Foams Based on Phenolic and Urea-Formaldehyde Resins Mixtures and their Applications for Heat Insulation of Pipelines. 5. Investigation of Ageing of Phenolic Foams during Long-term Exposure to High Temperature

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The specificity of long-term ageing of phenolic foam in the heat insulation of pipe lines is discussed. Apparent density distribution of foam across the thickness of the foam layer affected the service time of foam insulation in real conditions of application. After long-term exposure (up to 4000 h at 100–200° C) compressive strength of foams was studied. Assuming that the time-temperature dependences of foams follow the Arrhenius law, the duration of foam was predicted and compared with experimental data. Thermogravimetric analysis was applied, and kinetic constants of long-term ageing were calculated. Other properties, i.e. electrical properties and water sorption, were also studied.