摘要:

AbstractPoly(ethylene ether carbonate) polyols can be modified by chemical reactions with polyglycol modifiers under conditions of elevated temperatures and reduced pressures, where diethylene glycol is removed as distillate. Molecular weight builds in a predictable manner and can be controlled by the amount of distillate removed. A reaction pathway for this transformation is proposed. It is important that the modifier be stable to reaction conditions and have a higher boiling point than diethylene glycol. The process has been characterized by following the distillate formation and composition as a function of reactor temperature and product molecular weight build. The product has been characterized by molecular weight, CO2content, carbon–13 NMR and viscosity/temperature relationships. Carbon–13 NMR of the carbonyl and methyl regions of the spectra are particularly useful for following the chemical changes. A new family of modified poly(ethylene ether carbonate) polyols has been prepared which was not available with prior technology. The modification procedure permits the control of properties such as modifier type and content, molecular weight, CO2content, viscosity,Tg, density, etc., in the resultant polyol. Since poly(ethylene ether carbonate) polyols have predominantly polyester polyol properties, modification with polyether polyols can be used to adjust properties. These polyols are useful in polyurethane applicati

ISSN:0021-8995    

DOI:10.1002/app.1990.070410901

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

年代:1990

数据来源: WILEY

摘要:

AbstractDegradation resulting from weathering in low‐density polyethylene (LDPE) films used in agricultural applications was investigated by a series of mechanical and spectroscopic characterization techniques. An easy, nondestructive, and comparatively sensitive test for measuring the durability of these films based on microhardness indentations is presente

ISSN:0021-8995    

DOI:10.1002/app.1990.070410902

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn the present paper, the emulsion polymerization of methyl methacrylate–butyl acrylate and styrene–ethyl acrylate were carried out. Polymer emulsions with latex particles of different morphology were prepared. The relationship between the minimum film formation temperature of the polymer latexes and the morphology of the latex particles were studied, and the film‐forming mechanism of the polymer latexes with varied particle morphology was also disc

ISSN:0021-8995    

DOI:10.1002/app.1990.070410903

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

年代:1990

数据来源: WILEY

摘要:

AbstractPolysulfone ultrafiltration hollow fibers were chemically modified on the surfaces with propylene oxide and Friedel‐Crafts catalysts. A peak at 1.6 ppm was observed in H1‐NMR spectrum of the modified fibers at 45°C, while the peak was not observed at 27°C measurements. The peak was attributed to a hydroxide group from the peak shift at high temperature. Micro ATR spectra of the modified fibers also suggested existence of CH(CH3)CH2OH segments on those surfaces. The modified fibers showed 10–80% rejection of polyethylene glycol 6000 at feed concentration of 0.5 wt %, depending on the conditions of surface reaction, and were found to have smaller molecular cut‐off than nonmodified fibers. The fibers were also compared with modified fibers with propane sultone reported previously [A. Higuchi et al.,J. Appl. Polym. Sci.,36, 1753 (1988)], which had negatively charged segments of CH2CH2CH2SO 3−. Absorption of bovine serum albumin on the modified fibers was estimated to be less than the nonmodified fibers from permeation measurements. It is suggested that fibers having hydrophilic surfaces show better results of anti‐absorption of solutes than the non

ISSN:0021-8995    

DOI:10.1002/app.1990.070410904

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

年代:1990

数据来源: WILEY

摘要:

AbstractBlock copolymers containing segments of poly(ethylene oxide) and polystyrene were synthesized. Dihydroxyl‐terminated polyethers (PEG‐4000 and PEG‐20,000) were reacted with an aliphatic diisocyanate (3‐isocyanatomethyl‐3,5,5‐trimethyl‐cyclohexyl‐isocyanate) and with an aliphatic hydroperoxide (t‐butyl hydroperoxide). The resulting polymeric peroxycarbamates were used as free radical initiators for vinyl polymerization. Formation of block copolymers was illustrated by several characterization methods such as chemical and UV analysis, infrared spectroscopy, and DSC thermograms. Mechanical characterization of the copolymers was made on the basis of the stress—strain curves obtained from a mechanical testing in

ISSN:0021-8995    

DOI:10.1002/app.1990.070410905

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

年代:1990

数据来源: WILEY

摘要:

Abstract2‐Ethylhexanol‐blocked toluene diisocyanate (2‐EH‐blocked TDI) modified resin was first prepared from epoxy resin and 2‐EH partially blocked TDI and subsequently reacted with di(2‐methylisobutylketiminoethyl)amine to obtain ketimine‐terminated resins. These ketimine‐terminated resins were hydrolyzed and partially neutralized with acetic acid to give macrocations. The resulting cationic resins were dissolved in suitable solvents and mixed with deionized water to form various emulsions. The formation of a stable emulsion is strongly dependent on the pH value of the emulsion and the amount of solvent added. Electrodeposition of the emulsion produced films of amine‐terminated and 2‐EH‐blocked TDI modified epoxy resins on the surface of a cathode. Factors such as the pH value of the emulsion, the content of organic solvents, the amount of 2‐EH‐blocked TDI, applied voltage, and electrodeposition time on the electrodeposition properties (such as deposition yield and throwing power of the resins) were investigated. Moreover, the deposited film could be thermally cured to have a crosslinked structure. It was found that a temperature above 160°C is required to cros

ISSN:0021-8995    

DOI:10.1002/app.1990.070410906

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

年代:1990

数据来源: WILEY

摘要:

AbstractPlasma polymer hexamethyldisiloxane, ethyldichlorophosphate and tris(butoxyethyl)phosphate modified polyacrylonitrile fibers were examined by FTIR, XRF, and SEM and the extend of flame retardancy introduced were checked. Certain levels of concentrations of flame‐retardant elements grafted or coated at the fiber surface during plasma treatment are believed to overcome some negative effects of a number of reactions that usually are concurrent with plasma polymerization, such as crosslinkin

ISSN:0021-8995    

DOI:10.1002/app.1990.070410907

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe heterogenous polymerization of methyl methacrylate in the presence of cuprous oxide was studied. Adsorption measurements of stearic acid from benzene solution onto the surface of Cu2O were carried out. The specific surface area of cuprous oxide as obtained from the extrapolation to the concentration of monolayer surface coverage in the adsorption isotherm was compared with that evaluated from the BET‐equation. Sedimentation volume and sedimentation rate of the variably surface modified Cu2O samples were determined. It was found that the surface modification of Cu2O enhances its catalytic effect in the heterogenous polymerization of methyl methacrylate up to monolayer surface coverage. The viscosity average molecular weightsM̄vof the respective polymers as well as the apparent activation energy of the polymerization process were correlated with the reaction paramete

ISSN:0021-8995    

DOI:10.1002/app.1990.070410908

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

年代:1990

数据来源: WILEY

摘要:

AbstractEthyl methacrylate(EMA)‐n‐butyl methacrylate (nBuMA) copolymer containing anhydrous ferric chloride was prepared by free radical polymerization at 70°C. TGA studies show that the addition of ferric chloride increases the thermal stability of the copolymer. Mössbauer studies of the copolymers showed the presence of Fe3+species only. Mössbauer studies of the copolymer heated at 150°C, 250°C, and 500°C for 1 h showed that during the thermal degradation, Fe3+species are reduced to Fe2+and then finally α‐Fe2O3is formed. The mechanism of thermal degradation has been proposed on the basis of IR, TGA, and Möss

ISSN:0021-8995    

DOI:10.1002/app.1990.070410909

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe present study reports results on the processing and mechanical properties of composites modified by the addition of dicumyl peroxide (DCP). The addition of minute amounts of peroxide to the cellulose/polymer system during processing has been shown to significantly improve the physical properties of composites. SEM micrographs of fracture surfaces of the peroxide modified composites reveal direct grafting of polyethylene onto cellulose fibers. The existence of a critical peroxide concentration indicates that the grafting reactions terminate when cellulose surfaces are no longer accessible. Possible mechanisms involved are discussed.

ISSN:0021-8995    

DOI:10.1002/app.1990.070410910

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

年代:1990

数据来源: WILEY