A renewable approach to thermosetting resins

BIO-BASED CYANATE ESTER RESINS AND THERMOSTABLE POLYMER NETWORKS DERIVED THEREOF. MINI REVIEW

This article is devoted to a review of the literature on a very promising direction in the chemistry of macromolecular compounds: the synthesis and study of polymers, more specifically, high performance polycyanurates based on bis(poly)phenols) of natural origin. Cyanate Ester Resins (CER) are characterized by a very regular structure of the polymer networks, namely polycyanurates (PCNs), obtained by their polycyclotrimerization. They have received much attention because of their unique combination of physical properties, including high thermal stability (> 400 °C), high glass transition temperature (> 270 °C), high fire-, radiation and chemical resistance, low water absorption and low outgassing, high adhesion to different substrates and excellent dielectric properties (ε=2,64−3,11). As a result, CER are currently used as structural or functional materials in aeronautics, space (composite strakes, fins, nose radomes, heat shields), printed circuit boards, adhesives etc. It has to be noted here that CER thermosetting resins, expanding the high-temperature operations regimes, are produced from synthetic petroleum-derived bisphenols, such as bisphenol A, which are toxic and dangerous for environment. In the past decade, naturally occurring phenolic derivatives have arisen as attractive precursors for developing new materials from renewable bio-sources for use in eco-friendly processes. Resins have been prepared utilizing either the whole liquid product or a phenolic-enriched fraction obtained after fractional condensation or further processing, such as solvent extraction or use of greener extraction methods. However, to date, none of the phenolic production and fractionation techniques has been utilized to allow for substitution of 100% of the phenol content of the resin without impacting its effectiveness compared to commercial formulations based on petroleum-derived phenol. The variable nature of the percentage of phenolic compounds in terms of purity from different batches of crops from one season to another and geographical influence does not allow from the reproducibility of phenolic compounds, and hence the resulting polymers. However, the direction that needs to be explored should be oriented towards complete replacement of petro-based phenolics with bio-based ones in the face of an urgent petroleum crisis. In addition, there is a necessity for materials showing enhanced applicability and improved performance. It is a beginning of the era of such a step, which requires further exploration of natural phenolic sources aimed at their enhanced utilization.

Synthesis of thioamide containing polybenzoxazines by the Willgerodt–Kindler reaction

Benzoxazines with thioamide linkages were successfully prepared by the Willgerodt–Kindler route.

Synthesis and characterization of a small library of bisglucosides: Influence of the nature of the diol/diphenol used in O-glucosylation

In this paper, the synthesis of different bisglucosides is investigated through the reaction of two acetylated glucose units with a diol (or diphenol) in order to develop a versatile molecular platform for the future development of bio-based polymers. A panel of five diols and one diphenol is initially used in order to examine the influence of their chemical skeleton on the reaction yield and both nature and proportion of formed species. Reaction products are identified using ¹H and ¹³C NMR spectroscopies completed by MALDI-TOF MS technique. The nucleophilicity of these dihydroxy compounds is identified as being the main factor that governs the reaction characteristics. In particular, the best selectivity is obtained with the use of hydroquinone. Inversely, by-products (oligomers, deacetylated compounds) are observed with the diols defined by higher nucleophilicity despite the choice of stereoselective pathway using acyl protecting groups.

Tailoring Acrylated Soybean Oil-Containing Terpolymers through Emulsion Polymerization

This work focuses on the synthesis of terpolymers using methyl methacrylate (MMA) and vinyl pivalate (VPi), along with the incorporation of methacrylate acid (MA) and acrylated fatty acids (AFA) derived from commercial soybean oil. Emulsion polymerizations were carried out using different monomeric species, along with different initiator concentrations ranging from 0.5 g∙L−1 to 2.2 g∙L−1. The thermal properties of the terpolymers were improved when acrylated fatty acid was incorporated into the polymer chains, expressing glass transition temperatures (Tg) ranging from 70 °C to 90 °C and degradation temperatures in the interval between 350 °C and 450 °C for acrylated fatty acid concentrations ranging from 5 wt% to 10 wt%. Furthermore, a change was noted in the molar mass distributions as a result of acrylated fatty oil present in the polymers. The materials with 5 and 10 wt% of acrylated fatty oil presented mass-average molar masses of 225 kg∙mol−1 and 181 kg∙mol−1, respectively. As the results in this work suggest, the molar masses of the formed polymers are significantly altered by the presence of modified fatty acids.

Self-assembly of well-defined fatty acid based amphiphilic thermoresponsive random copolymers

Side-chain stearic acid containing thermoresponsive and crystalline random copolymers are synthesized via RAFT technique, which self-assembled to spherical micellar structures in aqueous solution depending on stearate content in the copolymer.

Toughened bio-based epoxy blend network modified with transesterified epoxidized soybean oil: synthesis and characterization

Novel bioresin epoxy methyl soyate was synthesized by transesterification process and subsequently used as reactive diluent for toughening of epoxy.

A curing system of benzoxazine with amine: reactivity, reaction mechanism and material properties

In addition to providing an acceleration effect on curing, suitable amines react with benzoxazine to form desired structures and improve the materials properties of the cured resins.