U.S. patent application number 09/828715 was filed with the patent office on 2002-11-21 for method of joining two or more substrates with a seam.
This patent application is currently assigned to Clemson University. Invention is credited to Bennett, Robert E., Frederick, Brian, Jarvis, Christine W..
Application Number | 20020172792 09/828715 |
Document ID | / |
Family ID | 25252550 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020172792 |
Kind Code |
A1 |
Jarvis, Christine W. ; et
al. |
November 21, 2002 |
Method of joining two or more substrates with a seam
Abstract
A method for joining two or more substrates with a seam is
provided. The seam is formed with a thermoplastic tape that is
capable of forming an adhesive bond and a physical bond with a
substrate. For instance, in one embodiment, the thermoplastic tape
is formed from a polyurethane film. In addition, the seam can be
utilized in a flat configuration or folded into a variety of
different shapes, such as in a z-shaped configuration. As a result
of the present invention, it has been discovered that a seam can be
formed to have improved strength without substantially sacrificing
the desired functional properties of the substrate materials.
Inventors: |
Jarvis, Christine W.; (Six
Mile, SC) ; Bennett, Robert E.; (Westminster, SC)
; Frederick, Brian; (Greenville, SC) |
Correspondence
Address: |
DORITY & MANNING, P.A.
POST OFFICE BOX 1449
GREENVILLE
SC
29602-1449
US
|
Assignee: |
Clemson University
|
Family ID: |
25252550 |
Appl. No.: |
09/828715 |
Filed: |
April 6, 2001 |
Current U.S.
Class: |
428/57 ; 156/157;
156/197; 156/227; 156/91 |
Current CPC
Class: |
B29C 66/91931 20130101;
B29C 66/435 20130101; B29C 66/929 20130101; B29K 2021/003 20130101;
B29K 2105/0836 20130101; Y10T 428/24959 20150115; B29C 66/91933
20130101; B29C 66/71 20130101; C09J 5/10 20130101; B29C 66/43
20130101; B29C 66/71 20130101; B29C 66/71 20130101; B29C 66/71
20130101; B29C 65/8253 20130101; B29K 2105/0845 20130101; B29C
66/71 20130101; B29C 66/73116 20130101; B29C 66/71 20130101; B29K
2101/12 20130101; B29C 65/18 20130101; B29C 65/08 20130101; B29C
66/729 20130101; B29C 65/8215 20130101; B29C 65/4815 20130101; Y10T
156/1051 20150115; B29C 65/5021 20130101; B29C 65/5085 20130101;
B29K 2007/00 20130101; B29K 2105/0854 20130101; B29C 65/04
20130101; Y10T 428/192 20150115; B29C 66/712 20130101; B29C 66/1122
20130101; B29C 66/71 20130101; B29C 66/83413 20130101; B29C
66/91411 20130101; B29K 2711/12 20130101; B29C 65/16 20130101; B29C
65/5071 20130101; B29C 66/919 20130101; B29C 66/91935 20130101;
B29K 2021/00 20130101; B29K 2313/00 20130101; Y10T 428/2419
20150115; B29C 66/73115 20130101; B29K 2311/10 20130101; Y10T
156/1003 20150115; Y10T 428/19 20150115; B29K 2067/00 20130101;
B29K 2023/22 20130101; B29K 2077/00 20130101; B29K 2075/00
20130101; B29K 2023/12 20130101; B29K 2023/06 20130101 |
Class at
Publication: |
428/57 ; 156/91;
156/157; 156/197; 156/227 |
International
Class: |
B32B 003/00; B32B
007/04 |
Claims
What is claimed is:
1. A method of forming a seam between substrates comprising:
providing a first substrate having an upper surface and a lower
surface, said upper and said lower surfaces of said first substrate
defining at least one edge; providing a second substrate having an
upper surface and a lower surface, said upper and said lower
surfaces of said second substrate defining at least one edge;
overlapping said edge of said first substrate with said edge of
said second substrate; positioning a first tape portion adjacent to
said first substrate such that said first tape portion is placed in
operative communication with said upper and said lower surfaces of
said first substrate, said first tape portion comprising a
thermoplastic material that is melt-flowable when subjected to a
certain amount of heat and pressure; positioning a second tape
portion adjacent to said second substrate such that said second
tape portion is placed in operative communication with said upper
and lower surfaces of said second substrate, said second tape
portion comprising a thermoplastic material that is melt-flowable
when subjected to a certain amount of heat and pressure; forming an
adhesive bond and a physical bond between said first tape portion
and said first substrate and between said second tape portion said
second substrate.
2. A method as defined in claim 1, wherein said first tape portion
and said second tape portion are attached together.
3. A method as defined in claim 1, wherein said first tape portion
and said second tape portion are continuous.
4. A method as defined in claim 1, wherein said first tape portion
and said second tape portion are unattached.
5. A method as defined in claim 1, further comprising heating said
first tape portion to a first predetermined temperature.
6. A method as defined in claim 5, wherein said first predetermined
temperature is between about 10.degree. C. below the thermal
melting temperature of said thermoplastic material to about
50.degree. C. above the thermal melting temperature of said
thermoplastic material.
7. A method as defined in claim 1, further comprising heating said
second tape portion to a second predetermined temperature.
8. A method as defined in claim 7, wherein said second
predetermined temperature is between about 10.degree. C. below the
thermal melting temperature of said thermoplastic material to about
50.degree. C. above the thermal melting temperature of said
thermoplastic material.
9. A method as defined in claim 1, further comprising subjecting
said first tape portion and said second tape portion to
pressure.
10. A method as defined in claim 9, wherein said pressure is
between about 40 pounds per square inch to about 120 pounds per
square inch.
11. A method as defined in claim 1, further comprising subjecting
said first tape portion to simultaneous heat and pressure and
subjecting said second tape portion to simultaneous heat and
pressure.
12. A method as defined in claim 1, wherein said first substrate
and said second substrates are fabrics.
13. A method as defined in claim 1, wherein at least one of said
tape portions contains multiple layers.
14. A method as defined in claim 12, wherein one of said layers
contains a thermoplastic material having a first thermal melting
temperature and another of said layers contains a thermoplastic
material having a second thermal melting temperature, said second
thermal melting temperature being greater than said first thermal
melting temperature.
15. A method as defined in claim 1, further comprising folding said
tape portions into a certain shape.
16. A method as defined in claim 15, wherein said tape portions are
folded into a z-shaped configuration.
17. A method as defined in claim 15, wherein said tape portions are
folded prior to being placed adjacent to said first substrate and
said second substrate.
18. A method as defined in claim 15, wherein said tape portions are
folded after being placed adjacent to said first substrate and said
second substrate.
19. A method as defined in claim 1, further comprising imparting a
three-dimensional topography on at least one of said surfaces of
said first substrate.
20. A method as defined in claim 1, further comprising imparting a
three-dimensional topography on at least one of said surfaces of
said second substrate.
21. A method as defined in claim 1, wherein said edge of at least
one of said substrates is non-linear.
22. A method of forming a seam between substrates comprising:
providing a first substrate having an upper surface and a lower
surface, said upper and said lower surfaces of said first substrate
defining at least one edge; providing a second substrate having an
upper surface and a lower surface, said upper and said lower
surfaces of said second substrate defining at least one edge;
overlapping said edge of said first substrate with said edge of
said second substrate; positioning a first tape portion adjacent to
said first substrate such that said first tape portion is placed in
operative communication with said upper and said lower surfaces of
said first substrate, said first tape portion comprising a
thermoplastic material that is melt-flowable when subjected to a
certain amount of heat and pressure; positioning a second tape
portion adjacent to said second substrate such that said second
tape portion is placed in operative communication with said upper
and lower surfaces of said second substrate, said second tape
portion comprising a thermoplastic material that is melt-flowable
when subjected to a certain amount of heat and pressure; folding
said tape into a z-shaped configuration; subjecting said first tape
portion to simultaneous heat and pressure; subjecting said second
tape portion to simultaneous heat and pressure; and forming an
adhesive bond and a physical bond between said first tape portion
and said first substrate and between said second tape portion said
second substrate.
23. A method as defined in claim 22, wherein said tape portions are
folded prior to being placed adjacent to said first substrate and
said second substrate.
24. A method as defined in claim 22, wherein said tape portions are
folded after being placed adjacent to said first substrate and said
second substrate.
25. A method as defined in claim 22, wherein said first substrate
and said second substrates are fabrics.
26. A method as defined in claim 22, further comprising imparting a
three-dimensional topography on at least one of said surfaces of
said first substrate.
27. A method as defined in claim 22, further comprising imparting a
three-dimensional topography on at least one of said surfaces of
said second substrate.
28. A method as defined in claim 22, wherein said edge of at least
one of said substrates is non-linear.
29. A seam for joining two or more substrates of an article, said
seam comprising: a first substrate having an upper surface and a
lower surface, said upper and said lower surfaces of said first
substrate defining at least one edge; a second substrate having an
upper surface and a lower surface, said upper and said lower
surfaces of said second substrate defining at least one edge, said
edge of said second substrate overlapping said edge of said first
substrate; a first tape portion comprising a thermoplastic material
that is melt-flowable when subjected to a certain amount of heat
and pressure, said first tape portion being adhesively and
physically bonded to said upper and said lower surfaces of said
first substrate; a second tape portion comprising a thermoplastic
material that is melt-flowable when subjected to a certain amount
of heat and pressure, said second tape portion being adhesively and
physically bonded to said upper and said lower surfaces of said
second substrate.
30. A seam as defined in claim 29, wherein said first and said
second substrates are fabrics.
31. A seam as defined in claim 29, wherein said edge of at least
one of said substrates is non-linear.
32. A seam as defined claim 29, wherein at least one of said
surfaces of said first substrate has a three-dimensional
topography.
33. A seam as defined claim 29, wherein at least one of said
surfaces of said second substrate has a three-dimensional
topography.
34. A seam as defined in claim 29, wherein at least one of said
tape portions comprises polyurethane.
35. A seam as defined in claim 29, wherein at least one of said
tape portions contains multiple layers.
36. A seam as defined in claim 35, wherein one of said layers
contains a thermoplastic material having a first thermal melting
temperature and another of said layers contains a thermoplastic
material having a second thermal melting temperature, said second
thermal melting temperature being greater than said first thermal
melting temperature.
37. A seam as defined in claim 29, wherein said tape portions form
a z-shaped configuration.
38. A seam as defined in claim 29, wherein said first tape portion
and said second tape portion are attached together.
39. A seam as defined in claim 29, wherein said first tape portion
and said second tape portion are continuous.
40. A seam as defined in claim 29, wherein said first tape portion
and said second tape portion are unattached.
Description
BACKGROUND OF THE INVENTION
[0001] Separate sheets of materials, such as fabrics, have been
traditionally attached together for a variety of purposes using
seams that were stitched or sewn into the fabrics. However, the
stitching of seams into fabrics can be a relatively slow, expensive
process that is undesired in some applications. Moreover, the use
of sewn stitches may be completely undesired for certain types of
materials, such as barrier fabrics, that require the seam area to
also retain a barrier function.
[0002] Thus, in response to such problems, various other methods
for attaching separate fabrics have been developed. For instance,
various thermal methods that rely on the melting behavior of the
fabrics have been utilized to produce seams. Specifically, the
fabric and seam are heated to a certain temperature such that the
materials of the fabric and seam begin to melt. Upon melting,
thermal bonds are formed at the crossover points of the melted
fabric and seam fibers. Other methods have also utilized adhesives,
such as solvent-based liquid adhesives or glues. However, one
problem with these techniques is that the seams are subject to
stress fracture at low temperatures, and even at elevated
temperatures, the divergent thermal melting points cause the
resulting seam to be relatively weak.
[0003] In an attempt to improve strength, some methods have also
utilized adhesive and/or thermal methods in conjunction with a
conventional sewn seam. For instance, one such method includes
sewing a seam, such as a lap seam or double-felled needle seam,
between two fabrics. Thereafter, one piece of a tape is placed in
its entirety only on the upper surface of the first fabric, while
another piece of tape is placed in its entirely only on the lower
surface of the second fabric. The tapes are then sealed under heat
and pressure. Nevertheless, one problem with such a process is that
it is relatively inefficient and costly. In particular, during
manufacturing, a seam must be first sewn into the substrates and
then the tapes are applied. Such multiple tasks add manufacturing
costs and raw material costs. In addition, holes are often formed
in the substrate by the needles during sewing. Although the tape
can sometimes seal the needle holes, it is still possible that the
fill-in might be incomplete. Unfortunately, the presence of any
holes in a substrate can be undesirable for certain applications,
such as when the substrate is used as a barrier fabric.
[0004] As such, a need currently exists for an improved method of
forming a relatively strong seam between two or materials.
SUMMARY OF THE INVENTION
[0005] In accordance with one embodiment of the present invention,
a method of forming a seam between substrates (e.g., fabrics) is
provided. For example, the method includes providing a first
substrate and a second substrate. Each substrate has an upper
surface and a lower surface that define at least one edge.
[0006] A first tape portion is placed adjacent to the first
substrate such that the tape portion is placed in operative
communication with the upper and lower surfaces of the first
substrate. Further, a second tape portion is placed adjacent to the
second substrate such that the second tape portion is placed in
operative communication with the upper and lower surfaces of the
second substrate. Each tape portion comprises a thermoplastic
material that is melt-flowable when subjected to a certain amount
of heat and pressure. For example, in one embodiment, the tape
contains polyurethane.
[0007] In addition, the method also includes forming an adhesive
bond and a physical bond between the first tape portion and the
first substrate and between the second tape portion the second
substrate. An "adhesive bond" generally refers to a bond that
results from attractive forces between two or more materials. For
instance, adhesive bonds may sometimes result from "dipole-dipole
forces" between materials, which are a type of van der Waals force
that occurs upon the interaction of the dipole moments of two polar
molecules. In addition, a "physical bond" can refer to the physical
intermingling of a material within the interstices of a
substrate.
[0008] In some embodiments, the method can also include heating the
first tape portion and/or the second tape portion to a certain
predetermined temperature. For example, in some embodiments, the
first tape portion and/or the second tape portion can be heated to
a temperature of between about 10.degree. C. below the thermal
melting point of the thermoplastic material to about 50.degree. C.
above the thermoplastic material. Besides being heated, the first
and/or second tape portions can also be subjected to a certain
pressure. For example, in some embodiments, the first and/or second
tape portions can be subjected to a pressure of between about 40
pounds per square inch to about 120 pounds per square inch.
[0009] If desired, the tape portions may also be folded or shaped
before and/or after being placed adjacent to the first and second
substrates. For example, in one embodiment, the tape portions can
be folded into a z-shaped configuration.
[0010] In accordance with another embodiment of the present
invention, a seam is provided that includes a first substrate and a
second substrate. Each substrate has an upper surface and a lower
surface that defines at least one edge. In addition, the seam
comprises a first tape portion and a second tape portion that are
adhesively and physically bonded to the first substrate and the
second substrate, respectively.
[0011] Other features and aspects of the present invention are
discussed in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of one embodiment of a tape
that can be used to form a seam in accordance with the present
invention;
[0013] FIG. 2 is a perspective view of one embodiment of a folded
tape used to form a seam in accordance with the present
invention;
[0014] FIG. 3 is a perspective view illustrating one embodiment of
the present invention for forming a seam between two substrates
using the tape of FIG. 2;
[0015] FIG. 4 illustrates one embodiment of a seam formed according
to the present invention;
[0016] FIG. 5 illustrates one embodiment of a multi-layered tape
used form a seam in accordance with the present invention; and
[0017] FIG. 6 are SEM photomicrographs of a seam formed according
to one embodiment of the present invention in which FIG. 6A is a
seam formed by a polyurethane bilayer thermoplastic tape bonded at
380.degree. F., shown at a magnification of .times.100, and FIG. 6B
is the seam shown in FIG. 6A at a magnification of .times.200.
[0018] Repeat use of reference characters in the present
specification and drawings are intended to represent same or
analogous features or elements.
DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS
[0019] It is to be understood by one of ordinary skill in the art
that the present discussion is a description of exemplary
embodiments only, and is not intended as limiting the broader
aspects of the present invention, which broader aspects are
embodied in the exemplary construction.
[0020] In general, the present invention is directed to a method of
joining two or more substrates with a thermoplastic tape. For
example, a thermoplastic tape used in the present invention is
capable of forming both an adhesive bond and a physical bond with a
substrate. As a result, it has been discovered that the tape can
form a seam between two substrates that has excellent tensile
strength in comparison to conventional seams. In addition, such
enhanced tensile strength can be achieved without having a
substantial adverse affect on the functional properties of the
substrates (e.g., barrier properties, etc.).
[0021] A variety of substrates can generally be joined with a
thermoplastic tape in accordance with the present invention. For
instance, some substrates that can be utilized include fabrics,
such as woven, knitted, nonwoven fabrics, or composites thereof.
When utilized, the fabrics may contain synthetic fibers, natural
fibers, or blends thereof. In addition, other materials may also be
utilized, such as elastomeric materials (natural or synthetic),
paper-based materials (e.g., natural pulp or a blend of natural and
synthetic short fibers), extruded films (e.g., films of
thermoplastic or thermoplastic elastomeric polymers), etc.
[0022] The substrates can also have any desired shape, size, or
configuration. For example, a substrate may be provided as a flat
sheet of material having linear and/or nonlinear edges. In some
instances, the substrates may also have extended lengths and/or
substantially parallel longitudinal edges. If desired, the edges of
one or more of the substrates may be finished by cutting and/or by
a selvage. In some embodiments, one or more of surfaces of a
substrate may also be coated or surface-treated with a treatment,
such as a silicon treatment, to alter or enhance the surface
properties or barrier performance of the materials. It should be
understood that the substrates described above are only examples of
some substrates that can be utilized, and that the present
invention is not limited to the use of any particular
substrate.
[0023] As mentioned above, a seam can be formed between two or more
substrates utilizing a thermoplastic tape. In general, any of a
variety of thermoplastic materials can be utilized in the
thermoplastic tape of the present invention. For instance, some
examples of suitable thermoplastic materials that can be used in
the present invention include, but are not limited to,
polyurethane, polyethylene, polypropylene, copolyesters, and the
like. In one embodiment, for example, the thermoplastic tape is
formed from an extruded polyurethane film. The thermal melting
point of the thermoplastic materials used to form the thermoplastic
tape may be the same or different than the materials used to form
the substrate(s). For example, in some instances, the substrate
materials have a thermal melting temperature that is greater than
the thermal melting temperature of the tape material(s) so that the
substrate substantially retains its structure and functional
properties upon the application of heat and pressure.
[0024] In many instances, the tape may also contain more than one
type of thermoplastic material. For example, the tape can be a
composite of a thermoplastic polymer that is blended or layered
with another thermoplastic polymer. In one embodiment, for
instance, the tape contains a blend of at least two thermoplastic
polymers that have thermal melting points that differ by at least
about 5.degree. C. In another embodiment, the tape is a layered
composite material such that one portion of the tape is formed from
a first thermoplastic polymer component, while another portion of
the tape is formed from a second thermoplastic polymer component.
For example, up to 75% of the tape width can be formed from the
first thermoplastic polymer component, while the remainder of the
tape width can be formed from the second thermoplastic polymer
component. Each polymer component may contain one or more types of
thermoplastic polymers.
[0025] Other materials may also be utilized in conjunction with the
thermoplastic polymer(s) to form the thermoplastic tape of the
present invention. For example, in some embodiments, various
materials can be coated onto one or more surfaces of the tape
and/or along the edges of the tape to enhance the ability of the
tape to bond to one or more substrates. Some examples of additional
materials that can be utilized in conjunction with a thermoplastic
polymer include, but are not limited to, solvent-based adhesives,
discrete raised beads of an adhesive material, etc.
[0026] In some embodiments, the tape may be utilized in a flat
configuration, while in other embodiments, the tape may be utilized
in a folded or shaped configuration. For example, referring to
FIGS. 2-3, one embodiment of the present invention is illustrated
in which a thermoplastic tape 10 is shown folded in a "z-shaped
configuration" to form a first section 16, a second section 17, and
a third section 18. The sections 16, 17, and 18 may be a single
continuous strip or two or more separate strips. When formed from
separate strips, such strips may be unattached (e.g., two or more
U-shaped sections) or attached using conventional techniques.
Moreover, the separate strips, when utilized, may be formed from
the same or different materials. It should be understood that the
tape 10 need not possess three sections, but can possess any number
of sections desired.
[0027] Regardless of the particular method used to construct the
section(s), in the embodiment of the z-shaped configuration
illustrated in FIG. 3, the lower surface 36 of the first section 16
faces the upper surface 27 of the second section 17, while the
lower surface 37 of the second section 17 faces the upper surface
28 of the third section 18. The tape 10 may generally be shaped or
folded, such as described above, using a variety of different
techniques. For example, in some embodiments, a thermoplastic
material can be extruded onto a forming surface that has the shape
of the desired fold. Thus, as the polymer is deposited onto the
forming surface, it naturally assumes the shape of the forming
surface. In other embodiments, the thermoplastic material can be
extruded as a flat ribbon and then folded through the use of a
series of guide bars. Once folded, light heat and pressure can be
applied to set the folded shape.
[0028] In accordance with the present invention, once the
particular thermoplastic tape and substrates are provided, they are
then placed into operative communication such that the tape can
form a seam between the substrates. In this regard, various
embodiments for placing the thermoplastic tape into operative
communication with the substrates to form a seam will now be
described in more detail. It should be understood, however, that
the embodiments discussed below are only intended to illustrate
some examples of the present invention, and that other embodiments
and techniques for placing a thermoplastic tape into operative
communication with one or more substrates are also contemplated by
the present invention.
[0029] For example, referring to FIG. 3, one embodiment of a method
of forming a seam between two substrates and a tape folded in a
z-shaped configuration is illustrated. As shown, a first substrate
11 is positioned between the lower surface 36 of the first section
16 of the tape 10 and the upper surface 27 of the second section 17
of the tape 10. In addition, the second substrate 14 is positioned
between the lower surface 37 of the second section 17 of the tape
10 and the upper surface 28 of the third section 18 of the tape 10.
In most embodiments, the substrates are positioned such that the
edges 64 and 62 are in an overlapped position, such as shown in
FIG. 3. As a result, the tape 10 can be more readily placed into
contact with the upper and lower surfaces of each of the substrates
11 and 14.
[0030] In some embodiments, the tape 10 may also be placed into
operative communication with the substrates 11 and 14 before the
tape 10 is shaped or folded. For example, in one embodiment of the
present invention, a flat thermoplastic tape 10 (See FIG. 1) is
placed in communication with two substrates 11 and 14 by
overlapping the tape 10 over certain portions of the substrates 11
and 14. Thereafter, heat and pressure can be applied to lightly
bond the flat tape 10 to the substrates 11 and 14. Once lightly
bonded, a series of guide bars can then be utilized to shape or
fold the tape 10 as desired.
[0031] After the substrates 11 and 14 have been placed in
communication with the tape 10, such as described above, they can
then be supplied to a conventional seam assembly device (not shown)
where heat and pressure are applied to seal the materials and form
the desired seam. Although not required, heat and pressure are
typically applied simultaneously. In general, any of a variety of
conventional methods for applying heat and pressure to a material
can be utilized in the present invention. For instance, some
examples of suitable methods for applying heat and pressure
include, but are not limited to, the use of heated nip rolls, hot
calendering techniques, ultrasonic welding techniques, the use of
lasers in conjunction with nip rolls, the use of certain radio
frequencies in conjunction with nip rolls, combinations thereof,
and the like.
[0032] The particular pressure and temperature utilized can vary
depending on a variety of factors, such as the materials utilized
for the tape and/or substrate(s), the size and shape of the tape
and/or substrate(s), the desired seam width, the desired strength
of the seam, the type of seam construction, etc. For example, in
most instances, the seam can be formed at a temperature that ranges
from about 10.degree. C. less than the thermal melting temperature
of the thermoplastic material of the tape 10 having the lowest
thermal melting temperature, up to a temperature of about
50.degree. C. above such thermal melting temperature. For example,
in one embodiment, a bilayer polyurethane tape having a thermal
melting point of 147.degree. C. can be heated at a processing
temperature of between about 170.degree. C. to about 195.degree. C.
In addition, the seam can be formed at a processing pressure
between about 40 pounds per square inch to about 120 pounds per
square inch. Thus, in the embodiment shown in FIG. 3, pressure can
be applied to compress the z-shaped configuration of the tape 10 by
applying a compressive force to the first section 16 and/or the
third section 18. In one embodiment, for instance, the materials
can be hand pressed at a temperature of about 110.degree. C. for
about 5 seconds. In another embodiment, the materials can be hand
pressed at a temperature of between about 170.degree. C. to about
195.degree. C. for 10 seconds.
[0033] Once heat and pressure have been applied, the tape 10 can
form a seam with the substrates 11 and 14. As described above, the
seam can have any of a variety of configurations and constructions.
For example, referring to FIG. 4, one embodiment of a seam 70 is
shown in which the seam 70 is defined by the region of the tape 10
positioned between the substrates 11 and 14.
[0034] In accordance with the present invention, it has been
discovered that the seam formed between the thermoplastic tape and
the substrates utilizes both "adhesive bonds" and "physical bonds"
to enhance the strength of the seam. An "adhesive bond" generally
refers to a bond that results from attractive forces between two or
more materials. For instance, adhesive bonds may sometimes result
from "dipole-dipole forces" between materials, which are a type of
van der Waals force that occurs upon the interaction of the dipole
moments of two polar molecules.
[0035] Besides forming an adhesive bond with the substrates,
however, it has also been discovered that the thermoplastic tape
can also form a "physical bond". For example, in one embodiment,
after being heated to a certain temperature, at least a portion of
the first section 16 and/or the second section 17 of the tape 10
can be softened or melted such that the portion becomes relatively
melt-flowable. Moreover, upon being subjected to a certain
pressure, the polymer of such melt-flowable portions of the tape 10
can be forced between the interstices of the topography of the
substrates 11 and 14. Thereafter, the seam is allowed to cool,
whereby the melt-flowable portions solidify within the interstices
of the substrates 11 and 14 to form a contiguous "physical bond"
therewith. For example, referring to FIGS. 6A-6B, certain
melt-flowable portions 88 of a polyurethane bilayer tape 10 are
shown in physical contact with two substrates 11 and 14.
[0036] Thus, because the tape is capable of forming adhesive and
physical bonds with one or more substrates, the strength of the
resulting seam can be significantly enhanced. In particular, it has
been discovered that seams formed according to the present
invention can attach substrates without the use of conventional
needle stitching, but can nevertheless possess a strength that
approximates the strength obtained using conventional stitching.
However, it should be understood that conventional stitching may be
used in conjunction with the seam of the present invention if
desired.
[0037] Moreover, it should also be understood that, in some
instances, the tape 10 may only form a small amount of physical or
adhesive bonds with a particular substrate. In particular, one
unique aspect of the present invention is the ability to form a
seam between materials that may not readily able to form adhesive
or physical bonds with the thermoplastic tape. In such instances,
it may be desired to control certain aspects of seam formation in
order to better control the extent of adhesive bonding and/or
physical bonding.
[0038] For example, in some embodiments, the processing
temperatures and/or pressures can be selected to favor certain
types of bonding. For instance, a lower processing temperature can
be utilized to produce a seam that is bonded to the substrates 11
and 14 primarily through adhesive bonding. Specifically, at lower
processing temperatures, a smaller amount of the thermoplastic
polymer(s) used in forming the tape 10 will become melt-flowable.
As a result, the tape 10 physically bonds to the substrates 11 and
14 to a lesser extent. On the other hand, at higher processing
temperatures, a greater amount of the thermoplastic polymer(s) used
in forming the tape 10 will become melt-flowable, thereby
increasing the extent of physical bonding between the tape 10 and
the substrates 11 and 14.
[0039] In addition, besides varying the processing conditions, the
particular tape and/or substrate construction can also affect the
nature of bonding between the tape 10 and the substrates 11 and 14.
For example, in certain embodiments, the substrates 11 and/or 14
may be formed from a non-fibrous or non-porous material, such as a
butyl rubber sheet. In such instances, it may be desired to
increase the surface area of the substrate to facilitate physical
bonding therewith. For example, the edge of the substrate can be
cut in a non-linear pattern to increase its surface area. Such
non-linear patterns can be provided by a "pinking" saw-tooth shear
cut or patterns created by a knife or die cutter (e.g., ultrasonic
die cutter). Furthermore, etching (e.g., plasma etching) can be
utilized to create a three-dimensional topography on one or more
surfaces of a substrate. Such a three-dimensional topography can
provide an "anchor" for the melt-flowable polymer during processing
to enhance physical bonding of the tape to the substrate.
[0040] In addition to varying the construction of the substrate(s),
the construction of the thermoplastic tape may also be varied to
control the extent of adhesive and physical bonding. For instance,
in some embodiments, a multi-layer thermoplastic tape (e.g., two
layers, three layers, etc.) can be utilized to vary the extent of
adhesive and physical bonding. Referring to FIG. 5, for example,
one embodiment a two-layer thermoplastic tape 10 is shown in which
a first layer 40 forms the upper surface 26 of the first section 16
of the tape 10 and a second layer 50 forms the lower surface 36 of
the first section 16 of the tape 10.
[0041] To alter the extent of adhesive and physical bonding, the
materials used in forming the layers 40 and 50 can be preselected
to result in a certain type of bond. For example, in one
embodiment, the layer 40 can be formed from a first material that
has a certain melting point, while the layer 50 can be formed from
a second material that has a melting point that is greater than the
melting point of the first material. Thus, certain portions of the
tape 10 can bond to a substrate primarily through adhesive bonding,
while other portions of the tape 10 can bond to a substrate
primarily through physical bonding. Specifically, in this
embodiment, the lower surface 36 of the first section 16 and the
upper surface 27 of the second section 17 can bond to the substrate
11 primarily through adhesive bonding, while the lower surface 37
of the second section 17 and the upper surface 28 of the third
section 18 can bond to the substrate 14 primarily through physical
bonding.
[0042] Such preferential bonding can be particularly useful when
the materials that form the substrate 11 differ from the materials
that form the substrate 14. For instance, in some embodiments, the
substrate 14 may be relatively "adhesively" incompatible with the
tape 10. Moreover, in other embodiments, the substrate 11 may have
a thermal melting point that is relatively incompatible with the
thermal melting point of the tape 10. Nevertheless, because the
tape 10 is capable of adhesive and physical bonding, it can still
form bonds having excellent strength with both the substrates 11
and 14.
[0043] In addition to being able to form a strong seam between two
substrates, the thermoplastic tape used in the present invention
can also protect one or more edges of the substrates. In
particular, as shown in FIG. 3, the tape 10 can substantially cover
the edge 62 of the substrate 11 and the edge 64 of substrate 14 so
that, upon the application of heat and pressure, the tape 10 forms
a seal over the edges 62 and 64. This seal can prevent various
objects from abrading or picking at the edges of the substrates,
which could eventually lead to the degradation of the bond between
the substrates.
[0044] The present invention may be better understood with
reference to the following examples.
EXAMPLE 1
[0045] The ability of two substrates to be joined with a
thermoplastic tape in accordance with one embodiment of the present
invention was demonstrated. Two substrates were obtained from the
U.S. Army Soldier Systems Center in Natick, Mass. The substrates
were prepared from a sheet material specified by Military
Specification MIL-C-13621. Specifically, the sheet contained three
layers and had an overall basis weight of between 370 to 460 grams
per square meter (gsm). The inner layer was a scrim of nylon fabric
having a twill weave. In addition, the outer layers were formed
from butyl rubber. The edges of the substrates were cut with
pinking shears prior to fabricating the seam.
[0046] The thermoplastic tape utilized was a modified polyurethane
two-layer film available under the name ST-52 from Bemis
Associates, Inc. of Shirley, Mass. In particular, one layer
contained a polyurethane adhesive and had a thickness of 0.064
millimeters, while the other layer contained a polyurethane barrier
material and had a thickness of 0.101 millimeters. The melting
temperature of the adhesive layer was 82.degree. C. and the melting
temperature of the barrier layer was 147.degree. C. The tape had a
width of 22.2 millimeters.
[0047] To form the seam, the thermoplastic tape was initially
placed into communication with the substrates to form a seam gauge,
which was defined by an overlap of 6.35 mm of the fabric edges. The
tails of the tape extended 1.6 mm beyond the fabric edges on the
upper and lower surfaces of the seam. One edge of the thermoplastic
tape was pre-attached to the edge of one of the fabric pieces using
a Sonobond Model SM8000 Ultrasonic Sewing Machine, available from
Sonobond Ultrasonics of West Chester, Pa. The sewing machine was
set with a horn height of 2.3 millimeters, an amplitude setting of
1.5, and a residence time of 1 second. Tack points were set
approximately 6 mm apart.
[0048] The second fabric piece was pre-attached to the
thermoplastic tape in a similar manner. The tape was then folded to
place the fabric edges in an overlapping position, such as shown in
FIG. 4. A flat buck press was then used to bond the materials. In
particular, the press was utilized at temperatures of 170.degree.
C. and 195.degree. C., a pressure of about 5.6 kg/cm.sup.2, and for
a residence time of about 10 seconds.
EXAMPLE 2
[0049] The ability of two substrates to be joined with a
thermoplastic tape in accordance with one embodiment of the present
invention was demonstrated. Two substrates were obtained from the
U.S. Army Soldier Systems Center in Natick, Mass. The substrates
were prepared from a tent shelter fabric as described in Military
Specification MIL-PRF-44103D, Class 2, Grade B. Specifically, the
fabric was a coated, woven nylon with a desert tan camouflage
print.
[0050] The thermoplastic tape utilized was a modified polyurethane
two-layer film available under the name ST-52 from Bemis
Associates, Inc. of Shirley, Mass. In particular, one layer
contained a polyurethane adhesive and had a thickness of 0.064
millimeters, while the other layer contained a polyurethane barrier
material and had a thickness of 0.101 millimeters. The melting
temperature of the adhesive layer was 82.degree. C. and the melting
temperature of the barrier layer was 147.degree. C. The tape had a
width of 22.2 millimeters.
[0051] The seam was formed as described in Example 1. In addition,
the Grab Tensile Strength of three samples of the fabric and seam
were tested according to ASTM D-5034. The fabric failed at loads of
155 to 160 kg. The average Grab Tensile Strength of the three seam
tests was 150.98 kg.
EXAMPLE 3
[0052] Example 3 was prepared according to Example 2, except that
the seam gauge was 3.175 millimeters and the thermoplastic tape had
a width of 19 millimeters. Three sample seams were again tested for
Grab Tensile Strength. For one of the seams, the fabric failed
before the seam, i.e., at a load of 157.4 kg. The other two seams
failed at loads of 134.3 kg and 136.3 kg.
EXAMPLE 4
[0053] The ability of two substrates to be joined with a
thermoplastic tape in accordance with one embodiment of the present
invention was demonstrated. Two substrates were obtained from the
U.S. Army Soldier Systems Center in Natick, Mass. The substrates
were prepared from a three-layer fabric as described in Military
Specification MIL-C-44187. Specifically, this fabric was
constructed of a plain weave nylon fabric having a basis weight
between 88 to 102 grams per square meter (gsm), laminated to a
polytetrafluoroethylene (PTFE) microporous film having a basis
weight of between 10 to 24 gsm. The backing of the fabric was a
nylon tricot knit fabric backing having a basis weight of between
34 to 62 gsm.
[0054] The thermoplastic tape utilized was a tape formed from three
separate strips of a modified polyurethane two-layer film available
under the name ST-52 from Bemis Associates, Inc. of Shirley, Mass.
In particular, one layer contained a polyurethane adhesive and had
a thickness of 0.064 millimeters, while the other layer contained a
polyurethane barrier material and had a thickness of 0.101
millimeters. The melting temperature of the adhesive layer was
82.degree. C. and the melting temperature of the barrier layer was
147.degree. C. The resulting tape had a width of 7 millimeters.
[0055] The seam was formed and as described in Example 2. The Grab
Tensile and Peel Strength of the fabric and the seam were tested
according to ASTM D-5034 and ASTM D-2724 (sections 14-15),
respectively. The average Grab Tensile Strength of the three seam
tests was 114 kg and the average Grab Peel Strength for these seams
was 2.28 kg.
EXAMPLE 5
[0056] For purposes of comparison, a conventional lap seam having a
seam gauge of 6.3 millimeters was utilized to attach the two
substrates described in Example 4. After sewing the seam through
the substrates, two strips of thermoplastic tape were also
utilized. In particular, one strip of thermoplastic tape was placed
in its entirety only on the upper surface of one substrate to
adhere one end of the seam thereto. The other strip was placed in
its entirety only on the lower surface of the other substrate to
adhere the other end the sewn seam thereto. The strips of tape were
then heated and pressed to set the tape.
[0057] The average Grab Tensile of these seams was 78 kg and the
average Peel Strength of these seams was 1.53 kg.
EXAMPLE 6
[0058] For purposes of comparison, a conventional double-felled
needle sewn seam was utilized to attach the two substrates
described in Example 4. The average Grab Tensile of these seams was
85.1 kg and the average Peel Strength of these seams was 4.03
kg.
[0059] A summary of the results obtained in Examples 2 through 6 is
provided below in Table I.
1TABLE I Summary of Examples Avg. Seam Grab Avg. Seam Peel Ex.#
Substrate Seam Tensile (kg) Strength (kg) 2 Coated Woven -z fold
150.98 -- Nylon 3 Coated Woven -z fold 135.3 -- Nylon 4 Three-layer
-z fold 114 2.28 5 Three-layer Lap 78 1.53 6 Three-layer Double
85.1 4.03 needle
[0060] Thus, as shown from Table I, a seam formed according to the
present invention can provide enhanced bonding strength in
comparison to seams formed according to conventional techniques. In
particular, the ability of the thermoplastic tape to form physical
and adhesive bonds can provide a seam of unexpected strength and
durability. Such seams can be utilized in a wide variety of
applications. For example, the seams may be useful in joining
barrier materials, particularly when the barrier function must be
maintained in the seam area. Examples of such barrier materials
include protective apparel for biological exposure areas, chemical
warfare, and underwater diving suits. Further, because the seams of
the present invention do not rely upon needle stitching, they may
have enhanced utility in applications requiring controlled air
porosity, such as in parachute constructions. Moreover, other
applications in which the seams may be useful include tents,
military uniforms, fabric-covered air ships (e.g., blimps), and the
like.
[0061] These and other modifications and variations of the present
invention may be practiced by those of ordinary skill in the art,
without departing from the spirit and scope of the present
invention, which is set forth in the appended claims. In addition,
it should be understood that aspects of the various embodiments may
be interchanged both in whole or in part. Furthermore, those of
ordinary skill in the art will appreciate that the foregoing
description is by way of example only, and is not intended to limit
the invention so further described in such appended claims.
* * * * *