摘要:

AbstractA study of oxidative instability versus molecular structure for a systematic series of well‐defined linear poly(carborane‐siloxane)s is reported. These polymers form the backbone components of the most recently developed high‐temperature elastomers. The basic structure iswhere (1)x= 1, 3, 4, 5, ∞ (2) A = endgroups (reactive and inert); (3)Z=meta‐carborane,para‐carborane (forx= 3); (4)R = CH3, R = C2H4CF3(forx= 3), one in five R's = C6H5with the remainder CH3(forx= 4); (5) molecular weight = ∼10,000, ∼50,000 (forx= 3). Thermomechanical spectra in air (∼1 cps) from 130°C → 625°C → 130°C at 3.6°C/min, thermogravimetric data from 25°C → 700°C in air (3.6°C/min), and differential thermal analysis data from 25°C → ∼450°C in air (15°C/min) are presented. Thermo‐oxidative stability is discussed in terms of structur

ISSN:0021-8995    

DOI:10.1002/app.1973.070170901

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

年代:1973

数据来源: WILEY

摘要:

AbstractDocumentation and preliminary analysis of the infrared and proton nuclear magnetic resonance spectra of a systematic series of poly(carborane‐siloxane)s containing CB10H10C cages are reported. Inconsistencies in the spectra are interpreted in terms of complications in the synt

ISSN:0021-8995    

DOI:10.1002/app.1973.070170902

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe graft polymerization of acrylamide onto filter paper preirradiated in air with electrons from a 200‐keV accelerator has been shown to lead to weight increases of up to 210%. The degree of grafting depends on the radiation dose, the moisture content of the paper, and the time interval between irradiation and grafting, but is independent of the radiation dose rate. The degree of grafting increases with the monomer concentration of the reaction medium, and increases as the grafting temperature is reduced. Irradiations in the presence of O2or N2and the effect of ferrous ions in the grafting solution indicated that peroxides derived from cellulose do not contribute significantly to the initiation reactions up to 60°C. The results are consistent with the degree of grafting depending primarily on the concentration of trapped radicals present in the paper at the time of copolymerization. The cellulose in the grafted material was degraded and the grafted acrylamide was isolated and its molecular weight measured and compared with a calculated value. The moisture regain characteristics of the grafted material are report

ISSN:0021-8995    

DOI:10.1002/app.1973.070170903

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

年代:1973

数据来源: WILEY

摘要:

AbstractPreemulsifying modifiers, or their solutions in monomers, with soap and water prior to charging the remaining ingredients of an emulsion polymerization system markedly changes the reactivity of high molecular weight modifiers. The increased reactivity of a mercaptan is seen in a higher regulating index as measured by the rate of depletion of the mercaptan. The regulating index oftert‐hexadecyl mercaptan for a styrene‐butadiene copolymerization (SBR) increased from 0.3 for the control to 3.0 after preagitation, and thus approached thetert‐dodecyl mercaptan control in efficiency on a molar basis. The regulating index ofn‐dodecyl mercaptan increased from 1.0 for the control to 16 for the experimental. The latter value is too high for efficient modification of SBR systems. This technique permits the attainment of a continuous range of regulating index values within limits based on the reactivity of the modifier and intensity and duration of preagitation. This paper presents solutions for two of the problems associated with the preagitation technique and proposes a mechanism to account for the changes in modification arising from preagitating modifiers in the soap solution. This report develops a variable in emulsion polymerization that has been little used and incompletely und

ISSN:0021-8995    

DOI:10.1002/app.1973.070170904

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe dehydrochlorination reaction of poly(vinyl chloride) was investigated by subjecting molded polymer discs to thermal treatments at comparatively low temperatures and for low degradation extents, such as to maintain practically unchanged the sample's composition and physical state. The HCl evolution‐versus‐time curves exhibited accelerating behaviors to be ascribed to the catalytic action of HCl accumulating in the samples owing to a hindered diffusion. By assuming a catalyzed dehydrochlorination reaction occurring independently from the uncatalyzed one and being first order with respect to HCl, a kinetic equation describing satisfactorily the experimental evidence was dedu

ISSN:0021-8995    

DOI:10.1002/app.1973.070170905

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

年代:1973

数据来源: WILEY

摘要:

AbstractAlternating block copolymers of bisphenol A carbonate and dimethylsiloxane at three different compositions were studied by mechanical and dielectric measurements. Both sets of data exhibit transitions characteristic of the primary glass transitions of the component polymers. This behavior is characteristic of heterophase polymers. Dielectric data for all three samples cast from methylene chloride solution are presented. In addition, one sample was also cast from the solution of methylene chloride–n‐hexane. The resulting morphologic differences among the samples are reflected in the activation energies associated with the low‐temperature transitions. The time–temperature superposition principle was invoked to construct master curves for both mechanical and dielectric data. It was found that there exist considerable discrepancies in the respective master curves and the shift factor data. These results indicate that this heterophase block copolymer is thermorheologically

ISSN:0021-8995    

DOI:10.1002/app.1973.070170906

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

年代:1973

数据来源: WILEY

摘要:

AbstractCurrently available small pore‐size porous glass packing materials have been characterized as substrates for gel permeation‐chromatographic separations. The elution volumes of narrow molecular weight‐distribution polystyrene standards and hydrocarbon solutes have been determined using tetrahydrofuran as solvent. The results show that none has a sufficiently small pore diameter to enable low molecular weight oligomers to be separated. New smaller pore‐diameter packing materials are required to enable these rigid materials to be used for separations of oligomer mixtures

ISSN:0021-8995    

DOI:10.1002/app.1973.070170907

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

年代:1973

数据来源: WILEY

摘要:

AbstractLexan polycarbonate and polysulfone P‐1700 were blended to various weight percentages by dissolution in methylene chloride. The blended material was reclaimed in the form of evaporated thin films which were dried, ground, and molded. Low‐frequency mechanical relaxation tests were run on specimens machined from this material as a function of composition and thermal treatment. In addition to the β‐peak, a second peak, β′, was resolved in unannealed 75 wt/o P‐1700 specimens. These results are presented and a possible interpretation is discussed and compared with previously proposed

ISSN:0021-8995    

DOI:10.1002/app.1973.070170908

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

年代:1973

数据来源: WILEY

摘要:

AbstractAcrylamidomethylated cellulose (AMC) was prepared by reacting cellulose with N‐methylolacrylamide or its ethers in acidic medium under a variety of conditions. The extent of the reaction, expressed as mmole double bonds per 1 g cellulose, increased by increasing the concentration of N‐methylolacrylamide or its ethers. However, the paddry‐cure technique produced AMC with greater amounts of double bonds than the pad‐batch technique. Also, the reactivity of the etherifying agents follow the order N‐methylolacrylamide>N‐methoxymethylacrylamide>N‐methoxymethylmethacrylamide. Furthermore, the behavior of AMC in neutral, alkaline, and acidic media was studied. No change in the amount of the pendent double bonds of AMC occurred in neutral medium regardless of the conditions employed. On the contrary, disappearance of the double bonds took place in alkaline medium. The extent of disappearance depends on the kind of alkali used as well as on the conditions implemented. It was disclosed that consumption of the pendent double bonds of AMC occurred mainly via addition of the cellulose hydroxyls to yield a crosslinked cellulose. Treatment with hydrochloric acid, on the other hand, resulted in partial splitting of the acrylamidomethyl groups as well as addition of the acid on the pendent double

ISSN:0021-8995    

DOI:10.1002/app.1973.070170909

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

年代:1973

数据来源: WILEY

摘要:

AbstractLow molecular weight atactic polypropylene hydroperoxide (APPH), m. (onset) ≈ 80°C, was prepared via oxidation of uninhibited low molecular weight atactic polypropylene (APP). The APPH was thermally decomposed over a temperature range of 115°–125°C in which the APPH was in a neat molten state. The reaction order (n) was found to be close to 2,n= 2.2 ± 0.2, and the activation energy of decomposition (E) was ca. 27 kcal/mole1. In contrast to solid‐state decompositions, such values would be anticipated for liquid‐phase decompositions due to enhancement of molecule mobility and hydro

ISSN:0021-8995    

DOI:10.1002/app.1973.070170910

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

年代:1973

数据来源: WILEY