摘要:

AbstractThe viscoelastic behavior of an ethylene–propylene copolymer is analyzed. Two different vulcanization procedures were followed; in the first a binary mixture of initiator‐polymer was used, while in the second the polymer was diluted by a solvent. The networks thus obtained show a different viscoelastic behavior depending on the different vulcanization procedure used. Results, analyzed in terms of supramolecular organization being present in the amorphous material, give some important information about the molecular nature of theC2coefficient of the Mooney‐Rivlin equation, and therefore about the well‐known deviations from the Gaussian theory shown by all rubber‐like

ISSN:0021-8995    

DOI:10.1002/app.1973.070171101

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

年代:1973

数据来源: WILEY

摘要:

AbstractMelting and crystallization behavior of virgin polytetrafluoroethylene have been studied using a differential scanning calorimeter. Following quantitative relationship was found between number average molecular weight of polytetrafluoroethylene and the heat of crystallization in the molecular weight range of 5.2 × 105to 4.5 × 107: M̄n= 2.1 × 1010ΔHc−5.16, where M̄nis number average molecular weight and ΔHcis the heat of crystallization in cal/g. The heat of crystallization is independent of cooling rate ranging from 4 to 32°C/min. This relationship provides a simple rapid and reliable method for measuring the molecular weight of polytetrafluor

ISSN:0021-8995    

DOI:10.1002/app.1973.070171102

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

年代:1973

数据来源: WILEY

摘要:

AbstractA dynamic mechanical study of four elastomeric threads has been made: the threads comprise natural rubber, nitrile rubber, Lycra, and Spanzelle. The dynamic loss modulus (E″) and the dynamic storage modulus (E′) were studied over a wide range of temperature (−110°C to 180°C) and the transitions were interpreted in the light of the chemical composition of the materials. The threads were investigated at 2%, 200%, and 400% static strain at a frequency of

ISSN:0021-8995    

DOI:10.1002/app.1973.070171103

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

年代:1973

数据来源: WILEY

摘要:

AbstractAn experimental study of the linear viscoelastic and friction properties of passenger tire tread compounds containing realistic black and oil contents and several different types of elastomers includingcis‐polyisoprene,cis‐polybutadiene, emulsion polymerized polybutadiene, and three emulsion polymerized butadiene—styrene copolymers (SBR's) has been carried out.E′ (ω) and tan δ were determined as a function of frequency and temperature. At any specific frequency and temperature, tan δ was an increasing function ofTgor a decreasing function ofT−Tg. When the tan δ–frequency data were plotted at the sameT−Tg, all of the treads based upon emulsion‐polymerized butadiene polymers yielded nearly the same curve. Wet coefficients of friction of the tread compounds correlated with both tan δ andT−Tgsupporting the idea that lubricated friction is largely due to hysteresis. The correlation among the butadiene—styrene polymers was much better than with the natural rubber, which exhibits a lower tan δ and a higher wet coefficient of friction than an SBR of the sameTg. The experimental results are used to investigate the heat buildup and skid properties of tires contain

ISSN:0021-8995    

DOI:10.1002/app.1973.070171104

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

年代:1973

数据来源: WILEY

摘要:

AbstractA simple, generalized equation of state has been developed for molten polymers. The equation yielded calculated pressure–volume–temperature data that deviated by 1% or less from experimentally determined data. The use of the equation requires only that the polymer's glass temperature and density at 25°C and 1 atm be known. Polymer glass temperatures can also be estimated with the equa

ISSN:0021-8995    

DOI:10.1002/app.1973.070171105

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

年代:1973

数据来源: WILEY

摘要:

AbstractDrawn polyacrylonitrile can be characterized only insufficiently with regard to its molecular and supermolecular structures which substantially determine the physical properties. This paper points out that the so‐called “superstructure” of polyacrylonitrile fibers can be cleared up after suitable thermooxidative treatment using x‐ray small‐angle scattering technique. The chemical reactions during the thermo‐oxidative treatment lead to a “self‐contrasting” effect so that the fibers as such are severely damaged yet information about the supermolecular structure can be obtained. The investigations show that changes in the course of fiber production (spinning, drawing, and annealing processes) affect alterations of the superstructure. The described method of investigation represents a so far unknown possibility for the purpose of detecting the supermolecular structure of drawn

ISSN:0021-8995    

DOI:10.1002/app.1973.070171106

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

年代:1973

数据来源: WILEY

摘要:

AbstractAntioxidant additives in polyethylene films have been shown to diffuse to the surface where they are subsequently lost, exposing the polymer to oxidation. Compatibility of antioxidants with polyethylene may be increased by use of silane coupling agents. In this study, three approaches to antioxidant modification are examined: (1) bonding antioxidant directly to silicon, (2) coupling the silane to an antioxidant hydroxyl function, and (3) dissolving antioxidants in silanes. All three approaches are shown to be effective in reducing antioxidant loss by diffusion.

ISSN:0021-8995    

DOI:10.1002/app.1973.070171107

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

年代:1973

数据来源: WILEY

摘要:

AbstractElectron spin resonance (ESR) spectra of free‐radical intermediates formed during photo‐initiated graft polymerization reactions of acrylamide, methacrylamide, and diacetone acrylamide onto purified cotton cellulose were recorded. Purified cellulose was saturated with aqueous solutions of the vinyl monomers (0.5M) and then photolyzed under nitrogen by near‐ultraviolet light (3100–4100 Å, peak near 3500 Å) at −196° and 40°C. Other samples of cellulose were saturated with aqueous solutions of the monomers, dried, and then photolyzed at 40°C. In the absence of cellulose, either poorly resolved or no free‐radical spectra were generated on photolysis of the monomers. Photolysis of dried cellulose at 40°C and wet cellulose at −196°C initiated formation of a cellulosic radical that generated a singlet spectrum. Photolysis of wet cellulose at 40°C generated no ESR detectable radical; however, photolysis of wet cellulose that contained monomer at 40°C generated poorly resolved spectra. The ESR spectra of the propagating copolymer radicals recorded were poly(acrylamide), three lines; poly(methacrylamide), five lines; and poly(diacetone acrylamide

ISSN:0021-8995    

DOI:10.1002/app.1973.070171108

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

年代:1973

数据来源: WILEY

摘要:

AbstractTurbulent drag reduction data were obtained at Re = 9000 in a 0.62‐cm‐I.D. pipe for five Polyox compounds covering a wide range of molecular weights. The concentration dependence of drag reduction was shown to obey an improved form of Virk's drag reduction equation, which was previously applied only to flows in capillary tubes. The efficiency of the drag‐reducing polymer additives on a unit concentration basis at infinite dilution was determined by using a characteristic parameter,DRm/[c], for each compound. A linear relationship was found to exist between this parameter and polymer molecular weight. The polymer degradation data were analyzed through use of a variable related to the dissipated energy in the wall region. The polymer molecular weight was found to decrease as a hyperbolic function of the dissipated energy function. By examining the change of molecular weight with respect to this function, a degradation index characteristic of the entire Polyox polymer family was established. This index may be of general application and provide a method by which the shear stability of various species of drag‐reducing polymers may be meaningfully c

ISSN:0021-8995    

DOI:10.1002/app.1973.070171109

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

年代:1973

数据来源: WILEY

摘要:

AbstractThis paper describes a general theory for the optimization of multicomponent blending to achieve a desired chromatographic distribution. A procedure for compound blending is also discussed, where optimum replication of both the chromatographic spectra and a second independent parameter can be achieved. Lastly, this theory is applied in a hypothetical example.

ISSN:0021-8995    

DOI:10.1002/app.1973.070171110

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

年代:1973

数据来源: WILEY