Polyurethane casting materials mainly consist of three core components: polyol, isocyanate, and additives. The choice of different raw materials directly determines the performance of the final product.
Polyol is a key factor determining the material's flexibility and elasticity, and is generally divided into polyether polyols and polyester polyols. Polyether systems have good hydrolysis resistance, while polyester systems have higher mechanical strength and abrasion resistance.
Common isocyanates include MDI (4,4'-diphenylmethane diisocyanate) and TDI (toluene diisocyanate). MDI systems are more stable and safer, suitable for industrial casting products, while TDI is mostly used in flexible foam materials.
Additives include catalysts, chain extenders, crosslinking agents, defoamers, and colorants. Catalysts control the reaction rate, chain extenders (such as MOCA) determine hardness and strength, and defoamers are used to reduce bubble defects.
In formulation design, it is necessary to balance hardness, elasticity, abrasion resistance, and processing performance according to the product's intended use. For example, high-abrasion rollers typically use a high-hardness formula, while cushioning pads require lower hardness and higher resilience.
