Statistical Optimization of Ammonium Sulfamate and Urea-Based Fire …
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than 15 % sulfamic acid causes more than 30 % loss in fabric tenacity and the use of
more than 15 % ammonium sulfamate causes more than 25 % loss in fabric tenacity.
Irrespective of % application, only urea treatment does not confer any noticeable
fire retardant property on jute fabric, though the loss of fabric tenacity is much less,
which is obvious as urea as a nitrogenous agent acts as a reaction promoter for fire
retardant chemicals such as phosphates and sulfamates for promoting the reaction of
phosphates/sulfamates with cellulose, where urea individually is not acting as a fireretarding agent at all. So, in the next set of preliminary experiment, a suitable binary
mixture of ammonium sulfamate and urea or sulfamic acid and urea as a selective
mixture in varying proportions were applied on bleached jute fabrics to achieve an
acceptable level of fire-retardant action on it.
Understanding the superiority of ammonium sulfamate and urea combination
for fire retardancy performance over sulfamic acid and urea admixture, ammonium
sulfamate and urea combination is considered to be preferable for use as the main
fire retardant agent for application on bleached jute fabric in presence of low dosage
of MgCl 2 (1/5th of the main fire retardant chemical used) as the catalyst. It is also
found that without MgCl 2, only sulfamic acid generated from ammonium sulfamate
or during direct use of sulfamic acid, the reaction of sulfamate with cellulose was poor
and hence fire retardant performance was lower, which may be due to less acidity and
lesser acidic pH than required for such reaction to occur. So, the addition of MgCl 2
helped to promote the reaction between sulfamates and cellulose for blocking –
CH 2 OH group of cellulose at C6 position to reduce levoglucosan formation. The
function of urea is considered to be manifold, for example it acts as a swelling agent
for cellulose, act as positive supporting action to promote reaction potential between
cellulose and phosphates or between cellulose and sulfamate s(as main fire retardant
agent) by the contribution of lone pair of nitrogen of urea, and also provides some
buffer action reducing acidity in the formulation, which reduces % loss in fabric
tenacity.
Relevant results in Table 2 (for formulation 1 and 2 thus indicate that for formulation 1(a-g) with the application of 10–20 % ammonium sulfamate (AS) along with
10, 12.5 and 15 % urea in presence of 1/5th of MgCl 2 catalyst, LOI values are
found to be nearly to 30–38 (while, LOI value for control bleached jute is 20 only)
with 24–32 % loss in the tenacity of treated jute fabric. Results of this preliminary
study finally show that the use of 12.5 % urea and 15 % ammonium sulphamate
(AS) combination (formulation 1e) gives more or less better balance of fire-retardant
performance associated with some loss of tenacity of jute fabric having the highest
LOI value of 38 and minimum char length of 2 cm. Increase in urea from 12.5 to
15 % with 15 % AS do not further improve LOI, rather reduces it to 35 from 38, as
obtained in formulation 1f, vide Table 2.
It may also be noted that treatment with 10 % urea and 15 % ammonium sulfamate
(AS) combination (formulation 1b) in presence of said MgCl 2 catalyst shows almost
nearer or at per results with formulation 1e, showing a bit lower LOI 34 and char
length 3.5 cm associated with 26 % loss of fabric tenacity, whereas application of
10 % urea and 20 % AS combination (formulation 1d) treatment causes 27 % loss
107
than 15 % sulfamic acid causes more than 30 % loss in fabric tenacity and the use of
more than 15 % ammonium sulfamate causes more than 25 % loss in fabric tenacity.
Irrespective of % application, only urea treatment does not confer any noticeable
fire retardant property on jute fabric, though the loss of fabric tenacity is much less,
which is obvious as urea as a nitrogenous agent acts as a reaction promoter for fire
retardant chemicals such as phosphates and sulfamates for promoting the reaction of
phosphates/sulfamates with cellulose, where urea individually is not acting as a fireretarding agent at all. So, in the next set of preliminary experiment, a suitable binary
mixture of ammonium sulfamate and urea or sulfamic acid and urea as a selective
mixture in varying proportions were applied on bleached jute fabrics to achieve an
acceptable level of fire-retardant action on it.
Understanding the superiority of ammonium sulfamate and urea combination
for fire retardancy performance over sulfamic acid and urea admixture, ammonium
sulfamate and urea combination is considered to be preferable for use as the main
fire retardant agent for application on bleached jute fabric in presence of low dosage
of MgCl 2 (1/5th of the main fire retardant chemical used) as the catalyst. It is also
found that without MgCl 2, only sulfamic acid generated from ammonium sulfamate
or during direct use of sulfamic acid, the reaction of sulfamate with cellulose was poor
and hence fire retardant performance was lower, which may be due to less acidity and
lesser acidic pH than required for such reaction to occur. So, the addition of MgCl 2
helped to promote the reaction between sulfamates and cellulose for blocking –
CH 2 OH group of cellulose at C6 position to reduce levoglucosan formation. The
function of urea is considered to be manifold, for example it acts as a swelling agent
for cellulose, act as positive supporting action to promote reaction potential between
cellulose and phosphates or between cellulose and sulfamate s(as main fire retardant
agent) by the contribution of lone pair of nitrogen of urea, and also provides some
buffer action reducing acidity in the formulation, which reduces % loss in fabric
tenacity.
Relevant results in Table 2 (for formulation 1 and 2 thus indicate that for formulation 1(a-g) with the application of 10–20 % ammonium sulfamate (AS) along with
10, 12.5 and 15 % urea in presence of 1/5th of MgCl 2 catalyst, LOI values are
found to be nearly to 30–38 (while, LOI value for control bleached jute is 20 only)
with 24–32 % loss in the tenacity of treated jute fabric. Results of this preliminary
study finally show that the use of 12.5 % urea and 15 % ammonium sulphamate
(AS) combination (formulation 1e) gives more or less better balance of fire-retardant
performance associated with some loss of tenacity of jute fabric having the highest
LOI value of 38 and minimum char length of 2 cm. Increase in urea from 12.5 to
15 % with 15 % AS do not further improve LOI, rather reduces it to 35 from 38, as
obtained in formulation 1f, vide Table 2.
It may also be noted that treatment with 10 % urea and 15 % ammonium sulfamate
(AS) combination (formulation 1b) in presence of said MgCl 2 catalyst shows almost
nearer or at per results with formulation 1e, showing a bit lower LOI 34 and char
length 3.5 cm associated with 26 % loss of fabric tenacity, whereas application of
10 % urea and 20 % AS combination (formulation 1d) treatment causes 27 % loss