2. Common Reagents Used in the Preparation of PUFs and Their Respective Influence on the Properties of the Final Material .

Entry	Reactant	Function
1	Isocyanate	Determines PUF reactivity and provides rigidity and strength to the final material. Generation of secondary bonds responsible (i.e., urea, biuret, allophanate, isocyanurate, etc.).
2	Polyol	Main reactant along with isocyanates. Determines flexibility, density, and thermal properties of the PUF.
3	Blowing agent	Provides the foam structure. It affects the cell size and structure, thus impacting in the foam density.
4	Surfactant	Key component for stabilizing the foam cells during expansion. It controls cell size and structure while preventing collapse during synthesis.
5	Catalyst	Boosts the reaction between isocyanates and other substrates (i.e., polyol, blowing agent, etc.).
6	Chain extender/cross-linker	Enhances mechanical strength and hardness.
7	Additives	Affect specific properties, such as flame retardancy, color, UV resistance, thermal conductivity, or stiffness.

^aInformation provided by public–private partners (e.g., Technological Centre for Wood and Furniture of the Region of Murcia (CETEM) and INTERPLASP S.L.).