Influence of Varying Rockwool Fibre Length on Properties of Intumescent Coating

Intumescent coating is the most common passive fire protection for steel structure.
Four formulations of intumescent coating reinforced with different Rockwool fibre
lengths, i.e. 4 mm, 6 mm, 8 mm and 10 mm, and a controlled formulation, were
developed and tested accordingly to investigate the influence of variable lengths on
the properties of the intumescent coating and its char.
In the 800oC furnace fire test, intumescent coatings expanded 6 to 10 times their
initial thickness and experienced weight loss between 72-79%. The formulation with
longest fibre expanded and lost weight the least and appeared to be more compact,
denser and contained smaller pores. In the direct fire test of ~1022oC, formulation
with longer fibre retarded flammability better, enhanced the adhesion of the coating
to the steel substrate and the ability to retain its original form, and provided thermal
insulation up to 85-88% of directed heat. From the char strength test, it was found
that the formulation with the longest fibre has the highest strength to sustain the char
structure before destruction.
Degradation temperature, Td, was determined to be at ~380oC for all formulations in
TGA yet residual weight increases with the increase in fibre lengths. From the XRD
test, char samples of all formulations appeared to be in amorphous state and the
major components determined were boron phosphate and boric acid.