Sustainable Hybrid Composite Ceiling Tiles from Waste LDPE Reinforced with Sida acuta Fibers and Recycled Paper Pulp Nanofillers: Mechanical, Thermal and Microstructural Performance

• Novel hybrid composites made from waste LDPE, Sida acuta fiber, and waste pulp. • At 50 wt.% fiber: 95.8% tensile, 116.2% flexural, with enhanced impact and hardness. • Water uptake rose with fiber, density rose from compaction and low porosity. • SEM and thermal tests showed strong adhesion and improved thermal stability. • Low-cost, sustainable composite is a viable alternative to gypsum ceiling tiles. This study investigates the development of sustainable ceiling panel composites using recycled low-density polyethylene (LDPE) reinforced with Sida acuta fibers and waste-derived paper pulp nanofillers, addressing the environmental burden of plastic waste. The composites were fabricated via melt mixing and compression molding at 160°C, with fiber contents ranging from 10 to 50 wt.% and a fixed nanofiller content of 5 wt.%. Mechanical, thermal, microstructural, and physical properties were evaluated using tensile, flexural, impact, hardness, and water absorption tests in accordance with ASTM standards, supported by SEM, DSC, TGA, FTIR, and XRD analyses. Results showed progressive enhancement in stiffness-related properties with increasing fiber loading, with optimal performance at 50 wt.% fiber content, where tensile and flexural modulus increased by 95.8% and 116.2%, respectively, relative to unreinforced LDPE. Enhanced impact resistance and surface hardness were also observed, placing the composite within a competitive performance range compared to conventional ceiling materials such as gypsum boards and polymer panels. One-way ANOVA confirmed statistically significant variations in tensile properties (p ≤ 0.05), indicating reinforcement-controlled behavior. SEM analysis revealed improved fiber-matrix interaction at optimal loading, while FTIR confirmed hydroxyl-rich functional groups facilitating interfacial bonding. XRD indicated crystallinity modulation due to restricted polymer chain mobility. Thermal analysis showed retained stability with increased residual char formation, despite slight reductions in degradation onset temperature. Although water absorption increased due to fiber hydrophilicity, high structural density and dimensional integrity were maintained. The developed composite demonstrates strong potential as a lightweight, cost-effective, and sustainable alternative for non-load-bearing ceiling applications.