Formaldehyde-Free and Phenol-Free Non-toxic Phenolic Resins with High Thermostability

Today, phenolic resins are polymers still widely used,with a globalproduction of about 12 million tons/per year. However, their synthesesneed the use of formaldehyde and phenol, which are highly toxic. Notably,formaldehyde is carcinogenic. Therefore, the reagents used for thesynthesis of phenolic resins must be substituted by non-toxic compoundsto preserve the health of users. These resins are extensively usedas a char precursor for composite-based thermal protection systems.For thermostability, aromatic structures are preferred, so this workproposes to study the substitution of formaldehyde by aromatic aldehydes,as well as the substitution of phenol by less toxic phenolic analogues.The resin composition, chemistry, and reaction mechanisms of polymerizationwere deeply studied. The thermostability and thermomechanical propertieswere also investigated. It was possible to use terephthalaldehydeas formaldehyde replacement and 2-hydroxymethylphenol as phenol replacementto obtain resins without phenol or formaldehyde, with extremely interestingthermomechanical properties [temperature at 5% of mass loss (Td(5%)) = 390 & DEG;C, char yield = 62%, and T & alpha; > 200 & DEG;C].In addition, the synthesis of these resins remains easy to implementand upscale.

Automated summary

Phenolic resins, widely used polymers, have an annual production of about 12 million tons. However, their synthesis requires highly toxic formaldehyde and phenol. This study proposes the substitution of these toxic compounds with less toxic phenolic analogues. The resulting resins show excellent thermomechanical properties and can be easily synthesized and scaled up.