Synthesis and characterization of novel vinylester prepolymers from cardanol

A novel thermosetting vinylester (VE) resin was prepared form cardanol, coming from cashew nut shell liquid (CNSL), a renewable resource and waste of the cashew industry. A VE cardanol-based prepolymer was synthesized by reacting commercial cardanol diepoxy and methacrylic acid. The VE cardanol-based prepolymer was polymerized by free radical polymerization to yield a thermoset resin with different monomers used as reactive diluents such as styrene (ST), isobornyl methacrylate (IBOMA), dibutyl itaconate (DBI), butanediol dimethacrylate (BDDMA), and hexanediol dimethacrylate (HDDMA). The resulting VE resin was characterized by TGA, DSC, and DMA analyses and compared to diglycidyl ether of bisphenol A (DGEBA)-based VE resin. Cardanol-based VE resins exhibit interesting mechanical and thermal properties for composite materials. The T-g value is 86 degrees C with 40% by mass of ST and 116 degrees C with 40% by mass of IBOMA. Around 70 degrees C of T-g are lost compared to DGEBA-based VE resin, whereas with an oil-based VE resin the loss of T-g value is around 150 degrees C. Practical application: The acrylated cardanol-based monomer described in this contribution, that is, acrylated cardanol from CNSL, provided new biobased aromatic building blocks for further free radical polymerizations with various reactive diluents. The obtained VE materials are partially biobased and may be used as binders in composite applications.