Improving Thermal and Mechanical Properties of Wood Flour-Based Nanocomposites with Added Nanographene

Background and Objective:
Nanocomposites have attracted significant attention due to the combination of nanomaterials' properties with polymer matrices. This study aims to investigate the effect of the amount of nanographene and wood flour on the physical, mechanical, and thermal properties of nanocomposites made from wood flour of spruce and recycled polypropylene. Nanographene is introduced as an effective reinforcement for improving the mechanical and thermal properties of these composites.
Materials and Methods:
In this study, recycled polypropylene (fixed at 50%), wood flour of spruce (fixed at 50%), nanographene at four levels (0, 0.5, 1, and 1.5% by weight), and maleic anhydride grafted polypropylene (fixed at 3%) were mixed using a twin-screw extruder. Standard test samples were produced through injection molding. Mechanical properties, including tensile and flexural strength, tensile and flexural modulus, and impact resistance, as well as thermal and flammability properties, were measured according to ASTM standards.
Results:
The analysis of variance revealed that the effect of nanographene on tensile modulus, flexural resistance, and impact resistance at a 95% confidence level is not significant. However, the impact of nanographene on tensile and flexural strength, as well as the oxygen index, is significant at the 95% confidence level. Results indicated that increasing the amount of nanographene up to 1% by weight significantly enhanced tensile and flexural strength, flexural and tensile modulus, and impact resistance of the nanocomposite. Conversely, adding 1.5% by weight of nanographene led to a reduction in these properties. Additionally, increasing the amount of nanographene resulted in a higher residual ash content and improved thermal stability.
Conclusion:
This research investigates the effect of graphene nanoplatelets and wood flour on the physical, mechanical, and thermal properties of nano-composites made from walnut wood flour and recycled polypropylene. The results indicate that increasing the amount of graphene up to 1% by weight enhances mechanical properties, including tensile and flexural strength, as well as tensile and flexural modulus. This improvement is attributed to the enhanced adhesion between graphene and the polymer matrix, which strengthens the overall structure and increases durability.
However, the addition of 1.5% by weight of nanographene results in a decline in these properties due to agglomeration and improper distribution of nanographene within the matrix, leading to weaknesses in the material structure and reduced mechanical performance. Furthermore, results indicate that increasing the amount of nanographene also increases the residual ash content and improves the thermal stability of the nanocomposite. Nanographene reduces thermal degradation rates at high temperatures by forming a char layer, acting as an effective agent for enhancing thermal stability.
Therefore, the results of this study emphasize the need for careful management of nanographene amounts and ensuring uniform distribution within the polymer matrix to achieve optimal properties. Utilizing lower amounts of nanographene can enhance mechanical and thermal properties, while higher amounts may weaken these properties. Overall, these findings can assist in the design and optimal production of nanocomposites.