Industrial rockwool fiber wastes as reinforcement in rigid polyurethane foam: Preparation and characterization

Abstract

Unrecyclable industrial rockwool fiber waste is a worldwide problem that demands an effective yet sustainable solution. This paper presents a work on repurposing industrial rockwool fiber wastes as fillers for rigid polyurethane (PU) foam. The fillers are varied from 1 to 10 wt% and the obtained reinforced foams are characterized for their thermal stability, combustibility, foam morphology, and mechanical response. Marked improvement in thermal stability was observed in the presence of rockwool inside the foam formulation as denoted by delayed thermal degradation temperatures. Unfortunately, a similar finding was not obtained for its fire-retardancy as no distinguishable differences in Limiting Oxygen Index (LOI) and UL-94 combustion test was observed. Microscopy imaging indicated reduced cell size with increased filler loading, and the rockwool fillers are homogenously scattered within the polymer matrix. Drop in normalized compressive properties was detected, suggesting rockwool fillers pose no mechanical reinforcing effect on the foam other than through increased apparent foam and cellular density.