Content area
Full text
Abstract. The main goal of this work was the development of fully biobased unsaturated polyesters (UPs) that upon crosslinking with unsaturated monomers (UM) could lead to greener unsaturated polyester resins (UPRs) with similar thermomechanical properties to commercial fossil based UPR. After the successful synthesis of the biobased UPs, those were crosslinked with styrene (Sty), the most commonly used monomer, and the influence of the chemical structure of the UPs on the thermomechanical characteristics of UPRs were evaluated. The properties were compared with those of a commercial resin (Resipur 9837®). The BioUPRs presented high gel contents and contact angles that are similar to the commercial resin. The thermomechanical properties were evaluated by dynamic mechanical thermal analysis (DMTA) and it was found that the UPR synthesized using propylene glycol (PG), succinic acid (SuAc) and itaconic acid (ItAc) presented very close thermomechanical properties compared to the commercial resin.
Keywords: thermosetting resins, biobased unsaturated polyester, thermomechanical properties
1. Introduction
Unsaturated polyester resins (UPRs) are currently one of the most important types of thermoset polymers in the industry. These polymers are well-known for their excellent balance between mechanical, electrical and chemical properties. They have found applications in diverse sectors, including: coatings, reinforcement materials in construction, marine and automotive industries [1-3]. 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). In the market, there are already a considerable number of available renewable monomers for the synthesis of UPs and UPRs [6-8] and, in the last years, some authors have focused their work on the development of UPRs partially based on these raw materials [4, 9-11]. The work of Gonçalves et al. [4] reports the preparation of UPRs for microstereo-thermal-lithography (^STL), with a biobased content between 24 and 47 wt%. The UPs were prepared using some biobased monomers such as fumaric acid (FuAc), SuAc, adipic acid (AdAc), sebacic acid (SeAc) and PG. The obtained UPs were characterized by a good thermal stability and a glass transition temperature (Tg) that has shown to be dependent on...