Itaconic Anhydride as a Green Compatibilizer in Composites Prepared by the Reinforcement of a Tung Oil-Based Thermosetting Resin with Miscanthus, Pine Wood, or Algae Biomass

Abstract

Unsaturated vegetable oils with conjugated carbon–carbon double bonds, such as tung oil, can undergo free-radical polymerization, originating alternatives to petroleum-based materials. The introduction of fillers to vegetable oil-based polymer matrices results in composites with improved mechanical properties. In this work, thermosets were synthesized by the free-radical polymerization of a mixture of tung oil, divinylbenzene, and n-butyl methacrylate, and reinforced with bio-based fillers, namely Miscanthus, Pinus taeda (also known as southern pine), and algae (Microspora and Oedogonium) biomass. The effect of filler particle size on the composites’ properties was evaluated. Additionally, to develop a better interaction between the hydrophobic resin and the hydrophilic reinforcements, and improve the mechanical properties of the composites prepared, itaconic anhydride, a bio-based molecule derived from itaconic acid, was added to the resin. Thermogravimetric analysis (TGA) showed that the presence of itaconic anhydride improved the overall thermal stability of the composites. The storage modulus of the composites at room temperature, assessed by dynamic mechanical analysis (DMA), was increased by approximately 32% and 68%, for Miscanthus and southern pine composites, respectively, when itaconic acid was added to the resin. It was also observed that the glass transition temperatures were not significantly affected by the presence of itaconic acid. Scanning electron microscope (SEM) images indicated better matrix-reinforcement adhesion in the presence of itaconic anhydride.

Itaconic Anhydride as a Bio-Based Compatibilizer for a Tung Oil-Based Thermosetting Resin Reinforced with Sand and Algae Biomass

“…Since the organic material of the resins was completely degraded at temperatures up to 650 • C, that was arbitrarily chosen as the final temperature of the tests. As previously reported, the presence of itaconic anhydride in the resin does not impact its thermal stability, resulting in overlapping thermal degradation profiles [36]. According to Figure 2A, high-silica algae biomass lost approximately 5% of its weight before 150 • C, most likely due to the evaporation of moisture.…”

“…Thus, the stress is better transferred from the matrix to the filler, resulting in higher storage moduli. This phenomenon was also observed between tung oil-based resins reinforced with other lignocellulosic biomass, such as maleic anhydride [35], asolectin [34], and itaconic anhydride [36].…”

“…The presence of a compatibilizer promotes a better interaction between the matrix and filler and should, consequently, improve the material's thermal stability. A previous study showed that the addition of ITA indeed considerably improved the thermal stability of tung oil-based matrices reinforced with lignocellulosic biomass, due to the better interaction between continuous and disperse phases, leading to a higher demand for energy necessary to degrade the fillers [36]. In this case, however, the filler barely degraded because of its high inorganic content, even if the compatibility was sufficient.…”

“…E ′ at Tg + 50 °C (MPa) TO Resin [36] 518 ± 108 26 ± 6 146 ± 52 TO Resin ITA [36] 232 ± 118 Tukey's HSD test confirmed that the addition of ITA affected the storage moduli at 25 °C in the case of unreinforced resins (p = 0.024). In fact, this effect was also observed when asolectin was added to the formulation of a tung oil-based resin due to the inferior amount of carbon-carbon double bonds in the structure of asolectin compared to tung oil, leading to a lower crosslink density [34].…”

“…The hydroxyl groups of the reinforcements can then open the anhydride group present in the resin, favoring their interaction and therefore leading to a composite with enhanced mechanical properties. Recently, it has been determined that the addition of ITA to a tung oil-based thermosetting resin matrix reinforced with Miscanthus, pine wood, or algal biomass indeed increased their thermal-mechanical properties, confirming its role as a compatibilizer [36].…”