Fireproof paints
Intumescent Paints Intumescent Fire Resistive Material
Today, coatings, composites, fire retardants and intumescent coatings are used for fire protection.
Intumescent coatings are a recent development as a passive fire retardant in load-bearing structures.
Intumescent coatings have been used for fire protection for more than 20 years.
This coating swells in the presence of fire and creates a protective carbon layer.
Behavior of steel structures in the face of fire
Fire changes the physical properties of steel with increasing temperature, resulting in the destruction of steel structures.
According to ASTM E_119, the critical temperature for columns is 538 ° C and for beams is 598 ° C.
The time to reach the critical temperature for a column with the specifications of W14*193 in the cellulose fire temperature curve is 15 to 18 minutes
and this time for the hydrocarbon fire temperature curve is between 6 and 7 minutes. The reduction in mechanical strength
, tensile strength and increase in length are the factors of deformation and bending of the metal frame. The destruction of the building will be certain if the fire time increases.
Fire protective coatings are used to protect the skeleton of the structure in order to increase the resistance of the structural elements
to the thermal stresses caused by fire, which in addition to keeping the structure stable, provides more opportunity
for escape/rescue operations. The resistance level of the materials to provide such protection is measured by special furnaces and in accordance with the standard
and the results are presented based on the required dry thickness, among which the BS 476-part 2 standard can be mentioned [2].
Characteristics of fire-retardant coatings:
Retardant
Maintaining the appearance and preventing cracks from forming when exposed to increased temperatures
Lightweight in order not to impose additional load on the structure
Proper adhesion to the metal surface, especially after increasing temperatures
No production of toxic and dangerous gases when exposed to fire
Proper mechanical resistance in order to maintain the appearance and health of the coating before exposure to fire in order to maintain efficiency during a fire
Proper resistance to environmental and atmospheric conditions and the possibility of easy repair and ease of application [2]. Fire-retardant paints
Categorizing paints and materials:
Intumescent paints themselves are classified into 2 categories: blue-based intumescent paints and epoxy and acrylic-based intumescent paints.
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Intumescent mineral coatings
Intumescent mineral silicate materials containing CaO, MgO, Al2O3 and calcium magnesium silicate are used with acrylic or polyvinyl acetate as the coating or adhesive. A coating can then consist of a polymer latex and a swelling agent comprising granules of alkali metals and silicates.
An aqueous swelling composition of alkali silicates, clays and minerals such as hydrated alumina, hydrated borates, carbonates, bicarbonates can be used for metal and wood and polymeric materials.
Minerals such as alkali silicates have the following characteristics:
They are inexpensive, have drawbacks in durability and water resistance [3].
Organic swelling coatings
These coatings are more stable to weather and have higher water resistance than silicate-based coatings. Architects are increasingly interested in these coatings, as they allow them to design elements using the steel itself. Materials include:
Carbon donor or char generator such as PER
Acid donor or catalyst such as APP
Blowing agent: MEL
Binder: polyvinyl acetate, epoxy
The only problem with the coating: the possibility of creating soft char that can be carried by the wind [3].
Swelling mechanism: Fire retardant paints
Initially, breaking down the acid source releases a mineral acid that dehydrates and carbonizes the char forms.
The blowing agent then decomposes and releases gases that are reduced in the molten matrix, causing swelling and the formation of a multicellular protective char layer [3]