COMPOSITES OF POLYMERS BASED ON PHENOLFORMALDEHYDE RESINS AS A SOURCE OF HARMFUL EMISSIONS OF FORMALDEHYDE AND PHENOL INTO THE ENVIRONMENT

Abstract

Environmental aspects related to the harmful emissions of phenol and formaldehyde into the environment by polymer composites based on phenol-formaldehyde resins during the production of a number of building materials and during their disposal are considered. Formaldehyde and phenol as substances of the 2nd toxicity class are the starting components for obtaining phenol-formaldehyde resins, which are widely used in the production of a number of electrical engineering and construction materials (chipboards). Release into the air space occurs due to the thermal emission of volatile substances (mainly formaldehyde) during the manufacturing and operation process, and pollution of the water environment (phenol) – during the vulgar disposal of spent polymer materials and products. It was determined that the residual amounts of phenol at the level of permissible values according to the normative document were present in all the tested samples of plates. However, during the period of 60 days in the temperature range of 20–50°C, no significant changes in the amount of phenol desorption were observed. That is, it can be argued that the adsorption of phenol on the sawdust surface is quite significant and is due to the chemical nature of both the phenol itself and the cellulosic base of the sawdust board. In this paper, we summarized the previously obtained results and made a more detailed study of the chemistry of the processes occurring in the massif of chipboards during their production and long-term operation. Phenol, having a high adhesion to the surface of sawdust, due to the formation of stable intermolecular compounds with cellulose, is retained on the surface of sawdust. These compounds are formed as a result of the esterification reaction of the hydroxyl group of phenol with alcohol groups of cellulose. Thus, molecules of phenol and macromolecules of phenol-formaldehyde polymer are “cross-linked” with macromolecules of cellulose, which enhances their chemisorption on the surface of the substrate. Formaldehyde is retained by the surface of sawdust due to unstable intermolecular bonds, which is indicated by the growth of its desorption in the investigated temperature range of 20–50°C from the surface of the material. These studies showed that the adsorption of formaldehyde on the surface of sawdust depends on environmental conditions, primarily on the temperature factor. This indicates a significant disadvantage of using chipboard boards based on composites of phenol-formaldehyde resins for the production of cabinet furniture and their use in everyday life.