摘要:

AbstractDiallyl brassylate (DAB), a new monomer, and diallyl azelate (DAA) were converted to new prepolymers for comparison with analogous commercial products from diallylo‐andm‐phthalate (DAMP). Respective prepolymers from DAB and DAA had M̄n28,000 and 40,000 and contained approximately 0.8 free allyl moiety per repeating unit. Only the DAB prepolymer exhibited crystallinity at low temperatures as detected by differential scanning calorimetry and x‐ray diffraction. Aliphatic prepolymers have greater heat stability than aromatic ones and evolve fewer calories per double bond during curing than reported for DAMP prepolymer. Low shrinkage (<1%) on curing and clear, hard end products indicate the potential of aliphatic prepolymers as thermosetting plastics. Their liquid state at room temperature should be advantageous in many applic

ISSN:0021-8995    

DOI:10.1002/app.1974.070180201

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe bond strength of unetched aluminum–epoxy joints induced by tap and distilled water pretreatment at 10°C increased to a maximum, then decreased as a function of immersion time. In distilled water, the maximum bond strength occurs after an immersion time of about 1 hr, after which the bond strength decreases. In the case of tap water pretreatment, the maximum bond strength occurred at about 12 hr of immersion time. The bond strengths at the maxima found for the tap water‐pretreated samples were greater than those found at the maxima for the joints pretreated in distilled water. Growth of the hydrated oxide bayerite is proposed as the controlling factor; the bayerite grows more rapidly and less perfectly in distilled water than in tap water. Thick layers of bayerite are structurally weak, while thin layers seem to promote adhesion. A slight surface roughness effect was also obse

ISSN:0021-8995    

DOI:10.1002/app.1974.070180202

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe bond strength of an amine‐cured epoxy resin to etched aluminum washed with, or washed with and immersed in, 10°C tap water was found to be greater than joints similarly pretreated in 10°C distilled water. The higher bond strength was found to be induced by soluble cations of less than 0.8 Å radius; larger cations had no effect. When aluminum is etched in a solution of chromic acid at 65°C, the aluminum surface is oxidized to γ‐Al2O3. It is possible that the small, soluble cations can occupy the cationic vacancies in the defect spinel structure of the γ‐Al2O3and reduce the negative charge on the surface of the aluminum joints. Joints pretreated in 60°C tap water exhibited higher bond strengths than those pretreated in 60°C distilled water, as the growth of a thick, weak layer of bayerite was inhibited by large anions present in

ISSN:0021-8995    

DOI:10.1002/app.1974.070180203

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe effect of some factors including temperature, pressure, film thickness, and grafting ratio on the fractionation of binary liquid mixtures has been investigated by pervaporation through poly(tetrafluoroethylene) films grafted with N‐vinylpyrrolidone or 4‐vinylpyridine. The purpose was to estimate the best conditions in which the pervaporation process must be carried out. It was concluded that the pervaporation rate is increased at roughly constant selectivity when the temperature of the liquid charge is higher or when the downstream vapor pressure or the film thickness are decreased. A pressure higher than 1 atmosphere above the liquid does not increase the rate. When the grafting ratio is increased, the rate shows a maximum, and for particular conditions, the selectivity becomes much hig

ISSN:0021-8995    

DOI:10.1002/app.1974.070180204

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

年代:1974

数据来源: WILEY

摘要:

AbstractSteady‐state concentration and composition gradients of pervaporating liquids inside the membranes were measured using stacks of membranes. The experimental results on pure components agree well with a simple mechanism of diffusion down a chemical potential gradient in a nonporous membrane. For mixtures, concentration gradients are similar to those obtained for pure liquids, and composition distribution shows that the selection between the two species does not take place at a given interface in the membrane but is progressive along the diffusional paths through the membrane. Data are also listed to show that solubility and diffusivity enhancements occur for components which are hydrogen bonded with the basic groups of the membranc

ISSN:0021-8995    

DOI:10.1002/app.1974.070180205

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe possibility of eliminating sodium alkylbenzenesulfonate (ABS) from water by reverse osmosis was examined by operating with polypropylene membranes grafted with poly(acrylic acid). Flux through the membranes decreases with increasing thickness. For 23μ thickness and 0.5 1./hr‐m2flux, the rejection is 100% (operating pressure, 50 atm: concentration, 1 g ABS/l.). For 5μ thickness the rejection is lower and is related to ABS concentration: rejection increases with increasing concentration and reaches 60% for concentrations higher than 5 g ABS/l. (flux, 51./hr‐m2; operating pressure, 50 atm). This is ascribed to the prevailing ultrafiltration as regards the reverse osmosis. ABS, at higher concentrations than the critical value, gives micelles whose dimensions might be compared to pores. The membrane behavior is influenced by previous treatments; when the membrane has been conditioned in NaCl solution, it is more selective and more permeable; the rejection reaches 90% with fluxes of 6.8 l./hr‐m2for concentrations of 5 g ABS/1. (operating pressure, 50 atm). In order to relate the properties to the structure of membranes, we have examined them by electron microscope. The ion exchange which takes place between membrane and NaCl and between membrane and ABS has also been

ISSN:0021-8995    

DOI:10.1002/app.1974.070180206

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

年代:1974

数据来源: WILEY

摘要:

AbstractKinetics of heterogeneous oxidation of starch with hypochlorite were studied under varying conditions of temperature, pH, buffer components, buffer concentration, and concentration of substrate and oxidant. The kinetic data show that the reaction is first order with respect to hypochlorite. A plot of first‐order rate constant for varying starch concentrations versus starch concentration is linear. The rate of oxidation of starch is highest at pH 7.0 and decreases with increasing acidity or alkalinity of the medium. In unbuffered system, pH of the medium decreases from 10 to 3.4 during the reaction. Based on observed trends of reaction rate, energy, and entropy of activation, a mechanism for hypochlorite oxidation of starch is propose

ISSN:0021-8995    

DOI:10.1002/app.1974.070180207

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

年代:1974

数据来源: WILEY

摘要:

AbstractA study of the performance at low temperatures of various polyurethane elastomer systems, prepared from polyether and polyester diols with 2,4‐toluene diisocyanate and 4,4′‐methylenebis(2‐chloroaniline),p,p′‐diphenylmethane diisocyanate and 1,4‐butanediol, and 4,4′‐methylenebis(cyclohexylisocyanate) and methylenedianiline, has shown the polytetramethylene ether diols to impart the best low‐temperature behavior to the elastomers. The properties studied were the apparent modulus of rigidity with the Clash and Berg torsional apparatus, the hardness with a Shore D Durometer, and the resiliency with the B

ISSN:0021-8995    

DOI:10.1002/app.1974.070180208

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

年代:1974

数据来源: WILEY

摘要:

AbstractLow‐temperature polarized phosphorescence spectroscopy of polystyrene polymerized under different conditions is used to detect emission from phenyl alkyl ketone endgroups in addition to triplet excimer emission from phenyl groups. The carbonyl group concentration can only be lowered by vigorous chemical reduction; and from the phosphorescence excitation spectrum, these carbonyl groups are considered responsible for the initiation of polystyrene photodegradation by solar radiatio

ISSN:0021-8995    

DOI:10.1002/app.1974.070180209

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

年代:1974

数据来源: WILEY

摘要:

AbstractA study was made of the effect of carboxylic monomers on the surfactant‐free emulsion polymerization of styrene and styrene–butadiene. Acid monomers, such as acrylic acid, methacrylic acid, and itaconic acid, were shown to play a critical role in particle formation and particle stabilization in such systems. In the emulsion polymerization of styrene, methacrylic acid forms particles more efficiently than acrylic acid. This difference is attributed to the more hydrophobic nature of the methacrylic monomer which allows it to diffuse more rapidly to the particle surface where it acts to prevent agglomeration. The ability of carboxyl groups to orient at the particle–water interface was studied by acid–base and soap titrations of carboxylated styrene–butadiene latices. The polymerization of itaconic acid onto the particle surface of a styrene–butadiene latex produces a surface carboxyl density much higher than is obtainable with classically adsorbed surfactants. This result is used to explain the greater stability of carboxylated versus noncarboxylated emulsion polymers. During the polymerization of styrene–butadiene latices, carboxyl groups dervied from methacrylic acid are shown to be buried more deeply into the particle as compared to carboxyls derived from the more hydrophilic acrylic acid which orient more at the particle–

ISSN:0021-8995    

DOI:10.1002/app.1974.070180210

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

年代:1974

数据来源: WILEY