What is Heavy Cardanol, also known as cashew residol?

Heavy Cardanol, widely called cashew residol or heavy CNSL residue, is a bio-based heavy byproduct generated during vacuum distillation of crude cashew nut shell liquid (CNSL). After extracting low-viscosity distilled cardanol, the high-boiling, polymer-rich residual fraction left in the distillation kettle becomes commercial Heavy Cardanol. Its chemical composition mainly contains oligomeric cardanol, high-content cardol and long-chain alkyl phenols with abundant active phenolic hydroxyl groups. Unlike refined light cardanol, Heavy Cardanol features ultra-low volatility, high cross-linking activity and superior thermal stability. As a low-carbon renewable industrial modifier, Heavy Cardanol can replace expensive petroleum-based phenol and refined cardanol to cut raw material costs for manufacturers across friction material, bioasphalt, anti-corrosion coating and adhesive industries. Heavy Cardanol is a dark, highly viscous oily paste at room temperature, and it only flows freely after gentle heating to 40–60°C.