International scientific-online conference HIGH MOLECULAR WEIGHT THERMOSETTING PHENOL- FORMALDEHYDE OLIGOMER: STUDY OF CURING CONDITIONS Tokhirov M.I. Alimukhamedov M.G.

Аннотация

This study investigates the synthesis of high molecular weight thermosetting phenol-formaldehyde oligomers and the conditions influencing their gelation and gel fraction yield. The results confirm the suitability of these oligomers for processing at 180–200°C and their potential applications in producing high-quality polymer products. Keywords: high molecular weight oligomer, phenol-formaldehyde resins, thermosetting properties, gelation time, gel fraction, processing temperature, copolycondensation, co-oligomer. Introduction. Traditional phenol-formaldehyde resins are characterized by various properties that are thermoplastic or thermosetting. They can initially be liquid or solid. Based on them, mixing with different polymers opens wide opportunities for the production of a material that combines the advantages of several polymers [1, 2, 3]. Research on the creation of this type of thermosetting oligomers usually includes the following most necessary steps: synthesis of monomers, synthesis of oligomers based on them, study of their physico-chemical properties and structure, study of the effect of synthesis conditions on their technological properties [4,5]. Phenol-formaldehyde oligomers provide durable and high-quality coatings used in various industries [6, 7]. Phenol-formaldehyde oligomers provide long- term protection against corrosion, scratches and cracks when used as a coating. Heat treated phenol-formaldehyde resin coatings have maximum chemical resistance even in highly acidic environments [8, 9]. Such materials are used as coatings for chimneys, pumps, pipes and tanks [10]. Therefore, one of the main technological properties of such composite materials is viscosity strength and thermosetting stability, which significantly depends on the degree of solidification (gel fraction). Results and analysis. To do this, we synthesized our monomers phenolalcohol based on phenol and formaldehyde, diethyleneglycoladipinatol based on adipic acid and diethyleneglycol. The copolycondensation process of our two synthesized monomers, diethyleneglycoladipinitol and phenolalcohol, 81 ACADEMIC RESEARCH IN MODERN SCIENCE International scientific-online conference in a ratio of 1:40 mol/mol, was carried out in the presence of a catalyst (30% solution of maleic anhydride) under conditions (pH=3). As a result, a high molecular weight thermosetting phenol-formaldehyde oligomer was synthesized. We studied the technological properties of the synthesized high molecular weight thermosetting phenol-formaldehyde oligomer. The main focus is on studying the conditions for the transition (solidification) of oligomers to the fixed state. As a result of studying these conditions, the ability to obtain press compositions will improve and labor productivity will increase. The gelation times of the synthesized (PhA:DEGA 40:1 mol/mol) high molecular weight thermosetting phenol-formaldehyde co-oligomer were performed according to GOST R 57779-2017 (ISO 8987:2005). The gelation times of the synthesized co-oligomer at temperatures of 130⁰C, 150⁰C, 180⁰C, and 200⁰C were studied. The temperature dependence diagram of the gelation time of a high molecular weight thermosetting phenol- formaldehyde co-oligomer is presented in Figure 1. 1600 1496 1400 c e s ,e 1200 m i 1000 889 t g n 800 i l l e 558 G 600 420 375 400 178 210 125 156 108 200 83 68 0 1 2 3 1 2 3 1 2 3 1 2 3 130ºC 150ºC 180ºC 200ºC Temperature, ºC 1-Figure. Susceptibility to gellanization times of high molecular mass thermoresponsive phenol-formaldehyde co-oligomer at FS:DEGA ratio of 40:1 mol/mol 1-synthesis duration 20 minutes; 2-synthesis duration 60 minutes; 3-synthesis duration 90 minutes; The gelation time decreases with increasing synthesis time. At 130°C, the gelation time is 1496 seconds 20 minutes after the start of synthesis, while after 90 minutes this indicator is reduced to 420 seconds. When the temperature was raised to 200°C, the gelation times were reduced to 156, 108, and 68 seconds. 82 ACADEMIC RESEARCH IN MODERN SCIENCE International scientific-online conference Changing the synthesis conditions improved the thermoresponsive properties of the oligomer. The diagram above shows that we observed that the gelation time increased with increasing synthesis time for our high molecular weight thermosetting phenol-formaldehyde co-oligomers. At the same time, we can see that the high molecular weight thermosetting phenol-formaldehyde co- oligomers we synthesized have a longer lifetime than traditional phenol- formaldehyde oligomers. This is because simple thermosetting phenol- formaldehyde oligomers in solid form (not in solution) partially gel after 20-30 days and become unusable [1]. While the gelatinization time of the thermosetting oligomers discussed above determines the time they remain in a liquid state at a given temperature, the degree of cross-linking is determined by the yield of the gel fraction during extraction. This technological property of thermosetting o