Learn All About Scorching in This Article Polyurethane foams are produced through the polymerization of aromatic isocyanates and aliphatic polyols. The process involves simultaneous polymerization and expansion facilitated by blowing agents such as chlorofluorocarbon (CFC – HCFC) or carbon dioxide generated by the reaction of isocyanate with water in the formulation. Since both the polymerization […]12 de dezembro 2024 – Publicado por Amino
Learn All About Scorching in This Article
Polyurethane foams are produced through the polymerization of aromatic isocyanates and aliphatic polyols. The process involves simultaneous polymerization and expansion facilitated by blowing agents such as chlorofluorocarbon (CFC – HCFC) or carbon dioxide generated by the reaction of isocyanate with water in the formulation. Since both the polymerization and decarboxylation reactions are highly exothermic, polyurethane foam can undergo thermal oxidation. The discoloration resulting from this thermal oxidation is commonly referred to as central scorching, central yellowing, or “scorching,” derived from the English term meaning “scalded” or “burned.” This central discoloration in foam blocks is characterized by a yellow hue, which, in more severe cases, can turn brown or black.
The Effect of Scorching or Central Yellowing in Foam Blocks
Figure I: The Effect of Scorching or Central Yellowing in Foam Blocks
The presence of scorching or yellowing in foam blocks is economically significant for foam producers, as it negatively impacts the foam’s aesthetics and, consequently, its commercial value. In severe cases, it can degrade the physical properties of the foam, and if the scorching is intense, it may even lead to spontaneous combustion.
The standard approach to reduce foam scorching involves the addition of one or more antioxidants. Butylated hydroxytoluene (BHT) has traditionally been the cornerstone of stabilization packages. Phenolic antioxidants are used to protect the polyol from oxidation during manufacturing, minimize hydroperoxide formation during storage, and reduce central scorching during foam production. However, the relatively high volatility of BHT poses concerns as it can volatilize during processing, leading to BHT accumulation issues. BHT is also known to cause staining, prompting the polyurethane industry to seek more effective, non-staining, and low-volatility antioxidants.
Also Read: Flame Retardants for Polyurethane Foam
high demand. Moreover, high-performance products have recently emerged, delivering excellent results at feasible costs.
The AMITHERM XYZ99 liquid temperature stabilizer from AMINO QUÍMICA is a new anti-scorching system that is free of amines and aromatic solvents, designed for use in producing polyether-based flexible foams. It offers strong resistance to scorching or yellowing and prevents fabric staining. The stabilizer ensures low VOC and FOG emissions, excellent resistance to gas fading, and discoloration induced by light. It enables dust-free handling, automatic dosing, and shorter mixing times.
Effects of Temperature Stabilizers on Gas Fading in Flexible Foams
Figure II: Effects of Temperature Stabilizers on Gas Fading in Flexible Foams
