Kinetics and Mechanism of the Chemical Degradation of Flexible Polyurethane Foam Wastes with Dimethyl H-phosphonate with Different Catalysts

Abstract

Flexible polyurethane foams (PU) based on toluene diisocyanate and polyether polyol have been degraded by dimethyl H-phosphonate (DMP) in the presence of catalysts such as potassium tert-butoxide, potassium and azobisisobutyronitrile (AIBN). The structure and molecular weight of the degraded products were monitored by 31 P-NMR and GPC. The degradation process was controlled by the polydispersity (PD) of the reaction product. Potassium tert-butoxide enhances interchange reactions compared to the non catalyzed process. The product of degradation contains mainly the original polyol capped with a phosphonate group and a phosphorous dimmer of the original polyol.

Insight into Chemical Recycling of Flexible Polyurethane Foams by Acidolysis

“…Several recycling technologies have been developed with different mechanisms of urethane bond degradation. Glycolysis − and acidolysis ,− have been successfully used at the industrial scale, hydrolysis , has been introduced at the pilot scale, while aminolysis − and phosphorolysis − have been developed only at the laboratory scale. Chemical recycling of PUFs is carried out at high temperatures, mainly by conventional heating, although there are some reports on microwave (MW)-assisted degradation processes, especially in the case of glycolysis, where MW heating shortens the reaction time and improves the reaction yield. , Theoretically, all recycling technologies for polyether-based PUFs lead to hydroxyl-functionalized polyether polyol and oligourea hard segments end-capped with the applied degradation reagent. ,, Unfortunately, the existing methods of chemical recycling of PUFs mainly suffer from incomplete and/or nonselective degradation of urethane linkages, as partial cleavage of urea groups in the hard segments also occurs.…”

Upgrading Polyurethanes into Functional Ureas through the Asymmetric Chemical Deconstruction of Carbamates

“…Although it was the first method to be explored for the depolymerization of flexible PU foams, hydrolysis was rapidly discarded as an option because of the high pressures and temperatures required. , The methanolysis process suffers from similar issues as the reactions are typically conducted at temperatures >200 °C, which requires the use of supercritical methanol. , Glycolysis has been the most studied process, and various catalysts including alkaline salts , and organometallic complexes − have been employed. For both types of catalysis, the products obtained are rarely selective, and the amine(s) and polyol(s) formed prevents the possibility of recovering the carbamate function.…”

Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis

“…[ 2,7,8 ] For example, hydrolysis of PUs can be employed in certain cases to recover the original alcohol monomer (polyol), along with the amine analogue of the original isocyanate monomer. [ 9–13 ] Similarly, various amines, [ 14–20 ] alcohols, [ 14,15,17–19,21–25 ] and acids [ 5,26–32 ] have been used to displace the carbamate linkage and thereby depolymerize PUs. Generally speaking, however, these depolymerization strategies are energy intensive, requiring high temperature, high pressure, and/or long reaction times, and they are inefficient, requiring stoichiometric quantities of cleavage reagents to yield complex mixtures of monomers and oligomers (i.e., incomplete depolymerization) that must be further separated and purified.…”