Epoxidized and Maleinized Hemp Oil to Develop Fully Bio-Based Epoxy Resin Based on Anhydride Hardeners

Abstract

The present work aims to develop thermosetting resins using epoxidized hemp oil (EHO) as a bio-based epoxy matrix and a mixture of methyl nadic anhydride (MNA) and maleinized hemp oil (MHO) in different ratios as hardeners. The results show that the mixture with only MNA as a hardener is characterized by high stiffness and brittleness. In addition, this material is characterized by a high curing time of around 170 min. On the other hand, as the MHO content in the resin increases, the mechanical strength properties decrease and the ductile properties increase. Therefore, it can be stated that the presence of MHO confers flexible properties to the mixtures. In this case, it was determined that the thermosetting resin with balanced properties and high bio-based content contains 25% MHO and 75% MNA. Specifically, this mixture obtained a 180% higher impact energy absorption and a 195% lower Young’s modulus than the sample with 100% MNA. Also, it has been observed that this mixture has significantly shorter times than the mixture containing 100% MNA (around 78 min), which is of great concern at an industrial level. Therefore, thermosetting resins with different mechanical and thermal properties can be obtained by varying the MHO and MNA content.

Use of Bio-Epoxies and Their Effect on the Performance of Polymer Composites: A Critical Review

“…The samples composed of commercial epoxy and EHO exhibited superior flexural performance. However, it was observed that the maximum bio content (40%) exhibited inferior performance in flexural properties, both in comparison to the hemp-based epoxy thermoset outlined in Lerma-Canto et al’s study [ 64 ] and the conventional epoxy thermoset (refer to Table 12 ). Beyond 30% bio content, there was a significant reduction in the crosslinking density, resulting in a notable decline in the mechanical properties of the epoxy.…”

“…Epoxidation reaction also offers a possible pathway for incorporating natural oils into bio-epoxy resin formulations. Among edible oils, options such as soybean [ 56 , 57 , 58 , 59 , 60 ], linseed [ 59 , 61 , 62 , 63 ] and hemp [ 60 , 64 , 65 ], stand out as potential sources for developing environmentally sustainable epoxy systems, as extensively analyzed in the comprehensive overview by Mustapha et al [ 66 ]. From triglyceride vegetable oils, such as coconut, soybean or palm oil, it is possible to obtain the glycerol , which is also commercially used to produce commercial resins [ 67 , 68 , 69 ] and proposed in the literature for the synthesis of new epoxy systems [ 38 , 70 , 71 ].…”

“…Lerma-Canto et al [ 64 ] utilized epoxidized hempseed oil (EHO) as a precursor to develop bio-based epoxy systems, with an emphasis on investigating their thermomechanical properties. This was achieved through the incorporation of MNA and maleinized hemp oil (MHO) as crosslinkers (with proportion ranging from 0 to 100%), resulting in the attainment of a completely bio-based epoxy configuration.…”

“…Finally, it is important to stress that the analyzed edible oils can also be incorporated in epoxy systems simply as hardeners [ 63 , 64 , 65 ]. While this strategy certainly prioritizes the preservation of the mechanical performance of the final thermoset, it may not be as groundbreaking or innovative from a sustainability perspective as the direct incorporation of oils as epoxy monomers.…”

Innovative Materials Based on Epoxy Resin for Use as Seat Elements in Bulk Transport

“…Due to high mechanical strength, good adhesiveness, low cost, high thermal stability, good chemical resistance, and ease of use of epoxy resins, they are successfully used in load-bearing applications (aerospace, automotive, construction, and marine). In addition, they are also utilized in the production of coatings, adhesives, insulation, and high-performance composites [4,[12][13][14][15][16]. However, due to the insolubility and non-fusibility of epoxy resins, they are difficult to recycle, which results in a waste of resources and limits their applications [17].…”