Research on the Resourceful and Efficient Recycling Technology of Waste Thermal Insulation Pipe Material

This study was conducted to explore a new method for degrading and recycling waste chemical pipe insulation and cooling materials. A chemical degradation method was employed, utilizing alkali metal catalysts and a two-component alcoholysis system consisting of specific ratios of diethylene glycol and butylene glycol. The system effectively degraded the polyisocyanurate (PIR) insulation with the aim of reusing the waste material. The experimental results show that the best reaction performance is obtained with 1,4-BG/DEG ratio of 43:57 at 180 and 190 °C 1 h. The resulting regenerated pipe has an apparent density of 0.041 g/cm³ and a compressive strength of 0.413 MPa. With remarkable thermal stability, well-preserved porosity, and strong skeletal structure, the cold loss on the outer surface of the insulated pipe is lower than the design requirement of 23 W/m², which is qualified for the energy efficiency of the insulated pipe. The proposed strategy for degradation and recycling of waste chemical pipe insulation and cold insulation materials provides a pioneering green treatment method for the task of recycling polyurethane waste with fire-resistant degradability and a high cross-linking degree.