Evaluation of the effectiveness of methods of physical modification in production of reinforced thermosetting plastics

Abstract

It is proposed that the efficacy of different methods of physical modification be evaluated with the physicochemical activity of the physical effects that unavoidably affect the rate of chemical curing. Of the three methods of physical modification examined, treatment of prepregs with ultraviolet radiation and exposure to a constant electric field can be considered the most reliable and effective.The use of different physical effects (vibration, ultraviolet radiation, constant electric and magnetic fields) is an economical and highly effective direction for regulating and improving the characteristics of reinforced thermosetting plastics [1,2].In manufacturing samples of polymer composite materials (PCM), epoxy-4,4′-isopropylidenediphenol resin (ED-20, GOST 10587-93) cured with polyethylene-polyamine (PEPA, TU 6-02-594-85) was used as binder and polyacrylonitrile twist (nitron, TU 13-239-79), polycaproamide industrial (capron) and viscose industrial fibre (IF), as well as basalt (BF) and glass fibre (GF) were used as reinforcing fillers. The fibres were impregnated with the binder, wound with a large pitch on a wire coiling machine, and the prepreg obtained was placed in a thermostat. A OBN-150 bactericidal wall irradiator with a DB-30 lamp at a wavelength of 253.7 nm was used as the source of ultraviolet radiation (UVR). The linear density of the initial and impregnated fibres and the degree of conversion X of the initial oligomeric binder to an insoluble cross-linked product were monitored in the experiments. Quantity X was determined by extraction of sol with acetone at room temperature. The following physicomechanical characteristics were determined for the materials made from the prepregs with standard methods: -static flexural breaking stress (σ f , MPa, GOST 4648-93); -tensile breaking stress (σ b , GOST 11262-80); -static flexural modulus of elasticity E f , MPa; -impact strength (α im , kJ/m 2 , GOST 4647-80); -Brinell hardness (H B , MPa, GOST 4670-77); -24-h water absorption (W, %, GOST 4650-80); -density (ρ, kg/m 3 , GOST 15139-81).Physical modification was conducted either by physical processing in the stage of impregnation of the reinforcing fibre with the binder using vibration or as a brief physical action on the fibre freshly impregnated with the binder using a constant electric field (CEF) or UVR followed by curing in traditional conditions.The efficacy of the methods of physical modification can be assessed by the effect of the physical action used on the physicomechanical characteristics of the PCM (criterion 1) and the physicochemical activity of this physical action (criterion 2).The first criterion is obtained by comparing the characteristics of samples of PCM formed with and without physical modification.Saratov State Technical University.