Characterization of Polypropylene Composite Reinforced on Bio-waste from the Production of Tung Oil

The aim of the conducted study was to develop wood-polymer composites (WPCs) using secondary polymer waste and agricultural technology waste materials, which would have lower environmental impacts than WPCs made from virgin resources. The study focused on developing WPCs based on polypropylene filled with finely dispersed powders of waste products from tung oil production (PP+TOPW composites). Finely scattered powder (with an average grain size of 0.5–1.5 mm) was obtained from crushing and grinding the outer pericarp of tung fruit waste, which resulted from tung oil extraction. Tung oil is produced in Georgia from tung fruit that is grown in Tsalenjikha district, Georgia. In addition, to modify the properties of the WPCs, organic silicon oligomer tetraethoxysilane and powdered aluminum hydroxide were used as additives.  The study found that the strength properties of the PP+TOPW composites can be optimized by modifying them with tung oil and other mineral additives. The optimal strength properties were observed at a filler content of 40 wt.%, where the compression and bending strength limits were 63.5 and 36.7 MPa, respectively. The water absorption of the PP+TOPW composites was reduced by modifying them with tung oil. The PP+TOPW composites with a filler content of 30 wt.% showed 0% water absorption, and the water absorption of composites with a filler content of 40 and 50 wt.% (modified with tung oil) was very low, ranging from 0.2–0.8%.  The study also investigated the effect of modifying PP+TOPW composites with tetraethyl orthosilicate (TEOS), which increased all the strength parameters, including impact strength, and reduced water absorption, although not as much as when modified with tung oil. The introduction of a flame retardant, aluminum hydroxide, into the composite composition in the amount of 25–30 wt.% made the composites flame-retardant and low-combustible materials, expanding their potential applications, particularly in construction.  Overall, the study successfully developed WPCs using waste materials with optimized properties, which have potential for various applications, including in construction, due to their flame retardant and low-combustible properties.