This study evaluates the effect of Calcium carbonate (CaCO₃) on the mechanical properties and structure of SEBS-compatible PA6/ABS composites. Composites consisting of 50/50 PA6/ABS, 5% SEBS, and 0–20% by weight CaCO₃ were fabricated by injection molding. Tensile and flexural strengths were determined according to ISO 527-2:2012 and ISO 178:2019, respectively. The tensile strength increased with filler content, peaking at 15 wt% CaCO₃ (24.72 MPa), while flexural strength reached a maximum at 10 wt% (32.51 N/mm2). FESEM revealed a uniform dispersion of CaCO₃ particles and strong interfacial adhesion at optimal filler contents, whereas agglomeration and microvoids occurred at higher loadings. The results demonstrate that moderate CaCO₃ addition enhances stiffness and strength through effective stress transfer, while excessive loading induces brittleness due to poor interfacial bonding. This study contributes to the optimization of hybrid polymer composites for structural, automotive and precision engineering

In recent years, water hyacinth (Eichhornia crassipes) has been widely recognized as an invasive aquatic plant that proliferates rapidly on rivers, canals, ponds, and lakes, obstructing waterway transportation, impeding water flow, and contributing to environmental degradation. Despite its abundance in large river systems such as the Bach Dang River in Thu Dau Mot City, Binh Duong Province, this biomass resource remains largely underutilized, leading to significant waste of natural materials and ongoing ecological challenges. This study proposes an eco-friendly alternative by transforming water hyacinth into handmade paper sheets with natural coloration, rustic aesthetic, and complete absence of harmful chemicals. The resulting products exhibit acceptable strength and surface quality, making them suitable for practical and decorative applications including coasters, shoe insoles, greeting cards, notebooks, biodegradable packaging, paper bags, and eco-handicraft items. Raw materials were collected directly from the Bach Dang River by a student research group. The research employed a combination of primary and secondary data collection methods, along with experimental, analytical, and synthesis approaches to develop and evaluate the manual paper-making process. The developed chemical-free production method successfully yielded durable paper sheets that are environmentally safe and biodegradable. The findings demonstrate the feasibility of converting an invasive plant into value-added sustainable products, thereby contributing to waste reduction, biomass reuse, and the promotion of green production practices. Although the study is preliminary and limited by manual processing, lack of mechanization, and absence of standardized quantitative testing (e.g., tensile strength, water absorption, and biodegradability under controlled conditions), it provides a promising foundation for further optimization and scale-up. Future research should focus on improving uniformity, enhancing mechanical properties through natural additives, and conducting comprehensive performance and life-cycle assessments to support practical commercialization and broader environmental impact