摘要:

AbstractTwo new flame‐retardation methods for polyester/cotton blend fabric were attempted with reference to thermal reactions of the blend fabric. One is the combination of phosphorylation of the cotton component and the addition of a phosphorus compound. The phosphorus compound must not interact with cotton component. The other involves the addition of a powerful flame retardant for the cotton component only. The flame retardant must induce only a small amount of carbonous products from the pyrolysis of the cotton componen

ISSN:0021-8995    

DOI:10.1002/app.1979.070240101

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

年代:1979

数据来源: WILEY

摘要:

AbstractStarch xanthate with degrees of substitution (D.S.) ranging from 0.12 to 0.56 reacted with vinyl monomers (acrolein, acrylamide, acrylic acid, acrylonitrile, methyl acrylate, or styrene) and hydrogen peroxide to form aqueous gels of starch–polyvinyl monomer graft copolymer. The same reactions conducted in a rubber latex medium resulted in a self‐acidifying, self‐heating, and self‐foaming coagulation to give a foam rubber. Such products were formed from several synthetic latices (NBR, SBR, polyisoprene, and polychloroprene types) and natural rubber latex; noted for each were the effects of the D.S., of monomer and peroxide concentrations, and of starch:elastomer ratios. The dried foams were evaluated by standard strength tests. Foam rubber of acceptable extensibility and enhanced tensile strength (up to 110 psi) was obtained with 0.12–0.15 D.S. xanthate and with proper balance of vinyl monomer, peroxide, and starch:elastomer ratio. Resilience was fair to good, but compression set was rather poor compared to most foam rubbers of ge

ISSN:0021-8995    

DOI:10.1002/app.1979.070240102

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe reaction of a carboxyl‐containing acrylonitrile copolymer with a macrodiisocyanate based on polypropylene oxide (Mn= 2000) in dimethylformamide (DMFA) and dimethylsulfoxide (DMSO) solutions was studied. The mechanism and main kinetic regularities of the grafting reaction were investigated. The reaction proceeds through formation of a mixed anhydride with its subsequent decomposition leading to liberation of CO2and formation of graft copolymers. Carboxyl and nitrile groups of the copolymer take part in the reaction. A side reaction involving interaction of isocyanate groups of macrodiisocyanate with DMFA proceeds during synthesis of graft copolymers in DMFA solutions. The dependence of graft polymer yield on temperature, macrodiisocyanate concentration and on the catalyst/NCO ratio was determined. The activation energy of the grafting reaction is 22.9 kcal/mole. The specific viscosity of graft copolymers in DMFA solutions increases with the number of grafted chain

ISSN:0021-8995    

DOI:10.1002/app.1979.070240103

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

年代:1979

数据来源: WILEY

摘要:

AbstractA new load cell for flywheel‐type impact tensile testing was designed and fabricated for specimens of polymer sheet and film. The cell employs a piezoelectric ceramic oscillator (toric in shape) as a load sensor, which has a high natural frequency (1800 kHz) and high sensitivity (ca. 0.1 V/N without amplification). The time constant for the electric circuit was improved substantially by the introduction of a voltage follower using an operational amplifier with excellent performance (common mode voltage ±120 V and slew rate 100 V/μsec). The positioning of the load sensor and the shape of specimen clamps are important design features, especially the halved Morse‐type taper pins in the structure of the specimen clamps. Signals of impact, passing through the piezoelectric oscillator and the voltage follower, are recorded by a transient time converter. The converter is equipped with a memorization system, an automatic pretrigger circuit, and a facility for reproduction under a slow time base, thus eliminating the need for troublesome photographing. For performance testing of the impact tester, oriented poly(ethylene terephthalate) sheets were used and good results were obt

ISSN:0021-8995    

DOI:10.1002/app.1979.070240104

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

年代:1979

数据来源: WILEY

摘要:

AbstractA model is presented to account for the large variations in tensile and tensile impact strength of amorphous polymers from a consideration of an idealized entanglement network. The material strength under tensile impact conditions is shown to be predictable and to increase with the “fineness” of the entanglement network; a higher entanglement density leading to more molecular chains supporting the stress. The entanglement density is, in turn, shown to increase with number‐average molecular weight and the quotient of the length to the molecular weight of the chemical repeat unit (empirically found to be related to the critical enganglement molecular weight). Ductile behavior is demonstrated to occur under tensile impact conditions when the material strength σBexceeds the yield stress σyand brittle behavior when σy>σB. It is further demonstrated that the large variation in tensile impact strength among the amorphous polymers studied can be adequately accounted for in terms of the large and predictable variation in σB; the larger σBis relative to σy, the more the polymer can draw (absorbing energy in the process) until σBis reached. Surprisingly, the predictions of strength for high‐molecular‐weight polycrystalline materials also gave good agreement with

ISSN:0021-8995    

DOI:10.1002/app.1979.070240105

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

年代:1979

数据来源: WILEY

摘要:

AbstractStyrene (St) was polymerized in the presence of poly(p‐nitrophenyl acrylate) (PNPA) with azobisisobutyronitrile as an initiator to prepare graft copolymers through the chain transfer reaction of growing polystyrene (PSt) radicals to the aromatic nitro groups on PNPA. The maximum number of branches attained was 16.4 (Pnof PNPA was 1780), which corresponds to 108 monomer units per PSt branch. This is far less than the value of 43, previously obtained for poly(vinylp‐nitrobenzoate) as a trunk polymer. Therefore, several model compounds for trunk polymers were prepared, and the chain transfer constants of PSt radicals to these model compounds were determined. As a result of the Hammett plot, it is concluded that higher electron attracting property of the substituents increases the reactivity of nitro groups to the growing PSt radicals, resulting in more highly branched graft copolym

ISSN:0021-8995    

DOI:10.1002/app.1979.070240106

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe effects of molecular structure and cooling conditions on the severity of draw resonance was investigated by carrying out carefully controlled melt spinning experiments. For the study, two types of polymeric materials were used: one which exhibits viscoelastic behavior (high‐density polyethylene, polypropylene, and polystyrene), and the other which exhibits almost Newtonian behavior [nylon‐6 and poly(ethylene terephthalate)]. In order to investigate the effect of cooling on the severity of draw resonance, different methods of cooling the molten threadline were employed. In one set of experiments, isothermal chambers of various lengths (3, 6, and 12 in.) were attached to the spinnerette face, so that the molten threadline, upon exiting from the spinnerette, began to cool in the ambient air only after it had passed through the isothermal chamber. This method of cooling is called “delayed cooling,” providing both an isothermal region (inside the isothermal chamber) where only stretching occurs, and a nonisothermal region (outside the isothermal chamber) where both stretching and cooling occur simultaneously. In other experiments, the temperature profile of the molten threadline was controlled by adjusting the temperature of the heated chamber. This method of cooling provides a gradual drop of the threadline temperature, compared to the more sudden drop when spinning into a cold environment provided at the spinnerette exit. The severity of draw resonance was recorded on movie film, and the thread tension was measured with a low‐force load cell transducer and recorded on a chart recorder. The temperature of the threadline along the spin direction was measured using a fiber optical probe attached to a Vanzetti Infrared Thermal Monitoring System (Model TM‐1). It was found that the severity of draw resonance depended on the molecular structure and the way the molten threadline was cooled. Of particular interest is the observation that, for the viscoelastic materials investigated, cooling destabilized the molten threadline outside the isothermal chamber. This gave rise to more severe resonant behavior, at and above the critical draw‐down ratio, in contradiction to the theoretical prediction by Fisher and Denn. It was observed, also, that the elasticity of the materials tended to destabilize the molten threadline (i.e., it increased the severity of draw resonance), again in contradiction to the theoretical prediction of Fisher and Denn. It is believed that morphological changes of polymers may play an important role in the occurrence of draw resonance when a melt threadline is stretched under cooling. Our study indicated that a good understanding of draw resonance of viscoelastic fluids requires more careful study than the classical hydrodynamic stability analysis reported by Fisher and Denn. They based their analysis on several convenient and yet unjustified assumptions, and solely on phenomenological considerations. We suggest that future theoretical analysis of draw resonance be carried out by considering a fluid model with a nonlinear memory function in order to properly account for the deformation history of the fluid, and the relaxation and cooling processes in the die swell region and the re

ISSN:0021-8995    

DOI:10.1002/app.1979.070240107

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

年代:1979

数据来源: WILEY

摘要:

AbstractPneumacel, a new kind of resilient closed‐cell foam, has characteristics especially useful for firm cushioning materials. A fluorocarbon inflatant in addition to air present in the closed cells provides a mechanism for recovery from long‐term loading for nonelastomeric polymer foams such as poly(ethylene terephthalate). The basic structural features characterizing pneumacel contribute to its performance as a resilient foam. Important principles in selecting the optimum combination of polymer and inflatant are described, as well as the process for making pneumatic cellular products. Development work on applications of pneumacel fibers has led to its utilization in cushions for under carpets, padding for use over springs in mattresses, automobile seats, and furniture. Properties of the assemblies of fibers for such uses are descri

ISSN:0021-8995    

DOI:10.1002/app.1979.070240108

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

年代:1979

数据来源: WILEY

摘要:

AbstractWater‐insoluble carboxyl‐containing starches were prepared by grafting acrylonitrile onto a highly crosslinked starch followed by base saponification to convert nitrile groups into a mixture of carboxamide and carboxylate groups. Ceric ammonium nitrate or ferrous sulfate–hydrogen peroxide was used to initiate graft polymerization of acrylonitrile. The isolated products were evaluated for the removal of Cd2+, Cu2+, and Pb2+from aqueous sol

ISSN:0021-8995    

DOI:10.1002/app.1979.070240109

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

年代:1979

数据来源: WILEY

摘要:

AbstractA D2‐m‐dodecacarboranesiloxane containing alternating block copolymer\documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--}[{\rm A}\hbox{---}{\rm B}\rlap{--}]_n$\end{document}was prepared by the reaction of a ureidosilane‐terminated polysulfone hard block with a carboranesilanol‐terminated carboranesiloxane oligomer. The resulting block copolymer exhibited thermoplastic elastomeric behavior. This unique polymer had excellent thermal stability up t

ISSN:0021-8995    

DOI:10.1002/app.1979.070240110

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

年代:1979

数据来源: WILEY