Unsaturated polyester resins for thermoset applications using renewable isosorbide as a component for property improvement

Abstract

Unsaturated polyester (UPE) resins are used in a variety of thermosetting applications due to the reduced cost when compared to epoxy resins; however, UPE resins also have reduced thermomechanical performance. Investigating avenues to improve the performance of UPEs has led to the use of bio-based starting materials as structural components of the synthesized prepolymers as a result of their advantageous structural features. Isosorbide, a compound derived from renewable feedstocks, has been utilized to provide additional stiffness from the diol component for novel unsaturated polyesters resins. These resins have been shown to possess T g 's (322728C) and storage moduli (54022200 MPa) that are in the desired range for composite materials with viscosities (1.2225 Pa s) amenable to a variety of liquid molding techniques.

Going greener: Synthesis of fully biobased unsaturated polyesters for styrene crosslinked resins with enhanced thermomechanical properties

“…Comparing the polyesters with saturated acids, BioUP_1, with SuAc, provides the polyester with higher viscosity, whereas the lowest value was observed for BioUP_3, with SeAc. This result can be explained by the high mobility of the polymeric chains provided by the diacid with longer aliphatic chains [4,5]. For these formulations, similar molecular weights were achieved and, consequently, M n does not have a significant effect on the viscosity of UPs.…”

“…It is interesting to note that, despite its low M n , BioUP_6 is the polyester with the highest viscosity. In the case of Iso, it is reported that the oxolane ring has the ability of establishing inter-chain hydrogen bonds, causing additional chain interactions [5] and, consequently, higher viscosities are expected. For the formulations with PDO and BDO (BioUP_4 and BioUP_5, respectively) it was not possible to determine the Gardner viscosity since UPs were immiscible with 2-ethoxyethanol used in the test.…”

“…In order to obtain the UPRs, the synthesized UPs were dissolved in Sty, the most widely used reactive solvent for industrial applications, and the mixture was thermally cured in the presence of an initiator and an accelerator [5,41].…”

“…The obtained UPs were characterized by a good thermal stability and a glass transition temperature (T g ) that has shown to be dependent on the formulation compositions. In another study, Fonseca et al [12] [5,9]. The developed Iso containing UPRs did not have properties (elastic modulus, glass transition temperature) to replace the commercial ones in their main applications.…”

“…They have found applications in diverse sectors, including: coatings, reinforcement materials in construction, marine and automotive industries [1][2][3]. The petroleum-based maleic anhydride (MA), phthalic anhydride (PhA) and PG are the most regularly employed monomers in the industrial synthesis of UPRs [4,5]. However, the increasing environmental concerns, as well as the need to develop sustainable alternatives to fossil based monomers, have led to a remarkable interest in the development of biobased UPRs (BioUPRs).…”