Influence of zinc borate on fire protection and thermal degradation of ...

INFLUENCE OF ZINC BORATE ON FIRE PROTECTION AND
THERMAL DEGRADATION OF INTUMESCENT COATING
CONTAINING A NOVEL CAGED BICYCLIC PHOSPHATE
You Zhou, Jianwei Hao*, Jianxin Du, Haixu Wen
National Laboratory <strong>of</strong> Flame Retardant Materials, School <strong>of</strong> Materials,
Beijing Institute <strong>of</strong> Technology, 5 south Zhongguancun Street, Haidian
District, Beijing 100081, P. R. China
(hjw@bit.edu.cn)
Keywords: Intumescent; Zinc <strong>borate</strong>; Fire protection; Coating.
Fire protection and thermal degradation <strong>of</strong> intumescent epoxy coatings
with a novel caged bicyclic phosphate (Trimer) [1], APP and <strong>zinc</strong> <strong>borate</strong>
(ZB) were investigated. The experimental results as follows: compared to
the coatings with ZB, No.1 coating shown the best initial fire protection
property up to 300s due to the earliest expansion (Fig 1, Fig 2 and Table 1),
however, at a longer time a plateau was achieved for No.2 and No.3
coatings and their final fire protection time was increased about 100%
respectively when compared with that <strong>of</strong> No.1 coating. Compared to
calculated TGA curve <strong>of</strong> No.3 coating in N 2 , the experimental one changed
slightly (Fig 3 (a) and Table 1), the experimental residue at 700℃ was
increased by 1.5% on the base <strong>of</strong> calculated one. Moreover, the difference
was obviously enlarged in air (Fig 3 (b) and Table 1), particular at
temperature higher than 550℃, significant improvement was observed in
thermo-oxidative stability <strong>of</strong> coating with the addition <strong>of</strong> 5%ZB. The final
residue <strong>of</strong> No.3 coating was 38.2% at 700℃ compared to 27.0% for No.1
coating and the beneficial effect <strong>of</strong> ZB was clearly demonstrated as well. It
is <strong>of</strong> interest to notice that the degradation curve <strong>of</strong> Trimer/APP abviously
changed from 480℃ by incorporating ZB and the final residue increased
from 14.6% to 47.8% (Fig 4). The 31 P solid-state NMR spectrum (Fig 4)
shown a high peak at -30ppm, which is attributed to B-O-P bonds [2]. This
result further confirmed that the interaction taken place between
Trimer/APP and ZB which lead to the formation <strong>of</strong> borophosphate. Above
mentioned results clearly indicated that an appropriate ZB may yield
synergistic effect on improving the thermal stability <strong>of</strong> coating with
Trimer/APP at high temperature, which could contribute to enhance the
fire protection property <strong>of</strong> coating.

Temperature (℃)
400
350
300
250
200
150
100
No.4
No.5
No.1
No.3
No.1 coating without ZB
No.2 coating with 3% ZB
No.3 coating with 5% ZB
No.4 coating with 7% ZB
No.5 coating with 9% ZB
No.2
a
b
b
50
0
0 300 600 900 1200 1500 1800 2100
Time (s)
Fig 1. Fire protection curves <strong>of</strong> coatings. Fig 2. Image <strong>of</strong> (a) No.1 and (b) No.3 coatings at
30s in the fire protection test.
(a)
100
(b)
100
90
ZB
90
ZB
80
80
Residue weight (%)
70
60
50
No.3 coating (exp)
Residue weight (%)
70
60
50
40
No. 3 coating (cal)
No.3 coating (exp)
40
30
No.3 coating (cal) No.1 coating
200 300 400 500 600 100 700
Temperarure (℃)
30
20
No.1 coating
100 200 300 400 500 600 700
Temperature (℃)
Fig 3. TGA curves <strong>of</strong> No.1 and No.3 coatings in (a) N 2 and (b) air.
100
ZB
H 3 PO 4
B-O-P
80
Residue weight (%)
60
40
APP/Trimer/ZB (exp)
APP/Trimer/ZB (cal)
P-O-C
20
APP/Trimer
0
100 200 300 400 500 600 700
Temperature (℃)
20 0 -20 -40
Chemical shift (ppm)
Fig 4. TGA curves <strong>of</strong> Trimer/APP, ZB Fig 5. 31 P solid-state NMR <strong>of</strong> Trimer/APP/ZB
and Trimer/APP/ZB in air.
treated at 600℃ in air
Table 1. Fire protection and TGA data <strong>of</strong> coatings
Fire protection time (s) N 2 , 10℃/min Air, 10℃/min
Samples
250℃ 300℃ 350℃ 400℃ T 5% /℃ CR/%
CR/%
T
(700℃) 5% /℃
(700℃)
No.1 80 200 530 1040 223 37.0 240 27.0
No.3 70 121 1030 1800 224 40.8 260 38.3
Reference
1. Weizhong J, Jianwei H, Zhidong H, Polymer degradation and stability. 97:632-637, 2012.
2. Grimmer A R, M¨uller D, G¨ozel G, Kniep R, Fresenius J. Anal. Chem. 357:485-488, 1997.