Preparation of low-toxicity cast foamed phenolic plastics

Introduction. Gas-filled polymers are highly efficient building thermal insulation materials, and therefore, researching to develop technologies to create them is a promising task. Phenol-formaldehyde foamed plastic can be a high-potential material with many significant advantages. However, the high toxicity of the phenol and formaldehyde compounds it releases is a significant deterrent to its usage. Therefore, the purpose of this study was to search for ways to reduce the toxicity of foamed plastic. The research considered the method of using ferric chloride as a complexing agent that binds phenol, with simultaneous use of sodium hexafluorosilicate to reduce material consumption. Materials and methods. The studies were carried out on phenol-formaldehyde resin FRV-1A (TU 6-05-1104-78 “Resin, phenol-formaldehyde, foaming, brand FRV-1A”) and curing agent VAG-3 (TU 6-55-1116-88 “Product VAG-3”). The number of free phenol monomers was determined through gas chromatography method following GOST 11235-2017 “Phenoloformaldehyde resins. Methods for determination of free phenol”. The tests were carried out using a Tsvet-4 chromatograph. Tests on determining the foaming rate were carried out according to TU 6-05-1104-78 “Resin, phenol-formaldehyde, foaming, brand FRV-1A”. The density of the samples was measured basing on the mass-to-volume ratio of the samples. Strength was determined using samples of size 50 × 50 × 50 mm mm at 10 % compression on a test press. Results. The conducted studies showed a decrease in the content of free phenol monomers in samples modified with ferric chloride. The use of sodium hexafluorosilicate allows significantly reducing the density of the finished material and, consequently, reducing the toxicity of foamed phenolic plastic per material mass unit. Conclusions. According to the obtained results, the most effective for detoxifying a cast foamed phenolic plastic is the use of ferric chloride in an amount of 2 % of the FRV-1A oligomer mass with the addition of 0.5 % of the sodium hexafluorosilicate mass. The use of this method for modifying phenol-formaldehyde resin foam in the future may make it possible to obtain a much safer material and expand its areas of application.