Ricinoleic and oleic acid based precursors as the sole constituents of thermosetting bioderived polymers

Abstract

This article reports the obtaining of materials based on fatty acids as well as their physical, thermal, and mechanical performance. Bio-based polymers are manufactured by radical polymerization of methacrylated maleated ricinoleic acid (MMRA) and methacrylated oleic acid (MOA) combined in different proportions. Differential scanning calorimetry in isothermal experiments reveals polymerization enthalpies between −210 and − 290 J/g for all formulations. The cured materials are hydrophobic, highly translucent, and, even though they are insoluble in common solvents, their gel contents are between 71.4 and 90.3 %. They exhibit very wide loss tangent peaks, with maxima between 51.5 °C and 61.5 °C, demonstrating elastomeric behavior at room temperature with storage modulus up to 216.5 MPa for 100 % MMRA. Their properties depend on the cross-linking degree, the shape of the precursors, the number of pendant chains and on the existence of phase separation. Thus, a larger content of the high-functional MMRA leads to more rigid polymers with enhanced thermostability. Preliminary tests demonstrated vitrimer behavior, with most of the samples displaying stress relaxations higher than 50 % at 190 °C, and the system obtained from the same mass of the two polymeric precursors (50MOA-50MMRA) exhibiting total relaxation of stress at 200 °C, in less than 40 min.