Silica-loaded perchloric acid as a catalyst for terpene phenol resins

Terpene phenolic resin with high softening point and strong adhesion has been increasingly studied worldwide, and it is widely used in the field of rubber and adhesives. A low-cost and easy-to-prepare heterogeneous catalyst, silica-loaded perchloric acid (HClO 4 /SiO 2 ), was prepared from perchloric acid and fumed silica, and utilized to synthesize terpene phenol resins for the first time. The polymerization conditions were optimized by single factor experiments, and the terpene phenol resin obtained under the optimal conditions achieved a yield of 85.1%, a softening point of 112.6 °C, a Ghanaian color number of 8, and an acid value below 1.00 mg KOH g −1 without washing with water, respectively. The possible copolymerization mechanism was inferred through other characterization methods such as infrared spectrum and hydroxyl value determination. After three cycles of the polymerization, the catalyst HClO 4 /SiO 2 still achieved a relative high yield of 65.2%, and no significant desorption for perchloric acid was observed. This means that the washing with water to remove desorbed perchloric acid in the resin can be avoided, which may prevent wastewater pollution to the environment, save production costs and simple production process. Therefore, HClO 4 /SiO 2 presents a promising option for the clean and cost-efficient production of terpene phenolic resins, with potential applications in large-scale manufacturing. Graphical abstract