A.A. Askadskii

Creep study of linear and network polymers based on polyarylates and epoxide polymers

Abstract A creep study has been carried out over wide temperature and stress ranges on uniaxially stretched linear and network polymers based on polyarylates and epoxide polymers. Generalized pliability curves point to nonlinearity of the mechanical behaviour of polyarylates, whereas the network systems are characterized by linearity over a wide range of stress, particularly for short term processes. For all the systems under study the generalized pliability curves are characterized by two distinct portions for which the rates of relaxation processes differ sharply.

Dynamic mechanical properties of networks produced from polyphenylquinoxaline and cyclotriphosphazene hexa-isothiocyanate☆

Abstract The relaxation properties of systems based on polyphenylquinoxaline (PPQ) and a low molecular weight additive, namely cyclotriphosphazene hexa-isothiocyanate (CTPH) have been examined by a dynamic mechanical method. The chemical process taking place in the solid phase of the polymer and resulting in a crosslinked structure have been studied by this method. Addition of CTPH to the heat resistant polymers produced a system capable of greater mechanical absorption on heating without softening; the system also retained its entirety and rigidity.

Investigation of relaxation processes in polyphenylquinoxaline

Abstract A study has been made of the relaxation behaviour of polyphenylquinoxaline under static conditions over a wide range of stress and temperature. Apart from the transition separating two temperature regions with a different relaxation rate for each stress level, the existence of a relaxation transition in respect to stress was detected. The latter transition separates two stress regions in which marked differences in the rates of relaxation processes are observed.

Synthesis and properties of chlorine-containing polyphenylquinoxalines☆

Polyphenylquinoxalines based on bis-o-phenyldiamine—a derivative of DDT and a number of bis-(α-diketones) of varied structure have been synthesized by low temperature polycondensation. It is shown that the polymers obtained possess all the properties peculiar to polyphenylquinoxalines — quite high strength and strain capacity and also good solubility.

Study of the mechanical properties of films of regular copolymers containing phenylquinoxaline and naphthoylene benzimidazole

Abstract The limiting strength and relaxation (stress relaxation and creep) properties of films based on copolyphenylquinoxaline naphthoylene benzimidazole of regular structure have been studied. A new criterion of solubility is employed to analyse the effect of the quality of the dissolving medium in obtaining the films on their mechanical properties and its is shown that they may change within wide limits for a polymer of the same chemical structure.

On the structure and mechanical properties of crosslinked polymers based on oligomeric dicyanates

A study has been made of the relaxation behaviour of crosslinked polymers based on different oligomeric dicyanates. Structural parameters of the crosslinked polymers were calculated, and the packing coefficients determined. Structural parameters of the studied polymers determined experimentally are in good agreement with theoretically calculated values, which points to structural regularity of the polymer networks. It was found that relatively loose packing is a feature of the polymers containing methylsiloxane internodal network fragments. The latter polymers have packing coefficients below 0·576, which is much below Keff = 0.681 determined for many linear and network polymers.