The World's
trongest Plas
Easily moldable and heat-resistant, thermotropic
LCPs have a bright future.
T SEEMS LIKE A MANUFAG
turer's dream: a moldable
material that's exceptionally
strong, thermally stable, inherently
flame resistant, and virtually insoluble.
TW
I
II
111
But it's a reality called a thermotropic 1
liquid crystalline polymer (LCP).
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4257
2M4
Thermotropism describes the ability , ,FHwtdefleclion
,
of a material to be molded a t high temProduct
Xydar
Vedm
PET-80PNB
peratures, a significant advance over
example
Series l
previous LCPs. Discovered and produced only within the last 25 years, the
Potential
Car-engine flectriml y k e r
opplicotions
parts
connectors dmphmgms
earliest commercial LCP was the lyotropic PPTA (poly-p-phenyleneter- - ephthalamide), introduced in-1973 and
still marketed by E.I. Du Pont de Nemours and Co. a s Kevlar. But because
the lyotropic polymer decomposes before reaching its melting point, it can be
processed only in solution, making
molding impossible. Fibers and coatings are its only applications.
Tensile Strength
16,800
7,000 to 10,500
However, LCP fibers boast extraorTensile Modulus
1,400,000 400,000
dinary physical properties thanks to the
ordered arrangement of the liquid crysflexuml Modulus l,MM,000
350,000
talline solution and the molecular orientation the fiber-spinning process pro- Top: comparative properties of an LCP (Xydar)
duces. The molecules "line up" in one vs, a conventionalpdyestw;mparative strength
direction, making the materials f a r (above], expressed in pounds per square inch.
u
20
HIGHTECHNOLOGY BUSINESS I JUNE 1989
I
stronger than those in which the molecules' directions are random.
Ounce for ounce LCP fibers are seven times stronger than steel, outmuscled only by high-strength carbon fibers. LCP fibers are widely used for
structural reinforcement in a variety of
products, such a s bulletproof vests,
high-strength composites for aerospace
components, sunglass frames, racing
catamarans, and tennis rackets.
Soon researchers realized that moldable LCPs would greatly expand the
range of applications. In the mid-1980s,
Amoco Performance Products Inc. introduced the Xydar copolyester resin.
At high temperatures, this resin can be
molded to form complex shapes in a
conventional injection-molding process.
The process produces parts with outstanding physical attributes (see Thermotropic LCP Strength, a t left).
The table clearly shouls that Xydar's
capabilities exceed those of normal
polyesters by a wide margin. They a r e
superior t o virtually all previously
available unreinforced thermoplastic
materials and are comparable to glassfiber- and carbon-fiber-reinforced ther-
moplastics. A microscopic examination
of these materials reveals their fibrous
nature as strikingly similar to that of
' wood. These materials are often described as "self-reinforcing polymers."
These polymers are also extrenlely
thermally stable and inherently flame
retardant. Xydar FG120, a glass- and
mineral-filled con~pound,begins to melt
a t 606 degrees Fahrenheit, meeting the
Underwriter's Laboratories flammability rating at a thickness of only 1/32 of
an inch. Many comparable materials
achieve the same level of flame resistance-at twice that thickness. The initial comn~ercialuse for Xydar FG120
was in Tupperurare Ultra 21 cookware.
Figure 1 illustrates the intense thermotropic LCP patent activity of the last
five years. Although U.S. firms hold
most of the original LCP patents, Japanese and European manufacturers are
now outpacing them in applications and
processing.
Many international resin producers
have followed Amoco with full commercia1 introduction or sampling of LCPs of
their own. Several other resin makers
are rumored to be in the research stage.
Such intense activity in one area is unparalleled in polymer development.
This outlay of R&D resources can be
justified only by looking a t the potential
of these materials for future applications. The total market for LCPs of all
types is currently about 52 million
pounds per year. Du PontJs Kevlar accounts for 45 million pounds and Tup-
als have extremely high melt temperatures, they often require special injection-molding processing.
LCPs in the second category, such as
Xydar Series I1 resins and Hoechst-Celanese Corp.'s Vectra, are characterized by moderate-to-high strength,
moderate impact resistance, and improved processibility over Category 1
resins. Category 2 materials have processibility equivalent to pure nylon,
making them suitable for long-flowlength, thin-walled parts, such as chemFig, 1: Will the lapanese take over still another
ical handling equipment, automotive
technology originated i~the United States?
fuel components and close-tolerance
electrical or electronic connectors.
perware's Xydar another 4 million to 5
For example, Matrix Inc., East Providence, R.I., is using Vectra LCP from
million pounds.
Thermotropic LCPs and their applica- Hoechst Celanese to make what is
tions fall into several categories, deter- claimed to be the first thermoplastic dimined by the temperatures a t which ode housing for fiber-optic cabling. The
they bend or become moldable (see new receptacles cost less than half a s
Thermotropic LCP Classes, p. 20). Each much to manufacture as the die-cast
of these categories serves a different zinc components they replace.
niche. Category 1, exemplified by XyCategory 3 LCPs, such as Eastman
dar Series I and Granmont Inc.'s Gran- Kodak Co.'s PET-80PHB, are noted for
lar A1200 resins, offers outstanding their excellent impact resistance, low
heat resistance and strength. Applica- melt viscosities, and high melt
tions include oven cookware, solderable strengths. These attributes make them
electrical connectors, automotive en- useful as coatings for optical cables,
gine parts, and components for machin- loudspeaker diaphragms, and various
ery used in high-temperature enriron- blow-molded and heat-molded products.
ments. These materials have lower
Thermotropic LCPs are also unique
impact resistance than members of the in that they are virtually insoluble in all
other LCP categories, although in stan- common solvents. This makes them idedardized tests some have achieved re- al for fuel and chemical-handling applisults comparable to glass-reinforced cations. For instance, Vectra is being
polyester. Because Category 1 materi- used to replace ceramic packing materi300
A
single thermoplastic now pr
insulation in all the small motors made by Superior
Electric Co. Applying Xydar U P G-445 has not
only simplified inventory, but enabled the Bristol, Conn.based manufacturer to speed production and cut costs.
Previously, making these motors incorporated steps to
glue on the motors' insulating material.
The LCP, supplied by Amoco Performance Products, is
not only strong enough to withstand the tension of tightly
wound wire, but has a coefficient of expansion that matches that of metal inserts-which are molded into the plastic. In addition, the plastic withstands the heat of soldering and paint bakeoff and doesn't creep under high
operating temperatures. It's also inlpervious to plating
chemicals.
Before specifying the thermotropic LCP, Superior's engineers rejected many other plastics, such a s Nylon 6.6,
which met only some of these demanding specifications.
Superior Electric is considering licensing the technology it
developed to utilize LCPs in its motors.
Xydar is the only 'mwlating material used m this motor stator made by
Superior Uectric. The little connector at right fils on the prongs molded
into the printed-wiringboard.
JUNE 1989
1 HIGH TECHNOLOGY BUSINESS B 21
/
Because LCPs can withstand temperatures 100 degrees Fahrenheit hotter than that of motten sdder,
they can be used as substrates tor printed boards on which integrated circuits are surfacemounted.
a1 for distillation columns, and the Japanese have used Kevlar29for a filtration
membrane that resists heat and the effects of chemicals. Another major potential application for Vectra is for
automobile fuel distribution systems.
"Fuel rails" must be not only resistant
to gasoline but also able to withstand
w
high engine temperatures.
LCPs also retain their molded
shapes, rarely warping, shrinking, or
expanding after molding. These qualities make it possible to mold LCPs into
very precise shapes, such a s multipin
electronic connectors. Connector makers are moving to ever-smaller pin sepa-
rations that require great stability and
allow for little error in molding.
Shape retention also permits LCP
parts to be mated to metal and glass
components (see "LCPs Save Time and
Money"). This is particularly critical for
optical cable coatings and connectors
that must remain dimensionalljr stable
to avoid kinking the optical fibers connected to them. Because of their high
degree of rigidity, some LCPs can be
used in very thin cross sections and still
perform as well as thicker parts made
from other thermoplastics.
LCPs are easily processible because
they flow when melted, rather than
forming a blob, like many thermoplastics. This quality can also be achieved
by blending LCPs with conventional
thermoplastics. Researchers a t Imperial Chenlical Industries Inc. (ICI) have
discovered that as little as 5 percent to
10 percent of ICI's LCP, called Victrex
SRP, added to a conventional thermoplastic reduces the melt viscositv of the
blend to the level of Victrex itsAf. This
opens the door for LCPs to be used a s
processing aids for "problem" polymers, such as polyphenylene sulphide
(Ryton, for example) and polyamide-imide (such a s Torlon).
Researchers a t Virginia Polytechnic
Institute, Blacksburg, are exploring
LCP blends for additional valuable
properties. For example, under certain
e all make use of liquid crystals (LCs)--in
the
The property of LC formulations to change from transform of digital displays on watches, pocket parent to opaque when subject to an electric field is being
calculators, and so many common appliances. utilized in a comparatively new application. Taliq Corp.,
However, of the thousands of tons of melt-processible LC Sunnyvale, Calif., uses an LC film sandwiched between
polymers used annually, only a few tons of LCs meet the layers of glass to "opacify" windows and interior glass
worldwide demand for the minute amounts needed for dis- walls. The touch of a button can turn the glass walls--or
plays.
the windows--of an office from clear to translucent.
Low molecular weight LCs are a unique "fourth state"
In addition, LCs are used in medical diagnostics because
of matter that are fluid like ordinary liquids but exist in an of their ability in film form to indicate small but signifiordered arrangement similar to that of a crystalline solid. cant temperature differences by changing color when
This order, or mesophase, is due almost exclusively to the held against body parts.
molecular shape of these materials. The molecules are
Naturally occurring LCs were discovered about 100
asymmetric with a distinct aspeci (length to width) ratio gears ago. At f i s t they were considered laboratory curiand are usually rigid structures c,ontaining phenyl rings. osities, but nour they are the object of considerable interThis molecular asymmetry causes the molecules to coop- est by scientists in many disciplines. For instance, they are
eratively align with one another. This cooperatively shedding light on the poorly understood transition bealigned LC is lyotropic in the liquid state. In the molten tween the liquid and solid states and also helping manustate,the LC is thermotropie. .
facturers of detergents understand surface-active pheThe mesophase has interesting and important charac- nomena.
teristics, such as color changes upon heating and the abiliThe packing of DNA and RNA in the nucleus of the huty to become aligned in low-voltage electric fields. These man cell has also been hypothesized a s due to LC behavcharacteristics are what highlight LC displays. Some ior. Thus, the study of LCs could light the way to impor10,000 different LC formulas have been developed.
tant insights into biological processes.
22 m
HIGH TECHNOLOGY BUSINESS l JUNE 1969
processing conditions, LCPs will elongate into fibers in conventional thermoplastics, thus becoming a reinforcing
and stiffening agent. This could prove
to be a cost-effective method of producing composite materials for many products from high-performance sports
equipment to appliance parts.
In addition, researchers a t the Institute for Materials Science, University
of Connecticut, Storrs, are investigating finely divided LCPs as particles in
electrorheological fluids-fluids that
change from a liquid to solid state.
Finally, in the solid state, LCPs make
excellent barriers to water and oxygen.
This advantage is gained even in very
thin films, making them ideal for use as
coatings over cheaper materials. Packaging materials-potato chip bags, for
instance--might be made from a commodity plastic, but an LCP film over
that will help keep the chips fresher.
With all of these attributes, it's no
surprise that some observers say that
LCPs represent a materials evolution
as important as that from iron to steel.
However, LCPs do have their limitations. One barrier to widespread use is
price, which currently ranges from a p
proximately $7 per pound for highly
filled resins-those to which an inorganic substance, such as talc or glass fiber, has been added-to $12 per pound
for unfilled material. This represents a
significant drop from the $15 per pound
to $22 per pound price tags of just three
years ago, but it's still high compared
with the $3 to $5 per pound of other
high-temperature thermoplastics.
Italy's Montedison, owner of Granmont, claims that its technology uses inexpensive monomers that will allow it
to drop the price to the $5 per pound
range-in about two to four years. At
this price, most industry analysts agree
that the use of LCPs will grow even beyond the currently predicted 20 percent
per year.
Although processibility is one of the
biggest advantages of LCPs, the high
melt temperatures necessary often
mandate expensive machinery modifications, such as hot-oil or electric-car-
tridge heating of the mold and ceramic
heating elements. This can add as much
as $10,000 to the $80,000 to $90,000 basic
cost of an injection-molding press.
Another problem in processing LCPs
is the way the molecules orient themselves in the direction of flow. This is a
source of their strength, but it can also
cause some structural weaknesses. For
instance, where two flow fronts unite
inside the mold the knit-line strength
urill be poor and the material will separate easily. However, the addition of
mineral fillers and fiberglass reinforcement greatly reduces these undesirable
effects. 4nd sophisticated design engineering can circumvent such problems
and produce parts with optimum
strength where necessary.
These drau-backs are relatively minor considering the implications of LCP
use and the possibile emergence of
technologies that will override the price
and manufacturability problems.
Because LCPs have been commercially available for such a short time, little information exists about the practical aspects of their use. To assist LCP
users and suppliers, researchers at Battelle Laboratories, Columbus, Ohio,
have organized a multiclient study to
* These suppliers have not yet named their soon-to-be-introduced versions of
comprehensir~elyreview the worldwide
LCPs. The rest are either commercially available or in various sampling stages.
state of the art of LCP technology and
to project through the year 2000 the
Hoechsi-Cdonese Gorp. .........................................
...........................................W 2 3 5 - 2 6 3 7
markets that will be sewed by these ex(Enginewing Plastics Div.)
Eashnon Kodak Co. (Performance .............................KT-SOPHB ...................................
..830
citing new materials. The study costs
Plastics Eastman Chemical Div.)
$9,800. For information, contact R. P.
Arnou, Perfamonce Products Inc..............................
Xydar ............................................
BW-621-4557
Heggs at 614-424-7782or Alice Parsons
ICl lnc Advonced Moterials ....................................V i x ...........................................
3l2-575-3000
Gmnmoni Inc. ....................................................&anlor .........................................,614-5874665
a t 614-424-3912,or write to Battelle, 505
Dv P ~ n t...........................................................
W-ZD00. .....................................
,.W41-7515
King Ave., Columbus, OH 43201.
BASF AG .......................................................... h ...........................................
830-227-37U
.......................................................................................................... 412-777-2D00
.......................................................................................................................800-662-2927
General Electricf .................................................................................................800-255-8886
.
8ayw AG*
Richard P Heggs is a p'rincipal research
scie?~
tisl at Battelle Memorial I?~stitute,
Colunzbus, Ohio.
JUNE 1989 I HIGHTECHNOLOCI BUSINESS B
23