HNTs Improve Flame Retardant and Thermal Insulation of the PVA/CA Composite Aerogel
Taopeng Yang, Jiayou Xu, Shu Lv
Abstract
High Resolution Image Download MS PowerPoint Slide Porous materials are widely used in construction, batteries, electrical appliances, and other fields. In order to meet the demand for flame-retardant and thermal insulation properties of organic porous materials, in this work, poly(vinyl alcohol)/calcium alginate/halloysite nanotube (PVA/CA/HNTs) aerogels with a hierarchical pore structure at micrometer–nanometer scales were prepared through freeze-drying using PVA as the substrate. The cross-linking reactions of PVA with H 3 BO 3 and sodium alginate (SA) with CaCl 2 constructed a double cross-linking network structure within the aerogel. And the HNTs were incorporated as reinforcing agents. The experimental results showed that the PVA/CA/HNTs aerogels had excellent flame-retardant and thermal insulation properties, and the heat release rate (HRR) and total heat release (THR) were effectively reduced compared to the PVA/CA aerogel. In addition, PVA/CA/HNTs aerogels had a high limiting oxygen index (LOI 60%) and low thermal conductivity (0.040 W/m·K). While their surface was subjected to a flame (800–1000 °C) for 25 min, the temperatures of the back surface were still lower than 80 °C. The low thermal conductivity of HNTs with hollow nanotube-like structures and the excellent flame-retardant properties of CA contributed to this phenomenon. The presence of HNTs and CA facilitated the formation of a dense carbon layer during combustion, enhancing the flame retardancy for PVA. In addition, the interpenetrating cross-linking network and the unique nanopores of HNTs collectively established a hierarchical pore structure within the gel, effectively impeding substance and heat exchange between the substrate and external environment. As the flame-retardant and thermal insulating material, PVA/CA/HNTs aerogels have a promising development prospect and potential in the fields of construction, transportation, electronics, and electrical appliances.