摘要:

AbstractA pulse method for the simultaneous determination of thermal diffusivity, α, specific heat capacity,Cp, and thermal conductivity, λ, are measured for a series of curing of polyester and styrene in the presence of 10, 20, and 30% carbon black in the temperature range 300–450 K. The results show a dependence of the above‐mentioned properties on temperature and composition. The mechanism of heat transfer through the specimens is also discussed. © 1993 John Wiley&Son

ISSN:0021-8995    

DOI:10.1002/app.1993.070490401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA dry process of chemical vapor deposition and polymerization (CVDP) was employed to prepare a polyimide composite membrane for water–ethanol separation, using an apparatus newly developed for this investigation. The characteristics of the apparatus were studied by depositing pyromellitic dianhydride (PMDA) and 4,4′‐diaminodiphenyl ether (P,P′‐oxydianiline, ODA) in a vacuum of 10−6Torr. Deposited layers were converted to a thin polyimide film by heating at 200°C for 3 h in a vacuum. The composite membranes were prepared by forming a polyimide layer of 0.2 μm thickness on the surface of asymmetric supporting membranes made by the phase‐inversion process. The polyimide composite membranes prepared under the best conditions exhibited a separation factor α (H2O/EtOH) of over 140 for 95 vol% aqueous ethanol solution with flux of 0.1 kg/m2h at 25°C in pervaporation mode. Also, it was demonstrated that this new technique of chemical vapor deposition and polymerization (CVDP) was very useful for the preparation of a solvent‐resistant composite membrane in a completely dry process. © 1993

ISSN:0021-8995    

DOI:10.1002/app.1993.070490402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of fiber loading, fiber length, matrix type, and interface adhesion on mechanical properties of PET short fiber‐styrenic block copolymer TPEs, SIS, and SBS, was investigated. A strong bonding between PET fiber and TPE was obtained by surface treatment of TPE with isocyanate in toluene solution. The stress of the composites, filled with treated fiber, increased with increasing strain by two steps; the modulus for the first step was higher than the one for the second step, and the composites yielded obviously at about 50% strain, with higher stress than that of matrix TPE. With increasing fiber loading and fiber length, the modulus for the first step and the yield stress increased, but the yield elongation decreased. It seems that the matrix elastomer underwent most of the deformation and that the filled fiber underwent large internal stress with little deformation during extension of the composite, which may be an important phenomenon to influence short fiber reinforcement. The stress softening of composites showed a somewhat larger decreased rate than that of the matrix with repeated stress‐strain cycles, and the stress softening in the first cycle increased linearly with increasing fiber loading and increased in anSshape with increasing fiber length. In comparison with the SIS elastomer, the hysteresis of the SBS elastomer showed a big residual strain after the first elongation of 30%, and its retraction and subsequent re‐extension curves were obviously different from the extension curve, which was considered to be due to the destruction of parts of the styrene hard domai in SBS. The stress softening of the composites was influenced by the matrix elastomer, as well as by the loading fiber. The interface separation around the end of a fiber under large strain, and the breaking and restructuring of hard domain in the matrix, were considered to be important sources of softening of the composite. © 1993 John Wiley&Son

ISSN:0021-8995    

DOI:10.1002/app.1993.070490403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractElectropolymerization of N,N‐dimethylacrylamide has been performed in aqueous sulfuric acid solution, using unsized AS‐4 graphite fibers as the working electrode. The electro‐polymerized poly (N,N‐dimethylacrylamide) deposited on the surface of the graphite fiber working electrode. The formation of poly (N,N'dimethyl acrylamide) was inhibited by hydroquinone. The addition of about 0.05 moles of hydroquinone to the reaction solution resulted in about a 90% decrease in the weight gain of fibers, in agreement with the proposed free radical mechanism of aqueous electropolymerization. The rate of electropolymerization varied with the initial monomer concentration, current density, and sulfuric acid concerntration, raised to the power of 1.3, 0.42, and 0.07, respectively, that is,Rp∝ [M]1.3‐Cd0.42[H2SO4]0.07. A mathematical model, based upon free radical polymerization kinetics, is discussed. © 1993 John Wil

ISSN:0021-8995    

DOI:10.1002/app.1993.070490404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractChanges in physical properties of silk fibers, grafted with methacrylonitrile (MAN), were investigated as a function of the weight gain. The weight gain increased steadily during the first 60 min of reaction and gradually attained an equilibrium value (60%) after about 4 h. The initial tensile resistance of silk fibers decreased by MAN grafting. The crystalline structure of silk fibers remained unchanged, regardless of MAN grafting, however. a minor and broad peak appeared in the X‐ray diffraction curves of MAN‐grafted silk fibers with a weight gain of 60%, corresponding to the unoriented MAN polymer attached inside the fibers. Molecular orientation of silk fibroin chains in the crystalline regions, evaluated from X‐ray diffraction curves, did not change significantly, while both birefringence and isotropic refractive index decreased as the weight gain increased, implying that MAN polymer attached preferentially to the amorphous and not to the crystalline regions. Dynamic vis‐coelastic measurements showed that the position at which theE′ value began to decrease shifted to a lower temperature as the weight gain increased. These findings suggest that the thermal movement of silk fibroin molecules was accelerated by the presence of the poly‐MAN chains attached to the amorphous regions of silk fibroin fibers. © 1993 John Wil

ISSN:0021-8995    

DOI:10.1002/app.1993.070490405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractPolypropylene fibers and polyethylene hollow fibers were used as trunk polymers and were irradiated by electron beams with a dose of 200 kGy under N2atmosphere. Grafting of acrylonitrile to those irradiated fibers was carried out at 40°C for different periods of time. The degree of grafting was determined as a function of time. The fibrous adsorbents containing amidoxime groups were prepared by the reaction of acrylonitrile‐grafted polymers with 3% hydroxylamine in a methanol–water mixture (1 : 1). Distribution of copper ions complexed with amidoxime groups at various adsorption times was obtained by electron‐probe X‐ray microanalysis. The amidoxime groups are homogeneously distributed in the cross section of fibrous adsorbents. The fibrous adsorbents based upon polypropylene fiber of 40 μm showed a remarkable kinetic behavior for Cu2+. Even after 15 min, the adsorption capacity was 2.32 mmol Cu2+per gram of fiber. Also, the functionalization with hydroxylamine was carried out at different conditions to compare the adsorption characteristics of the resultant adsorbents. Despite having superficially different properties (elemental microanalysis, ion‐exchange capacities, adsorption capacity for UO 2+2), the polypropylene‐based fibrous adsorbents showed similar adsorption properties for uranium from sea water. The adsorption tests proved the performance of the polypropylene‐based fibrous adsorbents as a promising material for uranium recovery from sea water. In addition, uranium uptake of fibrous adsorbents increased in proportion to the volume of sea water. © 1993 Jo

ISSN:0021-8995    

DOI:10.1002/app.1993.070490406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractDisks in polypropylene were injected in a mold with an unbalanced cooling pattern to induce warpage. The internal stresses were determined using IR dichroism for molecular orientation measurement and an original method for thermal stress assessment, on the basis of the analysis of the dilatometrical behavior of microtomed cuts removed from the part. From both experimental results and structural observations with an optical microscope, a simple model is proposed to describe the warpage due to the effect of unbalanced cooling. A constant deformation was observed and cannot be described by our model, but calculated relative deformations of the part geometry are in good agreement with experimental results. © 1993 John Wiley&Sons, Inc

ISSN:0021-8995    

DOI:10.1002/app.1993.070490407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe 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

ISSN:0021-8995    

DOI:10.1002/app.1993.070490408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe processing, structure, and properties of filaments melt spun from three polypropylenes with similar rheology but substantially different crystallization kinetics were studied. The crystallization kinetics of the homopolymer was increased by the addition of a nucleating agent, whereas slower crystallization kinetics was obtained through a small amount of random copolymerization with ethylene. The relative crystallization kinetics of these three polymers was examined under quiescent conditions using differential scanning calorimetry. The technique of on‐line diameter and birefringence measurement was used to show the characteristics of the on‐line crystallization of the different resins. It was found that changing the quiescent crystallization kinetics by either the addition of a nucleating agent or through copolymerization with ethylene can produce profound effects on the structure and properties of polypropylene as‐spun filaments when they are spun under relatively low stress and low takeup velocity conditions. Higher takeup velocities and spinline stresses reduce the effect of differences in quiescent crystallization due to the influence of on‐line stress‐induced (molecular orientation‐enhanced) crystallization. © 1993 John Wil

ISSN:0021-8995    

DOI:10.1002/app.1993.070490409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe kinetics of the isothermal batch macroemulsion and miniemulsion polymerizations of methyl methacrylate (MMA) at 50°C have been studied. Hexadecane was used as the cosurfactant or swelling agent. The nucleation mechanisms were observed to be different between macroemulsions and miniemulsions. The effect of surfactant, cosurfactant, initiator, shear, and hold time on droplet nucleation was studied. The miniemulsion particles were found to contain more radicals on average than the macroemulsion particles using certain recipes. This resulted in higher polymerization rates for the miniemulsions at identical particle numbers. The latex‐particle‐size distributions were similar even though the mini‐emulsion droplets start out with a high polydispersity of around 1.5. Miniemulsion latexes were found to be more stable under shear. Conductance of emulsions during polymerization was found to be a valuable on‐line tool for investigating particle nucleation and growth. © 1993 John Wiley&

ISSN:0021-8995    

DOI:10.1002/app.1993.070490410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY