摘要:

AbstractPyrolysis mass spectrometry (Py‐MS), time/temperature resolved Py‐MS (TTR‐Py‐MS), and pyrolysis tandem mass spectrometry (Py‐MS/MS) were used to determine the structure of an additive present in Biomer and Lycra Spandex. The additive was found to form a second phase in the polymer matrix which was insoulble inN,N′‐dimethylacetamide. This insoluble portion (7% by weight) was separated by centrifugation. The structure of this additive is proposed to be poly(2‐diisopropyl amino ethyl methacrylate)(DPA‐EMA). The additive is present as a stabilizer for UV radiation and chloride and hypochlorite ion attack. A chloride containing compound of similar structure (2‐diisopropyl amino ethyl chloride) (CAS No. 96‐79‐7) is also detected. This chloride‐containing compound may be formed by reaction of the polymeric additive with chloride ions du

ISSN:0021-8995    

DOI:10.1002/app.1990.070400101

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe nature of the structure changes of a highly condensed resol resin during its aqueous solution storage was considered. To this end, the curing process of the resin was investigated by means of DTA and its structure was analyzed by means of NMR. The hypothesis relative to stability of the hemiformal bonds was made.

ISSN:0021-8995    

DOI:10.1002/app.1990.070400102

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe structures of polysulforne hollwo fiber membranes, spun from the propionic acid :N‐meth‐ylpyrrolidone complex and from a formylpiperidine/formamide mixture were investigated as a function of progressive surface removal with an oxygen plasma. Oxygen plasma ablation experiments were performed on both unexposed and isopentanetreated hollow fiber membrances. Pure gas permeation rates were obtained on these samples as well as oxygen plasma etched samples which were then subsequently coated with polydimethyl‐siloxane from an isopentane solution. The results show that the hollow fiber membrane spun from the propionic acid :N‐methylpyrrolidone complex has both a thinner active separating layer and a thinner skin than the polysulfone hollow fiber membrane spun from the formylpiperidine/formamide mixture. Also, the resistance to flow of the porous substrate of the complex spun hollow fiber membrane is significantly less than that of the polysulfone hollow fiber membrane spun from the mixture. Therefore, the substrate of the PA : NMP complex spun hollow fiber membrane has greater porosity and less tortuosity than its FP/FA congener. The oxygen plasma ablation results and the scanning electron micrographs demonstrate a nonequivalence between the active separating layer and the microscopically observable skin of the hollow fiber membrane. It is believed that membranes prepared from Lewis acid : base complex solvents possess a porous substructure and a nonuniform (graded‐density) skin which consists of a very thin active separating layer whose effective thickness varies depending upon the gases to be separated and a thin less dense transition layer, which may contain pores whose sizes are below the limits of resolution by SEM. Both are components of the microscopically observable skin. Membranes possessing this structure belong to the trilayer class of integrally skinned membranes. If membranes are so fabricated that the density gradient in the active separating layer approaches zero, a bilayer membrane with a porous substructure and a thin skin of uniform density results. Membranes prepared from conventional solvent/nonsolvent mixtures, i.e., formylpiperidine/formamide, exhibit a diminished density gradient in the skin approximating the bila

ISSN:0021-8995    

DOI:10.1002/app.1990.070400103

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

年代:1990

数据来源: WILEY

摘要:

AbstractAnionic polymerization of styrene in CSTR processes demands monomers which are highly pure. Lithium aluminum hydride (LAH) is a highly reactive material which reacts with the impurities in styrene that interfere with anionic polymerization. The LAH/impurity reaction products are not compatible with anionic polymerization and therefore must be isolated or removed from the styrene before polymerization. This problem is most readily solved by supporting the LAH on ion exchange resin beads such that the impurity reaction products are chemically bound to the support. We have demonstrated the preparation of>50 mol of polystyrene/mol ofn‐butyl lithium by passing the polymeization feed through a column filled with LAH/ion exchange resin. This represents>10‐fold improvement in yield (based onn‐butyl lithium) over previously described feed purification techn

ISSN:0021-8995    

DOI:10.1002/app.1990.070400104

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

年代:1990

数据来源: WILEY

摘要:

AbstractDiglycidyl ether of bisphenol‐A was cured, individually, with diaminoisopropyl benzene (DAIPB), diaminoethyl benzene (DAEB), blends of DAIPB/DAEB (up to 40 wt % DAEB), and DAIPB modified with up to 5 wt % amine‐terminated poly(butadiene‐co‐acrylonitrile) liquid rubber (ATBN). For each diamine system glass transition temperature (differential scanning calorimetry) and room temperature tensile properties (Instron) were determined. Blends of DAIPB/DAEB produced cured resins displaying greatly increased tensile strength (up to 50% higher) and slightly lower glass transition temperature compared with resins cured with either diamine alone. DAIPB modified with ATBN yielded moderately improved tensile properties over DAIPB alone. Blends of DAIPB/DAEB (from 10 to 40 wt % DAEB) were observed to be eutectic liquids at room temp

ISSN:0021-8995    

DOI:10.1002/app.1990.070400105

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

年代:1990

数据来源: WILEY

摘要:

AbstractA novel and easily processed conductive polymer was prepared from poly(vinyl alcohol)(PVA). Metal chelate onto PVA film exhibited excellent surface resistivity around 100–102Ω/cm2when it was treated with reducing agents. The surface of these films was treated with reducing agents which possessed a definite metallic luster. The conducting surface proved to be metallized by x‐ray and FSCA analysis. The strongly adhering metal on the film was believed to be responsible for the enhancement of electrical conductivity. The factors that affect the conductivity of metallized film were also stu

ISSN:0021-8995    

DOI:10.1002/app.1990.070400106

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe influences of molecular weight, temperature, and shear rate on the capillary flow properties of thermotropic hydroxypropycelluloses have been studied. The crystalline/liquid crystalline transition temperature and the temperatures at which the liquid crystalline/isotropic transition begins and ends are higher as the molecular weight is higher. The flow curves show yield stresses and, contrary to general thermoplastic resins, the slope of log(viscosity)–log(shear rate) curve decreases as the shear rate increases. This tendency is more notable as the molecular weight is higher. The temperature change of the viscosity shows a minimum and the minimum moves to a higher temperature with increasing shear rate. The moving rate is higher as the molecular weight is higher. This is because the molecular orientation of the isotropic phase increases with increasing shear rate. Contrary to general thermoplastic resins, the molecular weight dependence of the viscosity increases with increasing shear rate. The yield stress is higher as the molecular weight is higher and shows a minimum at 200–210°C. The molecular weight dependence of the entrance pressure loss is higher than that of the viscosity. The end correction coefficients of the hydroxypropylcelluloses are very much higher than those of general thermoplastic resins: They exceed 50 in some cases. The temperature change of the end correction coefficient shows a maximum and the temperature at the maximum is higher as the molecular weight is higher. The die swell ratio shows a minimum at 180–220°C at low shear rates and the minimum swell ratio is lower than unity in some cases. The die swell ratio is higher as the molecular weight is in

ISSN:0021-8995    

DOI:10.1002/app.1990.070400107

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

年代:1990

数据来源: WILEY

摘要:

AbstractReactive microspheres suitable for binding proteins were prepared using emulsifier‐free emulsion copolymerizations of styrene (St) and acrolein (AL) with various molar ratios of monomers St and AL. A maximum polymerization rate was obtained when the molar ratio of the monomers was 1 : 1. The diameter of the latex particles increased with increase in the amount of monomer AL. The amounts of aldehyde groups on the latex particle surfaces were determined by conductometric titration. The binding capacity of the copolymer latexes with spacer molecules was also examine

ISSN:0021-8995    

DOI:10.1002/app.1990.070400108

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

年代:1990

数据来源: WILEY

摘要:

AbstractAcidic functionality on the surface of oxidized carbon blacks modifies the cure processes of the tetrafunctional epoxy resin MY720 (largely tetraglycidyldiaminodiphenylmethane, TGDDM) crosslinked with diaminodiphenylsulfone (DDS). In the early stages of the cure (up to 60 min at 140°C), the rate of consumption of TGDDM and DDS and the rate of production of the 1 : 1 adduct are increased, together with an increase in the production of ether functionality. These chemical changes are associated with an increase in exotherm. an increase in gel fraction, and preferential adsorption of the amine curing agent on the carbon surface. During the middle stages of the cure (after 180 min at 140°C), the acidic carbon black has a slight retarding effect on the cure; but, on completion of the later stages of the cure, the effect of the carbon surface functionality diminishes, and, in contrast to earlier studies with difunctional epoxy resins, neither the total cure exotherm nor the final glass transition temperature is affected greatly. We attribute this difference to the greater ease of etherification reactions for the tetrafunctional resin compared to the difunctional case. Basic functionality on the surface of carbon black (induced by carbon dioxide treatment) has a slight retarding effect on TGDDM consumption in early stages of the cure. Less adsorption occurs on the basic carbon than on the acidic carbon, and the adsorbed material appears to be rich in resin. These results imply that treated carbon surfaces may advance or retard the local cure state of an MY720–DDS matrix, but will not affect markedly the final cure st

ISSN:0021-8995    

DOI:10.1002/app.1990.070400109

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn this work, a process for making high‐modulus (8GPa) laminates of poly(ethylene terephthalate) (PET) has been developed. Oriented films of the polymer were produced by a technique utilizing a very high extension rate, and these films were crossplied and consolidated to form the product laminates. The procedures for drawing the original film lamina and consolidating the laminates were optimized with respect to the material properties. Further, the possibility of chemical healing–bonding of the lamina together by chemical reaction, not diffusion–was investigated for these materials. It was found that laminates could be formed with both high moduli and strong interply bonding and that the moduli actually increase due to crystallization during pressing. Longrange diffusion during bond formation was ruled out, since crosslinked polyesters were found to bond as readily as uncrosslinked. Chemical reactions between contacted surfaces appear to be a likely mechanism of bo

ISSN:0021-8995    

DOI:10.1002/app.1990.070400110

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

年代:1990

数据来源: WILEY