摘要:

AbstractIn the dyeing of mineral Khaki on cotton fabrics, which are mainly used for military uniforms in India, a mixture of Fe2O3and Cr2O3is deposited in the fabric. When these garments are laundered using bleaching powder solution, the chromium oxide is likely to accelerate the oxidation of cotton cellulose. This aspect has been studied by oxidizing cotton yarn with sodium hypochlorite solution in the presence of chromium oxide, varying the chromium content, the pH of the oxidizing medium, and the concentration of the oxidizing agent. The properties of these chemically modified celluloses indicate that chromium oxide does accelerate the hypochlorite oxidation of cellulose and that the maximum extent of acceleration takes place when the oxidation is carried out at pH 7. The oxidized products were further modified separately by treatment with chlorous acid and sodium borohydride, and the effects of these agents on the properties of the oxidized products were studied.

ISSN:0021-8995    

DOI:10.1002/app.1979.070230111

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

年代:1979

数据来源: WILEY

摘要:

AbstractExtrusion experiments on eight polymers in our laboratory and eight additional polymers in other laboratories reveal that solid‐state extrusion and malleability occur in semicrystalline polymers that have a reversible crystalline transition,Tc, and do not occur in crystalline polymers devoid ofTc, The solid‐state extrusion takes place only in the temperature range ofTc≪T

ISSN:0021-8995    

DOI:10.1002/app.1979.070230112

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

年代:1979

数据来源: WILEY

摘要:

AbstractA method of preparation of an urethane emulsion which provides thermosetting film is described here. By reacting a urethane prepolymer containing terminal isocyanate groups with diethylenetriamine in the presence of ketones, poly(urethane‐urea‐amine) was prepared. In other organic solvents, however, gelation occurred immediately and preparation of polyurethane‐urea‐amine was not successful. The function of ketone was ascribed to the tentative formation of a Schiff base between the primary amino group of diethylenetriamine and ketonein situ, and the reaction of primary amine with isocyanate was partly masked to prevent gelation. Then the free amino group is generated when the polymer is treated with epichlorohydrin and the reaction occurs between them. After the solution was neutralized with an aqueous acid, the solvent was removedin vacuoto give a stable self‐emulsifiable thermosetting urethane emulsion. Typical mechanical properties of film from this urethane emulsion are also g

ISSN:0021-8995    

DOI:10.1002/app.1979.070230113

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

年代:1979

数据来源: WILEY

摘要:

Abstract2,2′,6,6′‐Tetrabromo‐3,3′,5,5′‐tetramethyl‐4,4′‐biphenol (TTB) is a new flame retardant monomer possessing a high degree of chemical and thermal stability. This brominated biphenol can be directly incorporated as a comonomer in condensation polymerizations. An example is the preparation of copolycarbonates of TTB and 2,2‐(4‐hydroxyphenyl)propane (BPA) via the aqueous caustic phosgenation method. The reaction of TTB with either ethylene oxide or ethylene chlorohydrin affords 4,4′‐bis(2‐hydroxyethoxy)‐2,2′,6,6′‐tetrabromo‐3,3′,5,5′‐tetramethylbiphenyl (TTB‐Diol). This diol is melt polymerized into a series of terephthalate copolymers with 1,4 butanediol. The above copolymers possess flame retardancy, thermal stability, and good mechanical properties. These high‐bromine‐content copolymers are blended with nonhalogen‐containing polymers to af

ISSN:0021-8995    

DOI:10.1002/app.1979.070230114

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

年代:1979

数据来源: WILEY

摘要:

AbstractIn the synthesis of low‐density polyethylene there is a direct relationship between the synthesis conditions, molecular structure, and technical properties of the product. The evaluation of the molecular structure of the polymer is therefore important. The most important structure parameters in low‐density polyethylene are molecular weight distribution (MWD), degree of long‐chain branching (LCB), and short‐chain branching distribution (SCBD). Through chain transfer to polymer it is possible to get composite molecules made up of chains with different amounts of short‐chain branching. By using temperature rising elution fractionation (TREF) and plotting the methyl contents or the DTA melt temperature of the fractions as functions of the elution temperature, the SCBD within composite molecules can be evaluated. The deviations from linear relationships are caused by such SCBD within composite molecules. In order to demonstrate the buildup of composite molecules, samples from different parts of a reactor were inv

ISSN:0021-8995    

DOI:10.1002/app.1979.070230115

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe technologically important studies on rubber friction and wear give strong support to rubber friction being a viscoelastic phenomenon. However, the basic concepts and conclusions derived from such studies appear to have general validity. Fiber‐to‐fiber friction studies are carried out on a number of polymeric flaments with a view to establishing the relationships between fundamental mechanical properties such as modulus, tan δ, and the coefficient of friction. The relationship between these three quantities is expressed by an equation. The results show that with these fibers adhesive contribution to friction is negligible and that temperature and humidity variations in end uses have a much more important effect in frictional properties than changes in draw ratio, heat setting, and s

ISSN:0021-8995    

DOI:10.1002/app.1979.070230116

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe sulfur vulcanization of NR by a MBT‐TMTD mixed accelerator system both in the presence and absence of ZnO and stearic acid with or without DCP has been studied. The rate of decomposition of DCP in the presence of both MBT and TMTD is quite similar to that in the MBT system alone. The reduction in crosslinking due to DCP is dependent mainly on MBT. The decomposition product of TMTD may contribute to it only at the later stage of vulcanization. Though TMTD has no influence on the decomposition rate, it reacts with MBT at least in the initial stage of vulcanization and suppresses the retardation caused by MBT on DCP vulcanization in accordance with the free sulfur decrease, the nature of crosslinking formation both in the presence and absence of DCP, and the methyl iodide treatment of the vulcanizates. The vulcanization process of the MBT‐TMTD‐S‐NR system has been interpreted in terms of both free radical and polar mechanisms. The domination of either of these depends on the dominant amount of either MBT or TMTD in the acclerator ratio. According to the initial high rate of crosslink formation, free sulfur decrease and also the initial additiveness of crosslinking in stocks containing DCP, the vulcanization process of MBT‐TMTD‐ZnO‐St. acid‐S‐NR system has been explained in terms of an ionic mechanism. The pronounced synergistic nature of such systems has been interpreted by the enhanced activation of MBT‐S‐ZnO‐St. acid complex due to the dithiodicarbamate ion formed in the initial stages of vulcanization, and also by the activation of TMTD accelerated vulcanization due to the

ISSN:0021-8995    

DOI:10.1002/app.1979.070230117

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe diffusivities of simple gases through a series of polyurethane block copolymers of differing aromatic urethane content and type of soft segment were measured using a quadrapole mass spectrometer as a detecting device. Although an Arrhenius expression generally described the temperature dependence of diffusion in this system, a discontinuity was observed in the Arrhenius plots for some materials, and the discontinuity was found to be related to the onset of the glass transition in the hard domains. Increasing the hard segment content of the materials decreased the diffusivity due to the increase in the activation energy of diffusion. Increasing the soft segment length brought about a decrease in the activation energy with an increase in diffusivity. Polyster urethanes had lower activation energies for diffusion than polyether urethanes of similar hard segment composition. Finally, as the penetrant diameter was increased, a decrease in the diffusivity and an increase in the activation energy was noted.

ISSN:0021-8995    

DOI:10.1002/app.1979.070230118

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

年代:1979

数据来源: WILEY

摘要:

AbstractVinyl acetate (VAc), styrene (St), and methyl methacrylate (MMA) were irradiated in dilute solution at an absorbed dose rate of 0.5 Mrad/hr in the absence of oxygen at room temperature. In homogeneous systems, telomers are formed with a rate ∝ [M]1at monomer concentrations [M]>ca. 0.4M. The chain length (D.P..n) increases with increasing [M]. (D.P..n)−1depends over large ranges of [M] linearly on the ratio [S]/[M] (S = solvent) in accordance with the Mayo equation. These findings were obtained with VAc in methanol and with St in cyclohexane. In heterogeneous systems, telomer is formed at all monomer concentrations. The 100‐eV yield for telomer formation passes a maximum ofGT(–M)= 40 (MMA in 2‐propanol) andGT(–M)= 27 (MMA in cyclohexane) at the onset of polymer formation ([M] ∼ 3 vol‐%). With the system St/2‐propanol,GT(–M)∼ 15 was found being independent of [M]. The molecular weightMn(telomer) increased from ca. 600 to ca. 1200 by increasing [M] up to 100 vol‐% (MMA/2‐propanol).Mn(telomer) does not depend on [M] in the other two cases (Mn∼ 500, MMA/cyclohex

ISSN:0021-8995    

DOI:10.1002/app.1979.070230119

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe magnitude of the activation energy for diffusion,EDis shown to be inversely dependent on the fractional free volume of the polymer aboveTg. From the proportionality ofEDabove and belowTg, the magnitude ofEDbelowTgis also inversely dependent on the free volume in that temperature range. While this correlation holds very well for our determinations of fractional free volume aboveTgit does not correlate with the Simha‐Boyer fractional free volume belowTg, contrary to expectation

ISSN:0021-8995    

DOI:10.1002/app.1979.070230120

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

年代:1979

数据来源: WILEY