news

This article reviews the research progress of water-based expansion type fireproof coatings for steel structures in recent years, analyzes their thermal insulation and protection mechanisms, introduces classic expansion flame retardant systems, new synergistic flame retardant systems, and measures to improve water resistance; Elaborate on commonly used film-forming substrates such as acrylic resin, epoxy resin, waterborne polyurethane, and organosilicon, as well as their modification techniques; Detailed exploration of the synergistic and synergistic effects of flame retardants, pigments, and nanomaterials; Finally, the future research directions of water-based expansion steel structure fireproof coatings are discussed.

1、 Expansion Fire and Insulation Mechanism (excerpt from original text)

Expansion type fireproof coatings undergo multi-step chemical reactions when heated: the acid source decomposes and releases inorganic acids; Acid source and carbon source undergo esterification dehydration reaction to generate carbonaceous intermediates; The thermal decomposition of the gas source releases inert gas, causing the carbonaceous intermediate to foam and expand, forming a porous, dense, and heat-insulating expanded carbon layer. The carbon layer isolates heat and oxygen, prevents further thermal degradation of the substrate, protects the steel structure substrate, and delays the temperature rise of the steel.

2、 Film forming matrix comparison (focusing on acrylic lotion)

1 Acrylic lotion (pure acrylic, styrene acrylic lotion)

Main points of the original text: acrylic lotion is the most commonly used matrix of water-based intumescent fire retardant coating, with excellent film forming performance, good weather resistance, low VOC, and suitable for indoor and outdoor steel structures; But there are obvious shortcomings: low thermal expansion ratio, poor mechanical strength of the carbon layer, and insufficient water resistance. Improvement measures:

1) Silicone/fluorine chemically modified acrylic lotion to improve the water resistance and damp heat resistance of the paint film;

2) Using melamine microcapsules to encapsulate the APP reduces the hydrolysis of flame retardants and improves the density and strength of the carbon layer in the acrylic system;

3) Introducing crosslinking monomers to construct a self crosslinking latex system, enhancing the overall mechanical properties of the coating.

2 Epoxy resin

Excellent adhesion and good chemical corrosion resistance; Disadvantages: Poor weather resistance, mostly used for indoor steel structures, limited for outdoor use.

3 Water based polyurethane

The paint film has good flexibility and can be compounded with acrylic acid to improve the brittleness of the coating; The cost is relatively high.

4 Organic Silicon Resin

Outstanding high-temperature thermal stability; High price, poor film-forming properties, generally used as a modified component, not as a separate base material.

Development trend of matrix: acrylic epoxy hybrid, acrylic silicone hybrid composite lotion, taking into account weather resistance, adhesion, high temperature carbonization.

3、 Flame retardant and synergistic system

1. The traditional APP PER MEL three source system has a simple process and good flame retardant effect; The core defect is that the APP is water-soluble and hydrolyzed, and the fireproof performance of the paint film deteriorates when it comes into contact with water. Improvement: Melamine MF and epoxy resin microcapsules encapsulate ammonium polyphosphate to reduce water solubility.

2. Nano synergistic fillers (commonly used in acrylic coatings) include graphene oxide, silicon dioxide, TiO ₂, alpha zirconium phosphate, molybdate, zinc borate, and layered bimetallic hydroxide LDH. Function: Enhance the density of the carbon layer, increase the residual carbon rate, suppress smoke and reduce toxicity; Limitations: High addition will destroy the film formation of lotion, reduce the storage stability, and make the film brittle.

3. New carbon sources: bio based carbon sources such as chitosan and starch, which are green and environmentally friendly, but their water resistance needs to be improved.

4、 Technical route for improving water resistance (summarized in the original text)

1. Encapsulation treatment with flame retardant microcapsules to isolate water from contact with the APP;

2. Chemical modification of lotion: silicon modification, fluorine modified acrylic copolymerization;

3. Organic inorganic hybrid, nano filler composite;

4. Introduce cross-linking system to improve the cross-linking density of paint film;

5. Optimize the ratio of pigments and fillers to reduce the amount of hydrophilic additives used.

5、 Existing industry issues

1. APP hydrolysis, poor water and moisture resistance, and long-term service fire resistance degradation;

2. Adding a large amount of flame retardant fillers can damage the adhesion and flexibility of the paint film;

3. Burning smoke and toxic release issues;

4. The storage sedimentation of thick coating system and the stability of lotion are poor;

5. There are relatively few outdoor weather resistant water-based expansion fireproof coating products.

6、 Future research prospects

1. Reactive intrinsic flame retardant acrylic lotion: phosphorus containing, DOPO type polymerizable monomer copolymerization, flame retardant groups chemically bond latex molecules to avoid migration and precipitation of flame retardant;

2. A new high-efficiency synergistic flame retardant system that reduces the total amount of filler added and balances fire prevention and film mechanics;

3. Development of bio based carbon sources and low smoke, low toxicity, halogen-free flame retardant systems;

4. Organic inorganic hybrid lotion matrix;

5. Develop high-performance outdoor weather resistant water-based expansion steel structure fireproof coating;

6. Carbon layer reinforcement technology enhances the high-temperature strength of the expanded carbon layer and prevents cracking and detachment of the carbon layer.