Effect of radiation on creep of microplastic made from high-strength aramid fibres

Abstract

The elevated radiation resistance of a microplastic based on Rusar fibres even in combined exposure to ionizing radiation and mechanical loading was demonstrated. This is probably due to the high degree of orientation of the polymer fibres, so that radiation chemical decomposition reactions are suppressed and the purely thermal effect of the radiation is experimentally recorded.Due to the unique combination of high strength properties and relatively low density, organic aramid fibres are widely used in industry [1][2][3][4][5]. They also have high radiation resistance [6], which allows using them in structures working in ionizing radiation fields (electron streams and gamma quanta). However, the question is significantly complicated when a structure made from plastics with aramid fibres is exposed to radiation in a mechanically loaded state. Creep accelerates under the effect of ionizing radiation on mechanically loaded polymer materials [7-9]. Ionizing radiation can have a dual effect: radiation-chemical, which damages the macromolecules in simultaneously occurring processes of cross-linking and degradation, and associated -thermal (heating). In both cases, acceleration of creep is possible, so that separating them is a very complicated problem. We investigated the features of creep of a microplastic based on Rusar high-strength aramid fibres in a field of ionizing radiation.We selected a microplastic based on Rusar high-strength complex aramid fibres made by dry-wet spinning, impregnated with EDT-10 epoxy binder; triethanolamine titanate was the curing agent. The mechanical characteristics of the microplastic before and after exposure to radiation were determined in stretching on an Instron universal tensile-testing machine with a mobile clamp movement rate of 100 mm/min. Irradiation was conducted at room temperature on a radiator with 60 Co isotope gamma quanta and an electron accelerator with electron energy of 300 keV. The absorbed dose was monitored with dosimeters made of cellulose triacetate film 120 μm thick [10]. The beam current in the electron accelerator was also continuously monitored during irradiation with a current-collecting electrode positioned on the measurement frame next to the sample, which allowed reliably maintaining the homogeneity of the electron beam current.The scheme for conducting the experiments to study creep of the microplastic in a field of ionizing radiation is shown in Fig. 1. An electron accelerator, system for mechanical loading of a constant load, a device for recording microstrains (accuracy of up to ~1 μm), and a micrometer screw for regulating its position were used in the measurements. To obtain precision creep measurements, special measures were instituted: reducing the effect of electrical interferences in the measurement circuits in operating the electron accelerator with optical recording of strains and nonadmission of slipping of the microplastic in the clamps by gluing the sample to the clamps.Radiation creep was determined as follows (see Fig. 1). The optical rec...