Upcycling fiber-based solid waste materials into vacuum insulation panel core: a promising sustainable solution

This critical review evaluates the use of fiber-based solid waste as core material for vacuum insulation panels (VIPs), with emphasis on feedstock classification, fiber-specific pretreatment, coupled heat-transfer and ageing mechanisms, performance evidence, and life-cycle implications. Reported laboratory results show that selected recycled cotton, kapok, glass-fiber-reinforced cellulose, and other hybrid cores can reach center-of-core thermal conductivities of approximately 2–6 mW·m −1 ·K −1 under carefully controlled high vacuum. However, these values are not directly interchangeable with full-panel effective conductivity, and long-term evidence for heterogeneous waste-derived cores remains limited. The synthesis identifies four governing factors: the fiber-contact network controlling solid conduction, the pressure–pore-size relationship controlling gaseous conduction, radiative extinction, and moisture/outgassing-driven vacuum degradation. It further shows that pretreatment must be matched to chemistry: alkaline or acetylation routes suit lignocellulosic fibers, silanes suit selected hydroxyl-rich or glass-fiber interfaces, plasma/corona treatments primarily modify surface energy, and mixed textile streams require composition-specific sorting and compatibility assessment. Environmental benefits are potentially substantial but are conditional on collection distance, drying energy, barrier-film service life, replacement rate, and end-of-life allocation. The review contributes a structure–processing–performance framework, a comparative assessment of candidate fibers, guidance on fiber-specific pretreatment, an evidence-maturity assessment, and six research questions that define the validation needed for standardization and scale-up.