This study focuses on evaluating the mechanical properties of biocomposites based on natural rubber, filled with natural fillers – walnut shell powder (WS) and cellulose (CEL). The fillers were incorporated into the polymer matrix at concentrations of 0 phr, 30 phr, and 40 phr. The influence of both filler type and content on key mechanical properties, such as tensile strength, elongation at break, and hardness, was investigated. Additionally, the resistance of the resulting vulcanized polymer composites to thermo-oxidative ageing was assessed to determine its effect on mechanical properties. The primary objective of this research was to explore the potential of these natural fillers as sustainable and cost-effective alternatives to conventional synthetic fillers in elastomeric composites. Experimental results demonstrated that both WS and CEL significantly improve the mechanical performance of the composites. The results indicate that both natural fillers contribute to the improvement of the mechanical properties of the composites, while also representing an environmentally friendly and economically efficient substitute for traditional fillers, with promising applicability in the development of sustainable polymeric materials.

Acknowledgement: This research work was created within the project „Biodegradable alternative fillers and their application in a new type of ecological polymer blends“, code of the project MVP06_2024, based on the financial support from the Internal Grant Scheme of the Alexander Dubček University of Trenčín (Call for proposals: Early Stage Grants),  it has been also supported by the Operational Program Integrated Infrastructure, co-financed by the European Regional Development Fund by the project: Advancement and support of R&D for "Centre for diagnostics and quality testing of materials" in the domains of the RIS3 SK specialization, Acronym: CEDITEK II., ITMS2014+ code 313011W442.