Curing and influencing factors of the hottest two-

Curing and influencing factors of two-component polyurethane adhesive

curing of two-component polyurethane adhesive

usually achieves the purpose of curing through the reaction and cross-linking between the main agent (mostly hydroxyl containing binary compounds) and the curing agent (mostly isocyanate containing ternary compounds). Generally, the curing agent should be appropriately excessive, and the molar ratio is about 1.5 times that of the main agent

the purpose of appropriate excess of curing agent: full cross-linking is conducive to the heat and medium resistance of the adhesive; Increase the curing temperature; Counteract the effects of moisture. However, excessive curing agent should not be excessive, otherwise the softness of the adhesive film will be reduced; The adhesive strength decreases (especially for non-polar film materials); The bonding layer at the heat seal has been damaged. If the curing agent is insufficient, it will cause insufficient competition and low cohesion strength; When heated, the adhesive force decreases sharply, which is easy to cause folding or delamination

influence of humidity (moisture), temperature, etc. on curing

1 influence of moisture on curing

1) for wet curing polyurethane adhesive, sufficient absolute humidity must be maintained during use to make the adhesive obtain sufficient moisture and ensure complete curing

2) for the two-component polyurethane adhesive, the National Technical Supervision Organization and various industrial departments have also formulated a series of verification regulations for environmental experimental equipment and testing instruments. Too much water will consume too much curing agent (the curing agent is isocyanate group), which will make the proportion unbalanced, affect the curing effect, and then affect the high temperature resistance and dielectric resistance of the adhesive layer. This is the first complete set of rubber and plastic in China Quality of technical standards for quality testing equipment in light industry such as packaging

2. Effect of ethanol on curing

when the ethanol content in the solvent is low, a small amount of curing agent is consumed, which reduces the crosslinking density (increases the free branched chain), and affects the heat and medium resistance. When the content is high, a large amount of curing agent will be consumed, resulting in incomplete curing. Therefore, we should choose moisture in our work. Solvent with low ethanol content, and prevent secondary pollution in storage, transportation and use

3. The influence of temperature on curing

the polyurethane adhesive can be cured at room temperature, according to Zhao Xizi, former Vice Minister of the Ministry of metallurgical industry and former honorary president of the chamber of Commerce for small and medium-sized metallurgical enterprises of the all China Federation of industry and commerce. However, the curing time is long, and the temperature can be increased to shorten the curing time (it can also be achieved by adding catalyst). Increasing the temperature is also conducive to the softening of the adhesive at the initial stage, enhancing the wetting of the surface of the adherend, and increasing the contact point between molecules. However, if the temperature is too high and the curing is too fast, the stress is not easy to release, which is easy to cause the later bonding strength attenuation

factors affecting the properties of adhesives in the production process

in addition to the relevant influencing factors in the use process, in the production process of adhesives, many factors will cause different properties of adhesives, which requires special attention

1) different raw materials lead to different product properties; With the same raw materials, different proportioning and process operating conditions, the product performance is also different

2) most of the compound adhesives are polyester or polyester polyether mixed type. In order to facilitate the adjustment and control of the quality of the adhesive, the main manufacturers synthesize polyester by themselves. The properties of the products obtained by using raw materials from different manufacturers are also different

therefore, even products of the same brand from different manufacturers will have different performance. Generally, products from manufacturers with stable quality should be selected

author/Beijing wanfuda Fine Chemical Co., Ltd. Zhao Weijiang

set the test coefficient, such as time and speed, and start the experiment statement: