108
A. K. Samanta et al.
of tenacity of jute fabric with no further significant improvement in LOI value (34–
34.5). With an increase in ammonium sulfamate (10–20 %), the increase in LOI
value up to a certain level (30 to 38) may be explained by increased blocking of C 6
position of jute cellulose by sulfamates preventing the formation of levo-glucosan
(the flammable gas produced for propagating fire). For approx. 10–15 % add on of
AS, treated jute fabric may become somewhat stiffer and hence, checking of bending
length, as an indicator of fabric stiffness (indirect indicator of fabric hand) is justified.
After such fire retardant treatment, there is some increase in bending length values
from 4.2 to 4.8 or so, Table 2, showing a very little increase in stiffness after such
treatment, not spoiling the hand value of fabric.
As said earlier, for comparison purpose, Saraflam-CWF (THPC-based), a
commercially available fire retardant agent was applied on the same bleached jute
fabric under comparable conditions of treatment and corresponding results are also
shown in Table 2. Comparison of relevant results of Formulations 1(a to g) with
Formulation 3 (a to d) indicate that the fire retardant performances for treatment
with 15 % ammonium sulfamate and 12.5 % urea with 3 % MgCl 2 are somewhat
appear to be better in terms of LOI value (38 for 15 %AS + 12.5 % urea treatment)
than LOI value obtained by the equal dosage of treatment with 15 % saraflam-CWF
(formulation 3b showing LOI as 33) with a somewhat higher loss of fabric tenacity
and higher char length.
Before proceeding to the characterization and analysis of detailed fire-retardant
performances for the said treatments and its optimization, it is better to discuss the
possible reaction mechanisms to be confirmed by FTIR.
3.2 Reaction-Mechanisms
The cellulose of jute may react with ammonium sulfamate at elevated temperature
possibly in the following manner as discussed under Reaction scheme 1, 2 and
3. Ammonium sulfamate at high temperature may react simply with the primary
hydroxyl group at C 6 position of jute cellulose as shown under Reaction scheme 1.
The chemical reactions as shown in Reaction 1–3 are considered to be possible, when
urea and ammonium sulfamate are applied together on jute cellulose in presence of
MgCl 2 as an additional acidic catalyst by pad dry-cure process at specific conditions,
that is, by drying at 100 °C for 10 min and curing at 130 °C for 3–4 min.
A. K. Samanta et al.
of tenacity of jute fabric with no further significant improvement in LOI value (34–
34.5). With an increase in ammonium sulfamate (10–20 %), the increase in LOI
value up to a certain level (30 to 38) may be explained by increased blocking of C 6
position of jute cellulose by sulfamates preventing the formation of levo-glucosan
(the flammable gas produced for propagating fire). For approx. 10–15 % add on of
AS, treated jute fabric may become somewhat stiffer and hence, checking of bending
length, as an indicator of fabric stiffness (indirect indicator of fabric hand) is justified.
After such fire retardant treatment, there is some increase in bending length values
from 4.2 to 4.8 or so, Table 2, showing a very little increase in stiffness after such
treatment, not spoiling the hand value of fabric.
As said earlier, for comparison purpose, Saraflam-CWF (THPC-based), a
commercially available fire retardant agent was applied on the same bleached jute
fabric under comparable conditions of treatment and corresponding results are also
shown in Table 2. Comparison of relevant results of Formulations 1(a to g) with
Formulation 3 (a to d) indicate that the fire retardant performances for treatment
with 15 % ammonium sulfamate and 12.5 % urea with 3 % MgCl 2 are somewhat
appear to be better in terms of LOI value (38 for 15 %AS + 12.5 % urea treatment)
than LOI value obtained by the equal dosage of treatment with 15 % saraflam-CWF
(formulation 3b showing LOI as 33) with a somewhat higher loss of fabric tenacity
and higher char length.
Before proceeding to the characterization and analysis of detailed fire-retardant
performances for the said treatments and its optimization, it is better to discuss the
possible reaction mechanisms to be confirmed by FTIR.
3.2 Reaction-Mechanisms
The cellulose of jute may react with ammonium sulfamate at elevated temperature
possibly in the following manner as discussed under Reaction scheme 1, 2 and
3. Ammonium sulfamate at high temperature may react simply with the primary
hydroxyl group at C 6 position of jute cellulose as shown under Reaction scheme 1.
The chemical reactions as shown in Reaction 1–3 are considered to be possible, when
urea and ammonium sulfamate are applied together on jute cellulose in presence of
MgCl 2 as an additional acidic catalyst by pad dry-cure process at specific conditions,
that is, by drying at 100 °C for 10 min and curing at 130 °C for 3–4 min.