Dr.Munir Ashraf Sb
Mr. Shehbaz Ali
Russian Aromatic Fibres (KEP)
Aromatic Fibres (KEP)
To produced aromatic fibres
with high modulus and strength. In 1970s, Russian Professor (Prof. Georgy I.
Kudryavtsev, All-Russia Research Institute of Polymeric Fibres) began it. SVM
is the first Russian p-polyamide fibre. Terlon and Armos were synthesized after
it. It replaced Kevlar. The investigation focused on:
The research led to the production
of the following fibres
copolymer including diamines selected from the left column of Fig. 1. Terlon is
an aramid copolymer fibre, based on PPTA with up to 10–15% comonomer content.
Its manufacture, structure and properties are similar to other aramid fibres,
although the Terlon copolymer is not the same as the copolymer in Technora.
of chemical constitution of Aromatic heterocyclic polyamide is that
Armos is a higher tenacity fibre and
yarn that retains the high thermal and fire-resistant properties of SVM. Creation of Armos was the principal step after the elaboration of SVM fibres. The high thermal properties
of aramids are the result of their wholly aromatic structure, but heterocyclic
units, such as those in Heterocyclic para-polyamides and para-copolyamides
(PHA) polymers, lead to increased thermal and fire resistance.Aromatic
heterocyclic copolyamide of principal chemical constitution
It is the heterocyclic diamine.
It is the residue of terephthalic
acid shown at the top of the right column in Fig.1
It is the residue of p-phenylenediamine shown at the top of
the left column in Fig.1
NOW in complete structure
fibre structures differ on all three levels (molecular, super-molecular and
micro) from the usual fibre structure of flexible and semi rigid polymers. The
main structural features are shown in Table 1
SVM and Armos fibres contain heterocyclic links and two kinds of polar
group, amide links and tertiary nitrogen atoms. The structure of these
poly-mers and copolymers is characterised by less regularity and less rigidity
than PPTA. The absence of liquid crystalline domains in solution makes it
possible to regulate structure building at the fibre forming and thermal
treatment stages to give maximal orientation order. Owing to the lack of a
plane of symmetry in the heterocyclic groups and to the mixed linking of
monomers (head-to-head, tail-to-tail and head-to-tail), the extended chain
conformations are irregular and lead to minimal crystalline order, with a
consequent reduction in the possibility of axial movement. The less regular
molecular chain structure leads to a higher proportion of stress-holding
molecular chains and therefore to mechanical properties that are superior in SVM and especially in Armos fibre to those of aramid fibres
such as Terlon, which is similar to Kevlar and Twaron.
PPTA and co- polymers;
main polar group:
para-aramid copolymer; statistical
Stress-holding molecular chains proportion 0.6–0.75
cross-section, low heterogeneity
Principal scheme for fibre production based on
heterocyclic polyamides and co polyamides.
Stress–strain plots for Terlon yarns
1 at 220 °C; 2 at 180 °C; 3
at 140 °C; 4 at 100 °C; 5 at 80 °C; 6
at 60 °C; 7 at 40 °C; 8
at 20 °C
Stress–strain plots for SVM yarns
1at 220 °C; 2 at 180 °C; 3 at 140 °C; 4 at 100 °C; 5 at 60 °C;
6 at 20 °C.
Stress–strain for Armos yarns
1 at 220 °C; 2 at 180 °C; 3
at 140 °C; 4 at 100 °C; 5 at 60
at 20 °C.
SVM and Armos fibres have mechanical properties
superior to those of Terlon as shown by the data in Table 2
Stress–strain curves at different temperatures
for Terlon, SVM and Armos yarns are presented in Figs.3, 4&5. An
interesting feature is that the high strength of SVM and Armos fibres is due to
a higher breaking elongation, not to a higher modulus. The energy to break is
Fibre tenacity depends on
moisture content owing to two influences, the plasticization effect and the
intermolecular interactions caused by hydrogen bond bridges, which are created
by water molecules. These two influences lead to tenacity increasing to some
extent with increasing moisture content up to a maximum value and then falling
when wet to 90–95% of the dry value.
High orientational, structural
and energy anisotropy of the fibres lead to anisotropy of their mechanical
three para-aramide types are characterized by high glass transition temperatures,
high thermal and thermal-oxidative resistance, high ignition and self-ignition
temperatures, and high limiting oxygen indexes. All three, especially SVM and
Armos, are dimensionally stable on long heating. The tendency to spontaneous
elongation in technological heat treatment (‘self-ordering effect’) leads to
the same effect in the first stage of heating slight elongation or very small
shrinkage with rise in temperature. The data show that change in dimensions is
practically absent up to 300°C. There is a small shrinkage of SVM and Armos
yarns by 350°C; the shrinkage at 400–450 °C is not more than 2–3%.
It is known theoretically and
practically that thermo-oxidative degradation includes three main reactions
of substances with low molecular weight
chain destruction by oxidation or hydrolysis
From this point of view, carbocyclic aromatic polyamides
are more stable than heterocyclic ones.If chain degradation leads to loss of
mechanical properties, on the other hand, the intermolecular bridges lead to
tenacity preservation. Therefore the resultant effect of all three kinds of
reaction is indefinite in terms of change in mechanical properties.
Effect of ageing on mechanical properties
Fire resistance and thermal characteristics
The comparative thermal-ageing
characteristics of Terlon and Armos fibres at 200–300°C are presented in Table
4.At higher temperatures, the loss of strength is greater. For Armos, the
retention of tensile properties (strength and elongation at break) is slightly
higher than for Terlon.
high glass transition temperature and practically zero shrinkage for para-aromatic
fibres give thermo resistant goods made from them important advantages in high
temperature media, in comparison with meta-aramid fibres. SVM and Armos fibres are
highly fire resistant and superior to PPTA fibres, owing to the nitrogen containing
heterocyclic structure and the presence of hydrogen chloride, which is a good
fireproofing compound. The main thermal characteristics and fire resistance
indices are shown in Table 5.
Armos fibres and its types
present, Armos fibres and yarns have
the highest mechanical properties among aramids and related fibres. Armos yarns are produced by the
Tver-chimvolokno Joint-Stock Company in Tver city.
High-modulus reinforcement yarns and
roving (Armos HMR)
High-modulus yarns for technical
textiles (Armos HMT)
Highly thermally stable yarns for
textiles (Armos HTS).
All values were measured by Russian standard methods
Properties of high-modulus reinforcement and
Properties of highly thermally stable yarns
chemically and physically modified fibres based on heterocyclic polymers and
copolymers have been produced with properties depending on the modification
use of different monomers for new
polymer or copolymer synthesis at the stage of polycondensation
additives to polymer solution
way is to include meta-links or other non-para-links in polymeric chains. This
leads to increased chain flexibility and therefore lower fibre modulus. These
copolymers have better solubility and their solutions are isotropic.
The principles of fibre formation are
approximately the same as for traditional flexible chain polymer processing –
wet-spinning, stretching for orientation, and additional thermal treatment to
fix fibre structure. The fibre properties are characterised by modulus and
tenacity, which are similar to general purpose fibres, of the type required for
some kinds of technical textiles and reinforcement of rubber goods.
up to 50% of the terephthalic links in the heterocyclic polymer to isophthalic
links at the polycondensation stage leads to decrease of fibre rigidity and
increase of elongation to normal textile values. This kind of fibre has good
thermal and fire resistance (high oxygen index), but it has the disadvantage of
water action on mechanical properties,the tenacity in the wet state is only 70%
of that in the conditioned state.
up to 30% of heterocyclic diamine to m-phenylenediamine
in the polycondensation stage.This polymer also gives fibres with good thermal properties. The properties of these two
fibres are presented in Table 8 in comparison with the ‘mother-fibres’ – SVM and Armos
Therefore the production technology
of these fibres is similar to Terlon
and other aramid fibres.
aramid fibres, created by adding different polymers in the spinning solution,
lead to new application possibilities. The best result was obtained by adding
flexible chain polymers to the solution of PPTA in sulphuric acid.A modified Terlon yarn with 10% addition of polycaproamide
(nylon 6) had improved adhesion to rubber in tyres or other elastomeric
manufactured goods.At the same time this polymer addition led to an increase in
mechanical properties. These practically important effects may be due to
formation of intermolecular bonds and increase in super molecular structural
order. Addition of rigid chain polymers did not have a positive effect.
modification is useful for barrier creation against water and protection
against external influences. Surface treatment of SVM and other fibres by silicon organic substances as emulsions in
water leads to higher moisture resistance.Surface grafting of
polytetrafluorethylene decreases wettability and water sorption.
of Armos yarn is 20–50% higher than that of other aramid and related yarns and
glass yarns. The thermal characteristics show the advantages of heterocyclic
polymers (SVM, Armos, Togilen, Tverlana) in comparison with aramid fibres based
on PPTA (Terlon, Twaron, Kevlar) and meta-aramid fibres (Fenilon, Nomex),
especially to open fire resistance.
yarn S-type are following:
ü Density 2.52–2.55 g/cm3
ü Elasticity modulus 85–90 GPa
ü Tenacity 4–4.6 GPa.
Comparison of tenacity and fire
resistance of various aramid and other fibres.
of fire resistance with respect to tenacity
The applications found for the
Russian aromatic HM-HT fibres are similar,high-strength and high-stiffness
technical textiles loaded in the axial direction. This includes
ü high-strength composites,
ü conveyor belts,
ü protective clothing
ü a host of similar uses