How to choose the curing agent suitable for synthetic resin materials of waterborne environmental protection coatings?

Choosing a curing agent suitable for synthetic resin materials of waterborne environmental protection coatings requires comprehensive consideration of many factors. The following are some key points:

Depending on the resin type

Acrylic resin: For hydroxyl acrylic resin, amino resin is often used as curing agent, which can cross-link at a certain temperature to form a coating with excellent performance, good hardness, gloss and weather resistance. Waterborne acrylic resin can also use polyisocyanate curing agent, which can provide excellent water resistance, chemical resistance and mechanical properties, and is suitable for occasions with high performance requirements.

Epoxy resin: Waterborne epoxy resin usually uses waterborne amine curing agent, such as polyamide curing agent, which has good compatibility with epoxy resin, and the cured coating has good adhesion, corrosion resistance and mechanical strength. In addition, modified amine curing agent can also be selected to adjust the curing speed and performance to meet different construction needs.

Polyurethane resin: waterborne polyurethane resin generally adopts curing agent containing isocyanate group, and aliphatic isocyanate curing agent can make the coating have good weather resistance and gloss retention, which is suitable for outdoor application; Aromatic isocyanate curing agent can provide high hardness and strength, and is often used in occasions with high requirements on wear resistance and mechanical properties.

Considering curing conditions

Temperature: If the construction environment temperature is low, low-temperature curing agents, such as some modified amine curing agents, should be selected, which can react with the resin at low temperature to ensure the normal curing of the coating. For coating systems that need to be cured at high temperature, curing agents with high reactivity at high temperature, such as some amino resin curing agents, can be quickly crosslinked at high temperature to improve production efficiency.

Humidity: In high humidity environment, water-based curing agent may be affected by moisture, resulting in poor curing. At this time, a curing agent insensitive to humidity, such as blocked isocyanate curing agent, can be selected. It is stable at room temperature and does not react easily when it meets water. Only under certain conditions can it be unsealed and react with resin, which can effectively avoid the influence of high humidity on curing.

Pay attention to the performance requirements of coatings

Water resistance: If the coating needs good water resistance, aliphatic polyisocyanate curing agent can be selected. The cured coating has low water absorption, which can effectively block the penetration of moisture, and is suitable for coatings in humid environments such as toilets and kitchens.

Chemical resistance: For coatings that need to be corroded by chemicals such as acid, alkali, salt, etc., curing agents with high crosslinking density after curing can be selected, such as the system of some epoxy resins and amine curing agents, which can form a three-dimensional network structure and improve the chemical corrosion resistance of coatings, and are often used as anticorrosive coatings for chemical equipment, pipelines, etc.

Flexibility: If you want the coating to have good flexibility, you can choose a curing agent containing flexible segments, such as polyether amine curing agent, which can form flexible connections between resin molecular chains, so that the coating can deform to a certain extent without breaking when subjected to external force, and is suitable for surface coating of some objects that need to be bent or stretched frequently.

Consider environmental protection requirements

VOC content: With the increasingly stringent environmental protection requirements, the curing agent with low VOC content should be selected as far as possible. Water-based curing agent itself has low VOC emission, which meets the requirements of environmental protection. However, some solvent-based curing agents will release a lot of organic solvents during use, so it should be avoided or strictly treated.

Restriction of harmful substances: ensure that the curing agent does not contain harmful heavy metals, formaldehyde and other harmful substances, in line with relevant environmental standards and regulations. For example, some lead-free and chromium-free curing agents are more suitable for coatings in food packaging, children's toys and other fields that require high environmental protection.

Considering cost and supply stability

Cost: The cost of different curing agents is quite different, so the cost factors should be considered comprehensively on the premise of meeting the performance requirements of coatings. For example, the price of amino resin curing agent is relatively low, which is suitable for some cost-sensitive common coating products; However, the cost of polyisocyanate curing agent is high, and it is generally used in high-end coatings with extremely high performance requirements.

Supply stability: When selecting curing agent, the production capacity and supply stability of the supplier should be considered to ensure that the required curing agent can be obtained continuously and stably in the coating production process, so as to avoid affecting the production progress due to supply interruption.