Sustainable phenolic thermosets coatings derived from urushiol. Issue 2 (21st November 2020) - Xia, Jianrong
Abstract: The over‐exploitation of finite fossil resources and/or the increased environmental and sustainable awareness inspire scientists and technologists to search for inexpensive alternatives from renewable chemicals. Phenol formaldehyde (PF) resins, the oldest type of synthetic polymers with good mechanical properties and heat resistance, are widely used in the production of coatings, laminates, molding compositions, and glues. Here, biobased urushiol‐derived PF resins were synthesized from the alkali‐catalyzed reaction between urushiol and formaldehyde. The chemical compositions and molecular structures of resole resins were characterized by carbon‐13 nuclear magnetic resonance and Fourier transform infrared spectroscopy, and their curing behaviors were studied by differential scanning calorimetry. The as‐prepared urushiol‐derived resole resins had methylol (Ph−CH2 OH), ortho‐ and para‐hemiformal groups (Ph−CH2 OCH2 OH), and the para−para/ortho−para/ortho−ortho links of methylene groups (Ph−CH2 −Ph), whereas the resole resins had low curing temperatures at about 100–113°C. Additionally, given the long side alkyl group moiety on the aromatic rings of urushiol, the films of cured urushiol‐derived resole resins had low glass transition temperatures of 132 ± 2°C. Furthermore, the as‐prepared urushiol‐derived coatings exhibited excellent physical and mechanical properties. Abstract : An alternative from renewable urushiol to prepare phenol formaldehyde resins was provided here. Given the long side alkyl group moiety on the aromatic rings of urushiol, the films of cured urushiol‐derived resole resins, with exhibited excellent physical and mechanical properties, had low Tg of 132 ± 2 °C. The decreased Tg and cured temperature rendered by long side alkyl groups will result in significant prospects in the field of biobased phenolic resins.