Physico - Mechanical characterization property evaluation of polyvinyl butyral composites filled with macadamia nutshell

In the current research, tensile, flexural, and compression were done, as well as the effect of water absorption on dimensional stability, to study the effect of adding different weight fractions of Macadamia nutshell about (10, 20, 30, and 40 wt %) to Polyvinyl Butyral composites. Different average grain sizes of Macadamia nutshell (75 µm, 150 µm, and 300 µm) were used. In addition, both FTIR analysis and morphological observation of composites were conducted. Findings reveal that M7501 (10% filler, 75 µm) consistently achieves the highest mechanical properties, including tensile strength (35% higher), Young’s modulus (15% higher), toughness (40% greater), tensile strain (25% greater), flexural strength (29% higher), and compressive strength (20% higher) compared to M7504 (40% filler). Conversely, composites with larger particle sizes and higher filler content, such as M3004 and M1504, exhibited significant reductions in mechanical properties, with up to 43% lower flexural strength and 41.7% lower compressive strength compared to their counterparts with lower filler content. Higher filler contents exacerbated this issue by increasing the likelihood of particle clustering, which creates weak points and voids that compromise the structural integrity of the composite. Additionally, larger particle sizes (150 µm and 300 µm) showed more pronounced agglomeration and void formation compared to smaller particles (75 µm), further highlighting the challenges in achieving a homogeneous composite structure with larger fillers. SEM investigation demonstrated that increasing filler amounts led to noticeable particle agglomeration, aggregation and void formation, negatively impacts the composites, leading to weaker mechanical properties.