Mechanical reprocessing of polyurethane and phenolic foams to increase the sustainability of thermal insulation materials

In this work polyurethane (PU) and phenolic foam (PF) panels were mechanically grinded and incorporated within an expanded polyurethane matrix utilized for thermal insulation, in order to reduce the use of virgin material and to promote a circular re-utilization of recycled materials. As observed by scanning electron microscopy, the formulations containing both recyclates showed a rather homogeneous cell structure, however their presence led to a strong reduction of the closed porosity. This reflected in a slight increase in the thermal conductivity, reaching maximum values of 0.030 W/m∙K in foams with 7.5%wt of PF particles. The introduction of the recyclates slightly improved the thermal stability of the PU foams and led to a general decrease in flexural and compression properties. Cone calorimetry tests demonstrated that the inclusion of PF particles reduced the peak heat release rate up to 28 % compared to neat PU foam, enhancing the fire safety of the insulating panels.