Volume 6, Issue 4 (12-2022)
Abstract
Abstract
Research subject: In this research, the synthesis method of phenol-formaldehyde resin has been investigated, which can be used in the wood and chipboard industry. This resin is prepared in two forms, Novolac and Resole, which different products are formed by changing the reaction conditions. Resole is used as a liquid adhesive in the wood and chipboard industry.
Research approach: Various parameters are effective in the synthesis of the resin and the properties of the final product such as the molar ratio of formaldehyde to phenol, the pH of the reaction medium, the temperature and time of the reaction, and the amount of water released from the reaction. The synthesis of this material was carried out under reaction conditions with the molar ratio of formaldehyde to phenol from 1.84 to 2.50, the reaction medium pH from 4.0 to 10.85, the reaction temperature from 80 to 100 ◦C, the reaction time from 0.5 to 4 h, and the water output amount in the term of dehydration dimensionless number from 0.18 to 1.02.
Main results: The results showed that the maximum product stability time was obtained for 18 days at the molar ratio of 2, the alkaline medium at pH 9 to 10, the reaction temperature at 90 to 95 ◦C, and reaction time at 2 h. Moreover, viscosity, density, gelation time, and percentage of solids were obtained 180 cP, 1.224 g/cm3, 30 S, and 51.20%, respectively. Product properties were optimized by adding diethylene glycol and urea. The stability time increased to 105 days by adding 8% diethylene glycol and the free formaldehyde amount in the product decreased to 1.29% by adding 4% urea. According to the properties of the created product, the obtained reaction conditions can be used for the mass production of the resin.
H. Fotohi, I. Khezrian,
Volume 20, Issue 1 (1-2020)
Abstract
Today, composite materials have attracted much attention in many industries, such as aerospace, automotive and marine industries, due to the strength to weight ratio, as well as the ratio of stiffness to high weight. Thermoset resins are among the most widely used resins in making composites based polymer. In the meantime, phenolic resins are the oldest industrial and thermosetting resins, which have important applications in various industries. The distinctive feature of this resin has resulted to its application as industrial insulators, thermal shields composites and ablative composites, and abrasive parts such as brake linings and clutch plates, and many other components. One of the applications of phenolic resins, especially resole with a relatively high thermal resistance, is the use of thermal insulation composites in thermal shields and hot air nozzles. The thermal insulation composites are often phenolic resins and their reinforcement is mainly asbestos fibers with high thermal resistance. Today, due to the carcinogenicity of asbestos fibers and the problems caused by its use, these fibers are removed from the list of reinforcing insulators, and silica fibers, a new product with an asbestos thermal stability and no environmental problem, have replaced instead of them. In this study, talc mineral micro-particles with a mean particle size of 8 μm as reinforcing the mechanical properties and thermal stability, were added to 25, 15 and 35 phr in phenolic resins in several layers of silica-phenolic composites.
