As the molar ratio of TDI to polyols was fixed at 2.1/1, relative more excess TDI was applied for 20 based copolymers which would cause more allophanate crosslinks.

• 由于TDI与二醇的摩尔比固定为2.；1/1；对20系列来讲，过量的TDI就会多些，这将导致形成更多的脲基甲酸酯交联键。