ELASTOMERIC SURGICAL SUTURES-COMPRISING SEGMENTED COPOLYETHER/ESTERS

FIL CHIRURGICAL ELASTOMERIQUE CONTENANT DES ESTERS ET DES COPOLYETHERS SEGMENTES

English Abstract

ABSTRACT
ELASTOMERIC SURGICAL SUTURES COMPRISING
SEGMENTED COPOLYETHER/ESTERS
Elastomeric monofilament surgical sutures are character-
ized by the following combination of mechanical proper-
ties:
Yield elongation - from about 2 to 9 percent
Visco-elastic
elongation - from about 10 to 30 percent
Young's modulus - from about 30,000 to 200,000 psi
Tensile strength - at least about 40,000 psi
Knot strength - at least about 30,000 psi
The sutures are soft and flexible with superior knot
tying and knot security properties. The sutures may be
prepared from selected elastomeric copolyether/ester
polymers which may be melt extruded and drawn to obtain
the desired fiber properties.

Claims

ETH-467
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:-
1. An elastomeric surgical suture comprising a mono-
filament having the following combination of mechanical
properties:
Yield elongation - from about 2 to 9 percent
Visco-elastic
elongation - from about 10 to 30 percent
Young's modulus - from about 30,000 to 200,000 psi
Tensile strength - at least about 40,000 psi
Knot strength - at least about 30,000 psi
2. A suture of Claim 1 having a diameter of from about
0.01 to 1.0 mm.
3. A suture of Claim 1 wherein the Young's modulus is
50,000 to 150,000.
4. A suture of Claim 1 wherein the tensile stress at
the visco-elastic elongation yield point is less than
about one-third the suture tensile strength.
5. A suture of Claim 1 having an elongation to break
of about 30 to 100 percent.
6. A suture of Claim 5 wherein the elongation to break
is at least 1.5 times the visco-elastic elongation.
7. A suture of Claim 1 wherein the visco-elastic
elongation is at least about 2.5 times the yield elonga-
tion.
8. A suture of Claim 1 in a sterile condition.
9. A suture of Claim 8 with a needle attached to at
least one end thereof.
10. A suture of Claim 1 comprising a drawn and oriented
monofilament of a segmented copolyethertester polymer.

11. A drawn and oriented elastomeric surgical filament
comprising a segmented copolyether/ester polymer consisting es-
sentially of a multiplicity of recurring long chain ether/ester
units and long chain ester units joined head to tail through
ester linkages and having the following general formula:
<IMG>
wherein G is a divalent radical remaining after the removal of
terminal hydroxyl groups from a poly(C2-10 alkylene oxide)
glycol having a molecular weight of about 350 to 6,000: R is a
divalent radical remaining after removal of carboxyl groups
from an aromatic dicarboxylic acid having a molecular weight
less than about 300, and D is a divalent radical remaining after
removal of hydroxyl groups from an alkyldiol having a molecular
weight less than about 250, a and b are integers such that the
long chain units represented by a comprise from 50 to 90 percent
by weight of the composition, and n is the degree of polymeriza-
tion resulting in a fiber-forming polymer, said drawn filaments
being characterized by the following physical properties:
Tensile strength - at least about 40,000 psi
Knot strength - at least about 30,000 psi
Yield elongation - from about 2 to 9 percent
Visco-elastic
elongation - from about 10 to 30 percent
Young's modulus - from about 30,000 to 200,000 psi.
12. A filament of Claim 11 having a surgical needle attach-
ed to at least one end and useful as a surgical suture.
13. A filament of Claim 12 in a sterile condition.
21

14. A filament of Claim 11 wherein G is derived from
poly(tetramethyleneoxide)glycol, D is derived from 1,4-butane-
diol, and R is derived from a phthalic acid.
15. A filament of Claim 14 wherein R is selected from the
group consisting of terephthaloyl, isophthaloyl, orthophthaloyl,
and mixtures thereof.
16. A filament of Claim 14 wherein said poly(tetramethylene-
oxide)glycol has a molecular weight of about 1,000.
17. A filament of Claim 14 wherein the long chain units
represented by b comprise about 40 wt percent of the copoly-
ether/ester.
18. A filament of Claim 17 comprising approximately 51
percent terephthaloyl units, 16 percent units derived from poly-
tetramethylene ether glycol, and 33 percent units derived from
1,4-butanediol.
19. A filament of Claim 18 characterized by a visco-
elastic elongation of about 19 percent and a Young's modulus
of about 50,000 psi.
20. A filament of Claim 14 wherein the long chain units
represented by b comprise about 23 wt percent of the copoly-
ether/ester.
21. A filament of Claim 20 comprising approximately 45
percent terephthaloyl units, 4 percent orthophthaloyl units, 20
percent units derived from polytetramethylene ether glycol and
31 percent units derived from 1,4-butanediol.
22

22. A filament of Claim 21 characterized by a visco-
elastic elongation of about 13 percent and a Young's modulus
of about 170,000 psi.
23. A filament of Claim 16 comprising a mixture of indiv-
idual segmented copolyether/ester polymers, each of said poly-
mers having from about 18 to 40 percent by weight long chain
ester units, the mixture of said individual polymers containing
an average of from about 26 to 35 percent long chain ester units.
24. A filament of Claim 23 wherein said polymer-mixture
comprises from about 55 to 75 percent by weight of polymer
having about 40 percent long chain ester units, and from about
25 to 45 percent by weight of polymer having about 18 percent
long chain ester units.
25. A filament of Claim 23 wherein said polymer mixture
comprises approximately 40 percent by weight of a polymer having
about 40 percent long chain ester units, from about 30 to 40
percent by weight of a polymer having about 23 percent long
chain ester units, and from about 30 to 40 percent by weight of
a polymer having about 18 percent long chain ester units.
23

Description

-- 1 --
BACKGROUND OF THE INVENTION
The present invention relates to surgical sutures, and
more particularly, to soft, elastomeric sutures having
unique handling and ~not tying characteristics. The
sutures may be prepared from segmented copolyether/.
esters or other elastomeric polymers.
- .
Many natural and synthetic materials are presently used
as surgical sutures. These materials may be used as
single filament strands, i.e, monofilament sutures,
or as multifilament strands in a braided, twisted or
other multifilament construction. ~atural materials such
as silk, cotton, linen, and the like, of course do not
lend themselves to the fabrication of monofilament su-
tures and are accordingly generally used in one of the
multifilament constructions.
Synthetic materials which are extruded in continuous
lengths can be used in monofilament form. Common syn-
thetic monofilament sutures include polyethylene
terephthalate, polypropylene, polyethylene, and nylon.
Such monofilament sutures are preferred by surgeons for
many surgical applications due to their inherent smooth-
ness and noncapillarity to body fluids.

The presently available synthetic monofilament sutures
all suffer to a greater or lesser degree from one par-
ticular disadvantage, that is inherent stiffness. Be-
sides making the material more difficult to handle and
use, suture stiffness can adversely affect knot tying
ability and knot security. It is because of the in-
herent stiffness of available monofilament sutures that
most larger su~ure sizes are braided or have other multi-
filament constructions with better handling flexibility.
Monofilament sutures of the prior art are also charac-
terized by a low degree of elasticity, the most elastic
of the above-men~ioned synthetics being nylon which has
a yield elongation of about 1.7 percen~ and a visco-
elastic elongation of about 8.5 percent. The inelas-
ticity of these sutures also makes knot tying more dif-
ficult and reduces knot security. In addition, the in-
elasticity prevents ~he suture from "giving" as a newly
sutured wound swells, with the result that the suture may
place the wound tissue under greater tension than is de-
sirable, and may even cause some tearing, cutting or
necrosis of the tissue.
The problems associated with the use of inelastic sutures
in certain applications were recogni.zed in U.S. Patent
No. 3,454,011, where it was proposed to fabricate a
surgical suture composed of Spandex polyurethane. Such
sutures, however, were highly elastic with "rubbery"
characteristics and did not find general acceptance in
the medical profession.
It is accordingly an object of the present invention to
provide a novel soft, limp, monofilament suture mate-
rial. It is a further object of this invention to pro-
vide a monofilament suture with a controlled degree ofelasticity to accommodate changing wound conditions. It
is another object of this invention to provide a new, -
nonabsorbable suture having a diameter of from about
0.01 to 1.0 mm and possessing unique and desirable
~a~

b ~ . ETH-467
physical properties. These and other objects will be
made apparent from the ensuing description and claims.
SUMMARY
Monofilament sutures of the present invention are charac-
terized by the following cornbination of physical proper-
ties:
Yield elongation - from about 2 to 9 percent
Visco-elastic
elongation - frorn about 10 to 30 percent
Young's modulus - from about 30,000 to 200,000 psi
Tensile stxength - at least about 40,000 psi
Knot strength - at leas~ about 30,000 psi
Sutures possessing the above characteristics may be pre-
pared by melt extruding certain elastomeric polymers
such as copolyether/ester polymers to form a continuous
filarnentary strand, and thereafter drawing the extruded
filarnent to obtain the desixed suture properties. Cer-
tain copolyether/ester polymers available cornrnercially
from E. I. du Pont de Nemours & Co. under the tradename
-~ "HYTREL" have been discovered to be suitable starting
ma~erials for the preparation of sutures in accordance
with the present inVentiOrl.
Monofilarnent sutures having physical properties in ac-
cordance with the present invention are particularly
useful in many surgical procedures where the suture is
used to close a wound which may be subject to later
swelling or change in position. The cornbination of low
Young's modulus and significant yield elongation pro-
vides the suture with an appreciable degree of controlled
elasticity under low applied force. As a result, the
suture is able to "give" to accornrnodate swelling in the
wound area. The relatively high visco-elastic yield
elongation and high tensile strength of the suture allows
the suture to stretch during knot tie-down so that the
knot "snugs down" for improved tying ability and knot
security with a rnore predlctable and consistent knot
.

~TH-467
geometry regardless of variations in suture tying
technique or tension.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a representative stress-strain curve charac-
teristic of the surgical filaments o~ the present inven-
tion.
.
Figure 2 is a representative stress-strain curve compar-
ing filaments of the present invention with monofila-
ment sutures of the prior art.
:'
DESCRIPTION OF PREFERRE:D EMBODIMENTS
,. . .
The sutures of the present invention are characterized by
a combination of physical properties which are unique
for monofilament sutures, and which provide the sutures
of the present invention with unique and desirable func-
tional properties.
.
The characteristic properties of the inventive sutures
are readily determined by conventional test procedures.
Figure 1 illustrates a typical stress-strain or load-
elongation diagram for the sutures of this invention.
In Figure 1, yield elongation (Ey) is the point at which
permanent deformation of the suture begins to take place.
So long as the filament is not elongated beyond Ey,
elastic recovery is essentially complete. The sutures
of the present invention have an Ey with the range of 2
to 9 percent.
Young's modulus is a measure of the slope of the stress-
strain curve over the initial portion of the curve ex-
tending from the origin. In Figure 1, line a is a drawn
tangent to the curve at the origin, and Young's modulus
is equal to tan ~. The slope of the curve, and Young ' 5
modulus, are seen to be a measure of the resistance to
elongation in the initial elastic portion of the curve.
The sutures of the present invention are designed to have
a significant, but relatively low modulus of 30,000 to

I.ïr~-46 i
r ,
200,000 psi, and preferably within the range of 50,000 to
150,000 psi. A modulus within the claimed xange pro-
vides the correct amount of increasing tension on the su-
tuxe as the suture is extended toward its yield point
(Ey). At lowex yalues of Young's modulus, the sutuxe
readily elongates under very low tension to its yield
point and the advantages of having a significant yield
elongation are lost. At highex values of Young's modulus,
filament stiffness becomes the controlling consideration,
and the softness and good handling properties of the su-
ture diminish.
The portion of the stress-strain curve extending between
Ey and Ev on Figure 1 is the visco-elastic region during
which there is consi~erable elongation and permanent
deformation of the suture with only slightly increasing
tension. The visco-elastic elongation (Ev) of the su-
tures of the present invention is controlled to be with~
in the range of from about 10 to 30 percent. This
property of the suture allows the suture to draw down
during knotting to assure good knot security.
As the suture ls elongated beyond Ev, the load increases
rapidly as indicated in Figure 1. This rapid increase
in load imparts a positive feel to the suture which, in
the hands of a skilled surgeon, signals when Ev and
maximum knot security are achieved. Preferably, the
value of Ev is at least 2.5 times the value of Ey in
order to provide the surgeon with a broad visco-elastic
region in which to work during suture tie-down.
As seen in Figure 1, the load from 0 to Ev elongation is
relatively low compared to the breaking load (Sb).
Preferably, the breaking load or straight tensile strength
is at least 40,000 psi, and the load Sv corresponding to
visco-elastic elongation is less than one-third of the
breaking load, with the result that the suture may be
easily knotted under relatively low forces and without

risk of unintentionally breaking the suture. Knot
strength of the suture is preferably at least 30,000 psi.
The breaking elongatlon (Eb) of the sutures of the pres-
ent invention are generally within the range of 30 to
100 percent. Although this property is not critlcal to
`' the performance of the suture since suture elongation
in use does not generally exceed Ev, it is preferable
that Eb be at least 1.5 x Ev in order to' reduce the pos-
sibility oî inadvertently over elongating and breaking
the suture during tie-down.
The unique mechanical properties of the sutures of the
present invention will be more readily appreciated from
Figure 2 where such sutures are compared to nylon and
polyprop,,vlene sutures of the prior art. Representative
physical properties of these three suture materials are
given in Table I. Each of these prior art sutures has a
considerably higher Young's modulus which results in the
characteristic stiffness of these materials. In addition,
neither suture has a noticeable Ey or an extended visco-
elastic region which characterize the sutures of the in-
vention and impart the desirable properties discussed
above.
The mechanical properties of the sutures of the pre~ent
invention reflected in the relative values of Ev and Ey
~ in combination with the low Young's modulus and high
'~ tensile strength are unique in the field of surgical su-
tures and distinguish the monofilament sutures of the
present invention from all prior art materials.
:

ETH-467
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L5
Sutures having mechanical properties in accordance with the
present invention may be prepared from the segmented copol-
ether/ester compositions disclosed in U.S. Patent No. 3,023,
- 5 192, which states in part at Column 2, line 20 et seq,:
"The copolyetheresters of this invention
- are prepared by reacting one or more
boxylic acids or their ester-forming deriva-
tives, one or more difunctional polyethers
with the formula: ,
HO(RO) H
(in which R is one or more divalent organic
radicals and ~ is an integer of a value to
provide a glycol with a molecular weight of
between about 350 and about 6,000), and one
or more dihydroxy-compounds selected from the
class consistiny of bis-phenols and lower ali-
phatic glycols with the formula:
HOtC~2)qOH
(in which q is 2-lo~with the proviso that the
reactants be selected so that substantially all
of the repeating units of the polyester contain
:
'! at least one aromatic ring. The resulting
~ ester is then polymerized."
.,
' The preparation of other related segmented thermoplastic
copolymers are described in the following additional
: references: U~S. Patents Nos. 3,651,014, 3,763,109; 3,766,146, ;
and 3,784,520,
,; .
' 35 According to the above re~erences, the disclosed segmented
thermoplastic copolymers may be cast as films, injection
~; molded to form objects, or melt extruded to form filaments.
, me products obtained in accordance with these references,
however, are characterized by physical properties which are
not desirable for surgical sutures.
,
~'
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:

E-rH-467
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In particular, the filaments of the references are rub-
bery with a very high degree of elasticity as indlcated
by break elongations in excess of 500 percent. Tensile
strengths, on the other hand, are very low, generally
less than 8,000 psi. The filaments prepared from co-
polyether/esters in accordance with the teachings of
these references therefore do not possess the mechanical
properties of the sutures of the invention, and, in fact,
are obviously not at all suitable for use as surgical
sutures.
The disadvantages of the prior art references are over-
come by means of the present invention wherein filaments
extruded from certain copolyether/esters are quenched
and drawn with the result that the mechanical properties
of the filaments are controlled to be within the specific
limits discovered to be particularly desirable for surgi-
cal sutures.
The segmented copolyether/esters useful in the present
invention comprise a multiplicity of recurring long
chain ether/ester units and short chain ester units
joined head to tail through ester linkages according to
the following general formula:
O O O O
[(O ~ D - O - C - R ~ C)a~O ~ G - O - C - R - C ~ )b]n
The long chain ether/ester units of the polymer are rep-
resented by the general formula:
O o
Il 11
- - O - G - O - C - R - C - (IIj
wherein G is a divalent radical remaining after the re-
moval of terminal hydroxyl groups from a poly(C2 10
alkylene oxide)glycol having a molecular weight within
the range of about 350 to 6,000, and R is a divalent ..
radical remaining after the removal of carboxyl groups
from an aromatic dicarboxylic acid having a molecular
weight of less than about 300.

r . L ;~ b 7
, _
The short chain ester units are represented by the
general formula: .
:.
O O -
Il 11 ,
O - D - O - C - R - C - (III)
wherein D is a divalent radical remaining after removal
of hydroxyl groups from an alkyldiol having a molecular
weight of less than about 250, and R is as defined above.
; In the above Formula I, a is an integer such that the
short chain copolymer segments represented by a comprise
from 50 to 90 percent by weight of the total copolymer
composition; b is an integer such that the long chain
copolymer segments represented by _ comprise from 10 to
50 percent of the total copolymer composition; and n is
the degree of polymerization resulting in a fiber-
forming copolymer.
The copolyether/esters represented by Formula I may bemelt extruded, quenched and drawn to obtain filaments
having physical properties desirable for surgical su-
tures as above defined. Polymer to be extruded is driedat about 200-220F in a circulating hot air oven and/or
under vacuum in order to remove all traces of moisture
and other volatile materials. The polymer is then melt
extruded and water quenched in accordance with the con-
ventional melt spinning techni~ues for synthetic fibers.
The fiber is finally drawn at least about 5X, and - :
usually from about 7X to 9X to achieve molecular orien~
tation.
The preparation of fibers useful as surgical sutures from
copolyether/esters in accordance with the present in-
vention is demonstrated by the following examples which
are presented by way of illustration and are not limit-
ing of the present invention. The polymers utilized in
these examples are copolyether/esters prepared from
1,4-butanediol, dimethyl phthalate, and polytetra
methylene ether glycol (M.W. of about 1,000), and are
. . .

ll
commercially a~ail~ le ~from E. I. du Pont de Nemours &
Co. under the t~ ~ "HYTREL". The polymer contains
intrapolymerized butylenephthalate hard segments
~ (short chain ester units) and polytetramethvlene ether
terephthalate soft segments ~long chain ester units) and
has the following general structure as reported in the
. Journal of Elastomers and Plastics 9, 416-38 (Oct., 1977):
ICUZ~ - C - ~3 - cla~o~c8;~ 2cH~cd~o) - -~ - C~
(hard segment) (soft segment)
'~
.~ wherein a and b are às defined above and x is an integer
reflecting the molecular weight of the ether glycol re-
actant (x = 14 for M.W. of about 1,000).
In the following examples, physical properties of in-
dividual monofilaments were determined on an Instron~
tensile tester under the following conditions:
Crosshead speed (XH): S in/min
Chart speed (CS) : 10 in/min
Sample length (GL) : 5 in
Scale load (SL) : 2 lbs/in
With reference to Figure 1, Young's modulus is calculated
; from the slope a of the stress-strain curve in the initial
linear, elastic region as follows:
Young's modulu5 (psi~ = tan e X GL x CS x SL
wherein e = the angle indicated in Figure 1
XS = the cross-sectional area of the fiber, in L
SL, XH, CS, and GL are as identified above.
Yield stress (Sy) is the load at the point of inter-
section of lines a and b drawn tangent to the initial
elastic region and the visco-elastic region, respectivelv,
of the curve as illustrated in Figure 1. Yield elonga- ~_
tion (Ey) is the elongation corresponding to Sy and is ir
read directly off the stress-strain curve.
~ ~a~ k

12
Visco-elastic stress (Sv) is the load at the point of
intersection of line b with line c drawn tangent to the
curve as illustrated in Eiyure 1. Visco-elastic elonga-
tion (Ev) is the elongation corresponding to Sv and is
read directly off the curve.
Brea~ elongation (Eb) and breaking tensile strength (Sb)
are read directly off the stress-strain curve as illus-
trated in Figure 1.
EXAMæLE I
A sample of copolyether/ester of Formula IV having ap-
proximately 40 wt percent soft segments and comprising
approximately 51 percent terephthaloyl units, 15 percent
units derived from polytetramethylene ether glycol, and
33 percent units derived from 1,4-butanediol was dried
four hours at 200F in a circulating hot air oven and
then further dried under vacuum at 100 microns (no heat)
for 16 hours. The dry polymer was placed in a one-inch
horizontal extruder and extruded through a J/50/1 die at
an extrusion temperature of 380F.
The extrudate was quenched in water at ambient temperature
and drawn to a size 2-0 monofilament suture using a 8.8X
draw ratio at a temperature of 530F and with a take-up
speed of 485 ft/min. Physical properties of the result-
ing filaments are given in Table II.
, .
EXAMPLE II
A sample of copolyether/ester of Formula IV having ap-
proximately 23 wt percent soft segments and comprising
approximately 45 percent terephthaloyl units, 4 percent
orthophthaloyl units, 20 percent units derived from poly-
tetramethylene ethex glycol and 31 percent units derived ,
35 from 1,4-butanediol was dried and extruded at 400F as de-
scribed in Example I. The extrudate was quenched and
drawn into a size 2-0 monofilament using a 7.5X draw ratio
at a temperature of 450F and Wit}l a take-up speed of
.~

~ 4
13
412 ft/min. Physical properties of the resulting fila-
ments are given in Table II.
EXAMPLE III
S A sample of copolyether/ester of Formula IV haviny ap-
proximately 18 wt percent soft segments and comprising
approximately 41 percent terephthaloyl units, 35 per-
cent units derived from polytetramethylene ether glycol
and 24 percent units derived from 1,4-butanediol was
dried and extruded at 405F as descrlbed in Example I.
The extrudate was quenched and drawn into a size 2-0
monofilament suture using a 6.5 draw ratio at a tempera-
ture of 560~. The take-up speed was 75 ft/min. Physi-
cal properties of the resulting filaments are given in
Table II. It is noted that the Young's modulus of these
filaments exceeded the maximum desirable llmit for su-
tures of the present invention.
EXAMPLE IV
Three parts of a copolyether/ester of Exam~le I and two
parts of a copolyether/ester of Example III were dry
blended to provide a polymer having a total of 30.2 per-
cent soft segments. The blended material was dried in
a vacuum oven for two hours at 1-2 mm Hg (no heat), and
then heated at 50C for three hours at 1-2 mm Hg.
The dried mixture was melt blended in a 3~4-inch Brabender
extruder with a 25-inch barrel with a 20/1 screw and ex-
truded at 430F through a 5/32-inch die in a vertical
monofilament assembly. The extrudate was water quenched
at ambient temperature, pelletized, and again dried as
described above for the dry-blended material before ex-
truding into monofilament sutures. A size 2-0 monofila-
ment suture of this material was extruded at 400F using
a 7.9X draw ratio at a temperature of 460F and a take-up
speed of 435 ft/min. Physical properties of the resulting
filaments are given in Table II.

ETH-~167
LS
14
EXAMPLE V
- 3.5 Parts of a copolyether~ester of Example I and 1.5
parts of a copolyether/ester of Example III were dry-
blended for a total of 33.4 percent soft segments and
extruded following the general procedure of Example IV,
and using a flnal draw xatio of 7.5X with a draw tempera-
ture of 485F and a take-up speed of 412 ft/min to ob-
tain a size 2-0 monofilament suture. The physical
properties of the resulting filamen-ts are given in
Table II.
EXAMPLE VI
The procedure of Example IV was repeated using various
blends of copolyether/ester polymers of Examples I, II
and III having the compositions and blended in ratios as
shown in Table II. The physical properties of the re-
sulting filaments are also given in Table III.
EXAMPLE VII
~0 A copolyether/ester of Example I with 40 wt percent soft
segments was dried and extruded in accordance with the
general procedure of Example I using a 20 mil spinnerette
to obtain a size 5-0 suture, and a S0 mil spinnerette to
obtain a size 0 suture. Drawing conditions and physical
~: 25 properties of the resulting suture are compared in
; Table IV with a size 2-0 suture of the same composition
prepared according to Example I.

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u~ ~ ~ ~ ~ ~ ~ r~
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. ~iH-467
17
TABLE IV
Suture size
5-0 2-0 0
_ _ _
Draw ratio 7-5 8.8 7.3*
Draw temperature, F 340 530 370
Take-up, ft/min 205 485 110
Diameter, mils 7.08 11.10 14.03
~not strength, psi 48,60037,200 34,200
(Xg/cm2) .(3,400)(2,600)(2,400)
T~nsile strength, psi 67,50064,100 68,600
(Xg/cm2) (4,700)(4,400)(4,800)
Brea~ elongation, % 43.5 31.8 36.7
Visco-elastic elongation, ~ 10.8 18.6 17.6
Yield elongation, ~ 3.0 3.2 6.3
Young's modulus, psi 49,00050,~00 51,000
(Kg/cm2) (3,400)(3,5003(3,600)
_
~Two stage draw
EXAMPLE VIII
Monofilament sutures prepared from a copolyether/ester
of Example II with 23 wt percent soft segments were
sterilized by cobalt-60 irradiation and with ethylene
oxide in accordance wi~h conventional procedures for
sterilizing surgical sutures. The physical properties of
the sutures were affected only slightly by ethylene oxide
sterilization, and even less by cobalt-60, as shown by
the data in Table V.

18
TABLE V
. _
SutureNonsterile _ Sterilized
; control Co E.O.
; Diameter, mils 12.5 12.6 13.2
Knot strength; psi 35,300 33,400 29,900
(Kg/cm2) (2,500) (2,300) (2,100)
Tensile strength, psi70,300 70,000 67,700
(Kg/cm2) (4,900) (4,900) (4,800)
Break elongation, % 28.2 31.6 45.2
Visco-elastic elongation, ~i 13.2 15.0 23.5
Yield elongation, % 2.9 2.3 2.2
` Young's modulus, psi185,000 165,000 138,000
(Kg/cm2) (13,000) (11,600) (9,600)
The important physical properties of the sutures pre-
pared from copolyether/esters are responsive to changes
ln polymer composit.ion and processing conditions. For
example, visco-elastic elongation and yield elongation
increase as the proportion of sof-t segments in polymer
are increased, and conversely, Young's modulus decreases
with an increasing proportion of soft segments. The
break elongation may be decreased and tensile strength
increased by employing higher draw ratios during the
manufacture of the suture. By regulation of the com-
position and processing variables therefor, it is pos-
sible to obtain specific mechanical properties for in-
dividual sutures with a great degree of latitude.
While the preceding examples have been directed to thepreparation of monofilament sutures of copolyether/esters,
this was for the sake of convenience in describing one
polymer system and the effect of various polymer composi-
tions and spinning conditions on fiber properties. The
copolyether/ester polymers may also be used in the

L5
19
manufacture of braided or other multifilament suture con-
vl structions, and single filaments and braids may be used
in the preparation of surgical fabrics and knitted or
woven prosthetic devices such as vein and arterial grafts.
In addition, elastomeric filaments having a combinationof physical properties in accordance with the present in-
vention may be prepared from other polymer systems such
as polyurethane or sillcone elastomers or polyether co-
polymers of urethane or silicone elastomers. Furthermore,
elastomeric filaments of the present invention may be
blended with each other, with other elastomeric or non-
elastomeric filaments, and with either absorbable or non-
absorbable filaments in order tc provide yarns and fabrics
with special properties, all of which is deemed to be in-
cluded within the scope of the present invention.