thus, the overall SSP rate is expressed as −dC/dt = 2 ka (C − Cai)2, where C is the total end group concentration, t, the SSP time, ka, the apparent reaction rate constant, and Cai, the apparent inactive end group concentration. With this rate equation, the effects of all factors that influence the SSP rate are implicitly and conveniently accounted for by the two parameters, ka and Cai. For example, ka increases, while Cai decreases, with increasing SSP temperature, increasing prepolymer IV, and decreasing particle size. The proposed rate equation fits the IV or molecular weight build‐up curves for the SSP of PET under various conditions very well, and can be extrapolated beyond data with reasonable accuracy. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 857–870, 2002; DOI 10.1002/app.10370
Flocculation of montmorillonite by some hydrophobically modified polycations containing quaternary ammonium salt groups in the backbone
Authors: Dragan Stela , Maftuleac Alexei , Dranca Ion , Ghimici Luminita , Lupascu Tudor 
Published: October 2004

AbstractThe flocculating efficiency of some hydrophilic/hydrophobic cationic polyelectrolytes on montmorillonite suspension in water was investigated as a function of both the polycation structure and the flocculation parameters: polycation/montmorillonite contact time, suspension pH, polycation dose, and temperature. Cationic polyelectrolytes with quaternary ammonium salt groups in the backbone and hydrophobic side chains (hexyloxypropyl, PCA5H1 and PCA5H2; and decyloxypropyl, PCA5D1, respectively) were used as flocculants. The flocculation was time dependent. A negative influence of the stirring time and of the abrupt variation of pH from basic to acidic on the separation efficiency was evidenced. The increase of the polycation dose from 0.58 mg polycation/g montmorillonite up to 1.74 mg/g montmorillonite showed a positive influence on the sedimentation of montmorillonite particles for all the polycations taken into account. The influence of the polycation structure was reflected in the lower turbidity found in the case of the polycation PCA5D1 compared with that of PCA5H1, at the same concentration; this reflects the positive influence of the hydrophobicity increase on the suspension separation. A common characteristic for all the polycations is that, for more than about 60 min of settling, the lowest turbidity was found at 25°C and the highest at 5°C. The turbidity found at 15°C was in between, both before and after 60 min of settling time. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 871–876, 2002; DOI 10.1002/app.10371
Rheological study of polypropylene copolymer/polyolefinic elastomer blends
Authors: Paul Subhasish , Kale D. D. 
Published: October 2004

AbstractBlends of polypropylene copolymer (PP‐cp) and a polyolefinic elastomer (POE) were prepared by a melt‐blending process at 210°C and 60 rpm using a counterrotating twin‐screw extruder. The POE content was varied up to 25%. The shear viscosity over a wide range of shear rate was measured. All blend compositions showed well‐defined zero shear viscosity and shear thinning behavior. The melt viscosity values were between those of the principal components in all cases. Rheology of blends shows different behavior up to concentrations of POE corresponding to the tough–brittle transition. The linear viscoelastic properties (G′, G″, η*, η′, η″) were used to check the miscibility of the two components in the melt state. All blend compositions showed a good degree of miscibility over the range of POE concentrations studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 665–671, 2002; DOI 10.1002/app.10376
Effect of doping polyacrylic acid with some dopants as studied by different techniques
Authors: Mostafa N. , Mohamed Manal G. 
Published: October 2004

AbstractThe molecular weight of polyacrylic acid (PAA) was determined by a viscometric method using NaNO3 as solvent at 30°C. The specific electric conductivities (σ) of PAA as well as PAA doped with carbon black (CB), chromium oxide (Cr2O3), and cupferron with different concentrations (from 0.25 to 1 wt %) were measured at a temperature range 360–400 K. IR spectra of some polymers were determined and it was shown that when PAA was doped with 0.5 wt % CB, a COC band appeared at 775–875 cm−1. The positron annihilation lifetime (PAL) spectra in PAA doped with the above‐mentioned dopants were measured as a function of their concentrations. It was observed that the short lifetime intensity I1 decreased, whereas the intermediate lifetime intensity I2, which is related to the conductivity of the material, increased with increasing the wt % of Cr2O3 and cupferron as well as at low concentrations of CB. These results are discussed in terms of the conducting island model. It was found that there were distinct positive relationships between σ and I2. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 877–883, 2002; DOI 10.1002/app.10381
Effect of preparation method on the capture and release of biologically active molecules in chitosan gel beads
Authors: Ghanem Amyl , Skonberg Denise 
Published: October 2004

AbstractModel bioactive compounds with different molecular and functional characteristics were entrapped in gel beads prepared by polyelectrolyte complexation of chitosan and pentasodium tripolyphosphate (TPP). Three compounds of interest to the food and biomedical industries were tested: (1) lysine, (2) bovine serum albumin (BSA), and (3) β‐galactosidase. Effects of the compound concentration in the initial chitosan solution, pH of the curing solution, and length of the curing phase on the capture efficiency were evaluated. Release rates for lysine and BSA into a phosphate buffer, distilled water, and a synthetic ocean solution were observed, and the activity of the entrapped β‐galactosidase was determined. The capture efficiencies for lysine and BSA decreased as the concentration increased. The capture efficiency for lysine ranged from 90% at pH 5 to 20% at pH 8.6. There was no significant effect of the release media on the rate of release. BSA and lysine release reached 90% of the maximum after 100 and 50 min, respectively. The capture efficiency of β‐galactosidase was not affected by the pH of TPP; however, enzyme activity in the beads decreased as the pH increased. Beads prepared in the pH 8.6 TPP solution had significantly higher rates of enzyme release over time. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 405–413, 2002; DOI 10.1002/app.10393
Cellulose acetate and sulfonated polysulfone blend ultrafiltration membranes. II. Pore statistics, molecular weight cutoff, and morphological studies
Authors: Malaisamy R. , Mahendran R. , Mohan D. 
Published: October 2004

AbstractThe determination of the pore size, porosity, number of pores, molecular weight cutoff (MWCO), and morphology of an ultrafiltration membrane is necessary for predicting the performance of a membrane for a specific application. For ultrafiltration membranes prepared from cellulose acetate and sulfonated polysulfone in the presence and absence of various concentrations of the additive poly(ethylene glycol) 600, pore statistics and MWCOs were determined in studies with dextrans of different molecular weights. Surface and cross‐sectional morphologies of the membranes were analyzed with scanning electron microscopy at different magnifications. The pore size increased with increasing concentrations of sulfonated polysulfone and additive in the casting solution. Similarly, the MWCOs of the membranes ranged from 19 to 150 kDa, depending on the various polymer blend compositions and additive concentrations. Results from scanning electron microscopy provided qualitative evidence for the trends observed for the pore statistics and MWCO results. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 430–444, 2002; DOI 10.1002/app.10414
Influences of copolymerization conditions on the structure and properties of isotactic polypropylene/ethylene–propylene random copolymer in situ blends
Authors: Zhang Yu‐Qing , Fan Zhi‐Qiang , Feng Lin‐Xian 
Published: October 2004

AbstractA spherical TiCl4/MgCl2‐based catalyst was used in the synthesis of in situ isotactic polypropylene/ethylene–propylene random copolymer blends by propylene bulk polymerization and subsequent gas‐phase copolymerization of ethylene with propylene. Different copolymerization conditions, such as the reaction time, monomer pressure, and composition, were investigated, and their influences on the structure and properties of the products were studied. Raising the monomer pressure was the most effective way of speeding up the copolymerization, but it caused more increases in the random copolymer than the block copolymer fractions. Increasing the ethylene content of the monomer feed also resulted in higher reaction rates and copolymer contents, but the ethylene contents of both the random and block copolymer fractions were also raised. In situ blends that contain more than 50 wt % copolymer were prepared. The mechanical properties of the blends, including the impact strength and flexural modulus, were regulated in a rather broad range with changes in the copolymerization conditions. The properties were highly dependent on the amount, distribution, and chain structure of the copolymer fractions. The impact strength was influenced by both the random copolymer and block copolymer portions in a complicated way, whereas the flexural modulus was mainly determined by the amount of random copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 445–453, 2002; DOI 10.1002/app.10415
Effect of winding speed on the structure and properties of as‐spun poly(trimethylene 2,6‐naphthalenedicarboxylate) fibers as compared to poly(ethylene terephthalate) fibers
Authors: Stier U. , Oppermann W. 
Published: October 2004

AbstractWe present a comparative study of melt spinning of poly(trimethylene 2,6‐naphthalenedicarboxylate) (PTN) and poly(ethylene terephthalate) (PET) fibers with respect to the effect of winding speed (2000–6000 m/min): Structural changes were followed by X‐ray analysis, calorimetry, and measurements of density, boiling water shrinkage, and birefringence. As‐spun PTN fibers exhibited a low degree of crystallinity at relatively low speeds (< 2000 m/min). An increase in winding speed up to 6000 m/min only resulted in a minor enhancement of crystallinity and orientation. The small change of structural parameters accounted for the fact that tenacity and modulus did not rise significantly with increasing winding speed, contrary to the PET fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2489–2497, 2002
Preparation of high molecular weight poly(vinyl alcohol) with high yield by emulsion polymerization of vinyl acetate using 2,2′‐azobis(2‐amidinopropane) dihydrochloride
Authors: Lyoo Won Seok , Kwak Jin Woo , Choi Kyu Ha , Noh Seok Kyun 
Published: October 2004

AbstractTo prepare high molecular weight (HMW) poly(vinyl acetate) (PVAc) with high yield and high linearity as a precursor of HMW poly(vinyl alcohol) (PVA), vinyl acetate (VAc) was emulsion polymerized using, azo initiator, 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH). This was compared with the polymerization using potassium peroxodisulfate (KPS) as an initiator at various polymerization conditions. PVA, having a maximum number average degree of polymerization (Pn) of 3500 was obtained by the saponification of PVAc with Pn of 13,000–14,000, degree of branching (DB) for the acetyl group of about 3.4–3.5, and a maximum conversion of VAc into PVAc of 95%, which was polymerized by AAPH. These numerical values were superior compared with 14,500–15,000 of Pn of PVAc, obtained by KPS, and 3100 of maximum Pn of resulting PVA, DB of about 3.7–3.8, and maximum conversion of 90%. From the foregoing experimental results, we found that AAPH was a more efficient initiator than KPS in increasing both conversion of PVAc and molecular weight of PVA. In addition, PVAc microspheres, obtained by these emulsion polymerizations, can be converted to PVA / PVAc shell / core microspheres through a series of surface‐saponifications, maintaining their spherical morphology. Various surface morphologies, such as flat or wrinkled and swellable or nonswellable ones formed by the various molecular parameters and saponification conditions, were examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2356–2362, 2004
Effect of particle size on the properties of Mg(OH)2‐filled rubber composites
Authors: Zhang Qi , Tian Ming , Wu Youping , Lin Gui , Zhang Liqun 
Published: October 2004

AbstractA novel nanomagnesium hydroxide powder and three kinds of micro‐Mg(OH)2, with different particle sizes, were chosen as fillers and mixed with ethylene–propylene–diene monomer rubber (EPDM) to form a series of composites by a traditional rubber‐processing technique. The results showed that the mechanical properties of composites improved with decreasing particle size. The nanocomposites were far stronger than the microcomposites, which also supported the view that rubber reinforcement requires nanoreinforcement. The effect of particle size on the fire resistance of composites was investigated by cone calorimetry and limiting oxygen index analysis, which showed that the particle size of powder had an impact on the fire resistance of composites. For the composites filled with untreated powder, the peak value of heat release rate decreased and Tign increased with decreasing particle size. In conclusion, the fire resistance of nanocomposites was better than that of microcomposites. Surface modification of particles sometimes substantially improved the mechanical properties of nanocomposites, but had no effect on either the mechanical properties of microcomposites or the fire resistance of nanocomposites and flame retardance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2341–2346, 2004
Chain extension of PA1010 by reactive extrusion by diepoxide 711 and diepoxide TDE85 as chain extenders
Authors: Qian Zhenyu , Chen Xi , Xu Jun , Guo Baohua 
Published: October 2004

AbstractThe chain extension behaviors of two diepoxides, epoxide TDE85 and 711, were studied to evaluate their coupling effects on polyamide 1010 (PA1010). The former gave better coupling effects and a faster reaction rate. The torque of PA1010 melt increased dramatically with reaction time. The effect of the diepoxy chain extender on the flowability, thermal properties, and mechanical properties of chain‐extended PA1010 was investigated. The melt flow index (MFI) dramatically decreased as the diepoxide was added to PA1010, and the notched Izod impact strength of the chain‐extended products also increased. Furthermore, study on the usage of chain extender showed that there exists an approximate platform on the curve of melt torque versus content of chain extender, beyond which crosslinking may occur. Theoretical analysis of the occurrence of crosslinking was carried out by Flory criterion, which demonstrated that the average amount of functional groups in the chain extension system played a significant role in avoiding crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2347–2355, 2004
Comparative study of silicon‐containing polyimides from different oxydianilines
Authors: Lin Bao‐Ping , Pan Ying , Qian Ying , Yuan Chun‐Wei 
Published: October 2004

AbstractSilicon‐containing polyimides were synthesized by solution polycondensation of bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride with 3,4‐oxydianiline and 4,4′‐oxydianiline, respectively. All the poly(amic acid) films could be obtained by solution‐casting from N,N‐dimethylacetamide solutions and thermally converted into transparent and tough polyimide films. The physical properties of thin films of those polyimides were compared by DSC, TGA, UV–visible spectroscopy, and dynamic mechanical analysis. The polyimide from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 3,4‐oxydianiline exhibited superior energy‐damping characteristic, mechanical properties, and optical transparency, whereas that from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 4,4′‐oxydianiline possessed higher glass‐transition temperature and thermal stability. Because of the unsymmetric structure of the polyimide from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 3,4‐oxydianiline, its increasing rate of linear coefficient of thermal expansion with temperature was quicker than that of the polyimide from bis(3,4‐dicarboxyphenyl)dimethylsilane dianhydride and 4,4′‐oxydianiline. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2363–2367, 2004
Atomic oxygen resistant coating from poly(tetramethyldisilylene‐co‐styrene)
Authors: Devapal Deepa , Packirisamy S. , Korulla Raji M. , Ninan K. N. 
Published: October 2004

AbstractA polydisilahydrocarbon, namely, poly(tetramethyldisilylene‐co‐styrene), synthesized from dimethyldichlorosilane and styrene in 1 : 0.5 mol ratio under dechlorination conditions was evaluated as an atomic oxygen (AO) resistant coating for polyimide film and C‐polyimide composite. Exposure of the polymer coating on a quartz plate to an AO fluence of 2.1 × 1021 atoms/cm2 resulted in practically no mass loss, indicating the AO resistance of the polymer. Ten percent solution of the polymer in toluene was applied on aluminized Kapton® polyimide film (125 μm thick) to obtain a coating thickness of ∼ 5 μm on the unaluminized surface. In a similar way, the coating was applied on a C‐polyimide composite. The coated and uncoated samples of Kapton® film and C‐polyimide composite were exposed to AO in a plasma barrel system. The uncoated aluminized Kapton® film (125 μm) lost 6.35 mg/cm2 when exposed to AO fluence of 1.6 × 1021 atoms/cm2 whereas the corresponding coated film lost only 0.14 mg/cm2 even after exposure to AO fluence of 2.1 × 1021 atoms/cm2. In the case of the C‐polyimide composite, the uncoated sample lost 63.64 mg/cm2 on exposure to AO fluence of 1.8 × 1021 atoms/cm2 whereas the coated one lost only 0.21 mg/cm2 even after exposure to AO fluence of 2.1 × 1021 atoms/cm2. SEM studies suggest that the coating offers good protection to the substrates. Formation of cracks on some portions of the coating was noticed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2368–2375, 2004