On a nonlinear Volterra equation of nonconvolution type

The asymptotic behavior of bounded solutions of a nonlinear, nonconvolution Volterra integral equation is investigated under weaker kernel assumptions than previous works have assumed.     

Isomerism in poly(tetrafluoroethylene-alt-trifluoronitrosomethane)

The structures of samples of poly(tetrafluoroethylene-alt-trifluoronitrosomethane) prepared by bulk copolymerization at temperatures in the range ?30 to +90° have been investigated using ¹⁹F-NMR spectroscopy. Whilst the predominant mode of addition of CF₃NO to a growing copolymer chain gives the

radical, occasional reverse additions occur, giving

. The activation energy for the reverse addition is ca 8.5 kJ mol^?1 greater than that of the predominant propagation reaction.     

Amidrazones V. thermolysis of N1-benzyl-substituted amidrazone ylides

Thermolysis of 1,1-dimethyl-1-benzyl-2-(iminophenylmethyl)hydrazinium hydroxide inner salt gave dimethylamine, 2,4,6-triphenyl-s-triazine and 2,4,6-triphenyl-1,2-dihydro-s-triazine.     

The Application of a Digital Computer to Mechanical Testing

A digital computer is being used to record raw data and to provide automatic data calculations for mechanical tests. The computer which is connected through an analog-digital converter to a universal testing machine and to a torsion tester, stores the raw loadstrain data, converts it to stress-strain data, and calculates any of the mechanical properties desired from the test. The computer can also provice a printout and a paper tape, both of which contain the stress-strain data points and the calculated data. In addition, the loadstrain data that are normally obtained from the test machine are still available. An oscilloscope display is obtained as the data are being recorded. Tests which are presently being performed using the computer are: tensile, compression, pin bearing, double shear and torsion. Data which are being recorded include: ultimate strength, offset yield strength, elastic and shear moduli, energy under the stress-strain curve, and a mathematical expression for the stress-strain curve. In addition to the mechanical load-strain curve provided by the test machine, the computer can provide a stressstrain curve and a listing of stress-strain data points.     

Effect of finite extensibility on the viscoelastic properties of a styrene–butadiene rubber vulcanizate in simple tensile deformations up to rupture

Stress–strain and rupture data were determined on an unfilled styrene–butadiene vulcanizate at temperatures from ?45 to 35°C and at extension rates from 0.0096 to 9.6 min^?1. The data were represented by four functions: (1) the well-known temperature function (shift factor) a_T; (2) the constant strain rate modulus, F(t,T), reduced to temperature T₀ and time t/a_T, i.e., T₀F(t/a_T)/T; (3) the time-dependent maximum extensibility, λ_m(t/a_T); and (4) a function Ω(χ) where χ = (λ ? 1)λ_m⁰/λ_m, in which λ is the extension ratio and λ_m⁰ is the maximum extensibility under equilibrium conditions. The constant strain rate modulus characterizes the stress–time response to a constant extension rate at small strains, within the range of linear response; λ_m is a material parameter needed to represent the response at large λ; and Ω(χ) represents the stress–strain curve of the material in a reference state of unit modulus and λ_m = λ_m. The shift factor a_T was found to be sensibly independent of extension. At all values of t/a_T for which the maximum extensibility is time-independent, the relaxation rate was also found to be independent of λ. These observations indicate that the monomeric friction coefficient is strain-independent over the ranges of T and λ covered in the present study. It was found that λ_m⁰ = 8.6 and that the largest extension ratio at break, (λ_b)_max, is 7.3. Thus, rupture always occurs before the network is fully extended.