Synthesis of Rigid Polyurethane Foams Incorporating Polyols from Chemical Recycling of Post-Industrial Waste Polyurethane Foams

Abstract

The preparation and characteristics of rigid polyurethane foams (RPUFs) synthesized from polyols obtained by glycolysis of post-industrial waste RPUFs have been studied. More precisely, waste rigid foams that have been chemically recycled by glycolysis in this work are industrially produced pieces for housing and bracket applications. The glycolysis products have been purified by vacuum distillation. The physicochemical properties of the polyols, such as hydroxyl value, acid value, average molecular weight (Mn) and viscosity have been analyzed. The chemical structure and thermal stability of the polyols have been studied by means of FTIR and TGA, respectively. Partial substitution of the commercial polyol (up to 15 wt.%) by the recycled polyols increases the reactivity of the RPUFs synthesis, according to short characteristic times during the foaming process along with more exothermic temperature profiles. Foams formulated with recycled polyols have a lower bulk density (88.3–96.9 kg m−3) and smaller cell sizes compared to a conventional reference RPUF. The addition of recycled polyols (up to 10 wt.%) into the formulation causes a slight decrease in compressive properties, whereas tensile strength and modulus values increase remarkably.

Opportunities in Closed-Loop Molecular Recycling of End-of-Life Polyurethane

“…Alkali metal hydroxides and organic/inorganic metal salts are common catalysts for glycolysis. For example, addition of sodium hydroxide (NaOH), sodium acetate (NaOAc), or iron chloride (FeCl 3 ) improved both rate and conversion of glycolysis with EG. ,− With the addition of a catalyst, glycolysis with EG reached 90% conversion within 1 h, while without a catalyst glycolysis was limited to 80% overall conversion after 5 h. The addition of a potassium octoate catalyst to the glycolysis of PU with DEG expedited the kinetics to a rate comparable to that observed with EG which increased the yield of repolyol to 80%, compared to 40% without a catalyst . Furthermore, Maioli et al demonstrated glycolysis of PU assisted by ionic liquids, giving 70% yield of repolyol in DEG or glycerol medium with 1-butyl-3-methylimidazole trichloromanganate or 1-butyl-3-methylimidazole trichlorozincate catalysts .…”

Recycling of polyurethanes: where we are and where we are going

“…In a further research effort, Amundarain and co-workers 133 exploited the polyols, recovered from post-industrial rigid polyurethane foams by means of glycolysis reactions, for preparing new rigid foams. The recovered counterparts showed remarkably higher values for viscosity, acidity, and average molecular weight and more hydroxyl groups than those of commercial polyols: these findings were ascribed to both the residual ethylene glycol in the polyol after the purification of the glycolysate and in the presence of glycolysis by-products (such as amines and carbamates).…”

Accelerated Aging on the Compression Properties of a Green Polyurethane Foam: Experimental and Numerical Analysis

“…However, there is a lack of scientific publications regarding the lifespan of PUFs where their mechanical properties are relevant, such as sandwich panels [ 6 ]. Many studies regarding the synthesis, characterizations and applications of bio-based PUFs are being carried out every year due to its pairing characteristics with oil-based foams as well as its relative low cost and eco-friendly origin [ 7 , 8 , 9 , 10 ]. PUF is a two-phase material composed of a continuous polymer matrix and the gas in the discretely distributed cells.…”