Related effects of various indicators of polyether polyols on foam products-Unsaturation and moisture
The level of the polyether reaction temperature and the number of catalysts directly affect the degree of unsaturation of the polyether product. If the reaction temperature is high or the catalyst content is high (the number of activation centers of the polyether chain is large), the side reactions increase and the degree of unsaturation increases.The increase in unsaturation indicates that there is an increase in unsaturated substances such as aldehydes generated during the reaction. After the end group of the polyether forms an unsaturated double bond, the reactivity is lost, and the chain growth is terminated, which affects the average molecular weight of the polyether, causing the average molecular weight to decrease, the hydroxyl value to increase, and the function of the polyether to decrease.The level of functionality directly affects the performance of foam products. Therefore, in production control, the lower the degree of unsaturation, the fewer side reactions, and the smaller the impact on foam products.
Water as a foaming agent is one of the most important reactions in foams. A small amount of water can consume a lot of TDI, produce a lot of gas and release heat.The increase in the concentration of water in the reaction mixture can speed up the reaction speed.If the moisture in the polyether (which is ignored when calculating the TDI index) increases, not only will a large amount of TDI be consumed to reduce the activity of the polyether, causing cracking and collapse, but also due to the release of a large amount of CO[sub] 2[/sub] and heat in the reaction, the density of the foam product will be reduced. If the heat generated cannot be quickly removed, it will cause yellow heart and even catch fire in severe cases.If the moisture content of the polyether exceeds the standard seriously, the amount of urea bond and CO[sub]2[/sub] will be generated, the foam density will become smaller, the foam product will harden, and a large amount of heat will be released at the same time, which can easily cause heartburn.If the customer uses it without his knowledge, it is equivalent to an increase in the amount of water, but the amount of TDI and catalyst has not been adjusted, which can easily cause foaming, and when the standard is exceeded, the phenomenon of foaming will occur.Therefore, the lower the moisture content in the polyether control process, the better, which is conducive to the stability of the formula and performance of foam products.