U.S. patent application number 10/208954 was filed with the patent office on 2004-02-05 for dual windup drum extensional rheometer.
Invention is credited to Sentmanat, Martin Lamar.
Application Number | 20040020287 10/208954 |
Document ID | / |
Family ID | 31186914 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040020287 |
Kind Code |
A1 |
Sentmanat, Martin Lamar |
February 5, 2004 |
DUAL WINDUP DRUM EXTENSIONAL RHEOMETER
Abstract
An extensional rheometer comprises a rotatable primary windup
drum and one or more secondary rotatable windup drums wherein a
sample is attached to the primary windup drum and each secondary
windup drum. Counter rotation of the primary windup drum and each
secondary drum causes each affixed sample to stretch until rupture.
The load response on each primary and secondary windup drum set
caused by a stretching sample is measured with a load sensing
device. Environmental control may be provided for testing samples
under different conditions.
Inventors: |
Sentmanat, Martin Lamar;
(Akron, OH) |
Correspondence
Address: |
Howard M. Cohn
21625 Chagrin Blvd. Suite 220
Cleveland
OH
44122
US
|
Family ID: |
31186914 |
Appl. No.: |
10/208954 |
Filed: |
July 31, 2002 |
Current U.S.
Class: |
73/261 |
Current CPC
Class: |
G01N 2203/028 20130101;
G01N 33/442 20130101; G01N 3/16 20130101; G01N 11/00 20130101; G01N
2203/0094 20130101; G01N 2203/0278 20130101; G01N 2203/0282
20130101; G01N 3/08 20130101; G01N 2203/0017 20130101; G01N
2203/0037 20130101 |
Class at
Publication: |
73/261 |
International
Class: |
G01F 003/04 |
Claims
1. An extensional rheometer apparatus for measuring the extensional
flow response of samples of a material comprising: a primary windup
drum mounted to a power drive device for rotating the primary
windup drum; a secondary windup drum rotatably mounted in proximity
to the primary windup drum; means interconnecting the primary
windup drum to the secondary windup drum whereby rotation of the
primary windup drum by the power drive device causes the rotation
of the secondary windup drum; and a load sensing device for
measuring the response of the extensional flow of a low modulus
solid sample secured to the primary windup drum and the secondary
windup drum.
2. The apparatus of claim 1 wherein the primary and secondary
windup drums are in substantially parallel alignment.
3. The apparatus of claim 1 wherein the means for interconnecting
the primary and secondary windup drums are first and second gears
individually attached to the primary and secondary windup drums and
intermeshed such that the primary and secondary windup drums are
counter rotating.
4. The apparatus of claim 3 wherein the first and second gears of
the primary and secondary windup drums are intermeshed such that
the primary and secondary windup drums rotate at the same
speed.
5. The apparatus of claim 1 wherein the load sensing device is
attached to the secondary windup drum for supporting the secondary
windup drum.
6. The apparatus of claim 1 wherein the load sensing means is
attached to the primary windup drum driving means.
7. An extensional rheometer apparatus for measuring the extensional
flow response of samples of a material comprising: a primary windup
drum mounted to a power drive device for rotating the primary
windup drum; a plurality of secondary windup drums rotatably
mounted in proximity to the primary windup drum; means
interconnecting the primary windup drum to the plurality of
secondary windup drums whereby rotation of the primary windup drum
by the power drive device causes the rotation of the secondary
windup drums; and a load sensing device attached to each of the
secondary windup drums for supporting each of the secondary windup
drums and measuring the response to the extensional flow of low
modulus solid samples secured to the primary windup drum and each
of the plurality of secondary windup drums.
8. The apparatus of claim 7 wherein the primary and plurality of
secondary windup drums are in substantially parallel alignment.
9. The apparatus of claim 7 wherein the means for interconnecting
the primary and plurality of secondary windup drums are first and
second gears individually attached to the primary and plurality of
secondary windup drums and intermeshed such that the primary and
plurality of secondary windup drums are counter rotating.
10. The apparatus of claim 9 wherein the first and second gears of
the primary and plurality of secondary windup drums are intermeshed
such that the primary and plurality of secondary windup drums
rotate at the same speed.
11. An extensional rheometer apparatus for measuring the
extensional flow response of samples of material comprising: a
primary windup drum mounted to a primary power drive device for
rotating the primary windup drum; a secondary windup drum rotatably
mounted to a secondary power drive device for rotating the
secondary windup drum in proximity to the primary windup drum; and
a load sensing device attached to the secondary power drive device
for supporting the secondary windup drum and measuring the
extensional flow response of a low modulus solid sample secured to
the primary windup drum and the secondary windup drum.
12. The apparatus of claim 11 wherein the load sensing device is
secured at one end to a support member and at the other end to the
secondary power drive device.
13. An extensional rheometer apparatus for measuring the
extensional flow response of samples of a material comprising: a
primary windup drum mounted to a primary power drive device for
rotating the primary windup drum; a plurality of secondary windup
drums rotatably mounted to a plurality of secondary power drive
devices for individually rotating the secondary windup drums in
proximity to the primary windup drum; and a plurality of load
sensing devices, each attached to one of the plurality of secondary
power drive devices for supporting the plurality of secondary
windup drums and measuring the extensional flow response of low
modulus solid samples secured to the primary windup drum and each
of the secondary windup drums.
14. The apparatus of claim 13 wherein each of the plurality of load
sensing devices are secured at one end to a support member and at
the other end to one of the plurality of secondary power drive
devices.
15. A method for measuring the extensional flow response of a
material comprising the steps of: rotating a primary windup drum
with a power drive device; rotating a secondary windup drum in
proximity to the primary windup drum; and supporting the secondary
windup drum and measuring the extensional flow response of a low
modulus solid sample secured to the primary windup drum and the
secondary windup drum with a load sensing device.
16. The method of claim 15 further including the steps of: rotating
a plurality of secondary windup drums in proximity to the primary
windup drum; and supporting the plurality of secondary windup drums
and measuring the extensional flow response of a plurality of low
modulus solid samples secured to the primary windup drum and the
plurality of secondary windup drums with a plurality of load
sensing devices each attached to the plurality of secondary windup
drums.
Description
RELATED APPLICATIONS
[0001] This application relates to U.S. application Ser. No.
09/849,934 entitled Dual Windup Extensional Rheometer by Martin
Sentmanat and having a common assignee with the present
invention.
TECHNICAL FIELD
[0002] The invention relates to a rheometer or rheometer attachment
which is used to measure the viscosity and stress relaxation of
polymers, elastomers, and rubber compounds in simple extension.
More specifically, the present invention relates to the utilization
of a dual windup drum method to characterize the extensional flow
behavior of one or more material samples simultaneously.
BACKGROUND ART
[0003] Joachim Meissner, in the review article "Polymer Melt
Elongation-Methods, Results, and Recent Developments" in Polymer
Engineering and Science, April 1987, Vol. 27, No. 8, pp. 537-546
describes different extensional rheometers that have been developed
in the prior art. Meissner is also the author of several patents on
the subject including U.S. Pat. No. 3,640,127, dated Feb. 8, 1972,
German 2,138,504, dated Aug. 2, 1971, German 2,243,816, dated Sep.
7, 1972 and U.K. 1,287,367.
[0004] Extensional rheometer designs by Cogswell, Vinogradov, and
later Munstedt had in common that one end of the polymer fiber or
filament that was used for testing was fixed to a load
cell/indicator, while the other end was stretched by mechanical
means to a finite maximum elongation. Accordingly, these rheometers
operated with a non-uniform extensional rate throughout the sample
particularly near the clamped ends of the fiber. Meissner overcame
these difficulties with his dual rotary clamp design in which
rotary clamps stretched the fiber at either end over a fixed gauged
length. See, for example, "Rotary Clamp in Uniaxial and Biaxial
Extensional Rheometry of Polymer Melts" by J Meissner, et al.,
Journal of Rheology, Vol. 25, pp. 1-28 (1981) and "Development of a
Universal Extensional Rheometer for the Uniaxial Extension of
Polymer Melts", by J Meissner, Transactions of the Society of
Rheology, Vol. 16, No. 3, pp. 405-420 (1972). In a further
development of this type of rheometer, in order to improve the
transfer of the circumferential speed of the clamps to the local
speed of the sample at the location of clamping (strain rate lag),
two rotary clamps in the prior art devices were replaced by
Meissner and Hostettler as illustrated in "A New Elongational
Rheometer for Polymer Melts and other Highly Viscoelastic Liquids",
Rheological Acta, Vol. 33, pp. 1-21 (1994) with matched/grooved,
metal conveyor belts. With this design, however, a measurement was
limited to a single rotation of the clamps corresponding to a
Hencky strain of seven, and the maximum extensional rate was
limited to 1/s (a reciprocal second). The extensional viscosity was
determined from the force required to deform the fiber, which was
measured by the deflection of leaf springs supporting one set of
rotating clamps. However, as has been reported in the literature by
Erik Wassler in "Determination of true extensional viscosities with
a Meissner-type rheometer (RME)", Proceedings of the 15.sup.th
Annual Meeting of the Polymer Processing Society, Paper 200 (1999),
there can be large deviations between the nominal and the true
extensional strain with this type of extensional rheometer due to
sample slippage between the rotating clamps.
[0005] Other techniques used to measure extensional viscosity
involved winding one end of a fiber around a drum and measuring the
resultant stretching force at the other fixed end of the fiber, as
described in an article by R. W. Connelly, et al., "Local Stretch
History of a Fixed-End-Constant-Length-Polymer-Melt Stretching
Experiment," J. Rheol., Vol. 23, pp. 651-662 (1979). Like the
earlier designs, this method imparts a non-uniform extensional
deformation to the free gauge length of the stretched fiber,
particularly at the fixed end of the fiber that can lead to a false
material rupture condition during extension.
[0006] There remains a need to measure extensional viscosity and
stress relaxation of one or multiple polymers, elastomers, and
rubber compounds in uniaxial extension simultaneously. Steps to
overcome the latter limitations were disclosed in PCT Publication
No. WO00/28321 entitled Dual Windup Extensional Rheometer by Martin
Sentmanat and having a common assignee with the present invention.
Setting out to improve upon the shortcomings of sample slippage and
the non-uniform deformations encountered with other extensional
rheometer designs, Sentmanat in PCT Publication No. WO00/28321
described an apparatus in which both ends of a material sample are
wound around a set of mechanically coupled counter-rotating drums
housed in a torque armature. Upon stretching the sample, the
extensional resistance of the material sample hinders drum
rotation, and the extensional flow behavior of the sample material
can be characterized by monitoring the torque on the torque
armature required to rotate the windup drums at a fixed rate of
rotation. Like the earlier designs, the rheometer described in
WO00/28321 is only capable of assessing a single sample material at
a time. In addition, because the master and slave drums of the
device described in WO00/28321 are both mounted on bearings within
the torque armature, friction from the bearings due to the rotation
of the master and slave drums contribute to the measured signal
during an experiment.
[0007] There remains a need to provide a rheometer that can measure
a plurality of samples at one time and measures the samples with
torque signals that do not include friction from bearings
supporting the drums.
SUMMARY OF THE INVENTION
[0008] According to an embodiment of the present invention, there
is disclosed an extensional rheometer apparatus for measuring the
extensional flow response of samples of material, such as a low
modulus solid sample. The rheometer comprises a primary windup drum
mounted to a power drive device for rotating the primary windup
drum; a secondary windup drum rotatably mounted in proximity to the
primary windup drum; means interconnecting the primary windup drum
to the secondary windup drum whereby rotation of the primary windup
drum by the power drive device causes the rotation of the secondary
windup drum; and a load sensing device for measuring the response
of the extensional flow of a low modulus solid sample secured to
the primary windup drum and the secondary windup drum.
[0009] Further, according to the present invention, the primary and
secondary windup drums are preferably in substantially parallel
alignment. Further, the means for interconnecting the primary and
secondary windup drums are first and second gears individually
attached to the primary and secondary windup drums and intermeshed
such that the primary and secondary windup drums are counter
rotating and cause the primary and secondary windup drums to rotate
at the same speed.
[0010] Also, according to the present invention, the load sensing
device is attached to the secondary windup drum for supporting the
secondary windup drum. In an alternative embodiment, the load
sensing means is attached to the primary windup drum driving
means.
[0011] According to another embodiment of the present invention, an
extensional rheometer apparatus for measuring the extensional flow
response of samples of material, such as a plurality of low modulus
solid samples, comprises a primary windup drum mounted to a power
drive device for rotating the primary windup drum; a plurality of
secondary windup drums rotatably mounted in proximity to the
primary windup drum; means interconnecting the primary windup drum
to the plurality of secondary windup drums whereby rotation of the
primary windup drum by the power drive device causes the rotation
of the secondary windup drums; and a load sensing device attached
to each of the secondary windup drums for supporting each of the
secondary windup drums and measuring the response to the
extensional flow of low modulus solid samples secured to the
primary windup drum and each of the plurality of secondary windup
drums.
[0012] Further, according to the latter embodiment of the present
invention, the primary and plurality of secondary windup drums are
in substantially parallel alignment. Also, the means for
interconnecting the primary and plurality of secondary windup drums
are first and second gears individually attached to the primary and
plurality of secondary windup drums and intermeshed such that the
primary and plurality of secondary windup drums are counter
rotating and rotate at the same speed.
[0013] According to another embodiment of the present invention, an
extensional rheometer apparatus for measuring the extensional flow
response of samples of material, such as a low modulus solid
sample, comprises a primary windup drum mounted to a primary power
drive device for rotating the primary windup drum; a secondary
windup drum rotatably mounted to a secondary power drive device for
rotating the secondary windup drum in proximity to the primary
windup drum; and a load sensing device attached to the secondary
power drive device for supporting the secondary windup drum and
measuring the extensional flow response of a low modulus solid
sample secured to the primary windup drum and the secondary windup
drum. The load sensing device is secured at one end to a support
member and at the other end to the secondary power drive
device.
[0014] According to yet another embodiment of the present
invention, an extensional rheometer apparatus for measuring the
extensional flow response of samples of material, such as a of low
modulus solid samples comprises a primary windup drum mounted to a
primary power drive device for rotating the primary windup drum; a
plurality of secondary windup drums rotatably mounted to a
plurality of secondary power drive devices for individually
rotating the secondary windup drums in proximity to the primary
windup drum; and a plurality of load sensing devices, each attached
to one of the plurality of secondary power drive devices for
supporting the plurality of secondary windup drums and measuring
the extensional flow response of low modulus solid samples secured
to the primary windup drum and each of the secondary windup drums.
Each of the plurality of load sensing devices are secured at one
end to a support member and at the other end to one of the
plurality of secondary power drive devices.
[0015] According to yet another embodiment of the present
invention, a method for measuring the extensional flow response of
a material, such as a low modulus solid sample comprising the steps
of: rotating a primary windup drum with a power drive device;
rotating a secondary windup drum in proximity to the primary windup
drum; and supporting the secondary windup drum and measuring the
extensional flow response of a low modulus solid sample secured to
the primary windup drum and the secondary windup drum with a load
sensing device. The method includes the steps of rotating a
plurality of secondary windup drums in proximity to the primary
windup drum; and supporting the plurality of secondary windup drums
and measuring the extensional flow response of a plurality of low
modulus solid samples secured to the primary windup drum and the
plurality of secondary windup drums with a plurality of load
sensing devices each attached to the plurality of secondary windup
drums.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 illustrates a perspective view of a first embodiment
of the rheometer apparatus of the present invention including a
primary windup drum in parallel relation to a secondary windup drum
illustrated as mounted in a cutaway section of a mounting
bracket;
[0017] FIG. 2 illustrates a perspective view of the secondary
windup drum shown in FIG. 1 secured in a mounting bracket attached
to a vertical support frame via a load sensing device;
[0018] FIG. 3 is a cross sectional view through line 3-3 of FIG. 2
showing the secondary windup drum in a mounting bracket attached to
a vertical support frame via a load sensing device;
[0019] FIG. 4 illustrates a perspective view of an alternative
embodiment of the rheometer apparatus of the invention of FIG. 1
illustrating a primary windup drum in parallel relation to a
plurality of secondary windup drums;
[0020] FIG. 5 illustrates a side view of a second embodiment of the
present invention including a primary rotating drum with an
independent power supply in parallel relation to a secondary
rotating drum with an independent power supply;
[0021] FIG. 6 illustrates a side view of a second embodiment of the
present invention including a primary rotating drum with an
independent power supply in parallel relation to a plurality of
secondary rotating drums each with an independent power supply;
and
[0022] FIG. 7 is a graphic illustration of the top view of the
primary and secondary drums as a sample is stretched.
DETAILED DESCRIPTION OF THE INVENTION
[0023] With reference now to FIGS. 1-3, there is illustrated a
first embodiment of a rheometer apparatus 10. The rheometer
apparatus 10 has a primary windup drum 12 connected at one end 12a
to one end of a primary drive shaft 14. The opposite end of the
drive shaft 14 is mounted to a drive motor 16, such as a
conventional electrically powered motor. The primary windup drum 12
has a primary drive gear 18, typically a fine toothed, spur gear,
on the circumferential outward surface 20 of the drum.
[0024] In the illustrated embodiment, primary windup drum 12 is
illustrated as being in direct alignment with drive shaft 14. Those
skilled in the art will recognize that this alignment is not
necessary for operation of the apparatus, but is preferred to make
construction easier and simplify the calculations of torque.
[0025] A secondary windup drum 22 is disposed in parallel relation
to the primary windup drum 12. The secondary windup drum 22 is
supported by a support frame 24 as seen in FIGS. 1, 2 and 3. The
outward ends 22a, 22b of the secondary drum 22 can include bearings
26a and 26b respectively, to provide low frictional rotation
between the secondary drum and the support frame 24. While the
support frame 24 is illustrated with a square configuration to
completely enclose the secondary drum 22, it is within the terms of
the present invention to form the support frame with other shapes
as long as they can carry out the function as described
hereinafter. The secondary winding drum 22 has a secondary drive
gear 28, typically a fine toothed, spur gear, disposed about the
circumferential surface 30 of the secondary drum. The primary and
secondary windup drums 12 and 22 are disposed so that the primary
and secondary gears 18 and 28 intermesh so that the turning of the
primary gear causes the turning of the secondary gear.
[0026] As shown in FIGS. 1-3, the support frame 24 is affixed to a
load sensing device 34 such as a piezoelectric load cell or a
strain-gage force transducer via a support member 36. In turn the
load sensing device 34 is securely attached to a support member
32.
[0027] All of the windup drums referenced herein are typically but
not limited to axisymmetric cylinders of the same diameter. In the
case of non-axisymmetric cylinders, a non-constant rate of drum
rotation would need to be employed in order to maintain a constant
rate of extensional deformation with regards to a true strain
deformation, also referred to as a Hencky strain.
[0028] Each of the windup drums 12 and 22 have associated therewith
a securing means (not shown), such as a sample cradling pin or
other clamping mechanism, as shown and described in WO00/28321,
which is incorporated in its entirety by reference herein, to
attach a filament to the drums as required to carry out the
measurements desired. It can be appreciated in viewing FIG. 1 that
the drive motor 16 turns the drive shaft 14 which in turn rotates
the primary winding drum 12 and its attached primary drive gear 18
in a clockwise direction as indicated by arrow 44. Gear 18, in
turn, turns gear 28 in a counter-clockwise direction as indicated
by arrow 46, which causes rotation of the secondary windup drum 22.
The rotation of the primary and secondary drums 12 and 22 stretches
the sample material 50 of a polymer, elastomer, or compound. The
resistance provided by the stretched sample 50 to the turning of
the secondary windup drum 22 imparts a force on the support frame
24 via the bearings 26a and 26b, which is then imparted through the
support member 36 into the load sensing device 34, the latter being
fixedly attached to support member 32. The force imparted into the
load sensing device 34 tends to move the load sensing device in a
direction that follows the rotation of the primary windup drum 12.
The tendency of the support structure 24 to turn in the motion of
the primary drum rotation (even though it cannot turn because it is
secured to support member 32) creates a load on the support member
36 and load sensing device 34 that can be measured. The apparatus
in each of the embodiments of the present invention is designed so
that support member 36 does not actually move, but a load on
support member 36 activates the load sensing device which, through
a closed feedback loop in the apparatus, develops a current which
tends to counteract the load imposed on support member 36 by the
secondary windup drum 22 in the support frame 24, and the current
required to counteract this load is measured, thereby measuring the
load generated. Such force rebalance systems are well known to
those skilled in the art. Other techniques of measuring loads are
known to those skilled in the art, and such other techniques can be
used with the apparatus of the invention.
[0029] In the operation of the apparatus 10 of the first embodiment
of the invention, the ends of a prepared sample 50 are first
secured to the windup drums 12 and 22 by a securing means. In the
case of constant radius windup drums, constant rotation of the
windup drums 12 and 22 imparts a constant, uniform extensional
deformation rate to the unsupported length of the prepared sample
50. The zone of deformation, or stretch, for the material sample is
defined by the tangent line spanning the windup drum pair. The
extensional deformation of the material sample offers a resistance
to elongation (related to the extensional flow properties of the
material) which in turn offers a resistant load on the secondary
drum that is resolved with the associated sensing means. Thus by
measuring the resulting force that is perpendicular to the primary
axis of deformation on the secondary drum 22, the extensional
stress, or viscosity, of the associated material being deformed can
be determined for a given rate of extensional deformation.
[0030] In the special case for which the drive motor 16 has
incorporated therein a means of resolving the resistant torque on
the motor for a given rate of rotation, the resultant torque
imparted on the primary windup drum 12 may be resolved to determine
the resistance to elongation of the sample. In any case, the
extensional deformation of the stretched sample 50 offers a
resistance to deformation that is related to the extensional
viscosity of the sample, which in turn offers a resistance to the
primary drum rotation in the form of a resulting torque on the
drive motor 16. By measuring the resultant torque transmitted to
the drive motor 16, the extensional viscosity of the prepared
sample 50 may be calculated for a given rate of extensional
deformation.
[0031] While not shown, it is within the scope of the present
invention to place the apparatus 10 within an environmental
chamber, that can be used to heat or cool the sample as desired so
that extensional flow properties of a material may be calculated as
a function of extensional deformation rate and temperature. The
environmental chamber is designed to measure rheology of samples
from -70 degrees Centigrade (C.) to 300 degrees Centigrade.
Measurements at lower temperatures are designed to measure
extensional rheology as it relates to Tg (glass transition) of the
sample and the extensional flow of the materials at higher
temperatures is related to the melts/viscosity of the sample. The
environmental chamber can be in the form of an evan or an oil bath
or any other means known to those skilled in the art for
controlling the physical state of a sample.
[0032] Referring to FIG. 4, there is illustrated a second
alternative embodiment of the present invention wherein rheometer
system 58 is provided with a single primary drive shaft 60 that is
designed to operate a plurality of secondary winding drums 62, 64,
66, 68 (62-68). The primary drive shaft 60 includes a plurality of
spaced primary drive gears 70a, 70b, 70c, 70d. As in the first
embodiment shown in FIGS. 1-3, the primary drum 60 is operated by a
drive motor 72, which can be operationally connected to the primary
drum 60 by any means such as a drive shaft 74. Each of the
secondary drums 62-68 have secondary gears 76a, 76b, 76c, 76d,
respectively, which mesh with the primary gears 70a-70d,
respectively. As discussed with respect to the first embodiment,
each of the secondary drums 62-68 is mounted within a support frame
80a, 80b, 80c, 80d (80a-80d), which are secured to a support member
82 via load sensing devices 84a, 84b, 84c, 84d (84a-84d),
respectively, via support members 86a, 86b, 86c, 86d (86a-86d),
respectively.
[0033] In operation of the second embodiment, as shown in FIG. 4, a
plurality of prepared samples 90a, 90b, 90c, 90d (referred
collectively as 90 herein), are secured to the primary and
secondary windup drums 60 and 62-68, respectively. While four
secondary drums 62-68 are illustrated, it is within the terms of
the invention to have more or fewer secondary drums as desired.
Further, while it is illustrated that all of the primary and
secondary drums 60 and 62-68, respectively, are loaded with the
prepared samples 90, it is also within the terms of the invention
to operate the system 58 with any number of the secondary windup
drums 62-68 as desired. In the case where constant radius windup
drums are used, the constant rotation of the primary and secondary
windup drums 60 and 62-68 imparts a constant, uniform extensional
deformation rate to the unsupported pre-gauge length of the
prepared samples 60. The extensional deformation of the stretched
samples 60 offers a resistance to deformation which is related to
the extensional viscosity of the samples, which in turn offers a
resistance to the rotation of the secondary drums 62-68 in the form
of a resulting load on the load sensing devices 84a-84d. By
measuring the resulting force on the load sensing devices 84a-84d,
the extensional viscosity of each of the material samples 90a-90d
respectively, can be calculated for a given rate of extensional
deformation and temperature. Again, as with the first embodiment,
it is within the scope of the present invention to place the system
58 within an environmental chamber (not shown), which can be used
to heat or cool the sample as desired.
[0034] Referring to FIG. 5, there is illustrated a third embodiment
of the invention. The rheometer apparatus 100, as shown in FIG. 5,
includes a primary windup drum 102 connected at one end to a drive
shaft 104. The drive shaft 104 itself is mounted to a drive motor
106, such as a conventional, electrically powered motor of the type
described with regards to the first embodiment of the
invention.
[0035] A secondary windup drum 110 is disposed in parallel to the
primary windup drum 102. The secondary windup drum 110 is supported
on a drive shaft 112, which is attached at an opposite end to a
drive motor 114 of a desired type, such as electrically powered
motor 106. The motor 114 is affixed to a load sensing device 116
(compare load sensing device 34), via a support member 118. The
load sensing device 116 is secured to a support member 120. Each of
the windup drums 102 and 110 have associated therewith securing
means such as disclosed in WO00/28321, to attach a material sample
122 of the type sample described herein before as required to carry
out the measurements desired. Similar to the first embodiment, the
motors 106 and 114 are operated to turn the drive shafts, 104 and
112, respectively, and the primary and secondary winding drums 102,
110, respectively, in opposite directions. For example, the primary
drum 102 can turn in a clockwise direction while the secondary drum
110 can turn in a counter-clockwise direction as shown by the
arrows. The rotation of the primary and secondary drums 102 and
110, respectively, causes the sample 122 of a polymer, elastomer or
compound to stretch. The resistance provided by the stretched
sample 122 to the turning of the secondary windup drum 110 imparts
a force on the motor 114, which is then imparted through the
support member 118 into the load sensing device 116, the latter
being fixedly attached to support member 120. The load on motor 114
that is transmitted through support member 118 may be resolved by
load sensing device 116 with respect to support member 120 as a
force tending to bring secondary drum 110 towards primary drum 102
or as a resistant torque tending to hinder the rotation of
secondary drum 110. This force or torque response can be measured
from the load sensing device 116 by conventional means.
[0036] In operation of the rheometer apparatus 100 of the third
embodiment of the invention, the ends of the prepared sample 122
are secured to the primary and secondary drums 102 and 110.
Constant rotation of constant radius windup drums 102, 110 imparts
a constant, uniform extensional deformation rate to the unsupported
pre-gauge length of the prepared sample 122. The extensional
deformation of the stretched sample 122 offers a resistance to
deformation which is related to the extensional viscosity of the
sample, which in turns offers a resistance to the drum 110 rotation
in the form of a resulting load on the load sensing device 116. By
measuring the resulting load on the load sensing device 116, the
extensional viscosity of the material sample can be calculated for
a given extensional deformation rate and temperature.
[0037] Since the windup drums 102, 110 in the device 100 described
in the embodiment of FIG. 5 of the present invention can be mounted
directly on the driving means 106, 114, respectively, the use of
bearings for the windup drums is not required and thus the
frictional contribution from the drum rotation is obviated.
Furthermore, since the primary and secondary drums 102, 110,
respectively have unique drive systems, the frictional contribution
from any mechanical drive coupling (i.e. intermeshing gears) on the
measured signal may also be obviated.
[0038] Material sample strips/fibers 122 are prepared and secured
against a set of mated primary and secondary windup drums that
comprise an extensional rheometer system 100. The rheometer may be
comprised of either a single cell or multiple cells in which
multiple samples may be characterized simultaneously. The drive
means for the primary drum may be common to each to the multiple
cells whereas each secondary drum and drive means are unique to a
cell. The secondary drum of each cell rotates counter to the
rotation of the primary drum and has associated with it a sensing
means for resolving the load on the secondary drum. Rotation of the
primary and secondary windup drums imparts a uniform extensional
deformation to the secured material sample associated with each
rheometer cell. The zone of deformation, or stretch, for each
material sample is defined by the tangent line spanning each windup
drum pair. The extensional deformation of the material sample
offers a resistance to elongation (related to the extensional flow
properties of the material) which in turn offers a resistant load
on the secondary drum that is resolved with the associated sensing
means. Thus by measuring the resulting load on each secondary drum,
the extensional stress, or viscosity, or each associated material
being deformed can be determined for a given rate of extensional
deformation. Each cell may be accommodated within an environmental
chamber such that the extensional flow properties of materials may
be characterized with respect to temperature.
[0039] Referring to FIG. 6, there is shown an alternative
embodiment of a rheometer system 128 incorporating the invention
shown in FIG. 5. In the embodiment of FIG. 6, there is a single
primary winding drum 130 designed to operate in conjunction with a
plurality of secondary winding drums 132, 134, 136. As in the
embodiment shown in FIG. 5, the primary winding drum 130 is
operated by a drive motor 138 (compare 106) connected to the
primary drum 130 by means such as a drive shaft 140. Each of the
secondary winding drums 132, 134, 136 has a separate drive motor
142, 144, 146, respectively, (compare 114) adapted to rotate their
respective secondary winding drum through a drive shaft 146a, 146b,
146c, respectively. As in the embodiment shown in FIG. 5, each of
the drive motors 142, 144, 146, which act to support and turn the
secondary winding drums 132, 134, 136, respectively, is secured to
a load sensing device 148a, 148b, 148c (collectively known as 148),
respectively, by a support member 150a, 150b, 150c, respectively.
Each of the load sensing devices 148a, 148b, 148, (compare 116 in
FIG. 5) and are secured to a support member 152. Each of the
secondary winding drums 132, 134, 136 operate independently of each
other so that any or all of the plurality of secondary winding
drums can be used at the same time or at different times. As shown
in FIG. 6, the ends of the prepared samples 160a, 160b, 160c are
secured to the primary and secondary drums 130 and 132-136,
respectively, by a securing means. As described in the embodiment
shown in FIG. 5, the rotation of the primary and secondary drums
130 and 132-136, respectively, cause the sample of a polymer
elastomer compound to stretch. The resistance provided by the
stretched samples 160a, 160b, 160c to the turning of the secondary
windup drums 132-136, respectively, imparts a force on the motors
142, 144, 145, which in turn is imparted through the support
members 150a, 150b, 150c, respectively, into the load sensing
devices 148a, 148b, 148c, respectively. The latter load sensing
devices 148a, 148b, 148c are attached to the support member 152 so
that the force imparted into each of the load sensing devices moves
the load sensing device and creates a torque with respect to the
support member 152. The torque can be measured from the load
sensing devices 148a, 148b, 148c by conventional means. The primary
motor 138 and the secondary motors 142, 144, 145 are operated to
provide constant speed of rotation of the primary and secondary
winding drums 130 and 132-136, respectively, to impart a constant,
uniform extensional deformation rate to the unsupported pre-gauge
length of the prepared samples 160a, 160b, 160c. The zone of
deformation, or stretch, for each material sample is defined by the
tangent line spanning each windup drum pair. The extensional
deformation of the material sample offers a resistance to
elongation (related to the extensional flow properties of the
material) which in turn offers a resistant load on the secondary
drum that is resolved with the associated load sensing device. Thus
by measuring the resulting load that is parallel to the primary
axis of deformation on each secondary drum, the extensional stress,
or viscosity, or each associated material being deformed can be
determined for a given rate of extensional deformation. The
extensional deformation of the material samples 160a, 160b, 160c
offers a resistance to deformation which is related to the
extensional viscosity of the samples. This resistance, in turn,
offers a resistance to the secondary drum rotation in the form of a
resulting load on the load sensing devices 148a, 148b, 148c. By
measuring the resulting loads on each of the load sensing devices
148a, 148b, 148c, the extensional viscosity of the material samples
160a, 160b, 160c can be calculated for a given extensional
deformation rate and temperature.
[0040] While three secondary winding drums 132, 134, 136 are shown
in FIG. 6, it is within the terms of the present invention to use
any number of secondary winding drums as desired. Also, the
rheometer system 128 shown in FIG. 6 can be placed in an
environmental chamber, as described hereinbefore.
[0041] Since the primary windup drum 130 and the secondary windup
drums 132, 134, 136 of the extensional rheometer device 128
described with respect to the embodiment of FIG. 6 of the present
invention can be mounted directly on the driving means 138 and
142,144 and 145, respectively, the use of shaft bearings for the
windup drums is not required and thus the frictional contribution
from the drum rotation is obviated. Furthermore, since the primary
and secondary drums 130 and 132,134,136, respectively, have unique
drive systems, the frictional contribution from any mechanical
drive coupling (i.e. intermeshing gears) on the measured signal may
also be obviated.
[0042] Material sample strips/fibers 160a,160b,160c are prepared
and secured against a set of mated primary and secondary windup
drums 130 and 132,134,136, respectively, that comprise the
extensional rheometer system 128. The rheometer system may be
comprised of either a single set of drums, as shown in FIG. 5 or
multiple drums, as shown in FIG. 6. In the latter embodiment,
multiple samples may be characterized simultaneously.
[0043] The invention is further illustrated with reference to the
following example.
EXAMPLE 1
[0044] The apparatus 10 shown in FIGS. 1-3 is used for illustrative
purposes in this example.
[0045] Both ends of an uncured polymer filament 50 are secured by
the sample securing clamps of the equal diameter, primary and
secondary windup drums 12,22, respectively, of the extensional
rheometer 10. A motor 16 rotating at a fixed rotational rate drives
the primary windup drum 12 and a fine toothed, spur gear 18 on the
same shaft 14. This spur gear 18 intermeshes with a similar spur
gear 28 on the secondary windup drum 22.
[0046] Since both spur gears 18 and 28 are similar, motion of the
primary drum 12 drives an equal but opposite rotation of the
secondary drum 22. The secondary drum 22 is affixed with precision
bearings 26a, 26b to the frame support 24. The constant rotational
speed (.OMEGA.) of the windup drums 12 and 22 of equal radius (R)
imparts a constant, uniform extensional true strain rate, or Hencky
strain rate ({dot over (.epsilon.)}) to the unsupported length (L)
of the sample 50 such that:
{dot over (.epsilon.)}=2.OMEGA.R/L
[0047] as illustrated graphically in FIG. 7.
[0048] The extension of the sample 50 offers a resistance to
deformation due to the extensional viscosity .eta..sub.E(t) of the
material, which in turn offers a resistance to the drum rotation in
the form of torque T.sub.E. The extensional viscosity of the
material can be expressed in the following relationship:
.eta..sub.E(t)=.sigma..sub.E(t)/{dot over (68
)}=F.sub.E(t)/A(t)/{dot over (.epsilon.)}
[0049] where .sigma..sub.E(t) is the instantaneous extensional
stress in the unsupported sample, F.sub.E(t) is the instantaneous
force required to stretch the unsupported sample, and A(t) is the
instantaneous cross-sectional area of unsupported sample. The
resultant torque acting on the drums 12 and 22 may then be
expressed as:
T.sub.E(t)=F.sub.E(t)2R
[0050] Both of these expressions may be combined to yield:
.eta..sub.E(t)=T.sub.E(t)/(2R{dot over (.epsilon.)}A(t))
[0051] By measuring either the resultant torque on the drive drum
or the load monitored by the sensing device 34, the extensional
viscosity of the material sample may be calculated for a given
extensional deformation rate and temperature.
[0052] T.sub.E can be resolved by a summation of torques about the
axis of rotation of the primary windup drum, point 0 from FIG. 7.
During stretch, the resistance of the sample to extend imparts a
torque on the gear teeth which in turn imparts a resultant torque,
T.sub.R, on the system that is borne by the frame support 24, the
support member 36, and the load sensing device 34 assembly. Since
the bearings 26a, 26b and intermeshing gears 18, 28 also offer
resistance to rotation, a summation of torques yields:
.SIGMA.T.sub.0=0=T.sub.R-T.sub.E-T.sub.Gears-T.sub.Bearings=T.sub.R-T.sub.-
E-T.sub.Friction
[0053] Thus, the above expression for .eta..sub.E(t) can be
rewritten as:
.eta..sub.E(t)=(T.sub.R(t)-T.sub.Friction)/(2R{dot over
(.epsilon.)}A(t))
[0054] where T.sub.R(t) is the instantaneous resultant torque on
the system, and T.sub.Friction is the torque losses from the
bearings and gears which can be determined from calibration. The
instantaneous resultant torque, T.sub.R(t), may then be resolved by
monitoring the instantaneous torque on the primary windup drum
motor 16 or by monitoring the instantaneous force on the load
sensing device 34 and multiplying by the appropriate moment arm, L,
about the axis of rotation of the primary windup drum, point 0, as
illustrated in FIG. 7.
[0055] Now for a sample in simple extension, A(t) can be expressed
as:
A(t)=A.sub.O exp (-.epsilon.)
[0056] where A.sub.O is the original cross-sectional area prior to
sample extension, and .epsilon. is the true strain in simple
extension. For a constant true strain rate of deformation in simple
extension, A(t) can be rewritten as:
A(t)=A.sub.O exp (-{dot over (.epsilon.)}t)
[0057] where {dot over (.epsilon.)} is the constant true strain
rate of deformation in simple extension. Substituting the initial
expression for {dot over (.epsilon.)},A(t) can be rewritten as:
A(t)=A.sub.O exp (-2.OMEGA.R t/L)
[0058] Since .OMEGA.=d(.theta.(t))/dt where .theta.(t) is the
angular rotation of the primary windup drum 12 as a function of
time, then for a constant rotational drum speed, .OMEGA. may be
expressed as:
.OMEGA.=(.theta..sub.2-.theta..sub.1)/(t.sub.2-t.sub.1)
[0059] If it is assumed that .theta..sub.1=0 at t.sub.1=0 and that
a constant rotational speed is achieved instantaneously then the
expression for .OMEGA. simplifies to:
.OMEGA.=.theta..sub.2/t.sub.2=.theta.(t)/t
[0060] Assuming no-slip of the fiber on the drum, the above
expression can be substituted into the expression for A(t) and the
following can be obtained:
A(t)=A.sub.O exp(-2.theta.(t)R/L)
[0061] Thus, the resulting expression for the instantaneous
cross-sectional area of a sample is only a function of the angular
rotation of the primary windup drum at a given time, t. Beyond the
realm of validity of the aforementioned assumptions, however, more
rigorous empirical methods for determining instantaneous fiber
cross-sectional area should be applied and are well known to those
skilled in the art.
[0062] Note that each windup drum 12 and 22 can be threaded to
allow for fiber alignment and multiple drum rotations to allow for
very large true strains as described in Serial No. WO00/28321. In
doing so, however, the increased extensional deformation per drum
revolution must be accounted for in the expression for extensional
deformation rate, {dot over (.epsilon.)}. In addition, a
non-circumferential force component must be accounted for in the
torque measurement, T.sub.R(t).
[0063] While the invention has been specifically illustrated and
described, those skilled in the art will recognize that the
invention may be variously modified and practiced without departing
from the concepts of the invention. The scope of the invention is
limited only by the following claims.
* * * * *