The modern production of products made of composite materials based on thermosetting binders is mainly based on the use of pre – impregnated reinforcing technical threads-prepregs. The binder used for such semi-finished products must meet two important technological requirements: have a low reactivity (high viability) when stored in the temperature range from -5 to +25 ° C and the ability to adjust the curing time at the molding temperatures of the product. To eliminate the disadvantages of the traditional method of obtaining polymer composite materials, to improve their strength characteristics and reduce the cost of the resulting reinforced composites, it is proposed to use the method of layered application of components. The essence of the method consists in layer-by-layer impregnation of the fibrous filler with a binder solution, and then a developed curing system consisting of an amine hardener that prevents the interaction of the hardener with the resin under storage conditions and protective polymer emulsions. The binder-filler system is activated only at an elevated temperature under curing conditions. It is established that the optimal parameters for processing by direct pressing of the pre-pegs components obtained by the method of layer deposition are a pressure of 15 MPa and a temperature of160-170 ?С with a pressure exposure of 15 minutes. If you get products by winding, then for such products, heat treatment for 6 hours at a temperature of 120 ?С is optimal. In the conditions of forming products, that is, at an elevated temperature and at an increased pressure, the mutual diffusion of components occurs due to the movement of oncoming flows. Oligomeric molecules from the resin volume diffuse from the inner layer to the outer one, and the components of the curing system meet them from the outer layer to the inner one. The method of layered application of components makes it possible to create a macroheterogenic system of interpenetrating polymer meshes in the contact area of sequentially applied layers. The result of the research is an increase in the shelf life, the viability of prepregs (up to 10 days) and an improvement in the complex of physical and mechanical properties of composites: the destructive stress during static bending increases to 60 %, during dynamic bending (impact) - up to 50 %. The use of carboxymethylcellulose as a protective polymer provides higher indicators of the studied properties than when using butadiene styrene latex as a protective polymer..
The use of various physical influences is an economical and highly effective direction for regulating and improving the characteristics of the modified reinforced polymer composite materials developed in this work. The methods of energy effects studied in this work were used at the stage of impregnation of technical threads of various chemical nature with an oligomeric binder and a hardener (when preparing prepregs by the traditional method) or with a binder solution and a curing system (when preparing prepregs by the method of layered application of components) Based on the conducted research, a classification of the applied methods of physical modification according to the principle of the influence of energy fields is proposed. The studied methods of energy effects are divided into orienting and energetically energizing effects. The first group includes treatments with constant magnetic (PMP) or electric fields (PEP), and constant mechanical loads. The second group includes energy effects that have a wave nature (energetically energizing), and vibration, ultrasonic effects, and ultraviolet radiation are attributed to them. Modification methods of the first group contribute to a decrease in the mobility of binder molecules during curing, while the formation of branches of polymer chains occurs during the curing process, which leads to a predominant increase in the destructive stress during static bending. Energetically energizing effects contribute to the relative acceleration of the process of linear growth of polymer chains during curing, which is accompanied by the formation of a more sparsely cross-linked mesh structure, which leads to a predominant increase in impact strength. Of the two competing processes in the curing of epoxy oligomers, this one requires a higher activation energy, which is confirmed by the results of studies. Analyzing the results obtained, it can be concluded that the modification methods used in the work allow not only to obtain polymer composite materials with high strength characteristics, but also to directly adjust the properties of composites depending on the requirements for the products. Orienting modification methods lead to hardening of the resulting polymer composite material with a predominant increase in the destructive stress during static bending from 20 to 47%. When using energetically energizing influences in the technology of producing reinforced reactoplasts, the impact strength increases mainly from 19 to 40%.
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.
The binders used were resin PN-15 (TU 6-05-861-73) and resol phenol-formaldehyde resin, and the fillers were hydrocellulose (viscose) technical cord (VC) (TU 6-06-N58-79), polycaproamide technical cord (nylon-6 fibre) (TU 15897-79), polyacrylonitrile technical cord (Nitron) (TU 13-239-79), and polypropylene fibrillated cord (PP) (GOST 26996). Carboxymethyl cellulose (CMC) (TU 6-12-1020-75) and distilled water were used as components of the curing system.
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