摘要:

AbstractVariation of the epoxy/curing agent ratio for a system containing a diglycidyl ether of bisphenol‐A (DGEBA) and a mixed aromatic amine was found to have a significant effect on the cure kinetics and final dynamic mechanical properties of both the neat resin and glass reinforced epoxy. For a partial B‐stage cure to an ultimate C‐stage cure, optimum cure temperatures were obtained as a function of stoichiometry. For the ultimately cured (C‐stage) resin, the molecular weight between crosslinks (Mc) passed through a minimum, and both the glass transition temperature (Tg) and a secondary (sub‐Tg) transition passed through a maximum at the stoichiometric ratio. In addition, the activation energy of the ultimately cured resin passed through a maximum at or near the stoichiometric ratio for both theTgand sub‐Tg

ISSN:0021-8995    

DOI:10.1002/app.1990.070411101

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effect of inert diluents on the properties of cation exchange membranes had been studied. The membranes were prepared by modification of high‐molecular polyethylene (M̄n= 1.19 × 106) with styrene and divinylbenzene in the presence of toluence or heptane and following sulphonation. In the monomer mixture the diluent content was in the range of 5–30 wt. % and divinylbenzene was 3 or 7 wt %. The results obtained indicate that the properties of thus obtained membranes depend on the kind and amount of the diluent. It was found that the membranes, obtained in the presence of toluene, have much better transport properties than the membranes obtained in the presence of heptane at the same concentration in the monomer mixture. The best diffusion coefficient for sodium chloride was found for the membranes, obtained in the presence of 5 or 10 wt % to

ISSN:0021-8995    

DOI:10.1002/app.1990.070411102

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

年代:1990

数据来源: WILEY

摘要:

AbstractPolyethylene terephthalate (PET), polypropylene (PP), polyamide fibres, and films have been discharge treated. The resulting surface modifications analysed via ESR, IR, UV contact angle measurements. Discharge treatment introduces radicals and OH groups into the surface. But it does not correlate with wetability. Discharge treatment also produces the changes in conformation of macromolecules and roughness. This process is largely responsible for the wetability.

ISSN:0021-8995    

DOI:10.1002/app.1990.070411103

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

年代:1990

数据来源: WILEY

摘要:

AbstractUltrasonic absorption measurements were made at 3.14 MHz on poly(methyl methacrylate) as a function of temperature and after various doses of γ‐irradiation. The measurements showed a relaxation phenomenon. The activation energy of the various doses was determined and the smallest doses that affected the specimen was found to be 4 Mr

ISSN:0021-8995    

DOI:10.1002/app.1990.070411104

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

年代:1990

数据来源: WILEY

摘要:

AbstractA number of resin copolymers have been synthesized by condensingp‐hydroxy phenacyl bromide, substituted benzoic acids, and formaldehyde catalyzed by acids. The resin copolymers were characterized by IR spectra. The solution, thermal and chemical properties of the resins have been investigated. Ion exchange selectivity with respect to Cu2+and Co2+has been studied at different pH. Bacteriocidal and fungicidal properties of the resins have also been evaluate

ISSN:0021-8995    

DOI:10.1002/app.1990.070411105

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

年代:1990

数据来源: WILEY

摘要:

AbstractTribochemical reactions of PTFE with aluminum, silicon, and iron during rubbing were detected by ESCA. No apparent relationship between this chemical reaction of the fillers with the PTFE in the composite and the wear‐reducing action of those fillers on the composite material was foun

ISSN:0021-8995    

DOI:10.1002/app.1990.070411106

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe products resulting from the propoxylation of sucrose and lactose under alkaline conditions have been studied using FAB mass spectrometry. Soft desorption/ionization, using fast atoms, was expected to show intense protonated molecules for each component of the reaction mixture, thus allowing the extent of propoxylation to be examined under various conditions. However, it appears that addition of the FAB matrix, namely thioglycerol, prior to mass spectral analysis, resulted in alteration of the analyte via hydrolysis/dehydration, with protonated molecules appearing only for matrix/analyte reaction products, and not the original compounds which were to be examined. The resulting mass spectra, however, provided information regarding the extent of propoxylation and were consistent with results obtained by other researchers examining acetylated sugars using CI‐M

ISSN:0021-8995    

DOI:10.1002/app.1990.070411107

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn order to allow manufacturers of fiber‐reinforced plastic (FRP) products to determine an optimum catalyst level for their application, an investigation was made of the effects of ambient temperature and catalyst level on the gel time of polyester resins. Gel times were determined using standards set by the Society of the Plastics Industries, Inc.5The gel times thus obtained compared favorably with published gel times for general purpose polyester resins. It will be left to the individual manufacturer to determine the optimum catalyst level for his or her application, as very short gel times will cause the resin to harden too quickly to allow fabrication of large parts. In general, the optimum catalyst level is defined as that which produces the shortest usable gel tim

ISSN:0021-8995    

DOI:10.1002/app.1990.070411108

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new series including eight structurally different self‐curing epoxy compounds bearing azomethine linkages were synthesized, characterized and polymerized. 4‐(2,3‐Epoxypropoxy)‐benzaldehyde (EPB) or 2,3‐epoxypropyl glyoxylate monohydrate (EPG), prepared by reacting 4‐hydroxybenzaldehyde or glyoxylic acid monohydrate, respectively, with excess of epichlorohydrin in the presence of benzyltrimethylammonium bromide as catalyst, were used as starting materials. EPB or EPG reacted with an equimolar amount of a substituted aromatic amine (4‐aminobenzoic acid, 5‐aminoisophthalic acid, 4‐aminophenol, or 1,4‐phenylene‐diamine) to afford the epoxy compounds. They were characterized by IR and1H‐NMR spectroscopy. Their thermal polymerization was investigated by DTA. The thermal stabilities of cured resins were evaluated by dynamic TGA and isothermal gravimetric analysis (IGA). The polymers of the epoxy compounds derived from EPB were stable up to 225–298°C in N2and afforded anaerobic cha

ISSN:0021-8995    

DOI:10.1002/app.1990.070411109

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

年代:1990

数据来源: WILEY

摘要:

AbstractEight new epoxy compounds bearing maleamic acid moieties were prepared starting from 4‐(2,3‐epoxypropoxy)benzaldehyde (EPB) or 2,3‐epoxypropylglyoxylate monohydrate (EPG). The monomaleamic acid derived from an aromatic diamine (1,4‐phenylenediamine, 4‐aminophenyl ether, 4,4′‐diaminodiphenylmethane or 4,4′‐diaminodiphenylsulfone) reacted with EPB or EPG to afford the epoxy compounds. They were characterized by IR and1H‐NMR spectroscopy. Their DTA traces showed that thermal polymerization started at 187–211°C. Network systems were obtained by crosslinking from the reaction of epoxy group with the maleamic carboxyl and through the olefinic bond. The TGA thermograms of crosslinked polymers showed that they were stable up to 275–295°C in N2or air and afforded anaerobic char yield of 47–65% at 800°C. In addition, isothermal gravimetric analysis (IGA) was used to evaluate the thermo‐oxidative stab

ISSN:0021-8995    

DOI:10.1002/app.1990.070411110

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

年代:1990

数据来源: WILEY