Microwave-Assisted Chemical Recycling of a Polyurethane Foam for Pipe Pre-Insulation and Reusability of Recyclates in the Original Foam Formulation

Considering the high demand for efficient chemical recycling and reusability of polyurethane foams (PUFs), combined microwave-assisted solvolysis routes have been applied to a widely used commercial PUF for pipe pre-insulation, and the reusability of as-received recycled products in the original formulation was studied. The influence of the type and amount of recyclate on the main foaming parameters, shrinkage behavior, density, compression properties, morphology, thermal stability, and humidity uptake was determined. Based on shrinkage as the main exclusion criterion, recycling products of two routes have been evaluated as suitable for reuse in the original formulation without any purification or fractionation. However, a maximum of 5 wt.% of the original polyol compound could be replaced by these recycled products to fulfill the requirement of ≤5% shrinkage, which also resulted in foam performance that is well acceptable for use in pre-insulated pipes. The most beneficial property profiles were achieved by replacing 3 wt.% of the original polyol component.