<p>Wood plastic composites (WPCs) have poor mechanical properties due to the incompatibility of hydrophilic wood fibers and hydrophobic thermoplastics, which results in weak adhesion at the interface. It is a significant barrier to the production of WPCs. Glycerol carbonate has the potential to improve the mechanical characteristics of WPCs. In this investigation, WPCs were meticulously developed using rubberwood flour (RWF) and recycled polypropylene (rPP). Bio-based additives, including glycerol, commercial glycerol carbonate, and synthesized glycerol carbonate, were incorporated into the study. The comprehensive analysis encompassed mechanical properties, including tensile and flexural strength, energy absorbed, water resistance, and hardness. The optimal composition was determined through a central composite design (CCD) methodology using Design-Expert software, resulting in a formulation consisting of 33.78% (by weight) RWF, 62.33% (by weight) rPP, and 3.89% (by weight) glycerol carbonate. Furthermore, the effects to modify the glycerol-to-glycerol carbonate ratio were examined, with increments of 0%, 20%, 40%, 60%, 80%, and 100% (by weight) of the additive in WPC manufacturing being examined while keeping the additive content constant at 3.89% (by weight). The results were remarkable, as the inclusion of additive substantially enhanced the mechanical properties of WPCs by improving adhesion at the interface. Of particular significance was that 3.89% (by weight) only glycerol as an additive exhibited the highest energy absorbed, and it also exhibited the lowest water absorption levels. Notably, the addition of 3.89% (by weight) only glycerol carbonate led to a 2.3% increase in composite hardness compared to composites without any additives.</p> Graphical abstract <p></p>