Fabrication and performance optimization of NiO coated wheat straw molded thermal insulation panels

This study addresses the sustainable valorization of wheat straw waste by developing a multifunctional thermal insulation composite modified with a NiO-based coating and an optimized internal pore structure. The core objective is to overcome the inherent limitations of raw biomass, including high hygroscopicity, poor mechanical strength, insufficient thermal stability, and rapid performance degradation under humid conditions. Key processing parameters, including straw composition, sol–gel conditions, nanofiller incorporation, and foaming parameters, were systematically investigated to regulate thermal conductivity, structural integrity, and environmental durability. Results show that optimized straw matrix modification and NiO–graphene/CNT composite coating effectively reduce thermal conductivity to 0.041 – 0.044 W/(m·K) and significantly improve moisture resistance, mechanical strength, and thermal stability. Accelerated aging tests reveal that even with local coating damage, the composite exhibits much lower moisture absorption, thickness swelling, and thermal conductivity degradation compared with uncoated straw panels, along with suppressed mold growth. Cost analysis confirms the economic competitiveness of the composite despite the addition of nanocarbons, owing to their low dosage. This work provides a feasible materials design strategy for converting agricultural waste into high-performance, durable biobased insulation suitable for interior dry environments. The proposed synergistic modification approach advances the fundamental understanding of coating–matrix interactions in biomass composites and supports the development of sustainable building thermal management materials.