Raw Materials for Polyurethane Production
The primary raw materials for polyurethane production are: "Black Component," "White Component," and blowing agents.
1. Black Component: The technical name for this material is polyisocyanate; due to its appearance as a black, viscous liquid, it is commonly referred to as the "Black Component." Major types of polyisocyanates include MDI, TDI, and PAPI; among them, MDI (diphenylmethane diisocyanate) is used in the production of polyurethane foam for refrigerators.
2. White Component: In the industrial production of refrigerator polyurethane foam, a blend of polyether polyols, catalysts, and foam stabilizers is typically prepared first. This mixture is a white, viscous liquid commonly known as the "White Component."
(1) Polyether Polyol Blend: The polyol used for refrigerator polyurethane foam is of the polyether type.
(2) Catalyst: The primary function of the catalyst is to accelerate polyurethane formation, shorten curing time, and improve foam quality.
(3) Foam Stabilizer: The primary functions of the foam stabilizer are to emulsify the raw material components within the system, ensuring a smooth reaction process; promote bubble nucleation; and enhance bubble wall stability. This results in a product with a uniform, fine cell structure and good mechanical properties. Although used in small quantities, stabilizers significantly influence the foam's cell structure, physical properties, and manufacturing process.
3. Blowing Agent: In polyurethane foaming, the primary role of the blowing agent is to generate gas, creating a distribution of fine, uniform bubbles within the polyurethane matrix. The blowing agent itself does not participate in the chemical reaction between the polyisocyanate and the polyether polyol blend. Foaming processes that do not utilize Freon are referred to as "Freon-free foaming."An example is cyclopentane foaming.
