The possibility was investigated of applying the Baly criterion for a fast determination of the parameters of the Zhurkov formula as applied to glass-cloth-base laminates in the bending test at constant rate of strain. The possibility of applying the Zhurkov formula to glass-cloth-base laminates was confirmed by means of dispersion and regression analysis of experimental data. Respecting the Baly criterion, all parameters of the Zhurkov equations cannot be determined. Data satisfactory in terms of an express method were only obtained in the determination of the structure-sensitive factor. The values of the pre-exponential factor and of the activation energy of the fracture process are in agreement with the kinetic strength theory and may be accepted a priori. The possibility of evaluating the structure-sensitive factor also from the correlation dependences on the stress-at-break value was proved experimentally.
The kinetics and mechanism of the emulsion homo- and copolymerization of methacrylate with the amides of acrylic and methacrylic acids are studied. The observed differences in the copolymerization constants for the emulsion process compared with reaction in solution are due to the changes in the concentrations of the comonomers in the reaction zone. Acrylamide has an insignificant effect on the rate of emulsion polymerization, and methacrylamide decreases it because of slowing down of the reaction in the aqueous phase. The nucleation of monomer-polymer particles is achieved by different mechanisms, the ratio between which depends on the presence of water-soluble comonomers and the initiation rate. Over a specific range of ammonium persulphate concentrations several radicals can coexist in the latex particles, and a gel effect arises. These features of the reaction lead to a situation where the kinetic orders with respect to the emulsifier and initiator depend on the polymerization conditions.
As part of our studies of structurization processes in polyurethanes (PU) synthesized in the presence of disperse fillers, the effect of surfactants on the supermolecular structure and thermophysical properties of polymeric composites was investigated. At 10 wt% of filler in the polymeric composite, an abrupt breakdown of the physical network with rigid domains acting as crosslink points takes place. By means of surfactants it is possible to increase the content of filler in the composite up to 20%, without appreciable deterioration of the degree of segregation in the polymer matrix.
Scattering of polarized light has been employed to investigate the structure of solutions of poly(4,4′-oxydiphenylene)pyromellitamido acid (PAA), linear PAN and modified PAN (PAN-1) and also their blends with a different content of the starting components in the concentration range 1–13%. In solutions of PAN-1 and its blends with PAA as compared with solutions of only PAA there is higher structural orderliness; PAN-1 and its blends with PAA in solution display a tendency towards crystallization. The polymer-polymer interaction PAA-PAN-1 in the solutions of the blends is confirmed. In a 13% solution of the mixture of PAA with PAN-1 (80:20) association processes were found developing in time to reach a maximum within 7–8 days. Combination of the considerable dimensions of the associates of the macromolecules peculiar to PAA solutions and the high microanisotropy appearing in the presence of PAN-1 ensures good deformation-strength properties of the composite materials based on blends of composition PAA:PAN-1 = 80:20 (% by weight).
The properties of polypropylene synthesized on a titanium-magnesium catalyst in a liquid monomer under various conditions are studied by X-ray spectroscopy, GPC and DSC. It is established that the properties of the polypropylene are independent of the type of titanium-magnesium catalyst used. The most important criterion, i.e. the isotacticity of the polypropylene is determined firstly by the type of stereo-regulating additives and the molar ratio of cocatalyst and additive, and also the polymerization temperature. The synthesized polypropylene has lower values of the degree of crystalline, enthalpy of melting, and of crystallization compared with polymers obtained on the basis of industrial, highly effective titanium trichloride.
By changing the mode of sample heating one may determine the coefficient of compressibility of a thermoplastic polymer by analysing the heating curve.
Aspects of the influence of the macrokinetics on the MM and MMD of a polymeric product formed in turbulent flow are examined. The specific phenomena of the influence of the amount of catalyst applied to the reaction zone and the number of reaction zones in conditions of adiabatic heating of the reaction mixture and different variants of heat removal on the MM and MMD of the polymer have been identified and quantitatively estimated. The conduct of fast polymerization processes calls for special methods of investigation and an individual approach to the implementation of the technological process: different grades (according to the MM and MMD) of the polymer may be obtained by changing the system of supply of catalyst and the means of heat removal. Some specific variants of the conduct of the process of oligo- and polymerization are considered. The non-traditional behaviour of rapid polymerization processes raises the problem of allocating them to a separate class of polymerization reactions.
Complexing in the aqueous and non-aqueous solutions of poly-1-vinylazoles has been studied by the calorimetric method. It is shown that mixing of poly-1-vinylazoles with stronly donor and strongly acceptor solvents is accompanied by major exothermal effects due to the formation of electron donor-acceptor bonds in solution. On dissolution in acceptor solvents, including water, the polymers act as electron donors through the unshared electron pairs of the nitrogen atoms of the heterocyclic substituents and on dissolution in donor solvents as electron acceptors via the aromatic rings. It is shown that during dissolution of poly-1-vinylazoles an important role is played by their self-association due to the presence in the polymers of both donor and acceptor properties.
Catalytic systems based on trialkylsiloxy derivatives of vanadium or vanadium compounds combined with titanium trialkylsiloxy derivatives possess high activity during copolymerization of butadiene with propylene. In the temperature range from −35 to + 20°C equibinary copolymers are obtained with a high degree of alternation of units. It is assumed that homogeneous solutions of vanadium compounds containing trialkylsiloxy substituents retain a number of advantages of heterogeneous compounds of the transition metals fixed on silica gel.
Electron absorption spectra of anionic centres in disodium α-methylstyrene tetramer (DSTMS), of benzylsodium and of their complexes with stilbene (STB) have been calculated. Downwards-shifted (< 0.5 eV) excited charge-transfer levels have been found for benzyl anion pairs separated by STB; thermal occupation of these levels leads to electron transfer resulting in the formation of the STB− Na+ anion radical. A comparison of the calculated and experimentally determined spectra provides evidence on the formation of the STB− Na+ anion radical also in the reaction of STB with DSTMS. The calculated spectra of benzyl, phenylisopropyl and stilbenyl radicals shows that the detection of these species is complicated because of the low intensity of transition in the visible part of the spectrum. Polymerization of α-methylstyrene in the system DSTMS-CTB was investigated.
The authors have studied the thermal stability of LDP films crosslinked photochemically in presence of sulphur monochloride or sulphuryl chloride using as anti-oxidants Irganox 1076, Phenozan 23, FAU-13, Irganox B 225 and Diafen NN. It is shown that the presence of a photo-initiator substantially hastens the process of consumption of the anti-oxidants on exposure of the films to UV1light. The photoproducts formed ensure the practically unchanged thermal stability of the crosslinked samples for one year. With use as photo-initiator of sulphur monochloride the thermal stability of the film during crosslinking after a fall at the initial stage begins to rise and as a result materials may be obtained with a content 80–90% gel fractions characterized by an induction period not inferior to and indeed often exceeding several times the values for the unirradiated samples.
During high-shear extrusion with a disc extruder, materials based on PP-HDPE blends are obtained that have properties that differ (towards an increase in the strength properties) from those of the same blends obtained by simple mechanical mixing. The difference is related to the fact that, in addition to the homogenization of the material during such processing, radical transformations occur that lead to the formation of a third component in the system, namely, a block-copolymer. These conclusions have been confirmed by radiothermoluminescence analysis of the blends.
Interpolymer interaction of poly-(4,4′-oxyphenylene)-pyromellitamide acid with poly-2-vinylpyridine is studied over a wide temperature range from the synthesis stage in solution to thermal degradation of composite films, by thermal analysis and IR spectroscopy methods, and determination of the mechanical characteristics of the composite films. Mutual stabilization of the polymers and the formation of a new structure because of the appearance of salt-like bonds and intermolecular cross-links is demonstrated.
A study was made of the strength and relaxation mechanical properties of block samples of polyketones and of polyketone composite materials. In addition, the mechanical properties of block samples of blends of polyketones and polysulphones were investigated. The samples were prepared by press moulding and injection moulding. The structure of the polyketones under study is partially crystalline, resulting in the appearance of two regions of mechanical serviceability. On the one hand there is the low-temperature region, in which the material withstands high mechanical stress levels without softening or failing; on the other hand there is the high-temperature region, where the material withstands relatively low levels of stress, but remains serviceable at elevated temperatures. The introduction of short-chopped glass fibre results in higher strength, and reduces the stress relaxation intensity; the introduction of polysulphone suppresses crystallization of polyketone by changing the mode of its relaxation behaviour. It is shown that polyketone based on iso-phthalic and tere-phthalic acids and on the polyketone-polysulphone blends, when processed by injection moulding, result in samples that have good mechanical properties over a rather wide range of temperature.
Adiabatic and isothermal calorimetry have been used to study the thermodynamic properties of allyloxy-ethyl-α-cyanoacrylate and polyallyloxyethyl-α-cyanoacrylate and the following properties have been determined: the isobaric heat capacity of the monomer and the polymer in the range 11–330 K, the glass-transition parameters and the parameters of the glassy state of the monomer, the energy of combustion of the monomer and the polymer. The following thermodynamic functions have been calculated from the experimental data obtained: H0(T) − H0(0), S0(T) and G0(T) − H0(0) for the range 0–330 K, and the enthalpy of combustion and the thermodynamic parameters of formation, ΔHf0, ΔSf0 and ΔGf0. These results been used to calculate the enthalpy, entropy and the Gibbs function for the polymerization of allyloxyethyl-α-cyanoacrylate in bulk in the range 0–330 K and the upper limiting temperature for polymerization has been estimated.
The coefficient of translational diffusion of a narrow-distribution polymer—poly(α-methylstyrene), M = 3.3 × 106—calculated from the low-frequency component of dynamically scattered light has been shown to coincide with the value determined by the classical method of macroscopic diffusion. The correctness has been shown of a method for decomposing the correlation function into a low- and a high-frequency component, based on a program which makes use of a regularization algorithm. The method has been used to separate the large-scale motion in polymer chains from the motion of the macromolecule as a whole.
Structuring under the action of FeCl3 and ZnCl2 in liquid butadiene rubbers with different positions and contents of nitrile and carboxyl groups in studied. It is shown that the effect of structuring is manifested much more in rubbers where the functional groups are located inside the macromolecular chain, and not at its ends. Increase in the carboxyl and nitrile group content promotes the appearance of coils of more convoluted form and more difficult access to the metal cations to the oligomer functional groups. This results in retarded vulcanization of the rubbers, impairment of their film forming power, and as a consequence, to a decrease in the protective properties of coatings based on them.
An ensemble of subchains simulating the amorphous region of oriented polyethylene, in accordance with the statistical distribution obtained previously by the authors is constructed by the Monte Carlo method, and the distribution of local density over the thickness of the amorphous region is studied. The principles determining the anomalous density in a thin layer close to the crystallite surface are analysed. The anomaly disappears if a requirement that the conformational freedom of long straight chains and loops in this layer is limited is introduced into the theory.
The concentrations of active propagation centres and rate constants for elementary acts of PE macrochain propagation and the limitations of its propagation by alumino-organic compounds in the polymerization of ethylene under conditions of the PE in a hydrocarbon solvent at 433 K on titanium-magnesium catalytic systems (based on a bulk catalyst and on a system with dissolved components), and also on a traditional Ziegler system based on titanium trichloride are determined by radiochemical methods. It is shown that titanium-magnesium catalytic systems have a several times higher content of active centres in their composition, and that the high temperature polymerization of PE under their action has larger values of the above constants than with the classical Ziegler system.
The phase equilibrium of PS gels with a network of different density in cyclohexane in the non-deformed state in conditions of uniaxial stretching and all-sided compression has been studied. The pulsing mechanism of phase separation of the gels was found manifest in the fluctuational character of the rate of their clouding, squeezing out of the solvent and non-monotonic change in their geometric dimensions and also the radii of the light-scattering particles.
