## 1 Introduction
Furthermore, a significant part of the plastic matrices used in WPCs is thermoplastic petroleum-derived polymers such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinylchloride (PVC), among others. However, there has been a tendency in recent years to replace these matrices by biobased and biodegradable (actually soil compostable) polymers such as polylactic acid (PLA) or polyhydroxyalkanoates (PHA) [37], to achieve fully biodegradable WPCs. Natural fiber reinforced plastics (NFRP) represent a wider group that includes WPCs and thermosetting-based composites, as well. For thermosetting resins, this trend is focused on the use of fully or partially biobased resins [38; 39; 40; 41; 42]. With this, it is possible to reduce the dependence on fossil fuels. Besides this, these fully/partially thermosetting resins, positively contribute to reducing the carbon footprint generated by their petrochemical counterparts such as phenolics (PF), epoxies (EP), or unsaturated polyesters (UP). A promising source for biobased epoxy resins and plasticizers are epoxidized vegetable oils, which are obtained by epoxidizing the C-C double bonds of unsaturated fatty acids contained in triglycerides, the main component of vegetable oils [43; 44; 45]. However, due to the long aliphatic chains in the triglycerides and their low cross-linking density, epoxy resins obtained from vegetable oils tend to have low glass transition temperatures (\(T_{g}\)) and lower mechanical properties than traditional epoxy resins [46]. Therefore, to obtain environmentally friendly materials with balanced mechanical and thermal properties, one of the most efficient approaches is copolymerization of epoxidized vegetable oils with petroleum-derived epoxy resins, thus giving rise to a partially biobased epoxy resin with high mechanical properties [47]. [PERSON] et al. [48] investigated the effect of the epoxidized soybean oil (ESO) content (0, 25, 50, 75, and 100 wt%) on bisphenol-A based aromatic epoxy resin (DGEBA). The results showed a decrease in \(T_{\mathrm{g}}\) as the ESO content increased but indicated that \(T_{\mathrm{g}}\) of the DGEBA/ESO system (75/25) was very similar (138 \({}^{\circ}\)C) to the base DGEBA resin (140 \({}^{\circ}\)C). Obviously, this was remarkably higher than the \(T_{g}\) of neat crosslinked ESO (75 \({}^{\circ}\)C). Similar trends were also observed for mechanical properties such as tensile strength and impact energy, where the addition of 25 wt% ESO decreased the mechanical properties of DGEBA resin but made them more resistant than ESO resin. Regarding the manufacturing of materials with these cast resins, [PERSON] et al. [49] reported impregnation bamboo with epoxy with previous delignification processes to obtain almost transparent bamboo goods. [PERSON] et al. [50], reported new environmentally friendly composites with epoxy resins and _Pinus sibirica_ lignocellulosic fillers at a constant wt% of 20%. These composites were manufactured at a laboratory scale by mixing the components and finally, a conventional cast method was used to pour the liquid mixture into a mold. Casting is the most widely used method to manufacture composites with thermosetting resins and lignocellulosic particles. [PERSON] et al. [51] reported manufacturing by casting and characterization of epoxy composites with up to 12.5 wt% wood particles. Centrifugal casting is a way to obtain gradation of the filler due to centrifugal forces as reported by [PERSON] et al. [52]. They report that as well as the particle gradation occurs, gradation of properties occurs too which could be interesting from different standpoints (decorative, percolation thresholds in some parts, and so on. The main objective of the present work was to obtain green composites from a partially biobased epoxy resin reinforced with flaxseed flour waste using the casting method.