Use of the time-of-flight mass spectrometer to study the volatile products from mechanical degradation of polymers in a vibration grinder

Problems about the use of the mass-spectrometry method to study the compositions and kinetics of evolution of volatile products formed during the process of mechanical degradation of polymers in a vibration grinder are examined. A vibration ball mill was directly connected to the vacuum chamber of a time-of-flight mass analyzer. By use of this method, mass spectra of the volatile products evolved during vibration grinding of samples of polymethyl methacrylate, polytetrafluoroethylene, polyethylene, and poly-α-methylstyrene have been obtained. The possibility of studying the kinetics of evolution of volatile products as a function of the amplitude and duration of grinding has been shown in the case of polymethyl methacrylate and of polytetrafluoroethylene.     

Investigation of the processes of thermal and mechanical degradation of polymers using mass spectrometers. Review

The review covers work with mass spectrometers during the last 5 years involving the study of the processes of thermal and mechanical degradation of polymers. Special attention is given to the effect of defects in the macromolecules on the development of the thermal and mechanical degradation processes. It is suggested that the defects of the chemical structure of the macromolecules have an important influence not only on the thermal degradation but also on the development of mechanical failure. The possible uses of mass spectrometry in investigating interfaces are also examined. The initial experiments along these lines are discussed.     

Intensity of mechanical action and mechanical degradation of rigid polymers

The authors have investigated the relation between the degradation of rigid carbon-chain polystyrene, polyvinyl acetate, and polymethyl methacrylate polymers with the kinetics of mechanical degradation during vibromilling. They determine the critical value of the intensity necessary for the onset of the degradation process.Moscow Technological Institute of Light Industry. Translated from Mekhanika Polimerov, No. 2, pp. 362–364, March–April, 1974.     

Comparison of the activation energies of the processes of thermal degradation and mechanical fracture of polymethyl methacrylate

On the basis of a comparison of the activation energies of the processes of thermal degradation and mechanical fracture of PMM with various additives it is concluded that in the presence of a "pole shift effect" it is more correct to calculate the activation energy U₂ of the mechanical fracture process on the assumption that ₀ = const and =f(, T). The energy U₀₂ is then correlated with the weak-bond rupture energy. In the general case, the activation energy U₀₁, calculated on the assumption that ₀=f(, T) const, i. e., from the slopes of the lg -1/T graphs, cannot be identified with the interatomic-bond rupture energy.Mekhanika Polimerov, Vol. 4, No. 3, pp. 467–473, 1968     

Description of the mechanical relaxation of highly oriented polymers based on their relaxation spectra

Both the shape and width of the relaxation spectra of polymers with different draw ratios are analyzed in regions of relaxation transitions. The analysis substantiates an empirically ascertained linear law governing the frequency distribution of the dynamic modulus E'(ω) of highly oriented polymers in E' = ln ω coordinates, which corresponds to the uniform distribution of a single relaxation time H(τ) ? const. The possibility of describing the temperature dependence of the modulus of highly oriented polymers within a broad temperature range is demonstrated, where a single relaxation time is used and consideration given to the nonuniform distribution of the energy of fundamental vibrations with respect to oscillatory modes.     

Formation of a linearly extended destruction zone in the body of transparent polymers

The action of pulsed laser radiation on solid transparent polymers has been studied. Analysis has been made of different methods of concentrating the light field: focusing to a point and focusing to a caustic. High effectiveness of injury to the material during the use of the method of linearly concentrated focusing is shown.Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 354–356, March–April, 1976.     

On the a-Browder and a-Weyl spectra of tensor products

Given Banach space operators A ∈ B( ) and B ∈ B( ), let A?B ∈ B( ? ) denote the tensor product of A and B. Let σ _a , σ _aw and σ _ab denote the approximate point spectrum, the Weyl approximate point spectrum and the Browder approximate point spectrum, respectively. Then σ _aw (A?B) ? σ _a (A)σ _aw (B) ? σ _aw (A)σ _a (B) ? σ _a (A)σ _ab (B) ? σ _ab (A)σ _a (B) = σ _ab (A?B), and a sufficient condition for the (a-Weyl spectrum) identity σ _aw (A?B) = σ _a (A)σ _aw (B) ? σ _aw (A)σ _a (B) to hold is that σ _aw (A?B) = σ _ab (A?B). Equivalent conditions are proved in Theorem 1, and the problem of the transference of a-Weyl’s theorem for a-isoloid operators A and B to their tensor product A?B is considered in Theorem 2. Necessary and sufficient conditions for the (plain) Weyl spectrum identity are revisited in Theorem 3.     

Friction and wear with lubrication by the products of the thermo-oxidative destruction of polyethylene

Results are given of a study of the friction and wear processes when the products of the rmooxidative destruction of polyethylene are used as a solid lubricant and modifying agent. It is established that their physicochemical properties provide a very low coefficient of friction and wear in metal-electronegative-polymer pairs.     

Comparison of the shapes of macro- and submicrocracks in loaded polymers

Small-angle x-ray scattering has been used to estimate the longitudinal (L) and transverse (L) dimensions of the submicrocracks formed in loaded polymers. The growth under load of macrocracks, initiated in the same polymers by a slit or a circular hole, has also been observed. The ratios L/L for the macro- and submicrocracks are found to coincide.A. F. Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 1013–1018, November–December, 1971.     

Elasticity of the intercrystallite zones and the mechanical properties of oriented polymers

As a result of a study of the behavior under load of the elements of the supermolecular structure of oriented amorphous-crystalline polymers it is shown that the stresses on the crystallites and the amorphous zones in series with them in the direction of the chain axes are equal to the mean stress applied to the specimen along the orientation axis. The nature of the elasticity and deformability of the amorphous zones is analyzed. A relation is obtained between the strength properties of oriented polymers and the number of load-carrying chains in the amorphous zones.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 1002–1007, November–December, 1969.     

Effect of the conditions of bond formation and destruction on the adhesion of polymers to synthetic fibers

It is shown that the adhesion of linear polymers can be measured by shearing a monofilament relative to a microblock of adhesive [1]. Experiments have been performed on polypropylene, polyethylene terephthaliate, polycaprolactam, polyvinyl alcohol, and glass fibers. Broad variation of the diameter, structure, and physicomechanical properties of the various kinds of oriented fibers had practically no effect on the adhesion. The physicochemical properties of the adhesive solutions at the moment of application to the fiber likewise do not affect the adhesion which, other things being equal, is determined by the nature and supermolecular structure of the polymers in the contact zone.Belorussian Lenin State University, Minsk. Branch of the Karpov Scientific-Research Physicochemical Institute, Obninsk. Translated from Mekhanika Polimerov, No. 6, pp. 1042–1048, November–December, 1970.     

Effect of external pressure on the physicochemical and mechanical properties of polymers

The behavior of crystalline polymers obtained by molding at high pressures has been investigated. External pressure can promote or retard polymer crystallization processes, depending on its intensity. Comparison of various physicochemical and mechanical properties of specimens obtained at different external pressures shows that the corresponding curves have two maxima: one at 200–800 kgf/cm² and another on the narrower interval between 1300 and 1500 kgf/cm². The position of the first maximum is associated with the molecular weight distribution and the flexibility of the polymer chain, and position of the second is determined by the chemical nature of the polymer. The data obtained help to make possible a rational choice of polymer processing methods in which pressure is involved.Mekhanika Polimerov, Vol. 4, No. 2, pp. 200–204, 1968     

Relationship between the molecular structure and certain mechanical properties of oriented polymers

The correlations between the molecular structure and intermolecular energy and the fatigue and elastic properties of fibers are considered. It is shown that the maximum of these properties corresponds to an optimal value of the intermolecular energy.Leningrad Branch of the All-Union Scientific-Research Institute of Synthetic Fibers. Translated from Mekhanika Polimerov, No. 4, pp. 734–735, July–August, 1969.     

Comparison of the lifetimes of polymers tested in a vacuum and in air

The temperature-time dependence of the strength of kapron (nylon 6) fibers has been studied in a vacuum and in air. In the vacuum tests a pole shift effect is observed, whereas in air no such effect is present. It is shown that the pole shift observed under vacuum conditions can be attributed to the inconstancy of the coefficient in the Zhurkov equation. In this case the activation energy of the fracture process U₀, calculated from the slopes of the log vs 1/T graphs, cannot be assigned the significance of a unit bond rupture energy.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, Voo. 5, No. 2, pp. 250–256, March–April, 1969.     

Relation between the mechanical properties of polymers and the kinetic flexibility of the macromolecules

Nuclear magnetic resonance combined with extension of the specimens in the NMR spectrometer on the reversible deformation range has been used to study the cooperative modes of motion of the macromolecules in polymers, specifically polycaprolactam and polyethylene terephthalate. For each of these polymers there are two temperatures near which the nature of the molecular motion changes sharply. At low temperatures there is a transition from independent hindered vibrations of the repeating units to correlated vibrations, as a result of which the chains in the amorphous regions acquire limited kinetic flexibility within the glassy state; at high temperatures there is a transition to segmental motion. The question of how changes in the modes of molecular motion are reflected in the macroscopic mechanical properties of polymers is examined.Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 24–29, January–February, 1971.     

Intermolecular interactions in fiber-forming linear polymers and certain of their mechanical properties

Values of the specific volumetric intermolecular interaction energies of a series of linear polymers have been calculated on the basis of data on the interatomic and intermolecular interactions of the functional groups in the polymer molecules. It is shown that the specific volumetric intermolecular interaction energy is closely correlated with the elastic and relaxation properties of the polymers, which makes it possible to predict a series of mechanical properties of chemical fibers.Leningrad Branch, All-Union Scientific-Research Institute of Synthetic Fibers. Translated from Mekhanika Polimerov, No. 5, pp. 790–795, September–October, 1971.     

Use of computers to calculate the mechanical characteristics of relaxation processes in polymers

A method of calculating the constants found in Kohlrausch's empirical function describing relaxation processes is proposed, which is based on the application of a well-known algorithm for solving nonlinear problems on a computer using the conjugate gradient method. All the experimental information is used by this method and the degree of calculation accuracy is increased. The reproducibility of calculations to find these constants is found to be satisfactory in the case under investigation when the duration of the experiment is varied.