On the principle of fireproof paint fire
I. Introduction
Methods steel structure fireproof paint mainly maintenance, fire board maintenance, concrete maintenance, flexible membrane maintenance, inorganic fibers maintain the structure of water cooling maintenance. Among them, brushing fire-resistant coating to facilitate the construction, light weight, low cost, component geometry without limitation, the use of a wide range of the highest power.
To overcome the practical application of steel data insufficient fire prevention, fire protection must be disposed of, its purpose is to improve the fire resistance of steel to the design specification limits. Prevent the rapid warming in the fire steel deformed slump, its measures are varied, the key is to take a different approach depending on the circumstances, such as the use of thermal insulation, fire information direct flame burning steel barrier, reducing heat transfer rate delayed steel temperature, strength becomes weak time. But no matter what method adopted, the principle is the same. Fire retardant coating is a fire in recent years more advanced technical measures.
Second, fireproof coatings principle and constitute fire
Foshan Steel fireproof insulation to maintain the principle is the use of the information or endothermic direct flame burning steel barrier, reducing the rate of heat transfer to the steel, the steel temperature and the weakening of delayed time. According to "fireproof coatings" (GB14907-2002), defined as the fireproof coatings applied to the exterior of buildings and structures of steel, fire-resistant insulating protective layer can be formed to improve the fire resistance of steel coatings. Currently, there are domestic and fireproof coatings matrix resin, catalyst, into carbon, foaming agents, and the like.
1 matrix resin
Matrix resin compatibility with other components, both to ensure the paint under normal use conditions with a variety of functions, but also has excellent flame resistance and functional expansion foam flame burning or under high temperature conditions. In general, the higher the quality of the acrylic resin carbonized layer fire retardant coating, it is commonly used acrylic resin as the main film-forming material, and its modification to improve the overall effectiveness of the coating.
A catalyst
A catalyst is a substance that breaks down the phosphoric acid under certain conditions, the decomposition of the acid polyol dehydration, so make it a non-flammable carbonized layer three-dimensional structure. In general, water-soluble melamine phosphate, ammonium phosphate than the Hangout, and both catalytic and foam double effect, the main choice of melamine phosphate catalyst.
3 into carbon agent
Into carbon agent is the material basis of three-dimensional structure of non-flammable foam coated carbide layer formed at high temperatures, carbonized layer of foam from the skeleton effect. Into carbon agent and catalyst on the decomposition temperature to match when using polyphosphate amine catalyst on the use of high thermal stability of the carbon-containing polyols made carbon agent, such as pentaerythritol, di-amyl alcohol ultra-thin fireproof coatings quarter Guangdong Daya Bay Nuclear Power plant for bare shelves housing has reached the ten years long, still normal use. But its drawback is the smell of large construction, coating easy to aging, such as starch. The use made of carbon agent starch, water resistance coating is not easy to solve the problem, but because of its quoted dipentaerythritol reasons, seldom used in the country, currently widely used as a fire retardant coating pentaerythritol into carbon agent.
4 foaming agent
Intumescent fire retardant coating effect only in the blowing agent to produce expansion layer at a high temperature flame. In case of fire, the blowing agent to decompose and release of ammonia, water, carbon dioxide, hydrogen halide such nonflammable gas, foaming expansion of the coating in the case of the softening point of arrival, the sponge-like structure is formed.
Third, the technical problem of
1. Durability
Due to the presence of thick paint from a major fire, decorative poor, it can only apply in some less demanding outdoor steel appearance. Widely used is thin and ultra-thin fireproof coatings, especially ultra-thin. This is mainly two types of coating materials by the use of ammonium polyphosphate, melamine and pentaerythritol are poor water resistance, with the existence of the environment, the dissolution time, decomposition, degradation and aging problems, so that such coating must be over time fire function decline, but has not yet figure out a way to identify fire-resistant coating durability. Fire resistance test report is given after paint coating maintenance inspection results 1-2 months, but the fire is unpredictable, the fire may be in one year after the paint coating may also be painted after 10 years happen, so intumescent fire retardant coating durability is the main problem.
2 Safety
Currently intumescent fireproof paint a fire may release ammonia, HCN, hydrogen halides, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, chlorine, bromine and other poisonous gases. If the concentration of these gases over the limits of the human body to endure, it will not escape the fire on the officers and firefighters harm.
3. Production, construction
Most of fireproof coatings scale domestic manufacturer of small, production process automation level is not high, there are some companies still in the hands of the workshop type in operation, a lot of the product formulation process is very different, for dedicated fire retardant coating materials research is not enough , the detection of the original data, the control is not enough, the failure detection means production process, improve construction equipment could be improved, and the rust of not supporting strict inspection.
4 Test Method
Fireproof coatings as a functional coatings, and its main function has two aspects constitute physicochemical and fire. The same fire resistance of fire-resistant coating for its use in different environments, different types affected by the fire, the maintenance of the substrate effect is different.
5. Detection norms
GB14907-2002 "fireproof paint" on the same kind of fire-resistant coating inspection report only provides a coating thickness, and fire resistance due to the practice of engineering steel beams, steel columns, steel floor specification requirements vary, such as indoor the ultra-thin thickness of 2mm fireproof paint for the fire resistance test report issued 1.5h, practical engineering requirements beams, steel, fire resistance of steel columns were 1.5h, 1.0h, 2.0h. Of steel, fire-resistant coating thickness steel columns which should be used for maintenance, regardless of the current lack of corresponding research from the theory or practice of engineering.
6. Detection component specification and practice of engineering components differences
Inspection of fire resistance of the substrate is utilized Q235 specification I36b or I40b ordinary hot-rolled-steel beams, and the use of engineering practice, the cross-sectional dimensions of a variety of steel components. Inspection report described the steel beam and practice of engineering steel members did not complete correspondence between the use of steel components between practice and norms of how steel beams should be translated, how to determine the practical application of the coating thickness of the steel members, the state still no provisions.
Fourth, appropriate countermeasures
1 steel buildings for the maintenance of fire science
Currently, we generally use methods: steel exterior spraying fire retardant coating; using in-situ concrete for cladding; filled with water in the steel components, of which the most widely used is steel exterior spraying fire retardant paint.
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