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Friday, 20 September 2019
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Raw materials & technologies, Applications, Protective & Marine coatings

Fire retardant performance of waterborne intumescent coatings improved

Wednesday, 6 March 2013

Chinese researchers have analysed effects of inorganic fillers on the fire retardant performance of waterborne intumescent coatings.

The fire retardant performance of waterborne intumescent coatings has been investigated

Source: Yantra/ Fotolia

The fire retardant performance of waterborne intumescent coatings has been investigated

Source: Yantra/ Fotolia

In a new study, scientists from South China University of Technology in Guangzhou have investigated effects of inorganic fillers on the fire retardant performance of waterborne intumescent coatings by thermogravimetry (TG), capillary rheometer, X-ray diffraction spectroscopy (XRD) and fire retardant test.

The TG results indicate that the thermal stability of vinyl acetate-vinyl ester of versatic acid copolymer (hereafter VAc-VeoVa) in VAc-VeoVa/Si–Al powder composite or in VAc-VeoVa/Halloysite nanometer-tube (HNTs) composite is improved mainly due to the release of the crystal water in Si–Al powder or HNTs.

Capillary rheometer analysis results demonstrate that the VAc-VeoVa/HNTs composite melt possesses the highest shear viscosity, because of the large specific surface area of HNTs and the strong interaction force between HNTs and VAc-VeoVa. Weight loss difference (ΔT) of filler/ammonium polyphosphate (APP) composites show antagonism effects at 300 °C < T < 650 °C and synergistic effects at T > 650 °C.

Coating obtains intumescent char layer

The fire retardant test results show the coatings using TiO2/Si–Al powder/HNTs (8/1/1) as multiple fillers obtains an intumescent char layer with intumescent ratio of 28.14 and presents excellent fire retardant performance (3327 s). It is found that the high melt viscosity, resulted from the effect of inorganic filler, immobilises the relaxation and rotation of polymer chain, restricts the intumescent behaviour of the coatings, which leads to the formation of an intumescent char layer with lower intumescent ratio and the shortening of the fire retardant time.

Moreover, the antagonism effect between filler and APP reduces the catalytic dehydration efficiency of pentaerythritol (PER) and VAc-VeoVa, which, as a result, also affects the final fire retardant performance of coatings.

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