摘要:

AbstractOxytriazine impurities are frequently considered as undesirable compounds in the production of melamine resins. In this study, we have determined the reaction conditions required for preparing water‐soluble sulfonated melamine–oxytriazines formaldehyde resins using a four‐step process involving cycling of temperature and pH to avoid gelation of the resins. The properties of the prepared resins as dispersants for cement mortars and concrete mixes were examined, and the products were found to be slightly inferior to comparable resins prepared from pure mel

ISSN:0021-8995    

DOI:10.1002/app.1988.070360101

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

年代:1988

数据来源: WILEY

摘要:

AbstractNovel organofunctional siloxanes from γ‐methacryloxypropyltrimethoxysilane (MPTMS) were synthesized by transesterification reactions with high monohydric alcohols, branched alcohols, ether alcohols, phenol, and mandelic acid. The factors effecting the substitution ratios were determined. Copolymers of these siloxanes with methyl methacrylate (MMA) were prepared by bulk copolymerization in glass molds and their swelling, thermal, oxygen permeability, and surface free energy characteristics were investigated in order to determine the effect of the substituted group on the produced copolymer. The changes in these properties by the crosslinking of the copolymer with ethylene glycol dimethacrylate (EGDM) were also investigated. The copolymers containing branched, nonpolar, and lengthy pendant groups were found to be highly oxygen permeable possibly due to the introduction of larger free volume by these groups. The surface energy analysis showed that the main variation was found to be in γ SVPvalues rather than γ SVdvalues and only ether alcohol substitution increased γ SVPvalues to a gre

ISSN:0021-8995    

DOI:10.1002/app.1988.070360102

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

年代:1988

数据来源: WILEY

摘要:

AbstractEucalyptus saligna meal and chips have been treated with HClO‐NaClO in order to increase their accessibility to cellulases fromTrichoderma virideand hence to increase the yield of hydrolysis of cellulose into glucose. Different experimental variables determine the efficiency of the pretreatment. These are the pH and temperature of the pretreatment, the granulometry and concentration of the substrate, the oxidant concentration and prior elimination of hemicelluloses by prehydrolysis with dilute acid. An incomplete factorial design has been used to study the effect of these experimental variables on the weight loss during the pretreatment, the composition of the pretreated substrate, and the quantity of glucose formed as function of time in the subsequent enzymatic hydrolysis. Delignification can reach 70% using 5 mol HClO‐NaClO per kilogram of w

ISSN:0021-8995    

DOI:10.1002/app.1988.070360103

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe adsorption of four dyes (Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114) onto bagasse pith has been studied using an agitated batch adsorber. The variables studied were initial dye concentration and pith mass. A mathematical model has been developed based on external mass transfer and solid‐phase diffusion. The model has been used to generate theoretical concentration–time decay curves, and these results were adjusted to experimental data by a best fit approach. The external mass transfer coefficients are 2.0 × 10−3, 1.5 × 10−3, 8.0 × 10−4, and 5.0 × 10−4cm s−1and the solid diffusivities are 1.1 × 10−8, 1.0 × 10−8, 6.0 × 10−9, and 3.0 × 10−9cm2s−1for Basic Blue 69, Basic Red 22,

ISSN:0021-8995    

DOI:10.1002/app.1988.070360104

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

年代:1988

数据来源: WILEY

摘要:

Abstractα,β,β‐Trifluoroethylenesulfonyl fluoride (TFESF) was grafted onto polyethylene (PE) film by a simultaneous‐irradiation method. The influences of the grafting conditions were analyzed kinetically. The dependencies of the grafting rate on the dose rates and monomer concentrations ranging from 10 to 75% were found to be of 1 and 0 order, respectively. The overall activation energy for the graft polymerization was 2.05 × 104J/mol. The grafting rate was found to be independent of the film thicknesses ranging from 25 to

ISSN:0021-8995    

DOI:10.1002/app.1988.070360105

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

年代:1988

数据来源: WILEY

摘要:

AbstractCertain properties of the membranes obtained by simultaneous‐irradiation grafting of α,β,β‐trifluoroethylenesulfonyl fluoride (TFESF) onto low‐density polyethylene (LDPE) were studied. Swelling, water uptake, electric conductivity, and transport number of the grafted membrane were measured, moreover, thermal and chemical stability were investigated. These properties were found to be mainly dependent on the degree of grafting. The electric conductivity and swelling of the membrane at less than ca. 25% grafting were found to be very low because the distribution of ion‐exchange groups is heterogeneous as revealed by X‐ray microscopy of the grafted films. At more than 25% grafting, the membranes showed good electrochemical and thermal properties, acceptable for the practical use as cation exchan

ISSN:0021-8995    

DOI:10.1002/app.1988.070360106

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe friction and wear characteristics of PTFE and one of its composites, JS material rubbing against stainless steel, were determined with a pin‐disk tester in this study. The JS material is a multilayer composite composed of PTFE layer containing metal oxide and others, porous bronze layer, copper‐plating layer and steel back. The submicroscopic features of frictional surfaces of stainless steel and JS materials were observed with an electron probe microanalyzer (EPM). By analysis of fractional surfaces of stainless steel pins in various operating stages with X‐ray photoelectron spectroscopy (XPS), chemical shifts of Cls, Ols, and Flspeaks, F‐ion gathering in surface transfer films, and generation of a metal fluoride and an unknown compound containing oxygen were found. The determination of JS material wear debris with electron spin resonance spectroscopy (ESR) showed that polymeric radicals different in structure and stable in air existed. The authors consider that these PTFE molecule structure variations might be of benefit to the adhesion of PTFE transfer film to the rubbed stainless steel surface, which is important to improve the friction and wear performance

ISSN:0021-8995    

DOI:10.1002/app.1988.070360107

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

年代:1988

数据来源: WILEY

摘要:

AbstractTo improve the performance of nylon 4 membranes, this study attempts to utilize chemical initiation which induces different hydrophilicities vinyl monomers grafted onto nylon 4 membranes. Sodium styrene sulfonate, chloromethyl styrene, styrene, and glycidyl methacrylate were used as grafting monomers. The factors that affect the degree of grafting considered were chemical initiators, pH values, kinds and concentrations of monomers, reaction time, and temperatures. The mechanical strength and the transport properties of these chemical‐initiated grafted nylon 4 membranes were also investigated. Both the water flux and the salt rejection of sodium styrene sulfonated‐grafted membrane were increased significantly, compared to our previous paper,1and the casein rejections of all of the four grafted nylon 4 membranes studied exceeded 90%. The quaternized nylon 4‐g‐poly(chloromethyl styrene) membranes were prepared and possessed high water uptake behavior and high transfer number (0.99) for electrodialysis. The sulfonating process was also applied to improve the hydrophilicity of nylon 4‐g‐poly(glycidyl methacrylate) membrane so that the water flux and the salt rejection were bot

ISSN:0021-8995    

DOI:10.1002/app.1988.070360108

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe epoxidized natural rubber was fragmented by ozonolysis and the ozonolyzed mixture was analyzed by gas chromatography/mass spectroscopy. The peak areas of the analyzed partial chromatograph were used to calculate the ratio of CC, CEC, and CEEC (dyad, triad, and tetrad) compared with the theoretical value calculated assuming random epoxidation of the latex. In this manner the epoxidation reaction was proved to be random.

ISSN:0021-8995    

DOI:10.1002/app.1988.070360109

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

年代:1988

数据来源: WILEY

摘要:

AbstractNylon 6 produced by the reaction injection molding (RIM) process is toughened through block copolymerization of caprolactam with functional, rubbery prepolymers. This article describes an alternate route, where caprolactam is polymerized in the presence of a dispersed particulate rubber. The particulate rubber employed in this study has a core‐shell morphology with a soft, crosslinked butadiene‐based rubbery core and a grafted styrene–acrylonitrile shell. The core‐shell rubber is dispersed as a latex in caprolactam to high quality dispersions which, on anionic polymerization, give tough castings. Incorporation of a reactive monomer such as hydroxypropyl methacrylate in the graft shell brings about further improvement in impact s

ISSN:0021-8995    

DOI:10.1002/app.1988.070360110

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

年代:1988

数据来源: WILEY