Toward Sustainable Phenolic Resins from Biobased Aldehydes Using Spark Plasma Sintering

Phenolic resins are an attractive family of thermosetmaterials.However, there are some concerns related to the high toxic natureof formaldehyde and phenol, i.e., the main buildingblocks for phenolic resins. Herein, a sustainable alternative methodis proposed to synthesize fully biobased and nonharmful resoles basedon the condensation of resorcinol (R) with 4-four differentaldehydes under alkaline conditions. Two aldehyde-based building blocksincluding 5-methylfurfural (MFu) and cinnamaldehyde (C) obtained from biobased renewable and abundant resourceswere successfully formulated with resorcinol, providing more sustainableand environmental-friendly alternatives to current commercially availableand hazardous phenol-formaldehyde resins. Two molar ratios of basiccatalyst (HO-)/(R) were consideredto study their effect on the prepolymerization reaction and on thethermo-mechanical properties of the final materials. The thermal decompositionbehavior of the cured resoles was investigated by thermogravimetricanalysis (TGA), showing high degradation temperatures and high charyields (up to 60%). Furthermore, the resoles also exhibited high chemicalresistance with insoluble fractions (IFs) up to 80%. Finally, to studythe mechanical properties of the obtained resoles, the fully cross-linkedresoles were consolidated using the spark plasma sintering (SPS) technique.The microstructures of the sintered resoles were investigated by scanningelectron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).Compression tests were also conducted to evaluate the mechanical resistanceof cured resoles with compression moduli and strength values rangingup to 1.25 GPa and 74 MPa, respectively. Pyrolysis-combustionflow calorimetry analysis (PCFC) revealed that MFu hasa very low flammability behavior, demonstrated with a peak of heatrelease (pHRR) of around 16 W/g and the total heat release (THR) of2.5 kJ/g. Overall, it was demonstrated that MFu as anontoxic, biobased, and inexpensive aldehyde can be advantageouslyused in the preparation of more sustainable phenolic resins. The mechanical properties of biobasedphenolic resins basedon resorcinol with furfural derivatives were obtained and showed promisingmechanical properties.