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Physical properties of refractory convex polymer composite coatings
Indicator
Flammable convex polymer composite
Density g/sm
3
1,09
Water solubility
Insoluble in water
Infrared spectroscopy with Fourier transform (UR-20 and UR-75) of the obtained
composite based on ED-20 epoxy resin and phosphorus, nitrogen and metal-containing additives
is shown in Fig. 1.
Figure 1. IR spectroscopy of flame retardant was expanded polymer
composites based on epoxy resins.
IR spectra of the composition based on the epoxy resin in the presence of a wideband at
≈3400 cm-1 are associated with the stretching of the O-H hydroxyl group. Signals in the range of
wavenumbers 2922–2817 cm–1 and around 1457 cm–1 are due to –CH2– symmetric and
asymmetric stretching and banding, respectively. Moreover, the signals located in the range 1295-
1060 cm-1 can be attributed to the stretching of C-C and C-O. The IR spectrum contains absorption
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bands in the region of 3000-3300 cm-1, corresponding to the epoxy ring and absorption bands in
the region of 750 -950 cm-1, asymmetric stretching vibrations of the ring. The absorption bands
at 800 and 1600 cm-1 confirm the presence of –NH2 groups. The presence of groups containing
phosphorus P=O and P–O–C in the range 1000-1250 cm-1 is confirmed by a broad intense band.
In addition, narrow low-intensity bands containing aluminium bonds appear in the IR spectrum in
the 800cm-1 and 1460cm-1 regions. (Fig. 2).
The thermal stability of the obtained samples was investigated in the mode of linear heating
at a rate of 10 ° C/min in an air atmosphere in the temperature range 50–800 °C. Thermal analysis
results are shown in Fig. 2. On the DTA curve of the derivatogram of the sample of fire retardant
expanded polymer composites based on epoxy resins, four endothermic effects were found at 175,
186, 200 and 430 oC and three exothermic effects at 250, 300 and 400 oC. (fig. 2).
Thermal destruction of the studied samples occurs in three stages. In the first two stages,
the formation of the carbonized residue occurs, in the third stage, it is oxidized [5, 6]. The
temperature of the onset of destruction, which was taken as the temperature at which a 3% weight
loss of the samples (T5%) occurs, for all fire retardant expanded additives in the samples is lower
than that of the original epoxy polymer (Table 2). From the analysis of the dependence of the
change in the mass of the samples on temperature (Fig. 2), it can be seen that the introduction of
fire retardant expanded additives into the epoxy resin leads to an increase in the weight loss when
the samples are heated to 150 °C as a result of the release and evaporation of water and sorbed
gases. epoxy resin ED-20, curing was carried out using polyethene polyamine, and intumescent
(intumescent) flame retardants, phosphorus-containing compounds (usually ammonium
polyphosphates) are catalysts for the coke formation process, the filler is nanosized aluminium
hydroxides, nitrogen-containing compounds are blowing agents. When heating nanosized
aluminium hydroxides of metals, desorption of water and gas vapours occur [4, 7]. Evaporation of
water lowers the temperature of the samples, which slows down the destruction process and
increases their thermal stability at temperatures above 150 °C.
The weight loss of fire retardant coatings of 6% was 24 min at 200 ° C. At a temperature
of 430 ° C and 50%, this process was carried out for 40 min.
Studies of fire retardant expanded polymer composites used epoxy resin ED-20 exhibit a
fire retardant effect by two mechanisms: it initiates the formation of a thin film and promotes the
formation of a "coke cap", which has a porous structure and low thermal conductivity.
At present, the tendency to use passive fire protection measures using thermally expanding
type compositions is becoming more and more pronounced. Under the influence of the flame, the
thermo-expanding coatings sharply increase in volume several times with the formation of a
foamed layer, which is a coking melt of incombustible substances (mineral residue), which covers
the protected surfaces. This layer has low thermal conductivity and high fire resistance. The
effectiveness of materials of the thermally expanding type is determined by the fact that very thin
coatings are sufficient to protect against fire - from a few tenths of a millimetre to several
millimetres thick.
Studying of the phosphorus-, silicon- and nitrogen-containing swell oligomeric fire
retardants exhibit a fire-retardant effect by two mechanisms: it initially the form of the thin film
and promotes the formation of a "coke cap", which has a porous structure and low thermal
conductivity.
Compositions on the basis of the interaction of phosphorus-, silicon- and nitrogen-
containing intumescent oligomeric fire retardant with ED-20 epoxy resin were investigated.
The main advantages of this type of fire retardant materials are the provision of a fairly
large range of fire resistance values; the small thickness of coatings may be up to 4 mm, and low
consumption and, accordingly, low loads on structures; high decorative qualities.
To compare the fire-retardant efficiency of phosphorus-, silicon- and nitrogen-containing
intumescent oligomeric flame retardant, samples of the construction metal material coated with a
thickness of 0.7 mm (content of the additive 10 %) were tested.
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In the study of the intumescent coating, the destruction of the porous structure occurs (55-
65 seconds) and a rapid increase in the heating temperature of the samples to 260-280 ° C is noted.
In this case, the limiting state of the sample sets in and the test is terminated. As a result, the
thickness of the expanded layer is 9.5-10.5 mm.
So, with the introduction of phosphorus-, silicon- and nitrogen-containing oligomeric
flame retardant in an amount of 0.5-7.5%, the adhesive strength of the bond between the coating
and the substrate increases two to four times. The best performance is achieved when the content
of the modifying additive is the amount of 5.0% transformations (foamed layer) and a layer of
coke foam (Fig. 1). Foam coke is a grey foam with a large number of small pores evenly distributed
over the volume of the expanded mass.
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