C36 Dimer Fatty Acid-Based Flexible Unsaturated Polyester Resin: Improvement of Properties by Adjusting the Intermolecular Crosslinking Structure

Abstract

The efficient use of vegetable oil and animal oil resources has enormous economic and ecological value and has attracted tremendous interest in the field of bio-based synthetic polymers in the past years. Given that conventional oil and their derivative polymers are subject to unsatisfactory mechanical properties or short-term use, these materials are not suitable for practical applications. Herein, a series of novel C36 dimer fatty acid-based unsaturated polyester resins with covalent and noncovalent networks were prepared by C36 dimerized fatty acid-based unsaturated polyester and crosslinking agents (styrene, acrylic acid, methacrylic acid, etc.). Owing to crosslinking structure of the polymers, their stable covalent bonds and hydrogen bonds, the matrix exhibits outstanding mechanical properties, including increased stretch ability (52.6% of unsaturated polyester resin (UPR)-St/acrylic acid (AA), 57.3% of UPR-St/methylacrylic acid (MAA)), tensile strength (15.2 MPa of UPR-St/AA, 17.1 MPa of UPR-St/MAA), elasticity modulus (327.1 MPa of UPR-St/AA, 316.8 MPa of UPR-St/MAA), and flexural strength (14.8 MPa of UPR-St/AA, 33.4 MPa of UPR-St/MAA). Micromorphological investigations indicated that the fracture features of the resin changed from brittle to ductile. Additionally, the resin is shown to possess an impressive thermal stability, solvent resistance, and certain autonomous self-healing properties.