An article comprises two areas of heat-recoverable woven fabric which are joined together along a line by means of a mechanical joining arrangement, such as stitches, staples or a stitched or stapled zip, which penetrates the fabric. The direction of crimp of the area penetrated is substantially perpendicular to the line of the join, or the two areas have substantially parallel directions of crimp.

This invention relates to dimensionally heat-recoverable articles and 
especially to dimensionally heat-recoverable articles formed from 
heat-recoverable fabrics. 
Recently a number of heat-recoverable articles which are based on fabrics 
have been devised and are the subject of copending British Patent 
Applications Nos. 8300217, 8300218, 8300219, 8300221, 8300222 and 8300223. 
The manufacture of heat-recoverable articles from fabrics containing 
heat-recoverable fibres has a number of advantages as compared with 
conventional heat-shrinkable products including ease of manufacture, since 
no subsequent expansion step is necessary, improved mechanical properties 
such as tensile strength, abrasion resistance and split resistance, and 
the ability to introduce very high strength heat stable fibres into the 
articles, all of which enable heat-recoverable fabrics to be employed in 
fields hitherto considered inappropriate for heat-shrinkable products. 
British Patent Application No. 8300219 describes and claims a dimensionally 
heat-recoverable fabric which comprises fibres that will recover when 
heated to a recovery temperature thereof, wherein the recoverable fibres 
have a tensile strength of at least 0.1 MPa at their recovery temperature 
and have been stretched to an extent that will cause the fabric to recover 
by at least 40% when heated to the recovery temperature of the recoverable 
fibres. 
British Patent Application No. 8300217 describes and claims a dimensionally 
heat-recoverable article for enclosing at least part of a substrate, which 
comprises a heat-recoverable fabric having fibres which will recover when 
heated and which have a tensile strength of at least 0.1 MPa at their 
recovery temperature, the fabric having an external surface that is coated 
with a layer of polymeric material of at least 0.3 mm thickness, the 
polymeric material being softenable when heated to accommodate recovery of 
the article without flowing. 
Patent Application No. 8300218 describes and claims a dimensionally 
heat-recoverable article comprising a composite structure of a 
heat-recoverable fabric and a polymer matrix material, wherein: 
(a) The heat-recoverable fabric comprises fibres that will recover when 
heated, the fibres having an axial recovery stress (Y) of at least 
5.times.10.sup.-2 MPa at a temperature above their recovery temperature; 
and 
(b) The polymer matrix material has an elongation/temperature profile such 
that there exists a temperature (T) which is at or above the recovery 
temperature of the fibres at which temperature the polymer matrix material 
has an elongation to break of greater than 20% and a 20% secant modulus 
(X) of at least 10.sup.-2 MPa (measured at a strain rate of 300% per 
minute), and at which temperature the inequality (1) is satisfied: 
##EQU1## 
wherein R is the mean effective volume fraction of heat-recoverable fibres 
in the composite structure along a given direction based on the total 
volume of the composite structure, or relevant portion thereof. 
Patent application No. 8300222 describes and claims a recoverable article 
suitable for enclosing a contoured substrate and comprising a recoverable 
fabric having zones of different or uniformly varying recovery ratios or 
forces, such that on recovery the volume enclosed by the fabric changes 
shape to conform to the substrate. 
Patent application No. 8300223 describes and claims a recoverable 
wraparound article which comprises a recoverable fabric cover portion, the 
fabric having a recovery ratio of at least 20%, and edge regions provided 
with a mechanical closure for maintaining the edge regions in proximate 
relationship during recovery of the cover portion. 
Patent application No. 8300221 describes and claims an assembly for 
enclosing a junction between elongate substrates, which comprises: 
(A) a sleeve comprising a recoverable fabric; 
(B) means for rendering the fabric substantially impervious when the fabric 
is recovered, and 
(C) a relatively rigid liner for the sleeve, the liner having a central 
region of larger cross-section, and end regions of smaller cross-section 
which provide transitions from the central region to the substrate and 
which locate the liner with respect to the substrate. 
In all these patent applications, and as used herein, the term "fibres" 
includes monofilaments as well as multifilament yarns, and in the 
preferred articles at least the heat-shrinkable fibres will be in the form 
of monofilaments. 
According to one aspect, the invention provides an article comprising two 
areas of woven fabric, at least one of which being heat-recoverable, 
joined together along a line by means of a mechanical joining arrangement 
that penetrates at least one of the areas of fabric, said area of fabric 
penetrated having a direction of crimp that is substantially perpendicular 
to the line at least along part of the length of the line. 
According to another aspect, the invention provides an article comprising 
two areas of woven fabric, at least one of which being heat-recoverable, 
joined together along a line by means of a mechanical joining arrangement 
that penetrates the two areas of fabric, the two areas of fabric having 
substantially mutually parallel directions of crimp along at least part of 
the line. 
The invention also provides a method of encapsulating a substrate which 
comprises recovering into engagement with the substrate the article of the 
invention. The two areas of fabric may be joined before or after their 
positioning around the substrate. 
The term "woven fabric" as used herein does not imply any method of 
production, but rather refers to the regular interlacing of its 
constituent fibres. Thus, "woven fabric" encompasses braids and other 
fabrics where fibres in one direction can (at least in the absence of 
crimp) pull through the fabric. By "direction of crimp" is meant the 
direction in which those fibres (either in the warp or in the weft in the 
case of a fabric made by weaving) that have the highest degree of crimp 
lie. The crimp of a fibre is a function of the deviation from a straight 
line which a fibre has to take in order to weave in and out of, i.e. 
interlace, the other fibres. Thus the crimp of a fibre may be defined as 
the difference in the distance between two points on a fibre in a fabric 
and the same two points on the fibre if it were removed from the fabric 
and straightened under a specific tension, expressed as a percentage of 
the distance between the points in the fabric. 
Preferably the fibres in the direction of crimp have a degree of crimp of 
at least 10%, more preferably at least 20%, especially at least 30% and 
most especially at least 40% although it is unlikely that the fibres would 
have a crimp in excess of 60%, more usually 50%. 
If desired it is possible to vary the degree of crimp in different regions 
or zones of the article. For example, with certain tubular article which 
are required to exhibit relatively high resistance to distortion in the 
radial direction, it may be necessary for the heat-recoverable fibres 
lying in the circumferential direction to have a relatively low degree of 
crimp. However, if the article has a join line extending axially along it, 
the circumferential heat-recoverable fibres in the region of the join line 
should have a relatively high degree of crimp. These conflicting 
requirements may both be achieved by "zoning" the properties of the fabric 
to form a fabric having heat-recoverable fibres of low crimp in all 
regions except those regions at the join line. Such a fabric may be formed 
by weaving the fabric using the heat-recoverable fibres as warp fibres and 
altering the warp tension at different times as the weave is formed. 
Alternatively fibres of higher titre and/or stiffness may be inserted at 
different positions either in the warp or in the weft in order to vary the 
crimp in the fibres perpendicular thereto. 
It has been found that by employing weave designs in which the direction of 
crimp of at least one of the areas of fabric is substantially 
perpendicular to the line along at least part of its length, or by 
embodying weave designs in which the two areas of fabric have 
substantially parallel directions of crimp irrespective of the direction 
of the join line, it is possible to join areas of fabric together without 
those areas either pulling apart completely under the recovery forces of 
the recoverable fibres or without those parts of the fabric adjacent the 
join line from being distorted to such an extent that the integrity of the 
article is lost. The reason for the ability of the join to withstand the 
recovery forces of the article is not completely understood but it is 
believed to be due at least in part to the ability of the fibres extending 
perpendicularly to the join line to stretch on account of their relatively 
high degree of crimp thereby allowing the join line to shift laterally to 
some extent and thereby relieve the stresses on the join line. 
Alternatively, or in addition, a high degree of crimp in the fibres 
extending perpendicularly to the join line may increase the strength of 
the join by preventing those fibres lying between the join line and the 
edge of the fabric area from being stripped off the fabric. 
By the term "substantially perpendicular" in connection with the crimp 
direction and the join line is meant an angle in the range of from 
45.degree. to 135.degree., preferably from 70.degree. to 110.degree. and 
especially from 80.degree. to 100.degree., and by the term "substantially 
parallel" is meant an angle between two lines in the plane of the fabrics 
of less than 45.degree., preferably less than 20.degree. and especially 
less than 10.degree.. In addition it is often the case that the two areas 
of fabric extend from the join line in different planes in which case in 
the terms "parallel" and "perpendicular" should be construed as if that 
portion of the article were flattened to bring both areas of fabric into 
the same plane. 
In certain forms of article according to the invention, for example where a 
tubular article is formed by joining opposed edges of a flat sheet, both 
the direction of crimp and the direction of recovery of the areas of 
fabric will coincide, and in the case of a tube will both be perpendicular 
to the line of the join. However, the invention allows more complex shapes 
to be formed, for example by joining together areas of fabric in which the 
direction of recovery are substantially perpendicular to one another. In 
such a case two different fabrics need to be used, one fabric having the 
crimp at least predominantly in the heat-recoverable fibres and the other 
fabric having the crimp at least predominantly in the heat-stable fibres. 
In addition, it is not always the case that the join line will be a 
straight line but rather it may be curved so that the angle between the 
directions of recovery of the fabrics and also the angle between the 
directions of crimp of the fabrics may vary along the join line. In this 
case, at least at one point on the join line the direction of recovery of 
one of the fabrics will be perpendicular to the join line, at which point 
the direction of crimp of at least one fabric and preferably both fabrics 
is also perpendicular to the join line. This may be achieved by forming 
one of the fabrics with the direction of crimp always in the direction of 
recovery. 
There is essentially no limit to the complexity of the structures that may 
be formed according to the invention. The articles may be made by 
relatively simple techniques involving weaving fabrics with the 
appropriate properties, cutting components of the articles from the 
fabrics and joining the components such that best use is made of the crimp 
directions and/or zones of different properties of the fabrics. 
Any of a number of joining arrangements that penetrate the fabric may be 
used, e.g. staples and the like although for all aspects of the invention 
it is preferred for the areas of fabric to be joined together by one or 
more lines of stitches. Preferably, although by no means always, the areas 
of fabric that are joined overlap each other to form a lap joint. 
Preferably the, or each line of stitches, has from 200 to 800, especially 
from 300 to 600 and most especially about 400 stitches per meter. 
Alternatively, or in addition, it is preferred for the line of stitches or 
that line of stitches lying closest to an edge of the recoverable fabric 
to be separated by at least four rows of fibres. In order to reduce the 
possibility of breakage of heat-recoverable fibres by the stitching or 
sewing operation the sewing needles or staples used should be very sharp 
at their tips and have a maximum diameter of the same order of magnitude 
as the distance between the heat-shrinkable fibres of the fabric. 
The mechanical joining arrangement may consist only of, say, staples or 
stitches. Alternatively, however, it may comprise stitches or staples 
together with a connecting means one part of which is attached (by means 
of the stitches or staples) to one of the areas of heat-recoverable woven 
fabric and another part of which is attached to the other area of fabric. 
The connecting means may be, for example, a zip, a web of material such as 
a heat-stable fabric or a sheet of generally non-perforate material. 
Another advantage of the present invention, especially where the areas of 
fabric are joined by one or more lines of stitches but also to some extent 
where staples are used, is that when the heat-recoverable fibres are 
recovered their diameter or titre increases, the increase in titre 
corresponding to their reduction in length, so that the perforations in 
the fabric through which the stitches or staples pass close up and the 
fabric grips the staples or stitches, thereby increasing the strength of 
the join. The reduction in size of the perforations also helps any 
adhesive layer or layer of laminated polymer to fill the perforations 
completely and so reduce the possibility of leakage of fluids through the 
recovered article. 
Preferred forms of the heat-recoverable fabrics are described in the 
British patent applications mentioned above. The heat-recoverable fibres 
are preferably formed from a polymeric material that imparts good physical 
properties and, in particular, good creep resistance to the fibres. Olefin 
polymers such as polyethylene and ethylene copolymers, polyamides, 
polyesters, acrylic polymers and other polymers capable of being 
cross-linked may be employed. A particularly preferred polymeric material 
for the fibres is based on polyethylene having a density of from 0.94 to 
0.97 g/cc, an Mw of from 80.times.10.sup.3 to 200.times.10.sup.3 and Mn of 
from 13.times.10.sup.3 to 30.times.10.sup.3. 
The fibres preferably have a minimum recovery stress of 10.sup.-1 MPa, more 
preferably 5.times.10.sup.-1 and usually at least 1 MPa at a temperature 
above the transition temperature of the fibres. There is in theory no 
upper limit of recovery stress, but in practice 200 MPa and more usually 
100 MPa is the highest figure normally achievable with polymeric fibres. 
The tensile strength of the fibres at their recovery temperature is 
preferably increased to 0.1 MPa or higher by cross-linking the polymeric 
material from which they are formed, either by chemical means or by 
irradiation e.g. high energy electron irradiation, gamma radiation or by 
ultra violet radiation. 
When the fibre is cross-linked by irradiation it is convenient to 
incorporate the cross-linking step into manufacture of the fibre. The 
fibre can be extruded, stretched at a temperature below its melting 
temperature, preferably by an amount of from 800 to 200%, then subjected 
to irradiation to effect cross-linking. A less preferred way of making the 
fibre is to extrude the fibre, irradiate to cross-link, then heat the 
fibre, preferably to above its melting temperature, stretch the fibre, and 
then cool the stretched fibre. High density polyethylene fibres are 
preferably irradiated with a dose of from about 5 to about 35 megarads, 
preferably from about 5 to about 25 megarads, and in particular from about 
10 to about 18 megarads. Usually the gel content of the cross-linked fibre 
is greater than 20%, preferably greater than 30%, most preferably greater 
than 40%. In practice, gel contents greater than 90% are not easily 
achievable. 
Although it is usually preferred for the heat-recoverable fibres to exhibit 
a recovery of at least 20%, and especially at least 40%, particularly at 
least 80% such as 100% to 200%, in certain instances, for example where 
the article is intended to have a very high pressure retention capability, 
it may be desirable to allow the heat-recoverable fibres to recover by a 
low percentage only e.g. as low as 5%. The fabric before installation 
preferably recovers at least 40%, particularly by at least 50%, especially 
by at least 60%. A percentage recovery refers to a change in dimension 
based on the original dimension. 
The fabric can be woven in a pattern, for example, twill, satin, sateen, 
Leno, plain, hop sack, sack, matt and various weave combinations in single 
or multiple ply weaves e.g. 2- or 3-ply weaves. Preferably the fabric is a 
woven fabric that has heat-recoverable fibres in one direction and 
dimensionally heat-stable fibres in the other directions so that the 
fabric as a whole is recoverable in a single direction only. 
Whatever forms of fabric are used in the present invention it is preferred 
that they are laminated or impregnated, preferably to form a composite 
material, as described, for example, in British Patent Application Nos. 
8300217 and 8300218 since, among other reasons, the presence of a 
laminated or matrix polymer increases the friction or adhesion between the 
fibres thereby strengthening the join. Also, if, as will usually be the 
case, the fabrics are laminated before the areas of fabric are joined 
together, at least one laminated layer of polymer will be sandwiched 
between two layers of fabric at the join and will help to seal the join 
against passage of fluid through it. The recovery that the composite 
material can exhibit will in general be less than that before lamination. 
Preferred possible extents of recovery of the composite material are at 
least 40%, especially at least 50%. 
The matrix material is preferably cross-linked, for example by means of a 
chemical cross-linking agent or by irradiation. Where irradiation is used, 
a dose of 10 megarads or less, preferably 3-7 megarads, is preferred. We 
prefer that the composite material is produced by applying the matrix 
material to cross-linked fibres or fabric and then cross-linking the 
result. 
The heat-recoverable article according to the invention has a wide variety 
of uses. For example it may be recovered over substrates, especially 
substrates having varying or discontinuous contours, to provide mechanical 
protection or protection from the environment. The fabric may employ heat 
stable fibres having high tensile strengths, e.g. glass fibres or fibres 
sold under the trade name "Kevlar" which, if laid in the axial direction 
of a radially heat-shrinkable tubular article enable the article to be 
used for example as a pipe coupling, the high strength heat-stable fibres 
providing the article with a high pull-out resistance. Whilst the fabric 
may be used alone, it is often advantageous for it to be employed in 
conjunction with an adhesive or sealant or other polymeric material that 
renders it substantially impervious to fluids, the adhesive, sealant or 
other material either being applied in situ when the fabric is installed 
or applied before sale of the fabric. Thus, for example, the fabric may be 
impregnated with a curable adhesive composition, e.g. a curable epoxy 
composition and especially an optionally b-staged epoxy resin that is 
cured by means of a polyamide, an anhydride or an isocyanate although 
other materials may be used such as phenolic resins or isocyanate/phenolic 
resin. The resin or other material may be laminated on to or impregnated 
into the fabric as mentioned above, or it may be employed in particulate 
form as described in U.K. patent application No. 82,24379. Alternatively 
an adhesive such as a hot-melt adhesive and especially an adhesive based 
on a polyamide or an ethylene-vinyl acetate copolymer may be applied 
either to the fabric or to the substrate during installation. 
Most preferably, however, the heat-recoverable fabric is used in 
combination with a matrix polymer layer which softens when heated to 
accommodate recovery of the fabric. The combination thus forms a single 
composite structure. 
The heat-recoverable fabric is preferably bonded to, and preferably 
embedded in, the polymer matrix material. At or above the recovery 
temperature of the fibres the polymer matrix material should be capable of 
limited flow under pressure so that it retains the integrity of the 
composite structure without substantially impeding recovery of the fibres. 
It preferably has, at the aforesaid temperature, an elongation to break of 
greater than 50%, most preferably greater than 100%, and a 20% secant 
modulus of preferably at least 5.times.10.sup.31 2 MPa, most preferably at 
least 10.sup.-1 MPa, measured at a strain rate of 300% per minute. 
The ability of the matrix material to flow when heated need not necessarily 
apply after recovery. Thus, for example, the polymer matrix material may 
eventually cure to a thermoset on heating, although it is preferred that 
the cure rate is sufficiently slow under the recovery conditions not to 
cause the material to drip off the fabric during the recovery of the 
fibres. Thus, for example, the polymer forming the matrix material may 
contain grafted hydrolysable silane groups which are capable of 
crosslinking the material subsequently in the presence of moisture. 
Examples of such materials are given in U.S. Pat. No. 1,286,460 to Dow 
Corning Ltd., the disclosures of which are incorporated herein by 
reference. Alternatively the matrix material may include a polymer, 
preferably a rubber and especially an acrylic rubber, which contains epoxy 
groups and a room temperature insoluble curing agent e.g. dicyandiamide. 
Preferred matrix materials are described in the patent applications 
referred to herein. 
The impregnated fabric may also be provided with one or more adhesives, 
e.g. pressure-sensitive, hot-melt or curable adhesives or mastics. As an 
example it may be provided with a layer of a mastic on its central region 
and a strong adhesive, e.g. a hot-melt or curable adhesive, on its edge 
regions for example arranged as described in U.K. Patent Specification No. 
2,108,625A. 
The article of the invention is preferably such that the joining 
arrangement serves to hold the article in a hollow configuration, such as 
a tubular configuration or a bifurcated (including multiple branched) 
configuration. Such a hollow article can be used for encapsulating, 
thereby environmentally protecting or mechanically fixing, pipes and 
joints therein, and cables and bus bars and splices therein, such as 
splices in telecommunications and power cables. A bifurcated configuration 
may be useful for encapsulating the joints and splices referred to.

Referring of FIG. 1 of the accompanying drawings, a tubular radially 
heat-shrinkable article is formed from a 2 up and 2 down twill employing 
0.29 mm diameter high density polyethylene filaments in the warp and 75 
E.C.G. glass fibre yarn in the weft. The fabric density (warp density/weft 
density, measured in fibres/2.5 cm) was 90/16. The fabric is irradiated 
with 1.5 MeV electrons to a dose of 15 Mrads to give the warp fibres a gel 
content of 37.3% (refluxing in xylene) and a 100% secant modulus of 0.60 
at 150.degree. C. 
The fabric is then extrusion laminated with low density polyethylene at a 
melt temperature of 260.degree. C. between a cooled metal roller and a 
rubber faced roller. The polyethylene has a thickness of 0.6 mm on one 
side of the fabric and a thickness of 0.3 mm on the other side and, after 
lamination, the composite is irradiated with high energy electrons to a 
further dose of 4 Mrads. The low density polyethylene used has a melt flow 
index of 3.0, a number average molecular weight Mn of 14,800 and a weight 
average molecular weight Mw of 114,800. During or after lamination the 
fabric was coated with a layer of a polyamide hot-melt adhesive. 
The high density polyethylene fibres, which had been irradiated to a dose 
of 20 Mrads, had the following properties: 
______________________________________ 
100% secant modulus at 150.degree. C. 
0.29 MPa 
tensile strength at 150.degree. C. 
2.18 MPa 
elongation to break at 150.degree. C. 
780% 
gel content (reflux in xylene) 
42.25% 
recovery force 0.62 MPa 
recovery percentage 87% 
percentage crimp 9% 
______________________________________ 
The fabric is cut and stitched along the edges parallel to the glass fibre 
yarn using two rows of "Kevlar" (trade name) sewing thread type T513, size 
200/3/3 sold by duPont, as the stitch thread with 386 stitches per meter 
to form a lap joint. The stitch rows are spaced apart by 5 mm and are 
separated from each fabric edge by 12 mm. The tubular article may be used 
to enclose a joint between two pipes or similar substrates simply by 
sliding the article onto one of the substrates before coupling them then 
sliding the article over the joint and recovering it using a conventional 
hot-air gun or gas torch. 
FIG. 2 shows a right-angled tubular article that is suitable for enclosing 
a right angled bend in a substrate for example in a bus-bar. 
The article is formed initially as two component tubular parts 21 and 22. 
Part 21 is formed from the same fabric as that used for the article shown 
in FIG. 1 so that the direction of crimp is the same as the direction of 
the heat-recoverable fibres (i.e. circumferential). Component part 22 is 
formed from a 2 up 2 down twill using the same fibres as those used for 
part 21 but in which the heat-shrinkable fibres were inserted in the weft 
direction. The resulting fabric had a fabric density of 20/48 (warp 
density/weft density measured in fibres per 2.5 cm), and the pick-rate had 
been adjusted to give the heat-recoverable fibres in the circumferential 
direction a degree of crimp of about 3% and the heat-stable fibres in the 
axial direction a degree of crimp of 14%. Each of the component parts 21 
and 22 may initially be formed from a flat fabric sheet which is formed 
into a tube by joining and stitching opposed edges of the sheet although 
it is preferable for one or both of the component parts to be provided 
with a rail-and-channel closure 23 or other closure as described in U.S. 
Patent application No. 8300223. 
The two component parts 21 and 22 are joined together by means of two rows 
of stitches 24 to form a lap joint substantially as described above with 
reference to FIG. 1. In this article the relative directions of recovery 
of the two fabrics forming the component parts 21 and 22 will vary along 
the join line formed by the rows of stitches 24. At the regions 26 and 27 
of the join line the join will be subjected to relatively little force 
between the different fabrics because, in those regions, the directions of 
recovery of both the component parts 21 and 22 are substantially parallel 
to the join line. In the region 25, the join line is subject to a 
relatively high recovery force, at least once the article has recovered 
into contact with the substrate, the recovery force of each component part 
has a significant vector component in the direction perpendicular to the 
join line. However, because the direction of crimp is parallel to the 
recovery direction in the component part 21 and perpendicular to the 
recovery direction in component part 22, the directions of crimp of the 
two component parts are substantially parallel to one another in the 
region 25 of the join line and therefore the row of stitches prevents the 
fabrics from being pulled apart. 
FIG. 3 shows a heat-recoverable fabric suitable for enclosing a "T" branch 
in a substrate, e.g. a district heating pipe. The article is formed from 
two component parts 31 and 32, component part 31 being in the form of a 
wraparound article using a rail-and-channel type closure 34 as described 
in Patent application No. 8300223, and component part 32 being in the form 
of a tube that has been formed by joining together the opposed edges of a 
flat heat-recoverable fabric. The component parts have been joined by 
forming a hole in part 31, inserting part 32 through the hole, splaying 
out one end 33 of the component part 32, e.g. after cutting lines into the 
end 33 for a short distance and optionally inserting gussets therein, and 
then stitching the end 33 of component part 32 to the margin surrounding 
the hole in part 31. One row of stitches is employed using the same Kevlar 
fibres as the stitching thread with 386 stitches per meter. The row of 
stitches is spaced from the edges of each area of fabric by 8 mm. 
The fabric forming part 31 is identical with that forming component part 21 
of FIG. 2 and the fabric forming component part 32 is identical with that 
forming component part 22 of FIG. 2. 
In this article, as with the article shown in FIG. 2, the relative 
directions of recovery of the two component parts will vary along the join 
line formed between the component parts. At points 36 the directions of 
recovery of both component parts will be parallel to the join line and so 
the join line will be subjected to a relatively low force tending to pull 
the fabrics apart. At point 37 the recovery forces of the two component 
parts 31 and 32 will act in mutually perpendicular directions and the 
recovery force of component part 31 acts in a direction perpendicular to 
the join line, so that a considerable strain is imparted on the join. 
However, at the point 37 the direction of crimp of the component parts is 
parallel and is perpendicular to the join line, thereby increasing the 
strength of the join. 
If desired, the hole component part 31 may be so cut that the overlap 
between the component parts is increased at point 38 as shown, and also 
one or more additional lines of stitches may be employed. This increase in 
overlap further increases the strength of the join at point 37 along the 
join line. 
The articles were tested in accordance with DIN Specification No. 30672 in 
which the articles were exposed to a salt fog for 24 hours and then tested 
for the presence of holidays (holes). All samples passed.