On the fireproof paint fireproof principles and techniques
Abstract steel as the main form of modern architecture, light weight, high strength, good seismic performance, short construction period, the high degree of industrialization building, the advantages of large space utilization at room temperature, for enterprises to save investment by investors a large number of applications. But poor performance steel building fire resistance characteristics are very obvious, because though it is a non-burning steel material, but it is a good conductor of heat, easily conduct heat. Steels at temperatures over 300 degrees after the yield point and ultimate strength decreased significantly, reaching 600 degrees almost zero intensity. Scientific experiments and examples show that unprotected steel in case of fire, just 15 minutes, its temperature will rise to over 540 degrees, resulting in distortion component itself, leading to the destruction of the buildings collapsed, deformed steel can not be repaired using. Therefore, the steel must take fire protection measures.
Key words fireproof coatings fire principle
I. Introduction
Steel structure fire method mainly paint protection, fire protection board, concrete protection, flexible membrane protection, inorganic fiber protection, within the structure of water cooling protection. Among them, brushing fire retardant coating construction convenient, light weight, low cost, component geometry without limitation, the widest range of applications, maximum efficiency.
For Steel Materials overcome deficiencies in the practical application of fire prevention, fire protection must be treated, and its purpose is to improve the fire resistance of steel to design specification limits. Steel prevent rapid warming in the fire deformed slump, its measures are varied, the key is to take different approaches under different circumstances, such as the use of insulation, refractory steel barrier direct flame burning, reduce the speed of heat transfer delayed steel temperature, strength becomes weak time. But no matter what method adopted, the principle is the same. Fire-resistant coating is a kind of fire in recent years, more advanced technical measures.
Second, fireproof coatings fire principle and composition
Fireproof protection principle is the use of thermal insulation or endothermic material direct flame burning steel barrier, reduce the speed of transfer of heat to the steel, steel postpone temperature rise and weakening of the time. According to "fireproof coatings" (GB14907-2002), defined as fireproof coatings applied to buildings and to build the steel surface, can form a protective layer of fire-resistant insulation to improve the fire resistance of steel coatings. Currently, domestic and fireproof coatings are mainly matrix resin, catalyst, into carbon, foaming agents and other components.
A matrix resin
Matrix resin compatibility with other components, both to ensure the paint under normal use conditions with a variety of features, but also has a flame resistance and excellent performance under expansion foam flame burning or high temperatures. Typically, the higher the quality of the acrylic resin carbonized layer fire retardant coating, it is usually an acrylic resin as the main film-forming material, and its modification in order to improve the overall effectiveness of the coating.
2 catalyst
A catalyst is a substance that breaks down the phosphate under certain conditions, the decomposition of the acid polyol dehydration, so make it a non-flammable carbonized layer of three-dimensional structures. Generally, the more water-soluble phosphate, melamine phosphate Hangout amine, and both catalytic and foam double effect, the main choice of melamine phosphate catalyst.
30% carbon agent
Into carbon agent is non-flammable material basis of three-dimensional structure of the foam carbide layer coating is formed at high temperatures, carbonized layer of foam from the skeleton. Into carbon agent on the decomposition temperature and the catalyst to be matched when using polyphosphate amine as a catalyst on the application of high thermal stability containing carbon-carbon polyol made agents, such as pentaerythritol, dipentylamine season alcohol thin fireproof coatings Guangdong Daya Bay Nuclear Power Plant for the bare frame houses reached than 10 years ago, can be used. But its drawback is the construction of smell great, coating easy to aging, such as starch. Starch made carbon agent, water resistance coating easy to solve the problem, but because of its price dipentaerythritol reason, rarely used in the country, currently widely used as a fire retardant coating pentaerythritol into carbon agent.
4 foaming agent
Intumescent fire retardant coating only in the role of a foaming agent to produce expansion layer at a high temperature flame. In case of fire, the blowing agent decompose and release ammonia, water, carbon dioxide, hydrogen halide nonflammable gas, the coating reaches the foaming expansion in the case of the softening point, forming a sponge-like structure.
Third, the technical problems
1 Durability
Due to the presence of thick fireproof paint since the major decorative poor, it can only be used in some less demanding outdoor steel appearance. Widely used is thin and ultra-thin fireproof coatings, especially ultra-thin. The major types of materials used in coating ammonium polyphosphate, melamine and pentaerythritol have poor water resistance, exist as environment, time and so on dissolution, decomposition, degradation and aging problems, therefore, such coatings will certainly over time Fire performance has declined, but has not yet find a way to assess the durability of fire retardant coating. The fire resistance test report is given after the paint coating maintenance inspection results 1-2 months, but the fire is unpredictable, the fire may be in a year after the paint coating may also painted 10 years after happen, so intumescent fire retardant coating durability is the most important issue.
2 Security
Currently intumescent fireproof paint a fire is likely to release ammonia, HCN, hydrogen halides, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, chlorine, bromine and other toxic gases. If the concentration of these gases over the body to endure the limit, it will not escape the fire on the officers and firefighters harm.
3 production, construction
The size of the majority of domestic manufacturers fireproof coatings little production process automation level is not high, there are some companies still in the hands of the workshop type in operation, many products of similar formulation process, dedicated to the fire-resistant coating materials research is not enough, detection of raw materials, control is not enough, the production process of incomplete testing methods, improve construction equipment could be improved, and the rust of not supporting a rigorous test.
4 Test Methods
Fireproof coatings, as a class of functional coatings, which are mainly composed of physical and chemical properties and fire in two ways. Also different because of the fire resistance of fire-resistant coating applications, different types by the fire, the protective effect of the substrate is different.
5 detection standards
GB14907-2002 "fireproof paint" the same kind of fire retardant coating inspection report only provides a coating thickness, and the fire resistance of the actual project due to steel beams, steel columns, steel floor specification requirements vary, such as indoor The thickness of 2mm ultra-thin fireproof coatings for fire resistance of the test report issued by 1.5h, practical engineering requirements steel beams, steel, fire resistance of steel columns were 1.5h, 1.0h, 2.0h. For steel, steel columns of fire retardant coating thickness which should be protected, regardless of the current lack of relevant research from theory or practical works.
6 difference detection standard components and the actual engineering components
Fire endurance test substrate used is a standard I36b or I40b Q235 hot rolled ordinary beam beam, but the actual engineering application, the cross-sectional dimensions of a wide variety of steel components. No complete correspondence between the steel beam and the actual engineering inspection report described the steel components, steel components and standard steel beam between the actual use should be how to convert, how to determine the thickness of the coating of steel components actually used, the state is still No provisions.
Fourth, the corresponding countermeasures
1 pair of steel buildings for scientific fire protection
Currently, the way we usually used are: steel surface spraying fire retardant coating; situ concrete used for cladding; water-filled inner steel components, of which the most widely used is the steel surface spraying fire retardant coating.
2 increase publicity and training and education efforts
Fire causes of fire hazards caused by the project are many, but a very important reason is that thinking and understanding in place, contempt fire prevention, there are chances of illegal construction. Fire departments should use newspapers, radio and other forms of widely publicized the importance and necessity of steel fire-retardant treated timely organizational design, construction units fire training, to improve the design, operational and theoretical level of construction workers and law enforcement awareness.
3 fireproof coatings market to strengthen and standardize management
Fireproof paint manufacturers who must have national institutions detection tested and reports are allowed to sell the factory, and should be accompanied by manual, marked with technical performance, manufacturing lot number, shelf-life, the scope; fire supervision departments should carry out batch fire retardant paint factory quality sampling and testing their packaging, labels, notes, and meets the requirements. For the construction unit fire retardant coating, clear requirements to hold the relevant construction qualification.
4 strict and approval
When accepting the audit steel project, designed specifically to use nature of the building units in the drawing, fire rating, fire hazard classification, production process, fire retardant coating construction methods and other fire design content. Undertake fire engineering construction unit should have appropriate qualifications and pre-construction program will be reported to the fire department and construction. For the design was incomplete, no construction scheme, the fire department can not accept notices issued and indicate the reasons for inadmissibility.
5 correct selection of fireproof coating species
Currently on the market a wide variety of fire retardant coatings, fire performance is different. Can not exist aspect composition, manufacturing processes, quality control methods and standards, and application technologies distinct decorative fireproof coatings used to protect steel; fireproof coatings should be used for different fire-resistant coating according to the requirements of the fire resistance of steel: When the fire resistance of not more than 1h, the choice of ultra-thin or thin fireproof coatings; when the fire resistance of not more than 2.5h, the choice of thin or thick paste fire retardant coating; refractory limit when 2.5h above should be used in Mastic fire retardant coating. Exposed parts and decorative high performance requirements, such as a roof load-bearing elements can be used ultra-thin fireproof paint, exposed columns and truss members can choose thin coating, the choice of the hidden parts of the paint thick paste. You can not only meet the technical performance indoor fireproof coatings requirements of the standard product plus technical improvements will not be used to protect steel outdoor, open-air fireproof coatings selection should consider its water, frost, corrosion and other factors, the only way to really play fire performance coatings.
6 timely construction site inspection
Fire retardant coating construction faster, strengthen supervision and inspection of the construction site is very important. Through the construction site inspection, construction team can grasp the situation, progress of the project, construction quality and product quality. Only on-site inspections, in order to discover hidden and timely supervision and rectification, to avoid unnecessary losses. Where conditions permit, you can also sample from the construction site and sample thermal performance analysis, comparison, inspection, to ensure project quality.
7 stringent acceptance criteria
Before project completion and acceptance, the fire department should make the building, construction and supervision units issued by quality inspection reports, master of the construction project. When the project is completed, not only to pay attention to the acceptance of fire-fighting facilities, but also the fireproof coatings of acceptance in an important position. Fire supervisors not only to watch, hand touch, thickness, etc. should also configure the necessary testing equipment. Meet the requirements for the quality of construction, which is to rework rework punishment the punishment to ensure the quality of the steel structure fire engineering, steel works to eliminate fire hazards exist fundamentally.
V. Conclusion
Because fireproof coatings are now and in the future of a society promising products, only inspection agency, production, design, construction, supervision and fire supervision departments jointly to work together to make our fire retardant coating areas healthy and orderly development .
References:
[1] Xu xiao nan, Zhou Zheng Mao. Fireproof paint [M]. Chemical Industry Press, 2004.
[2] Wang Jin, Wang Xianming, Zhao Rui. Problems and Solutions exist fireproof coatings [J]. China paints, 2005, (8): 11-12.
[3] fireproof coatings application specifications. Sichuan Fire Research Institute of Ministry of Public Security.
[4] building fireproof technical specifications. China Planning Press, 2006.
[5] Nijian Chun Liang sea. Application and construction elements fireproof coatings [J]. Coatings Technology & Abstracts, 2004, (2): 17-19.
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