Versatile Method To Reduce the Free Formaldehyde Content in Phenolic Resins for High-Temperature Applications

International audience; Discovered by Baekeland a century ago, phenolic resins are still widely used today with a global production of about 12 million tons/year. Typically, these resins contain residual free formaldehyde, which is highly toxic and carcinogenic and will soon be banned by the European REACh regulation. Consequently, phenolic resins must be substituted. These resins are extensively used as a char precursor for composite-based thermal protection systems. Commonly, urea is a widely used formaldehyde scavenger and can be added to phenolic resins to decrease their free formaldehyde content, but urea is not suitable for high-temperature applications. Thus, an easy-to-implement method was developed with an aminophenol, giving access to a noncarcinogenic resin while maintaining the thermomechanical properties. The chemistry and the reaction mechanism of aminophenols with formaldehyde were also studied. The interest of this additive is multiple: it allows trapping of formaldehyde, to comply with the European REACh regulation (wt % free formaldehyde