What are the common problems in the use of polyurethane adhesives?Issuing time:2020-04-20 16:05 It may be strange to mention polyurethane adhesives. I don't know what they are used for. They may never have heard of them. But when we talk about ceramics, foam, leather and other products, we are familiar with it. In fact, polyurethane adhesives are widely used in these industries according to their low VOC content, low or no environmental pollution and non combustible characteristics. As a chemical raw material for performance comparison, polyurethane adhesive must be used with extra care. Operators must know its chemical properties in detail to achieve safe operation. Even so, various problems will inevitably occur in the operation process, which will not be solved by everyone. The following is a brief introduction of common problems and corresponding solutions in the use process of polyurethane adhesive I have made the following detailed introduction for you, let's have a look! Hydrolytic resistance The hydrolytic resistance of polyester polyurethane adhesive is poor, which can be improved by adding hydrolytic stabilizers (such as carbodiimide, epoxy compounds, etc.). In order to improve the hydrolytic resistance of polyester, long-chain diols and diols (such as sebacic acid, 1,6-hexanediol, etc.) can be used. Branched diols such as neopentyl glycol can also improve the hydrolytic resistance of polyester. Polyether has good hydrolysis resistance, sometimes it can be used together with polyester to prepare polyurethane adhesive. Adding a small amount of organosilicon coupling agent to the adhesive formula can also improve the hydrolytic resistance of the adhesive layer. Improve curing speed One of the main ways to improve the curing speed is to make the polyurethane adhesive have a certain initial adhesion, that is, it is no longer easy to separate after bonding. Therefore, increasing the molecular weight of the main agent and using the raw materials that can produce crystalline polyurethane are effective methods to improve the initial adhesion and curing speed. Sometimes adding a small amount of triethanolamine, a kind of catalytic cross-linking agent, also helps to improve the initial adhesion. The addition of catalyst is also the main method to accelerate curing. High temperature resistance Polyurethane adhesive generally has insufficient high temperature resistance. If it is to be used in special temperature resistant occasions, polyurethane adhesive can be designed in advance. There are several ways to improve the heat resistance of polyurethane adhesive, such as: 1. The raw materials of polyether, polyester and isocyanate containing benzene ring are used; 2. Increase the content of isocyanate and chain extender; 3. Increase the amount of curing agent; 4. Polyisocyanate with high temperature resistance or isocyanurate produced during curing; 5. It is an effective way to improve the compatibility of polymer by blending polyurethane with epoxy resin or polysulfonamide. |