Note: Descriptions are shown in the official language in which they were submitted.
W092/~4776 PCT/U5~2/~1282
210~'~78
HIGH COMPRESSIVE STRENGTH LIQUID CRYSTALLINE
POLYNERS AND FIBERS AND FILMS THEREOF
BACKGROUND OF THE INVENTION
` This invention relates to fibers and films of rigid
rod heterocyclic liquid crystalline polymers having
improved compressive strength.
Ordered polymers are polymers having an "ordered,"orientation in space i.e., linear, circular, star
shaped, or the like, imposed thereon by the nature of
the monomer units making up the polymer. Most ordered
polymers possess a linear "order" due to the linear
nature of the monomeric repeating units comprising the
polymeric chain. Linear ordered polymers are also
known as "rod-like" polymers. As a result of their
rigid-rod-like molecular structures, these materials
form liquid crystalline solutions, and they are also
known as liquid crystalline polymers.
For example, U.S. Patent No. 4,423,20~ to Choe,
discloses a process for the production of
para-ordered, aromatic heterocyclic polymers having an
average molecular weight in the rang~ of from about
10,000 to 30,000.
U.S. Patent No. 4,377,546 to Helminiak, discloses a
process for the preparation of composite films prepared
from para-ordered, rod-like, aromatic, heterocyclic
polymers embedded in an amorphous heterocyclic system.
U.S. Patent Nos. 4,323,493 and 4,321,357 to Xeske
et al., disclose melt prepared, ordered, linear,
crystalline injection moldable polymers containing
aliphatic, cycloaliphatic and araliphatic moieties.
SUBSTITUTE SHEEJ
. .. ..
. . :, ...
"' ' ': !, ' ' ~:, , ,, ;
WO92/14776 PcT/u~ p2~
2`i~43~8 ,,.~
U.S. Patent No. 4,229,566 to Evers et al.,
describes para-ordered aromatic heterocyclic polymers
characterized by the presence of diphenoxybenzene
"swivel~' sections in the polymer chain.
U.S. Patent No. 4,207,407 to Helminiak et al.,
discloses composite films prepared from a para-ordered,
rod-like aromatic heterocyclic polymer admixed with a
flexible, coil-like amorphous heterocyclic polymer.
U.S. Patent No. 4,108,835 to Arnold et al.,
describes para-ordered aromatic heterocyclic polymers
containing pendant phenyl groups along ~he polymer
chain backbone.
Ordered polymer solutions in polyphosphoric acids
~including PBZT compositions) useful as a dope in the
production of polymeric fibers and films are described
in U.S. Patent Nos. 4,533,692, 4,533,693 and 4,533,724
(to Wolfe et al.). U.S. Patent Nos. 4,939,235,
4,973,442, and 4,963,428 disclose films comprising
multiaxially oriented liquid crystalline polymers and
apparatus for making such films.
The disclosures of aach of the above described
patents are incorporated herein by reference.
Polybenzazole ("PBZ") polymers are one class of
liquid crystalline polymers currently of great interest
in the art. Such PBZ polymers include polybenzoxazole
("PBO"), polybenzothiazole ("PBZT"), and
polybenzimidazole ("PBI").
Polybenzazole polymers and their synthesis are
described at length in numerous references, such as
Wolfe, Li~uid Crystalline Polymer Compositions. Process
and Products, U.S. Patent 4,533,693 (August 6, 1985)
and W.W. Adams et al., The Material science and
SuBsTlTuTE SH~ET
. . :
~ .... .
.~, .
,.. , .. , -. ... .
.
. ' ., . ~ :
WO92/14776 PCT/~S9~
211D~37~
Enqineerinq of Riqid-Rod Polvmers (Materials Research
Society 1989), which are incorporated herein by
reference.
The major problems confronting PBZT film and fiber
based composites are low compressive strength compared
with tensile properties and poor interlaminar
adhesion. This is attributed to buckling of the
fibrillar network, as evidenced by kinked regions which
are localized deformation. "Microbuckling" appears to
be the cause of low compressive strength in fibers and
is also observed in films.
Properties of a typical PBZT fiber are listed in
Table 1 by way of example.
Table 1 - Properties of PBZT Fiber
Tensile Strength > 500 Ksi
Tensile Modulus > 55 Msi
Compressive Strength 30-50 Ksi
Density = 1.6 g/cc
Thermal Stabilit~ > 650C (Nitrogen)
Flexible at -196 C
Electrically Insulating
Accordingly, ways of improving the compressive
strength of liquid crystalline polymers are being
sought.
BRIEF DESCRIPTION OF_DRAWINGS
Fig. 1 is a schematic d~picting the synthesis of
APBTZ.
Figs. 2 and 3 are schematic representations of the
articulated linkages formed in APBTZ.
Fig. 4 is a diagrammatic representation of the
morphology of PBZT versus APBTZ.
SUBSTITUTE SHEET
, ~ .. ,, ," . ..... . .
. ~ . . . . ,. . ..
W092/14776 P~T/USg~/O~
2~0437~
Fig. 5 is a schematic representation showing the
synthesis of one perferred articulated monomer in
accordance with the present invention.
Fig. 6 is a graph showing mole percent articulation
versus intrinsic viscosity.
Fig. 7 is a diagrammatic representation of one
fiber spinning apparatus for use in the present
inventlon .
Fig. 8 is a diagrammatic representation of fiber
drying for use in the present invention.
Fiy. 9 is a schematic representation of a tensile
test device for use in practicing the present
invention.
Fig. lO is a graph showing mole percent
articulation versus compressive strength.
Fig. ll is an illustration of one polymerization
apparatus for use in the present invetion.
SUMMARY OF THE INVENTION
The present invention provides fibers and films
having improved compressive strength and methods of
making such fibers and films. In one embodiment of the
present invention, the fiber or film comprises a
rigid-rod, heterocyclic liquid crystalline polymer
comprising up to about 25 mole % of at least one
articulated monomer unit. In one preferred embodiment
of the present invention, the compressive strength of
the fiber or film is improved by a factor of about 3 to
4 over the compressive strength of a comparable ~iber
or ilm consisting of the rigid-rod, heterocyclic
liquid crystalline polymer.
SUBSTIT(JTE SltEET
,.. . . .
~ . .
. .. ..... . .. .
W092/14776 PCTtUS92/~8~
2~378
Fibers and films wherein the articulated monomer
unit is present at up to about 10 mole % are preferred
in accordance with the present invention. Up to about
15 mole % articulated monomer unit is particularly
preferred, with a mole % of from about 0.5 to about 2.5
mole % being especially preferred.
Articulated monomer units for use in the present
invention are selected on the basis of compatibility
with the properties of the liquid crystalline polymer
into which they will be incorporated. The monomer unit
must be compatible, for example, with the morphology
and thermal properties of the host liquid crystalline
polymer, as well as with ~he chemical properties in so
far as how the material is polymerized. The
articulated monomer unit must provide the correct
spacing and length to allow the articulated polymer
formed to fit within the polymer crystal structure.
Preferred articulated monomer units for use in the
present invention include a 3,3'-biphenyl,
3,3'-triphenyl, 2,2'-bipyridyl, and
bisloxyphynylene)benzene units.
Polybenzazole (PBZ) liquid crystalline polymers are
one class of preferred rigid-rod, heterocyclic liquid
crystalline polymers for use in the present invention.
Preferred PBZ polymers are selected from the group
consisting of polybenzoxazole (PBO), polybenzothizole
(PBZT) and polybezimidazole (PBI) polymers and ran~om,
sequential or block copolymers thereof.
The present invention also provides liquid
crystalline polymers having less than about 5 mole %
articulation, 0.5 to 2.S mole % articulation being
preferred.
SUB~Tl~UTE SHE~T
WO 92~14776 PCr/~
DETAILED DESCRIPTION OF THE INVENTION
The improvements which are obtained by the rigid
rod heterocyclic liquid crystalline polymer structures
of the present invention are predicated upon the
unexpected discovery that the compressive properties of
such structures are surprisingly improved by
incorporation of articulated linkages within the
polymer backbone. The present invention provides
structures, such as fibers and films, comprising
ordered polymers having improved mechanical properties
by the incorporation in small amounts of articulated
monomer units between long, ordered polymer chain
segm~nts.
Articulated monomers units for use in the present
invention impart a three-dimensional order to the
de--ired liquid crystalline polymer that resists
compressive failure and interlaminar shear due to
microbuckling. In one embodiment of the present
invention, the preferred articulated monomer unit
comprises a ~'flexible swivel group." Such groups are
disclosed in U.S. Patent No. 4,229,566, supra; Evers
and Moore, J. Polvmer Sci., 24 (1986) 1863-~877; and
U.S. Patent No. 4,359,567.
The disclosures of each of the above references are
incorporated h~rein by reference.
In accordance with the present invention, small
quantities of articulated monomer units, e.g., flexible
swivel groups, are incorporated between long segments
of the rigid rod, ordered liquid crystalline polymer
chain. This produces microfibrillar structures that
contain covalent linkayes between the bundles of
SU~STITUTE SHIEE~
: . . ,.., . . .; .
. .
.. .
W092/14776 PCT/u~
~ 04378
microfibrils and have a three-dimensional network of
interconnected molecules. The resulting polymer
morphology produces articulated liquid crystalline
polymer structures, e.g., fibers and ~ilms, that are
more resistant to microbuckling when subjected to
compressive loads than liquid crystalline polymer
structures containing no such articulated units.
Fibers and films prepared from articulated liquid
crystalline polymer dopes will exhibit enhanced
compressive strength and higher interlaminar shear
strength as a direct result of three-dimensional
molecular interconnectivity.
Articulated monomers units for use in the present
invention are selected on the basis o~ compatibility
with the properties of the liquid crystalline pol~mer
into which they will be incorporated. The monomer unit
must must be compatible, for example, with the
morphology and thermal properties of the host liquid
crystalline polymer, as well as with the chemical
properties in so far as how the material is
polymerized. The articulated monomer unit must provide
the correct spacing and length to allow the articulated
polymer formed to fit within the polymer crystal
structure.
Polybènzazole (PBZ) liquid crystalline polymers are
one class of preferred ordered polymers for use in the
present invention. Preferred PBZ polymers are selected
from the group consisting of polybenzoxazole (PBO),
polybenzothizole (PBZT) and polybenzimidazole (PBI)
polymers and random, sequential or block copolymers
thereof.
PBZ polymers typically contain a plurality of mer
SUBSTITUTE SHEET
"
. : .:
....
.
~: .:. . ... .
.. : .,... : .
W092/14776 ~ PC~/U9~ 8
units that are AB-PBZ mer units, as represented in
~ormula l(a), and/or AA/BB-PBZ mer units, as
represented in Formula l(b)
r \ ~ ~ / \ Ar \ ~ DM
I ( a ) A~ -PBZ 1~ b) AA/B~- PBZ
wherein:
Each Ar and Ar' represents an aromatic group.
The aromatic group may be heterocyclic, such as a
pyridinylene groupJ but it is preferably
carbocyclicO The aromatic group may be a fused or
unfused polycyclic system. The aromatic group
preferably contains no more than about three
six-membered rings, moxe preferably contains no
more than about two ~ix-membered rings and most
preferably consists essentially of a single
six-membered ring. ~xamples of suitable aromatic
groups include phenylene moieties, biphenylene
moieties and bisphenylene ether moieties. Each Ar
and Ar' is most pre~erably a 1,2,4,5-phenylene
moiety, except wherein a predetermined percent of
Ar groups is replaced with articulated monomer
units in accordance with the present invention for
use in producing structures having enhanced
compressive strength.
SU~T~TUTE Sl~EE~
.
"` .
.. .
: : ;
:: . ; ~; .
., ... .' . ~
WO92/1477~ PCT/U~ 8~
2 ~ 7 8
Each Z is independently an oxygen atom, a
sulfur atom or a nitrogen atom bonded to an alkyl
group or a hydrogen atom. ~ach Z is preferably
oxygen or sulfur (the polymer is preferably P~0,
PBZT or a copolymer thereof);
Each DM is independently a bond or a divalent
organic moiety that does not interfere with the
synthesis, fabrication or use of the polymer. The
divalent organic moiety may contain an aliphatic
~roup (preferably cl to C12), but the divalent
organic moiety is preferably an aromatic group (Ar
or Ar') as previously described.
The nitrogen atom and the Z moiety in each
azole ring are bonded to adjacent carbon atoms in
the aromatic group, such that a five-membered azole
ring fused with the aromatic group is formedO
The azole rings in AA/BB-PBZ mer units may be
in cis- or trans-position with respect to each
othar, as illustrated in 11 Ency. Poly! Sci. &
En~., 601, at 602, (J. Wiley ~ Sons 1988) which is
incorporated herein by reference.
The PBZ polymer may be rigid rod, semirigid rod or
flexible coil. It is preferably rigid rod in the case
of an AA/BB-PBZ polymer or semirigid in the case of an
AB-PBZ polymer. It more preferably consists
essentially of AA/BB~PBZ mer units. Exemplary highly
preferred unmodified mer units, i.e., before
articulation in accordance with the present invention,
are illustrated in Formulas 2 (a)-~f)0
The unmodified polybenza~ole polymer most
preferably consists essentially either of the mer units
illustrated Formula 2(a) (cis-PB0) or of the mer units
SUBSTITUTE SHEET
.
... . . ..
. -. ~. :
.. . . .. ..
.... ..
. ... .; . . . . .
WO92~14776 PCT/U~
21~437~
illustrated in Formula 2(c) ttrans-PBZT).
Each unmodified polymer preferably contains on
average at least about 25 mer units, more preferably at
least about 50 mer units and most preferably at least
about 100 mer units. The intrinsic viscosity of
unmodified cis-PB0 or trans-PBZT in methanesulfonic
acid at 25C is preferably at least about 10 dL/g,
more preferably at least about 20 dL/g and most
preferably at least about 30 dL/g.
(a) ~ ~ 0
(b) ~ ~ N >
(C) ~ S ~ N
(d) ~ 0 ~ 9
SlJBSrlTUTE SHE~
.
~ , , ,; . .
.
, ... . .. ,;. . , .. .
, ~ .. i~. ,
., . ~ . . .
. . , .:.. ~
. ..
. . ..
.
Wo 92/14776 PCl'/U~i92/FI!~.2~2
~1~4378
11
~ nd
_~ N~N \> ~
The structures of the present invention will be
illu-~4trated with respect to PBZ liquid crystalline
polymers. However, the invention is not so limited. It
will be appreciated by those skilled in the art that the
preferred liquid crystalline polymer will be selected
depending upon its ultimate use.
The present invention will be specifically
illustrated by the incorporation of articulated monomer
units comprising 3,3'~biphenyl linkages into the
bacXbone o~ PBZT. However, the invention is not limited
to this articulated monomer. Preferred articulated
monomers for use with PBZT polymers are disclosed, for
example, in U.S. Patent Nos. 4,229,566; and Evers and
~oore; and U.S. Pat. No. ~,359,567; supra. Preferred
monomer units for use in the present invention include
3,3'-biphenyl, 3,3'~triphenyl, 2,2'-bipyridyl, and
bis~oxyphenylene) benzene units. Articulated monomer
units comprising 3,3'-biphenyl units are particularly
preferred for preparing modified, i.e., articulated,
SUBSTITUTE SEi_ET
.. . .. .
, .
. , . .
.,: ; ~ -
. .
W092/14776 PCT/U~9~128~
2~0~378 12
polymers in accordance with the present invention.
The articulated monomer unit chosen must have the
correct dimensions to align with two adjacent layers of
polymers in the ~ilm.
The mole percent of articulated monomer unit
incorporated into rigid-rod, heterocyclic liquid
crystalline polymers in accordance with the present
invention will vary depending upon the polymer and
monomer selected, as well as the desired end use for
such articulated polymer. Up to about 25 mole %
articulation is expected to be useful in the practice of
the present invention. A preferred mole % articulation
is between O.l to ~0 mole %, 0.5 to ~.S mole %
articulation being particularly preferred.
Fig. l illustrates one embodiment of the present
invention wherein the articulated monomer unit
3,3'-bis(carboxy)biphenyl is incorporated into the
polymer backbone of PBZT. The 3,3'-bistcarboxy)biphenyl
monomer unit was chosen for this embodiment of the
present invention, because it exhibited bond lengths and
bond angles that enabled the development of the desired
APBZT morphology shown in Figs. 3 and 4. In contrast to
PB2T crystallines, where individual modules were aligned
in parallel, APBZT crystallines contain molecules
linking the aligned PBZT rigid-rod molecules. The
all-aromatic structure of this monomer also provided
thermal and oxidative stability that was comparable to
the aromatic PBZT molecule itself. A morphologlcal
study indicated that articulated biphenyl units fit well
into the PBZT crystal lattice, causing only minor
decreases in lateral crystalline size and a 1% decrease
in crystalline density.
SUBSTITIJl E SHEET
.. . `,
, :.. . ,:
... . ..
.; , ...
WO92/14776 PC~/US92/012~2
21~378
Polymerizing equimolar amounts of DA~DT and
terephthalic acid monomers produced PBZT, which is shown
as the first repeating unit, M, in Fig. l. By removing
a molar amount of terephthalic acid monomer and
replacing it with an equimolar amount of the articulated
monomer, a polymer with the second repeating unit, N,
was created. The articulated monomer has the correct
dimensions and, being chemically similar to the
terephalic acid monomer, polymerized readily into the
polymer as is shown in Fig. 2.
With the articulation present within the polymer,
the rigid rod is able to rotate and swivel at this
linkage. With ona portion of the PBZT molecule in the
plane, another portion of the molecule can rotate and
protrude out of the plane as shown in Fig. 3. The APBZT
has significantly increased intermolecular and
interlayer interaction through this three-dimensional
reinforcement. Fig. 4 illustrates the interaction
between articulated molecules versus non-articulated
molecules of PBZT.
One method for preparing 3,3'-bis(carboxyl)biphenyl
monomers for use in the present invention is disclosed
in Evers and Moore, suPra. It has been found, however,
that 3,3'-bis(chlorocarbonyl)biphenyl monomer is
preferred and the presènt invPntion also provides an
improved method of synthesis for this compound which is
shown in Fig. 5. In this synthesis, the articulated
monomer 3,3'-bis(chlorocarbonyl)biphenyl was synthesized
in high purity, via a safer nd higher yield route than
previous published procedures.
In a typical preparation of articulated polymers for
use in the present invention, l00g batches of
S~ ~B~ E ~ET
. .. . ,: . ;
. . . .
. ~, ... . .
, .. - . :
.
.
,~. .. :: ~ . .
W092/]4776 PCT/~ f~ -~`J
2~0'1378 14
articulated PBZT ("APBZT") polymer were polymerized
using terephthalic acid, the more convenient articulated
3,3'~bis(chlorocarbonyl) biphenyl monomer, and
terephthaloyl chloride. DABDT monomer, was typically
added to 77 percent PPA and completely
dehydrochlorinated by heating the reaction in stages ~o
80C. Vacuum-degassing facilitated re~oval of HCl
from the mixture. Then, a stoichiometric amount of
terephthalic acid ("TPA") comonomer was added to the
flask along with sufficient P205 to produce PPA of
83 percent P205 content and the flask was heated
rapidly to the polymerization temperature of 170C.
After 24 hours at that temperature, the xeaction flask
was h~ated to 195C for an additional 24 hours to
complete the polymerization reaction. At this point, a
viscous, yellow-green dope of APBZT formed. PBZT
polymer was also prepared to serve as the control for
comparison with APBZT polymers durin~ fiber and film
testing.
PBZT and APBZT polymers of high molecular weight
were produced as evidenced by high intrinsic viscosity
values measured for PBZT and APBZT polymers. APBZT
polymers were prepared containing 2.5, 5, 7.5, 10, and
15 mole percent articulated units within the PBZT
backbone. Figure 6 illustrates the variation of
intrinsic viscosity ~IV) with degree of articulation for
APBZT polymers prepared.
Samples of 0, 5, and 10 mole percent APBZT polymer
dopes in polyphosphoric acid solution were extruded into
fibers and vacuum-cast into films.
PBZT and APBZT polymer dopes were spun into fibers
from 15 wt % solids solutions in PPA, using the
SlJBST~TUTE SHFET
W092/14776 PZT/~9~ ?~
'~10~37~
apparatus shown in Fi~. 7 and dried using the apparatus
of Fig. 8. The resultant fibers were characterized with
respect to tensile and compressive strength. Fig. 9
illustrates the structure of a ~iber compression test
specimen.
Incorporation of articulated monomers within the
PBZT polymer backbone increased the compressive strength
of the fibers by a ~actor of about 3 to 4 over the
compressive strength of PBZT fibers as indicated by
fiber recoil compression testing. This surprising
increase in compressive strength was observed even
though the fibers contained extrusion defects and voids
from the rapid drying process. It will be possible to
reali~e even higher compressive strengths and higher
mechanical performance through the ahsence of de~ects
within the fibers. This can be accomplished for
example, by extruding APBZT fibers under processing
conditions that are more appropriate for highly viscous
materials, such as higher temperatures, lower pressures
and longer air gaps to facilitate fiber cooling before
coagulation.
APBZT fiber compressive strength rapidly increased,
then decreased with increasing articulated linkage
content, the best results being obtained at 2.5 mole %
articulated monomer content as shown in Fig. 10.
Tensile strength decreased linearly with increasing
degree of articulation. However, it is expected that
higher tensile strength values will be obtained at
articulation levels lower than 2.5 mole %, between 1 and
2 mole %, as well as improved compressive strength.
Uniaxial films of APBZT were cast from solution
using conventional methodology. Films studies showed
SUBSTITUT~ SHET
., .. ; . .
- . , . ' . ~ . ,
. ~ "
WOgZ/~477~ PCT/US92/01282
8 16
1.
that the cast APBZT films contained the articulated PBZT
morphology illustrated in Fig. 4
.. . ........ . .~
STI~UTE SltEEI-
,
. , ~: .,'. :,
WO92/14776 PCT/US9~/01282
!
2~ 37~
17
Multiaxially oriented films comprising articulated
rigid-rod, heterocyclic liquid crystalline polymers and
having improved compressive strength, e.g., by a ~actor
of 3 to 4, over comparable films of the non-articulated
pol~mer, may be prepared following the teachings of U.S.
Patent Nos. 4,939,235; 4,973,442; and 4,962,428, supra.
The invention will be further understood with
reference to the following examples, which are purely
exemplary in nature, and are not to be utilized to limit
the scope of the invention.
Materials used in the following examples were
obtained from readily available commercial sources or
made in accordance with the indicated procedures or
publications.
EXAMPLE I - Preparation of PBZT and APBZT Polymers
A. The A~paratus
The custom-built apparatus shown in Fig. 11 or one
similar thereto was used for all polymerization
experiments.
A curved argon inlet tube 1 directed the constant
argon purge toward the bottom of the flask. Argon was
chosen in place of nitrogen because it was heavier than
air and tended to drift toward the bottom of the flask,
keeping the contents blanketed with inert atmosphere at
all times.
A vacuum-regulator 2 allowed degassing of the entire
flask under high vacuum while continuing to purge with
axgon makeup gas. The high torque stirrer motor 3 was
required to stir viscous PBZT dopes continuously, even
at very low rotational speeds. An outlet tube 4 on the
reactor vessel directed argon and volatiles from the
SUBSTITUTE SHEET
. . .
. ... , `~ -
.. . .
- ;; ,
. , .
,. . :,.
-
W092/14776 PCT/US9~ 8?
,_ I
210~37~
; 18
flask and into a gas bubbler 5 to indicate flow rate ofpurge gas, or alternatively by opening and closing the
appropriate valves, into a cold-trap attached to the
vacuum pump 6.
A fourth opening to the flask 7 was used for the
addition of P205 and PBZT monomers. Monomers and
P2O5 were added to the flask through a dry glass
tube fitted with a wide funnel to prevent spillage. The
tube was extended into the flask to a level close to the
surface of the reactant mixture to ensure placement of
monomer directly onto the surface of the reactant
mixture. A thin wire was used to dislodge small amounts
of monomer if they became trapped within the addition
tube. The entire reaction flask was oven-dried at
100C for several hours before use, along with any
~lassware that was to be used in the experiment.
In order to ansure the dryness of monomers used in
the polymerization, 2,5-diamino-1,4-benzendithiol
dihydrochloride (DABDT) and micronized terephthalic acid
(TPA) monomers were vacuum dried at 60C. This
temperature accelerated drying yet did not cause monomer
decomposition. Argon was used to break the vacuum when
drying was complete. This produced dry monomers that
contained adsorbed argon rath~r than air which might
have caused decomposition during polymerization.
PPA solvent was used at two P205 concentrations
during the PBZT polymerizations. The first function of
the PPA was to dehydrochlorinate the DABDT. Preparing a
77 percent P205 content PPA solution produced a
solution strong enough for dehydrochlorination but still
of sufficiently low viscosity for rapid devolatization
of evolving HCl. The second function of PPA was to
solubilize the PBZT polymer. A P205 content PPA of
'' ~
,, - . , - .
: :' . ' ':;. ~
WO92/14776 PC~/U5~J~
2~ a~
19
83 percent was required to maintain solubility of the
PBZT polymer, but at the 83 percent level was too
viscous for dehydrochlorination. The requisite P205
contents will be achieved by adding P205 powder
directly before the polymerization but after the
dehydrochlorination was completed.
B. Recrvstallization of TPC
In order to prepare about 15 yrams for monomer-grade
TPC from commercial sources, the recrystallization began
with 25 grams of TPC. Due to th~ severe lachrymatory
properties of TPC, all the work below was performed
under a fume hood.
In a 250-ml Erlenmeyer flask, 25 grams of TPC was
dissolved by several increments of boiling methylene
chloride totalling 150 ml. When the TPC was completely
dissolved, an additional 25 ml of ~ethylene chloride was
added. After adding 0.5 gram decolorizing carbon to the
methylene chloride/TPC solution, the hot solution was
filtered with No. 40 Whatman fluted filter paper. The
filter paper was preheated with 20 ml of hot methylene
chloride before the solution was filtered and collected
in a 250-ml beaker situated on a hot plate. After
filtration, the clear solution was reduced in volume to
45 ml by boiling off the solvent.
Slow cooling the beaker induced crystallization at a
slow enough rate to form crystals with no entrapped
solvent. A slow cool to room temperature for 16 hours
produced diffused needle-like white crystals. The
mother liqueur was decanted off and saved while a fresh
70 ml methylene chloride was added to recrystallize the
product. Boiling the solution down to 35 ml was
sufficient to induce crystallization upon cooling.
SUBST!TUTE SHEET
.
~ - ; ~ .- .;;.
: ; . .... ~ ............ . .
,
WO92/14776 PCT/~S92/01282
21 0 ~
Again, a diffused mass of white needle-like crystals
formed after 16 hours. The mother liqueur was decanted
into the first aliquot and saved.
The crystals were filtered, air dried quickly, and
vacuum dried ~or 2 hours at 60C argon replaced the
vacuum in the drying pistol. The yield of crystals (MP
149C) was about 70 percent for a recovered weight of
17.86 grams. The monomer-grade TPC crystals were then
immediately weighed for addition to the polymerization.
C. Recrystallization of Articulated Biphenyl Diacid
Chloride
Because 3,3'-bis(chlorocarbonyl)biphenyl is not
stable in vacuum storage, it was necessary to synthesize
sufficient quantities for this reaction. The 3,3'-
bis(chlorocarbonyl)biphenyl is converted into the
desired diacid chloride monomer by reaction with thionyl
chloride. Trace amounts of dimethylformamide (DMF)
effectively catalyzed the reaction to over 75 percent
yield. The crude product was recrystallized twice from
methylene chloride/hexane forming large needles (M.P.
148C). Vacuum drying the pulverized crystals at
60C for 200 hours prepared the articulated biphenyl
diacid chl~ride for immediate reaction addition.
D. PolYmerizatioin
Preparation of 5 mole % APBZT is described below.
Other mole % APBZT was prepared following the described
procedure.
Into the assembled, vacuum-dried, argon purged
reaction vessel, 41.235 grams of 86.1 percent H3PO4
and 26.260 grams of P2O5 were reacted to form 67.495
grams of 77.0 percent P2O5 polyphosphoric acid.
This solution was stirred for 22 hours at room
SUBSTITUTE Sl IEET
.
~.. ., ~ . :` :
. . . ~
,, ,, , ~
.. . .. . . . . . . i
WO92/14776 PCT/US9?/~l2?~
c~o~7~
21
temperature, degassed, heated to 80C, and again
vacuum degassed. The clear solution, strong enough to
dehydrochlorinate the DABDT, had reacted to completion.
After the flask cooled to room temperature, 17.2611
grams (0.0703966 mole) of DABDT monomer were added to
the flask. The solution, stirred at room temperature
for 16 hours, rose to 55C for 22 hours and plateaued
at 80C for 85 hours. After vacuum degassing, the
solution turned ~rom a cloudy yellowish solution to the
desired clear yellow.
The reaction flask cooled to 55C and 0.9825 grams
~0.0035199 mole) 3,3'-bis(chlorocarbonyl)biphenyl, the
articulated monomer, was added to the flask. This
mixture was mixed for 1 hour at 55C, and heated to
80C where it stirred or 24 hours to complete the
dehydrochlorination of the articulated monomer. The
viscosity was detectably higher after the articulated
monomer addition, due to the amine-thiol trimers forming
in solution. Again, this mode of addition was used to
maximize the chain distance between articulated linkages
on each PB2T polymer chain. The solution was vacuum
degassed, releasing volatiles, but when the foaming
ended, a clear yellow viscous solution had not
developed.
After vacuum degassing at 80C, 13.5778 grams
~0.066877 mole) of terephthaloyl chloride was added with
a glass tube ensuring the addition onto the PPA surface
instead of sticking to the walls, destroying the needed
stochiometry for the success of the reaction. For 88
hours the reaction stirred liberating gaseous
hydrochloric acid which the argon purge removed. Vacuum
degassing after 77 hours of stirriny the solution while
the temperature remained at 80C did not produce much
SU~STlTlJTE SHEET
! j ;
. .
W092/~4776 PCT/U59~T~
4~ ~ 22
foaming.
Next, 36.093 grams of P~05 were added to the
reaction flask. Almost immediately, the flask contents
began to foam. The stirring rate was increased greatly
to diminish the degassing that the addition of the final
P205 had caused. The foam coated the walls of the
flask but drill press motion of the stirrer shaft broke
the sticky coating form the walls and affixed the
solution to the stirrer. The solution then fell to the
bottom of the flask and mixed thoroughly with the rest
of the reaction components. No color change was
noticeable. From this observation, there was no
degradation of the monomers in the reaction.
After stirring for 77 hours to ensure homogeneity,
the flask was heated ~rom 804C to 170C and remained
for 48 hours. The polymer formed was removed by using
the Haake Buchler Mixer Rheometer, the dope was later
upgraded outside the flask.
A stainless steel grade 304 stirrer was used in the
polymerizations.
E. Intrinsic Viscosity_Measurements
A sample of APBZT dope was pressed and coagulated in
a neutral water bath for 4~ hours. After the acid was
extracted out of the APBZT dope, the disc of pressed
dope was fibrillated and vacuum filtered. When the pH
of ths wash water was over 5.0, the fibers were vacuum
air dried for another half an hour. At 165C, the
fibers were vacuum dried for 5 hours to remove any
residual moisture. Into 72.38 ml of methanesulfonic
acid (MS~), 0.1448 grams of PBZT fibers were solubilized
after 72 hours of stirring. The intrinsic viscosity was
tested to be 21.5 dl/g. After Haake Buchler mixiny, two
SlJBSrlTUTE SHEET
, . . . .. : .
.
~ . , .
. .
.
W092/14776 PC~/US~/QD~s~
23 2~0~7~
batches of APBZT prepared by this procedure measured
intrinsic viscosities of 25.2 and 33.8.
The metal stirrer, using the Haake Buchler Mixer,
and using the acid chloride form of terephthalic acid
all contributed positively to the increased viscosity of
the polymer.
EXAMPLE 2: Fiber Extrusion
The specialized fiber extrusion apparatus
illustrated in Figure 7 and located at the Air Force
Materials Laboratory, WRDC, Dayton, Ohio, was used to
extrude PBZT and APBZT fibers.
PBZT and APBZT dopes prepared in accordance with
Example l were pressure-filtered and degassed prior to
fiber extrusion. ~he fiber extrusion equipment i~cluded
a screw driven ram extruder with a funnel shaped lO~
extrusion die. This was coupled to a water bath and
take-up system that maintained tension in the fiber at
all times, while it was drawn on a pre-set draw ratio
and wound upon a l0 inch diameter drum. The large
diameter of the drum prevented kinking and damage to the
fiber due to compressive ~ailure.
The extruder was filled with APBZT dope and fibers
were extruded at two different draw ratios, namely, l0
to l and 5 to l. It was predicted at th~s time that the
lower draw ratio would produce a higher compressive
strength fiber, since more three-dimensional order would
be preserved. However, in some cases a higher draw
ratio may be desirable where it is sought to maximize
compressive as well as tensile strength.
Several hundred feet of each articulated polymer
fiber were extruded (0, 2.5, 5, 7.5, l0 and 15 mole %
SUI~S i ITUTE Sl IEEr
. . . .
., . . ;
,..... ` .. ; . ., ~ .
. .
WO92~1477~ PCT/US92/01~2
~ 24
articulation). This was wound upon a collecting drum
which was immersed in distilled water to extract the
residual amount of PPA. The drum was allowsd to ~oak in
distilled water to extract residual phosphoric acid from
the fiber. During this period, the rinse water was
changed several times to ensure removal of all traces of
acid which would otherwise weaken the fibers.
After the ~ibers had soaked in distilled water
overnight, they were stage-dried and heat-treated in the
apparatus illustrated in Fig. 8. Drying and
heat-treating steps were conducted in separate
operations and at different temperatures, by passing the
tensioned fiber through the heated tube oven at a speed
of approximately lS ~eet per minute.
Preliminary drying of wet ~iber was conducted at a
temperature of 200C, a temperature that had been
successfully applied to the drying of previous PBZT
fibers. Heat-treatment was performed at 535C, since
that temperature had also produced PBZT fihers with the
highest mechanical properties Fiber tension was
maintained throughout each operation to prevent damage
due to abrasion or kinking.
EXAMPLE 3: Fiber Recoil Compression and Tensile
Strenqth
Heat-treated PBZT and APBZT fibers prepared in
accordance with Example 2 were tested for compressive
strength using the single fiber recoil compression test
procedure developed by the Air Force Materials
Laboratory (5ee, e.g., Takahashi et al, J. ApPl. PolY.
Sci. 28, 579-586 (1983), DeTeresa et al., J. Mat. Sci.
19, 57-72 (1984), Allen, J. Mat. Sci~ 22, 853 (1987);
DeTeresa et al, J. Mat. Sci. 20, 1645 (1985); and
SlJB~lTUTE SHEET
. . .
.:
;.. , . ~ , ; .~ ... ..
: :: .. ...
- ... ~ ~ .. ....
~ .
WO92/1~776 PCT/US92/01282
21~37~
DeTeresa, J. Mat. Sci. 23, 1886 (1988)). This test was
conducted as follows:
A fiber specimen was mounted within a tensile test
fixture as illustrated by Fig. 9. The fiber was then
examined under the microscope for the absence of kink
bands or other defects and measured with respected to
average fiber diameter along its length.
~ he fiber was tensioned to a predetermined load
which was somewhere below the ultimate tensile failure
load for the fiber. An electric arc was used to sever
the fiber instantaneously, without causing spikes in the
fiber tensile load. The severed fiber specimen was
re-examined under the microscope for the presence of
kink bands at either side of the specimen. The presence
of a dark, swollen kink band, usually situated at the
junction between fiber and epoxy potting droplet, was
indication of compressive failure for that end of the
fiber.
Fail/No Fail notations were recorded for gradually
changing tensile loads, with a load being reached where
neither end of the fiber developed any kink bands. This
load, divided by the average fiber diameter, represented
the fiber recoil compression strength of the fiber
specimen.
Fig. lO illustrates the results of the fiber recoil
compression strength tests involvin~ PBZT and APBZT
fibers. The tests indicated significant improvement in
PBZT fiber compressive strength by incorporation of
articulated linkages, at low loadings, within the
polymer backbone.
APB2T fiber tensile strength measurements were
conducted using the same test apparatus. The test
results showed that tensile strength decreased by
SlJBSTlTUTE SHEET
.. : . . .
.... .
' ..... ,
. .
W092/14776 ~C~/U~
2~ ~37 ~
26
approximately 14% in 2.5 mole ~ APBZT fibers in
comparison to PBZT fiber. However, improved tensile
strength values are expected to be obtained at
articulation levels lower than 2.5 % tbetween 1-2%).
It is understood that the examples and embodiments
described herein are for illustrated purposes only, and
that various modifications and changes in light thereof
that will be suggested to persons skilled in the art are
to be included in the spirit and purview of this
application and the scope of the approved claims.
SUBSTITUTF Sl~FE~T
; , ' . :
., . ' . . ~
.1 ' ~ ' . ''' ~ :,
,. . '': , ,
' , ,'' ' . ' ,.. ~ ~ '
" , ,., ' ':' " " ' ~ ,.,~;
