Polyurethane products have many characteristics. Because the weight of the product changes in the post curing process, and the weight change of the self skinned product is a complex change because of its own characteristics.

In the production process of self skinning products, after the reaction is completed, the products are taken out from the mold cavity. First, the weight should be weighed, and then the holes should be opened to deflate, so as to avoid product shrinkage. After another period of time, the weighing products will find that the weight has changed, that is, the products become lighter.

The first is the weight loss caused by the volatilization of physical foaming agent (the molecular weight of physical foaming agent is greater than that of air). In this process, only physical changes have taken place.

Secondly, in the production ratio of polyurethane products, the black material isocyanate is excessive, and excessive isocyanate will react with water to release carbon dioxide. When - NCO reacts with hydroxyl in polyether, not all - NCO can react with hydroxyl due to the steric effect and other reasons, but there are still some free NCO groups, and this part of NCO group will react with water to release dioxide The carbon gas evaporates.

In the actual production, due to other side reactions, as well as the influence of operating conditions such as temperature and humidity, the quantity of weight loss is different. Different manufacturers, different products, different isocyanate indexes have different effects on the weight loss of products. Different polyether and isocyanate used by different manufacturers have different steric effect, which will also affect the weight loss of products. According to the calculation and the production experience of our factory, the general loss weight is between 7% and 10%, but the loss of different products is different, which needs to be explored from the production.

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