Cross-Linking Mechanisms of a Rigid Plant Oil-Based Thermoset from Furfural-Derived Cyclobutane

cis-Cyclobutane-1,2-dicarbocylic acid (CBDA-2) was synthesized and used as a biobased hardener to cross-link epoxidized linseed oil to produce a fully biobased thermoset. The polymerization mechanism was studied by means of real-time attenuated total reflection-Fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), stochastically modulated temperature DSC, and rheometry. The study highlights the importance of hydrogen bonding of CBDA-2 and catalytic effect of hydroxyl groups created during the reaction. Evolution of reactive functions with temperature and time, variation of activation energy, and pre-exponential factor was correlated to macroscopic changes, such as heat capacity variations and chemorheology. A macrokinetic model was proposed to describe the complete polymerization mechanism. It is shown that the obtained parameters accurately describe the polymerization using parameters with a real physical meaning

Radical Oxidation of Itaconic Acid-Derived Unsaturated Polyesters under Thermal Curing Conditions

Itaconic acid has attracted a lot of interest as a green and low-cost building block toward the synthesis of biobased polyesters and polyurethanes with a wide range of applications in the UV-curing field. However, the thermal curing of itaconic acid-derived polyesters has been not extensively investigated. To gain deeper insight into the thermally induced crosslinking process, the curing of poly(hexylene itaconate) was investigated by advanced isoconversional analysis performed under isothermal and non-isothermal conditions. Rheology and thermal analysis pointed out a three-step mechanism (initiation, propagation, and termination) typical of free-radical polymerization associated with the double bond conversion. Moreover, due to the comprehensive information obtained by different analytical techniques such as isothermal DSC, ATR-FTIR, and DMTA, we speculate that thermo-oxidative mechanisms occur under thermal curing conditions of poly(hexylene itaconate). Thus, β-scissions of poly(hexylene itaconate) chains might lead to the formation of anhydride and oligomeric radicals, which can recombine to a highly branched and crosslinked poly(hexylene itaconate) resin

Valorization of Biorefinery Side-Stream Products: Combination of Humins with Polyfurfuryl Alcohol for Composite Elaboration

A challenge of today’s industry is to transform low-value side products into more value-added materials. Humins, a byproduct derived from sugar conversion processes, can be transformed into high value-added products. Thermosetting furanic composites were elaborated with cellulose filters. Large quantities of humins were included into a polyfuranic thermosetting network. Comparisons were made with composites generated with polyfurfuryl alcohol (PFA) and with PFA/lignin. It was concluded that new chemical interactions were created between the side-chain oxygen groups of the humins and the PFA network. Analysis of the fracture surface of the composites containing humins lead to the conclusion that higher interfacial bonding and more efficient stress transfer between the matrix and the fibers is present. The higher ductility of the humins-based matrix allows for a two-fold higher tensile strength in comparison with other composites tested. Incorporation of humins decreases the brittleness of the furanic composites, which is one major drawback of the pure PFA composites