Synthesis and characterization of bio-based epoxy thermosets using rosin-based epoxy monomer

A Comparative Study on the Properties of Rosin-Based Epoxy Resins with Different Flexible Chains

This study aims to reveal the effects of flexible chain lengths on rosin-based epoxy resin's properties. Two rosin-based epoxy monomers with varying chain lengths were synthesized: AR-EGDE (derived from ethylene glycol diglycidyl ether-modified acrylic acid rosin) and ARE (derived from acrylic acid rosin and epichlorohydrin). Diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA) with different flexible chain lengths were used as curing agents. The adhesion, impact, pencil hardness, flexibility, water and heat resistance, and weatherability of the epoxy resins were systematically examined. It was found that when the flexible chains of rosin-based epoxy monomers were grown from ARE to AR-EGDE, due to the increased space of rosin-based fused rings, the toughness, adhesion, and water resistance of the rosin-based epoxy resins were enhanced, while the pencil hardness and heat resistance decreased. However, when the flexible chains of curing agents were lengthened, the resin's performance did not change significantly because the space between the fused rings changed little. This indicates that the properties of the rosin-based resins can only be altered when the introduced flexible chain increases the space between the fused rings. The study also compared rosin-based resins to E20, a commercial petroleum-based epoxy of the bisphenol A type. The rosin-based resins demonstrated superior adhesion, water resistance, and weatherability compared to the E20 resins, indicating the remarkable durability of the rosin-based resin.

Synthesis and Properties of Bio-Based Composites from Vegetable Oils and Starch

Natural polymers, such as starch, and polymers derived from renewable resources, such as vegetable oils, have been considered as alternatives to petroleum-based plastics during recent decades, due to environmental concerns. Indeed, these materials can offer a variety of advantages, such as low cost, wide availability, carbon neutrality, elevated thermal stability, and easily tunable mechanical properties. However, some of these polymers alone exhibit poor mechanical properties, making them not suitable for some applications. Hence, the reinforcement of these bio-based polymers with other materials is often considered to overcome this challenge. In this work, thermosetting composites based on tung and linseed oil resins were prepared using starch as reinforcement. Analyses from Soxhlet extractions showed that the higher the concentration of tung oil in comparison to linseed oil in the resins, the lower the mass of unreacted material, leading to an optimum resin entirely based on tung oil. Dielectric analysis (DEA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) indicated that the polymerization was completed in 3 h 20 min, at 140 °C, and that the composites were thermally stable until 270 °C. Finally, dynamic mechanical analysis (DMA) confirmed that the addition of starch to the resins increased the room temperature storage modulus (E′25) from 94 MPa to 893 MPa. Composites prepared with a resin formulation that did not contain a compatibilizer exhibited E′25 of 441 MPa. The composites investigated in this work are promising candidates for applications that require improved mechanical properties.