摘要:

AbstractSolutions of lithium perchlorate in a low molecular weight ethylene oxide/propylene oxide (EO/PO) co‐polymer were studied by differential scanning calorimetry. The pure co‐polymer was found to crystallise partially, while addition of the salt impaired crystallisation first by slowing crystal growth then by slowing nucleation. At high salt concentrations (∼1·0 molal) no crystallisation occurred. The solvation of Li+‐ions and the introduction of ‘transient crosslinking’ between cations and anions effectively suppresses the separation of the polymer into microregions of EO and PO. The crystallisation phenomena are relevant to the use of these copolymers as ‘model’ polymer ele

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330401

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMean‐square dipole moment values of styrene/4‐vinylpyridine (S4VP) copolymers determined at 25–60°C in 1,4‐dioxane solutions were related to the microstructure of the chains. Data on the synthesis and dipole moments of S4VP copolymers were used to calculate the distribution of triad fractions and effective dipole moments of styrene, S‐centred, and 4‐vinylpyridine, V‐centred, fractions in the copolymer chains. The relative magnitudes of the effective dipole moment values calculated for each type of triad reflect the effect of dipole–dipole interactions

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330402

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractConcentration relations for mutual diffusion coefficientsDm(C) in water of polyelectrolyte gelatin macromolecules at different temperatures were studied by optical interferometry. It is shown thatDm(C) values are in agreement with scaling predictions and are similar to those observed for solutions of neutral macromolecules under θ‐conditions. However, they are greatly influenced by the square‐law termC2, having a correlation to the conventional scaling lawDm∝︁C, and the mobility of solution components is influenced by physical gelation processes under certain thermodynamic conditions. It is demonstrated that the temperature relation of the diffusion coefficient at infinite dilutionD0(C→ 0) for the three gelating samples with various physico‐chemical properties can be described by a univer

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330403

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractGlass and carbon fibre reinforced epoxy composites were fabricated forN,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) and its formulated systems with tri‐ and di‐functional reactive epoxy diluents using 30% diaminodiphenyl sulphone (DDS) as a curing agent. The epoxy laminates were evaluated for their physical, chemical and mechanical properties [at room (26°C) and high (100°C) temperatures]. A marginal increase (<20%) in the mechanical properties of CFRP was found compared with GFRP laminates. Incorporation of epoxy diluents altered the mechanical properties of the composites significantly. The incorporation of triglycidyl‐4‐aminophenol diluent to TGDDM systems resulted in an improvement in mechanical pro

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330404

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractDynamic tensile and shear moduli measurements have been carried out on highly oriented thermotropic liquid crystalline copolymers formed by random copolymerization of 2‐hydroxy‐6‐naphthoic acid, terephthalic acid andp‐aminophenol. This liquid crystalline copolymer is known as HNATA. Application of the aggregate model of units of structure gives rise to an estimation of the orientation angle θ = 5° and a chain modulusEc= 230 GPa. The fall in tensile modulus with increasing temperature is related to two factors: a decrease in the intrinsic chain modulus and a reduction in the shea

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330405

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractDipole moments of poly(allyl methacrylate) prepared by group transfer polymerization and of allyl methacrylate were determined from dielectric constant, refractive index increment and density measurements performed on their dilute benzene and carbon tetrachloride solutions within a temperature range of 25–60°C. Dipole moments ratios and temperature coefficient, d ln〈μ2〉/dT, where 〈μ2〉 is the mean‐square dipole moment of the chain, were calculated. These results are compared with e

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330406

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractSynthetic calcium silicate, pretreated with various quantities of organofunctional silane (Si‐69®)‐based coupling agents, has been investigated in a compound based on styrene–butadiene rubber. The properties of the rubber compound with untreated synthetic calcium silicate and those observed after direct addition of an adequate quantity of Si‐69® during the mixing period have been

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330407

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe radical polymerization of vinyl monomers is usually initiated by physical and chemical means. After an increasing polymerization rate,Rp, at low monomer concentrations, some reactive systems show an unexpected minimum forRpat high enough monomer concentrations. The radical polymerization of methyl methacrylate (MMA) initiated by the redox systemD‐glucose–ceric ion at varying MMA concentration is discussed. The peculiar behaviour ofRpis explained by the presence of two circumstances: the initiation rate fromD‐glucose radicals does not depend on MMA concentration when most of theD‐glucose radicals formed react by adding to monomer, and the radical chains initiated byD‐glucose radicals undergo mutual termination with a portion of the radical chains initiated by monomer radicals. Some information about the nature of the polymer end‐groups is reached from the mechanist

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330408

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe influence of the chemical modification of the hydroxyl groups of phenoxy resin (PH) by benzoate, acetate and methoxy groups on its miscibility with poly(2‐vinyl pyridine) (P2VPy) is investigated. Both DSC and FTIR results permit the definition of three distinctive regions: up to 40% modification all 50/50 blends are miscible; between 40 and 55% modification all blends present partial miscibility and at higher than 55% modification the blends are totally immiscible. Specific interactions between the hydroxyl groups of PH and the amine groups of P2VPy are put forward as an explanation for these observation

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330409

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA series of fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups were prepared and investigated to determine their dielectric constants as a function of relative humidity and thermal characteristics. The fluorinated polymides and fluorinated poly(imide amide)s containing pendent cyano groups were prepared by reaction of bis(4‐aminophenoxy) benzonitriles with a fluorinated dianhydride and with a fluorinated di(acid chloride) containing preformed imide rings. The properties of the fluorinated polyimides and fluorinated poly(imide amide)s containing pendent cyano groups were compared with those of fluorinated polyimides and fluorinated poly(imide amide)s prepared from 1,3‐bis(4‐aminophenoxy)benzene. The introduction of the pendent cyano groups caused an increase in the dielectric constant and an increase in the glass transition temperature of the polymers compared with the polymers prepared without pendent cyano g

ISSN:0959-8103    

DOI:10.1002/pi.1994.210330410

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY