Wet compacting of fabrics for orthopedic casting tapes

The present invention provides an article, comprising: a fabric sheet which has been compacted using a heat shrink yarn; and a curable or hardenable resin coated onto the fabric sheet. The present invention involves compacting a fabric sheet to impart stretchability and conformability to the fabric while minimizing undesirable recovery forces. Suitable fabrics for compacting are fabrics which comprise fiberglass fibers which are capable of first being compacted and then being set or annealed in the compacted state. The article may be in the form of an orthopedic bandage and may optionally contain a microfiber filler associated with the resin.

FIELD OF THE INVENTION 
This invention relates to sheet materials coated with a curable or 
hardenable polymeric resin. More particularly, this invention relates to a 
curable or hardenable resin coated sheet material useful in preparing an 
orthopedic bandage. 
BACKGROUND OF THE INVENTION 
Many different orthopedic casting materials have been developed for use in 
the immobilization of broken or otherwise injured body limbs. Some of the 
first casting materials developed for this purpose involve the use of 
plaster of Paris bandages consisting of a mesh fabric (e.g., cotton gauze) 
with plaster incorporated into the openings and onto the surface of the 
mesh fabric. 
Plaster of Paris casts, however, have a number of attendant disadvantages, 
including a low strength-to-weight ratio, resulting in a finished cast 
which is very heavy and bulky. Furthermore, plaster of Paris casts 
typically disintegrate in water, thus making it necessary to avoid 
bathing, showering, or other activities involving contact with water. In 
addition, plaster of Paris casts are not air permeable, thus do not allow 
for the circulation of air beneath the cast which greatly facilitates the 
evaporation and removal of moisture trapped between cast and skin. This 
often leads to skin maceration, irritation, or infection. Such 
disadvantages, as well as others, stimulated research in the orthopedic 
casting art for casting materials having improved properties over plaster 
of Paris. 
A significant advancement in the art was achieved when polyisocyanate 
prepolymers were found to be useful in formulating a resin for orthopedic 
casting materials, as disclosed, for example, in U.S. Pat. No. 4,502,479 
(Garwood et al.) and U.S. Pat. No. 4,441,262 (Von Bonin et al.). U.S. Pat. 
No. 4,502,479 sets forth an orthopedic casting material comprising a knit 
fabric which is made from a high modulus fiber (e.g., fiberglass) 
impregnated with a polyisocyanate prepolymer resin which will form a 
polyurea. Orthopedic casting materials made in accordance with U.S. Pat. 
No. 4,502,479 provide significant advancement over the plaster of Paris 
orthopedic casts, including a higher strength-to-weight ratio and greater 
air permeability. However, such orthopedic casting materials tend not to 
permit tactile manipulation or palpation of the fine bone structure 
beneath the cast to the extent possible when applying a plaster of Paris 
cast. In this regard, knit fiberglass materials are not as compressible as 
plaster, and tend to mask the fine structure of the bone as the cast is 
applied, e.g., the care provider may be limited in "feeling" the bone 
during reduction of the fracture. 
Fiberglass backings have further disadvantages. For example, fiberglass 
backings are comprised of fibers which have essentially no elongation. 
Because the fiber elongation is essentially nil, glass fabrics do not 
stretch unless they are constructed with very loose loops which can deform 
upon application of tension, thereby providing stretching of the fabric. 
Knitting with loosely formed chain stitches imparts extensibility by 
virtue of its system of interlocking knots and loose loops. 
To a greater extent than most knitted fabrics, fiberglass knits tend to 
curl or fray at a cut edge as the yarns are severed and adjacent loops 
unravel. Fraying and raveling produce unsightly ends and, in the case of 
an orthopedic cast, frayed ends may interfere with the formation of a 
smooth cast, and loose, frayed ends may be sharp and irritating after the 
resin thereon has cured. Accordingly, frayed edges are considered a 
distinct disadvantage in orthopedic casting tapes. Stretchy fiberglass 
fabrics which resist fraying are disclosed in U.S. Pat. No. 4,609,578 
(Reed), the disclosure of which is incorporated by reference for its 
teaching of heat-setting. Thus, it is well known that fraying of 
fiberglass knits at cut edges can be reduced by passing the fabric through 
a heat cycle which sets the yarns giving them new three-dimensional 
configurations based on their positions in the knit. When a fiberglass 
fabric which has been heat-set is cut, them is minimal fraying and when a 
segment of yarn is removed from the heat-set fabric and allowed to relax, 
it curls into the crimped shape in which it was held in the knit. 
Accordingly, at the site of a cut, the severed yarns have a tendency to 
remain in their looped or knotted configuration rather than to spring 
loose and cause fraying. 
In processing extensible fiberglass fabrics according to U.S. Pat. No. 
4,609,578 (Reed), a length of fabric is heat-set with essentially no 
tension. The fabric is often wound onto a cylindrical core so large 
batches can be processed at one time in a single oven. Care must be taken 
to avoid applying undue tension to the fabric during wind-up on the 
knitter which would distort the knots and loops. To prevent applying 
tension to the fabric during winding, the winding operation is preferably 
performed with a sag in the fabric as it is wound on the core. 
Alternatively, U.S. Pat. No. 5,014,403 (Buese) describes a method of making 
a stretchable orthopedic fiberglass casting tape by knitting an elastic 
yarn under tension into the fiberglass fabric in the length direction, 
releasing the tension from the elastic yarn to compact the fabric and 
removing the elastic yarn from the fabric. The resulting fabric must then 
be collected under low tension in order to preserve the compact form. 
Likewise, any subsequent heat setting must also be performed under low 
tension. However, to avoid exceeding this low tension is difficult and as 
a result substantial amounts of the compaction imparted by the elastomeric 
yarn may be lost during subsequent processes. The elastic yarn is removed 
by a combustion process which may cause localized areas of high 
temperature which may degrade the fiberglass yarns. The physical 
properties of glass fibers are adversely affected when subjected to 
temperatures in excess of about 540.degree. C. Heating fiberglass fabrics 
to temperatures above about 540.degree. C. should be avoided, as 
subjecting the fiberglass to temperatures of greater than about 
540.degree. C. can weaken the fiberglass yarns in the fabric, which may 
result in reduced strength of casts made from such fabrics. 
Copending U.S. patent application: "Compacted Fabrics for Orthopedic 
Casting Tapes"--Ser. No. 08/141,830, filed on even date herewith by the 
assignee of the present invention, discloses an article comprising a 
fabric sheet (e.g., fiberglass) which has been compacted using a heat 
shrink yarn. The incorporation of the additional heat shrink yarn(s) into 
the knit structure requires an additional bar on the knitter and the 
attendant set-up and maintenance. Furthermore, care must be taken when 
optionally removing the shrunken heat shrink yarn to avoid a combustion 
process which causes localized areas of high temperature and degradation 
of the fiberglass yarns. 
Copending U.S. patent application: "Vibration Compacted Fabrics For 
Orthopedic Casting Tapes"--Ser. No. 08/142,177, filed on even date 
herewith by the assignee of the present invention, discloses an article 
comprising a fabric sheet (e.g., fiberglass) which has been compacted 
using an elastomeric yarn and a vibration process. The incorporation of 
the additional elastomeric yarn(s) into the knit structure requires an 
additional bar on the knitter and the attendant set-up and maintenance. 
Furthermore, care must be taken when removing the elastomeric yarn to 
avoid a combustion process which causes localized areas of high 
temperature and degradation of the fiberglass yarns. 
From the foregoing, it will be appreciated that what is needed in the art 
is an orthopedic casting material which has both the advantages of plaster 
of Paris, e.g., good moldability and palpability of the fine bone 
structure, and the advantages of non-plaster of Paris materials, e.g., 
good strength-to-weight ratio and good air permeability. In this regard it 
would be a significant advancement in the art to provide such a 
combination of advantages without actually using plaster of Paris, thereby 
avoiding the inherent disadvantages of plaster of Paris outlined herein. 
It would be a further advancement in the art to provide such non-plaster 
of Paris orthopedic casting materials which have as good or better 
properties than the non-plaster of Paris orthopedic casting materials of 
the prior art. Such orthopedic casting materials and methods for preparing 
the same are disclosed and claimed herein. 
RELATED APPLICATIONS 
Of related interest are the following U.S. patent applications, filed on 
Jan. 25, 1993 by the assignee of this invention: "Mechanically Compacted 
Fabrics for Orthopedic Casting Tapes"--Ser. No. 08/008,161; and 
"Microcreping of Fabrics for Orthopedic Casting Tapes"--Ser. No. 
08/008,751; and copending U.S. patent applications filed on even date 
herewith by the assignee of this invention: "Compacted Fabrics for 
Orthopedic Casting Tapes"--Ser. No. 08/141,830; and "Vibration Compacted 
Fabrics For Orthopedic Casting Tapes"--Ser. No. 08/142,177, which are 
herein incorporated by reference. 
SUMMARY OF THE INVENTION 
The present invention provides an article comprising a compacted fiberglass 
(or other high modulus fiber) fabric sheet and a curable or hardenable 
resin coated onto the fabric sheet. The fabric sheet is compacted using a 
lubricating solution thereby providing extensibility to the fabric and 
then is optionally heat set. The article may be in the form of an 
orthopedic bandage. The present invention also provides an article 
comprising a compacted fiberglass fabric sheet and a curable or hardenable 
resin coated onto the fabric sheet.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention relates to orthopedic casting materials and methods 
for preparing and using such orthopedic casting materials, wherein the 
materials comprise a fiberglass backing or fabric which is impregnated 
with a curable or hardenable liquid resin. In particular, the fabrics 
employed in the present invention have important characteristics and 
physical properties which allow the fabrics to be made highly extensible. 
One element of this invention is a flexible sheet upon which a curable or 
hardenable resin can be coated to reinforce the sheet when the resin is 
cured or hardened thereon. The sheet is preferably porous such that the 
sheet is at least partially impregnated with the resin. Examples of 
suitable sheets are knit fabrics comprised of inorganic fibers or 
materials such as fiberglass. The sheet may alternatively be referred to 
as the "scrim" or the "backing." 
The present invention involves compacting a fabric sheet using a 
lubricating solution to assist in imparting stretchability and 
conformability to the fabric while minimizing undesirable recovery forces. 
Suitable fabrics, after compaction, have important characteristics and 
physical properties which allow the fabrics to be loaded with resin to the 
extent needed to provide proper strength as an orthopedic casting 
material, while providing necessary porosity as well as improved 
extensibility leading to improved conformability, tactile manipulability, 
moldability, and palpability. Several important criteria for choosing a 
fabric which will provide the characteristics necessary for purposes of 
the present invention include: (1) lengthwise extensibility and 
conformability after compaction, and the related characteristics of 
moldability, tactility, and palpability once the fabric has been resin 
impregnated; (2) resin loading capacity; and (3) porosity. It is important 
that each of these parameters be carefully controlled in providing fabrics 
which will successfully form orthopedic casting materials (e.g., casts 
having high strength and good layer-to-layer lamination strength) within 
the scope of the present invention. 
Extensibility is important from the standpoint that the fabric must be 
extensible enough along its length, i.e., in the elongated direction, so 
that the resultant orthopedic casting material can be made to 
substantially conform to the body part to which it is applied. Materials 
which are not sufficiently extensible in the elongated direction do not 
conform well to the body part when wrapped therearound, often resulting in 
undesirable wrinkles or folds in the material. On the other hand, the 
extensibility of the fabric in the elongated direction should not be so 
high that the material is too stretchy, resulting in a material structure 
which may be deformed to the extent that strength is substantially 
reduced. 
For purposes of the present invention, the coated fabric, after compaction 
and after being coated with a curable liquid resin, should have from about 
10% to about 200% extensibility in the elongated direction when a 2.63N 
tensile load or force is applied per 1 cm wide section of the fabric, and 
preferably from about 25% to about 100% extensibility in the elongated 
direction when a 2.63N tensile load or force is applied per 1 cm wide 
section of the fabric, and more preferably from about 35% to about 65% 
extensibility in the elongated direction when a 2.63N tensile load or 
force is applied per 1 cm wide section of the fabric. 
Although not nearly as critical, it is also desirable that the fabric 
employed have some extensibility along its width, i.e., in the direction 
transverse to the elongated direction. Thus although the fabric may have 
from 0% to 100% extensibility in the transverse direction, it is presently 
preferable to use a fabric having from about 1% to about 30% extensibility 
in the transverse direction when a 2.63N tensile load or force is applied 
per 1 cm wide section of the fabric. 
The fabrics of the present invention, after compaction, although 
stretchable, are preferably not overly elastic or resilient. Fabrics which 
are overly elastic, when used as backings for orthopedic bandages, tend to 
cause undesirable constriction forces around the wrapped limb or body 
part. Thus, once the resin impregnated fabric has been stretched and 
applied around a body part, the stretched material preferably maintains 
its shape and does not revert back to its unstretched position. 
The resin loading capacity or ability of the fabric to hold resin is 
important from the standpoint of providing an orthopedic casting material 
which has sufficient strength to efficaciously immobilize a body part. The 
surface structure of the fabric, including the fibers, interstices, and 
apertures, is very important in providing proper resin loading for 
purposes of the present invention. In this regard, the interstices between 
the fibers of each fiber bundle must provide sufficient volume or space to 
hold an adequate amount of resin within the fiber bundle to provide the 
strength necessary; while at the same time, the apertures between fiber 
bundles preferably remain sufficiently unoccluded such that adequate 
porosity is preserved once the cast is applied. Thus, the interstices 
between fibers are important in providing the necessary resin loading 
capacity, while the apertures are important in providing the necessary 
porosity for the finished cast. However, a balancing of various parameters 
is needed to achieve both proper resin loading and porosity. The coated 
fabric should have preferably between about 6 and 70 openings (i.e., 
apertures) per square cm, more preferably between about 10 and 50 openings 
per square cm, and most preferably between about 20 and 40 openings per 
square cm when measured under a tensile load of 2.63N/cm width. As used 
herein an "opening" is defined as the area defined by adjacent wales and 
in-lay members. The number of openings per unit area is therefore 
determined by multiplying the number of wales by the number of courses and 
dividing by the area. 
As used herein, a "compacted" fiberglass sheet is one in which 
extensibility is imparted to the fabric due to the structural relaxation 
of loops by the "wet compaction" processes described herein. The wet 
compaction process is presently believed to impart extensibility to the 
fabric by "stress relaxing" the loops of the knit as described herein. 
Typically, when a fabric is knitted the inside surfaces of two adjacent 
rows of loops are in contact or nearly in contact and the loops are 
distorted in the lengthwise direction (e.g., in the shape of an oval). 
This contact and/or distortion is the result of the fabric being under 
tension while the knit is being formed. Each successive row of loops 
(i.e., chain stitches) is, in effect, formed against the preceding row of 
loops. The wet compaction process of the present invention imparts fabric 
compaction by relaxing the loops (i.e., to a lower stress configuration) 
and optionally setting or annealing the fabric in the compacted form. 
Extensibility is thus imparted to the fabric due to the greater capacity 
of the more circular loops to be deformed. When tension is again applied 
to the fabric the loops can return to their original "stressed" position, 
i.e., the position they occupied when originally knit. 
Fiberglass knitted fabrics with good extensibility are achievable with two 
common knitting methods: Raschel and tricot. Raschel knitting is described 
in "Raschel Lace Production" by B. Wheatley (published by the National 
Knitted Outerwear Association, 51 Madison Avenue, New York, N.Y. 10010) 
and "Warp Knitting Production" by Dr. S. Raz (published by Heidelberger 
Verlagsanstadt und Druckerei GmbH, Hauptstr. 23, D-6900 Heidelberg, 
Germany). Two, three and four bar Raschel knits can be produced by 
regulating the amount of yarn in each stitch. Orthopedic casting tape 
fabrics are generally two bar Raschel knits although extra bars may be 
employed. Factors which affect the extensibility of fiberglass Raschel 
knits are the size of the loops in the "chain" stitch, especially in 
relation to the diameter(s) of the yarn(s) which passes through them, and 
the amount of a loose yarn in the "lay-in" or "laid-in" stitch(es). If a 
chain loop is formed and two strands of lay-in yarn pass through it which 
nearly fill the loop, then the loop resists deformation and little stretch 
will be observed. Conversely, if the lay-in yarns do not fill the loop, 
then application of tension will deform the loop to the limits of the 
lay-in yarn diameter and stretch will be observed. 
Typical bar patterns for the knit fabric substrates of the present 
invention are shown in the drawings. 
FIG. 1 is a two bar Raschel knit in which bar one performs a simple chain 
stitch and bar two performs lapping motions to lay in yarn. 
FIG. 2 is a depiction of a two bar Raschel knit in which bar one performs a 
simple chain stitch and bar two performs lapping motion to lay in yarn. 
The bars are depicted in a overlapping view. 
It should be understood that the above bar patterns may be modified. For 
example, FIG. 2 may be modified by increasing or decreasing the number of 
chain stitches crossed by a particular lay-in stitch. Furthermore, 
additional lay-in stitches may be employed using, for example, a third 
bar. 
For orthopedic casting material, the fabric selected (preferably 
fiberglass), in addition to having the extensibility requirement noted 
above, should be of a suitable thickness and mesh size to insure good 
penetration of the curing agent (e.g., water) into the roll of 
resin-coated tape and to provide a finished cast with adequate strength 
and porosity. Such fabric parameters are well-known to those skilled in 
the art and are described in U.S. Pat. No. 4,502,479 which is herein 
incorporated by reference. 
The present invention is to a method of compacting high modulus knits by 
the "wet compaction" processes described herein to achieve a highly 
extensible high strength fabric. It is presently believed that this 
process will work for a variety of high modulus materials including 
fiberglass, ceramic fibers such as Nextel.TM., and polyaramides fibers 
such as Kevlar. While not being bound to any theory, the process is 
believed to result in fabric compaction due to the high modulus yarns 
relaxing to a lower stress configuration in the presence of a lubricating 
solution. For example, after being knit fiberglass fabrics typically have 
"oval" shaped loops in the wale stitch resulting from the tension applied 
by the take up rollers when removing the fabric from the needle bed. A 
loop having a "circular" shape, i.e., having a larger minimum radius of 
curvature, would have a lower energy than a more stressed oval loop. 
Attaining this lower stress configuration results in compaction of the 
fabric. 
The "wet compaction" process comprises the steps of: knitting a high 
modulus yarn to form a fabric comprising adjacent rows of loops; 
contacting the knit fabric with a lubricant (preferably a lubricating 
solution); allowing or assisting the loops to stress relax; and optionally 
removing (e.g., by drying) the lubricant from the knit. The lubricant may 
preferably comprise a lubricating solution (e.g., water) and may be rinsed 
from the knit, if desired, after the knit has been relaxed. The relaxed 
knit may optionally be heat set to prevent or decrease fraying. 
In order to achieve effective compaction of the knit it is necessary to 
contact the knit fabric with effective amounts of a lubricant. Commercial 
fiberglass yarns are often sized with a lubricating composition in order 
to facilitate processing (such as warping and knitting) and to prevent 
damage to the yarn during such processing. For example, some typical 
commercial sizings comprise starch and oil mixtures and may include 
additional additives and processing aides. In the case of ECDE 75 1/0 0.7Z 
fiberglass from PPG Industries the sizing is believed to be present at a 
level of approximately 1% by weight (0.75-1.35%). While this type and 
amount of sizing apparently facilitates production of the knit, it does 
not sufficiently lubricate the fabric so as to "wet compact" the fabric to 
a high stretch configuration. 
Ideally, a sufficient level of lubrication is imparted to the fabric in the 
sizing alone to facilitate compaction. Alternatively, it is sufficient and 
desirable to additionally lubricate the knit with a suitable lubricating 
fluid. Preferably the fabric is immersed in the lubricant but other 
techniques such as spraying the fabric with a lubricant or passing the 
fabric through a lubricating vapor are desirable. 
Suitable lubricants include any substance that controls or reduces the 
coefficient of friction between two surfaces (e.g., two contacting glass 
fiber surfaces). Suitable lubricants come in a wide variety of forms and 
modes of application. For example, neat liquids, solvent solutions, and 
solids such as powders and flakes may be employed. The lubricant may be 
applied to the surface of the fabric by any of the standard coating 
methods, including brushing, dipping, dusting, spraying, electrostatic 
coating, etc. 
Suitable liquid lubricants include water, organic solvents, silicone 
fluids, and fluorinated compounds. Suitable organic solvents include 
alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 
2-methyl-2-propanol, ketones such as acetone and methyl ethyl ketone, 
aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, acrolein, 
glutaraldehyde and 2-hydroxyadipaldehyde, amides such as acetamide esters 
such as ethylacetate and propylacetate, diesters such as diesters of 
succinic and glutaric acid, ethers such as tetrahydrofuran, 
propyleneglycols, ethyleneglycols, monoalkyl and dialkyl esters of 
glycols, and other substances such as n-methylpyrolidone and dimethyl 
sulfoxide. Of the suitable lubricants, water is presently preferred as 
this is most convenient and safe. Water is also believed to solubilize the 
starch sizing thereby increasing the lubricity of the sizing. Furthermore, 
a water lubricant does not contribute to an exothermic combustion reaction 
during subsequent heat setting of the fabric. A water lubricant may 
actually remove some of the commercially applied "sizing" and thereby 
reduce potential exothermic combustion reactions caused by the sizing. 
Preferably, when the lubricant is water, the water is applied to the fabric 
at an elevated temperature, e.g., 60.degree.-90.degree. C. More 
preferably, when the lubricant is water based, the water contains a 
detergent or surfactant which not only helps lubricate the fabric but also 
assists in the removal of any sizing. Once the sizing is effectively 
removed the fabric is "locked" into its compacted configuration in the 
sense that a significantly higher tensile force is required to extend the 
fabric and is therefore much more easy to collect by subsequent operations 
such as winding onto a core into a roll. When selecting a detergent or 
lubricating solution it is important to ensure that any materials left on 
the fabric (or on individual fibers) by the cleaning process are 
compatible with the curable resin. For example, if the fabric is to be 
coated with an isocyanate functional prepolymer resin, preferred 
lubricants would not contain organic or inorganic strongly basic 
impurities which could result in side reactions such as trimerization and 
allophonate formation. These side reactions can result in an increase in 
resin viscosity and thereby make the product eventually unusable. While 
organic basic impurities are easily removed in a subsequent heat setting 
process, inorganic bases may still remain and should therefore be 
particularly avoided. Similarly, strongly acidic impurities should be 
avoided due to potential inactivation of tertiary amine catalysts which 
may be present in the resin formulation. Therefore, preferred lubricants 
are substantially free of acidic or basic impurities which can limit the 
shelf life or alter the cure properties of the resin. 
After lubricating the fabric with a suitable lubricant as previously 
described, the fabric loops are allowed to stress relax. One method to 
assist this relaxation is to vibrate the lubricated fabric. For example, 
simply shaking the lubricated fabric composition is sufficient to effect 
compaction, however, such a process does not lend itself well to 
commercial scale application. Preferably, the knitted fabric is passed 
directly into a lubricating/washing bath. While in the lubricating bath 
the fabric may be vibrated by any suitable method including: sonic and 
ultrasonic vibration, mechanical vibration, agitation of the bath, and the 
like. The fabric is vibrated until the desired degree of compaction has 
been achieved. It should be noted that the amount of extensibility 
imparted to any particular fabric will be a function of the fabric 
construction. Therefore, knitting parameters such as runner length, knit 
pattern, and stitch length are important parameters which will determine 
the maximum amount of extensibility imparted to a fabric. 
As outlined above, it may be desirable to rinse the fabric after 
compacting. This is desired not only to remove residual impurities which 
could result in poor resin aging but also to remove the lubricant and 
thereby effectively "lock" the knit into the compacted state. 
Surprisingly, it has been found that once a majority of the sizing is 
removed (e.g., in a scouring step with either hot water or a hot detergent 
solution) the compacted fabric resists being pulled back out. This enables 
the dried fabric to be easily handled by automatic equipment (such as 
winding equipment) without losing its compacted form. "Locking" the fabric 
into a compacted state facilitates collecting the fabric and coating the 
fabric since both of these operations must be done with some degree of 
tension on the fabric. Ideally the fabric is passed continuously through 
multiple rinse stations and then dried. Rinsing may be accomplished by 
passing the fabric through a bath or by spraying the fabric while it is 
supported on a porous belt. Drying may be accomplished using convection 
heating, IR lamps, heated roller, microwave, etc. Notably, coating the 
compacted fabric with a liquid resin may cause the "lock" to be lost or 
reduced. Therefore, care should be taken to not apply tension to such 
coated compacted fabrics that would distort the fabric and reduce its 
subsequent extensibility. 
In processing the knitted fiberglass fabric of the present invention, a 
length of fabric is optionally, and preferably, heat-set while the fabric 
is in a compacted form. Preferably, the fabric is compacted and then wound 
onto a cylindrical core so large batches can be heat set at one time in a 
single oven. Care must be taken to avoid applying undue tension to the 
fabric (before the heat set has occurred) which would distort the knots 
and loops and pull out the extensibility imparted by the compacting 
process. Alternatively, the fabric may be stabilized in order to resist 
low tension handling forces. Since the fabric must be collected in some 
manner as it comes off the knitter, e.g., wound, a certain amount of 
tension may be required. In a preferred method of the present invention, a 
significant amount of tension can be applied to the fabric once the fabric 
has been washed free of most or all of its sizing. Removal of the sizing 
and drying the fabric in its compacted form produces a fabric which is 
resistant to extension. This is illustrated in Example 2. 
A continuous heat-setting process may also be used in which a length of 
fabric is first compacted by the wet compaction process described herein 
and then the compacted fabric is placed on a moving conveyor system and 
passed through an oven for a sufficient time and temperature to achieve 
heat setting of the fabric. Alternatively, one may use the same oven to 
both "lock" the compacted fabric (e.g., by drying the lubricant) and heat 
set the fiberglass yarns. 
The heat-setting step may be performed in a number of conventional ways 
known to the art. In heat-setting a small piece of fiberglass fabric, 
e.g., 25 centimeters of tape, in a single layer, a temperature of 
425.degree. C. for three minutes has been found to be sufficient. 
Equivalent setting at lower temperatures is possible, but longer time is 
required. In general, batch processes require a longer residence time at 
the selected temperature due to the mass of glass fabric which must be 
heated and the need to remove all traces of sizing material which may 
undesirably color the final fabric. 
The optimum heat-setting process described above is sufficient in most 
cases to remove any sizing not previously removed by rinsing and drying 
the lubricant from the fabric. In general, to completely desize the 
fiberglass tape and not leave any visible residue it is necessary to heat 
the tape to a temperature between 370.degree. and 430.degree. C., more 
preferably between 400.degree. and 430.degree. C. The closer you get to 
430.degree. C. the shorter the cycle and more efficient the operation. 
Although the tape could be cleaned at higher temperatures, this may cause 
permanent degradation of the fiberglass fabric. For example, when the 
temperature of the fabric exceeds 480.degree. C. and especially when the 
temperature exceeds 540.degree. C. the tensile strength of the knit 
decreases very rapidly. When the tape is exposed to temperatures over 
590.degree. C. it becomes very brittle and wrapping a cast using normal 
tension is precluded. A preferred heat desizing cycle raises the oven 
temperature to about 430.degree. C. and maintains that temperature until 
the tape is clean (e.g., about 6-8 hours in a recirculating oven). 
However, obtaining this result is somewhat complicated since the tape's 
temperature is affected by both the heat of the oven and the heat of 
combustion resulting from burning the sizing. 
Controlling the exotherm from organic material in the knit is essential and 
can be accomplished most easily and economically by limiting the total 
amount of added organic material (e.g., sizing) which must be removed. In 
order to knit a fiberglass yarn without excessive damage a sizing is 
preferably present. Preferably the amount of sizing utilized is the 
minimum level necessary to prevent damage during knitting. A preferred 
amount of sizing for fiberglass fabrics is between 0.75 and 1.35% (based 
on weight of the fabric). 
Finally, it has been observed that the jumbo's winding tension can greatly 
influence the exothermic temperature rise due to combustion and therefore 
adversely affect web integrity. In general, jumbos wound under higher 
tension tend to reach a lower peak temperature and have a greater web 
integrity than those wound more loosely. It is believed that the organic 
content of more tightly wound jumbos burn more slowly and therefore have 
lower peak internal temperatures. While not intending to be bound by 
theory, this result is believed to be due to oxygen starvation within the 
jumbo. Within a jumbo (i.e., away from the surface of the roll) the 
availability of oxygen is controlled by the diffusion rate into the jumbo. 
Careful control of the roll's permeability to oxygen can be utilized to 
control the rate of combustion of the organic material. 
Alternatively, one may "set" the ends of the compacted fabrics of the 
present invention through the use of very soft conformable binders as 
described in U.S. Pat. No. 4,800,872 which is herein incorporated by 
reference. 
If desired, reactive functional silanes, titanates and/or zirconates could 
be added to the sizing. It is believed that such silanes would not be 
easily washed off since they would be covalently bound to the fiber 
surface. Alternatively, the silanes could be added to the fiber surface at 
the wet compacting step, e.g., in the lubricating tank. 
The fabric is preferably cooled prior to application of the resin. The 
resin is preferably coated on the fabric using an operation that minimizes 
the tension applied to the fabric. The tension applied after the resin is 
applied is critical since the resin will generally lubricate the fabric 
and allow it to extend much more easily. Therefore, a low tension coating 
process should be employed. 
In one embodiment of the present invention, a fiberglass fabric is knit 
according to the process described herein, compacted by the wet compaction 
process described herein, and then heat set in the compacted form. The 
compacted fabric is then coated with a curable resin. There are many 
advantages to this process over conventional knitting processes. First, 
unlike traditional uncompacted knit fiberglass fabrics, the fabric 
produced by this method has increased extensionability. Second, there is 
no need to knit a heat shrink yarn or an elastic yarn into the fabric to 
increase extensibility. Unlike these compaction methods, the present 
invention does not, in general, add combustible material to the fabric and 
in the preferred mode removes a substantial portion of the combustible 
sizing prior to heat setting. Therefore, the compacted fabrics of the 
present invention have very good integrity--as good or better than 
conventional heat set fiberglass fabrics. 
Suitable fabrics, after compaction, are compacted to between about 30 and 
90 percent of their original dimension. More preferably, the fabric is 
compacted to between about 50 and 80 percent of its original dimension. 
Most preferably, the fabric is compacted to between about 60 and 75 
percent of its original dimension. 
The resin selected to apply to the heat-set fabric is dictated by the 
end-use of the product. For orthopedic casting materials, suitable resins 
are well-known and described for example, in U.S. Pat. Nos. 4,376,438; 
4,433,680; 4,502,479; and 4,667,661 and U.S. patent application Ser. No. 
07/376,421 which are herein incorporated by reference. The presently most 
preferred resins are the moisture-curable isocyanate-terminated 
polyurethane prepolymers described in the aforementioned patents. 
Alternatively, one may employ one of the resin systems described herein. 
The amount of such resin applied to the fiberglass tape to form an 
orthopedic casting material is typically an amount sufficient to 
constitute 35 to 50 percent by weight of the final "coated" tape. The term 
"coated" or "coating" as used herein with respect to the resin refers 
generically to all conventional processes for applying resins to fabrics 
and is not intended to be limiting. 
To insure storage stability of the coated tape, it must be properly 
packaged, as is well known in the art. In the case of water-curable 
isocyanate-terminated polyurethane prepolymer resin systems, moisture must 
be excluded. This is typically accomplished by sealing the tape in a foil 
or other moisture-proof pouch. 
The curable or hardenable resins useful in this invention are resins which 
can be used to coat a sheet material and which can then be cured or 
hardened to reinforce the sheet material. For example, the resin is 
curable to a crosslinked thermoset state. The preferred curable or 
hardenable resins are fluids, i.e., compositions having viscosities 
between about 5 Pa s and about 500 Pa s, preferably about 10 Pa s to about 
100 Pa s. 
The resin used in the casting material of the invention is preferably any 
curable or hardenable resin which will satisfy the functional requirements 
of an orthopedic east. Obviously, the resin must be nontoxic in the sense 
that it does not give off significant amounts of toxic vapors during 
curing which may be harmful to either the patient or the person applying 
the east and also that it does not cause skin irritation either by 
chemical irritation or the generation of excessive heat during cure. 
Furthermore, the resin must be sufficiently reactive with the curing agent 
to insure rapid hardening of the cast once it is applied but not so 
reactive that it does not allow sufficient working time to apply and shape 
the cast. Initially, the casting material must be pliable and formable and 
should adhere to itself. Then in a short time following completion of cast 
application, it should become rigid or, at least, semi-rigid, and strong 
to support loads and stresses to which the east is subjected by the 
activities of the wearer. Thus, the material must undergo a change of 
state from a fluid-like condition to a solid condition in a matter of 
minutes. 
The preferred resins are those cured with water. Presently preferred are 
urethane resins cured by the reaction of a polyisocyanate and a polyol 
such as those disclosed in U.S. Pat. No. 4,131,114. A number of classes of 
water-curable resins known in the an are suitable, including 
polyurethanes, cyanoacrylate esters, epoxy resins (when combined with 
moisture sensitive catalysts), and prepolymers terminated at their ends 
with trialkoxy- or trihalosilane groups. For example, U.S. Pat. No. 
3,932,526 discloses that 1,1-bis(perfluoromethylsulfonyl)-2-aryl ethylenes 
cause epoxy resins containing traces of moisture to become polymerized. 
Resin systems other that those which are water-curable may be used, 
although the use of water to activate the hardening of an orthopedic 
casting tape is most convenient, safe and familiar to orthopedic surgeons 
and medical casting personnel. Resin systems such as that disclosed in 
U.S. Pat. No. 3,908,644 in which a bandage is impregnated with 
difunctional acrylates or methacrylates, such as the bis-methacrylate 
ester derived from the condensation of glycidyl methacrylate and hisphenol 
A (4,4'-isopropylidenediphenol) are suitable. The resin is hardened upon 
wetting with solutions of a tertiary amine and an organic peroxide. Also, 
the water may contain a catalyst. For example, U.S. Pat. No. 3,630,194 
proposes an orthopedic tape impregnated with acrylamide monomers whose 
polymerization is initiated by dipping the bandage in an aqueous solution 
of oxidizing and reducing agents (known in the art as a redox initiator 
system). The strength, rigidity and rate of hardening of such a bandage is 
subjected to the factors disclosed herein. Alternatively, hardenable 
polymer dispersions such as the aqueous polymer dispersion disclosed in 
U.S. Pat. No. 5,169,698, which is herein incorporated by reference, may be 
used in the present invention. 
Some presently more preferred resins for use in the present invention are 
water-curable, isocyanate-functional prepolymers. Suitable systems of this 
type are disclosed, for example, in U.S. Pat. No. 4,411,262, and in U.S. 
Pat. No. 4,502,479. Preferred resin systems are disclosed in U.S. Pat. No. 
4,667,661 and U.S. patent application Ser. No. 07/376,421. The following 
disclosure relates primarily to the preferred embodiment of the invention 
wherein water-curable isocyanate-functional prepolymers are employed as 
the curable resin. A water-curable isocyanate-functional prepolymer as 
used herein means a prepolymer derived from polyisocyanate, preferably 
aromatic, and a reactive hydrogen compound or oligomer. The prepolymer has 
sufficient isocyanate-functionality to cure (i.e., to set or change from a 
liquid state to a solid state) upon exposure to water, e.g., moisture 
vapor, or preferably liquid water. 
It is preferred to coat the resin onto the fabric as a polyisocyanate 
prepolymer formed by the reaction of an isocyanate and a polyol. Suitable 
isocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 
mixture of these isomers, 4,4'-diphenylmethane diisocyanate, 
2,4'-diphenylmethane diisocyanate, mixture of these isomers together with 
possible small quantities of 2,2'-diphenylmethane diisocyanate (typical of 
commercially available diphenylmethane diisocyanate), and aromatic 
polyisocyanates and their mixtures such as are derived from phosgenation 
of the condensation product of aniline and formaldehyde. It is preferred 
to use an isocyanate which has low volatility such as diphenylmethane 
diisocyanate (MDI) rather than a more volatile material such as toluene 
diisocyanate (TDI). Typical polyols for use in the prepolymer system 
include polypropylene ether glycols (available from Arco Chemical Co. 
under the trade name Arcol.TM. PPG and from BASF Wyandotte under the trade 
name Pluracol.TM.), polytetramethylene ether glycols (Polymeg.TM. from the 
Quaker Oats Co.), polycaprolactone diols (Niax.TM. PCP series of polyols 
from Union Carbide), and polyester polyols (hydroxyl terminated polyesters 
obtained from esterification of dicarboxylic acids and diols such as the 
Rucoflex.TM. polyols available from Ruco division, Hooker Chemical Co.). 
By using high molecular weight polyols, the rigidity of the cured resin 
can be reduced. 
An example of a resin useful in the casting material of the invention uses 
an isocyanate known as Isonate.TM. 2143L available from the Upjohn Company 
(a mixture containing about 73% of MDI) and a polypropylene oxide polyol 
from Arco known as Arcol.TM. PPG725. To prolong the shelf life of the 
material, it is preferred to include from 0.01 to 1.0 percent by weight of 
benzoyl chloride or another suitable stabilizer. 
The reactivity of the resin once it is exposed to the water curing agent 
can be controlled by the use of a proper catalyst. The reactivity must not 
be so great that: (1) a hard film quickly forms on the resin surface 
preventing further penetration of the water into the bulk of the resin; or 
(2) the cast becomes rigid before the application and shaping is complete. 
Good results have been achieved using 
4-[2-[1-methyl-2-(4-morpholinyl)ethoxy]ethyl]morpholine (MEMPE) prepared 
as described in U.S. Pat. No. 4,705,840, the disclosure of which is 
incorporated by reference, at a concentration of about 0.05 to about 5 
percent by weight. 
Foaming of the resin should be minimized since it reduces the porosity of 
the cast and its overall strength. Foaming occurs because carbon dioxide 
is released when water reacts with isocyanate groups. One way to minimize 
foaming is to reduce the concentration of isocyanate groups in the 
prepolymer. However, to have reactivity, workability, and ultimate 
strength, an adequate concentration of isocyanate groups is necessary. 
Although foaming is less at low resin contents, adequate resin content is 
required for desirable cast characteristics such as strength and 
resistance to peeling. One satisfactory method of minimizing foaming is to 
add a foam suppressor such as silicone Antifoam A (Dow Coming), or 
Antifoam 1400 silicone fluid (Dow Corning) to the resin. It is especially 
preferred to use a silicone liquid such as Dow Corning Antifoam 1400 at a 
concentration of about 0.05 to 1.0 percent by weight. Water-curable resins 
containing a stable dispersion of hydrophobic polymeric particles, such as 
disclosed in U.S. patent application Ser. No. 07/376,421 and laid open as 
European Published Patent Application EPO 0 407 056, may also be used to 
reduce foaming. 
Also included as presently more preferred resins in the present invention 
are non-isocyanate resins such as water reactive liquid organometallic 
compounds. These resins are especially preferred as an alternative to 
isocyanate resin systems. Water-curable resin compositions suitable for 
use in an orthopedic cast consist of a water-reactive liquid 
organometallic compound and an organic polymer. The organometallic 
compound is a compound of the formula (R.sup.1 O).sub.x MR.sup.2.sub.y-x) 
wherein: each R.sup.1 is independently a C.sub.1 -C.sub.100 hydrocarbon 
group, optionally interrupted in the backbone by 1-50 nonperoxide --O--, 
--S--, --C(O)--, or 
##STR1## 
groups; each R.sup.2 is independently selected from the group consisting 
of hydrogen and a C.sub.1 -C.sub.100 hydrocarbon group, optionally 
interrupted in the backbone by 1-50 nonperoxide --O--, --S--, --C(O)--, or 
##STR2## 
groups; x is an integer between 1 and y, inclusive; y is the valence of M; 
and M is boron, aluminum, silicon, or titanium. The organic polymer is 
either an addition polymer or a condensation polymer. Addition polymers 
are preferably utilized as the organic polymer constituent. Particularly 
useful addition polymers are those made from ethylenically unsaturated 
monomers. Commercially available monomers, from which such addition 
polymers can be formed, include but are not limited to, ethylene, 
isobutylene, 1-hexene, chlorotrifluoroethylene, vinylidene chloride, 
butadiene, isoprene, styrene, vinyl napthalene, ethyl acrylate, 
2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, 
poly(ethylene oxide) monoacrylate, heptafluorobutyl acrylate, acrylic 
acid, methyl methacrylate, 2-dimethylaminocthyl methacrylate, 
3-methacryloxypropyltris(trimethylsiloxy)silane, isobutyl methacrylate, 
itaconic acid, vinyl acetate, vinyl stearate, N,N-dimethylacrylamide, 
tert-butyl acrylamide, acrylonitrile, isobutyl vinyl ether, N-vinyl 
pyrrolidinone, vinyl azlactone, glycidyl methacrylate, 2-isocyanatoethyl 
methacrylate, maleic anhydride, vinyl triethoxysilane, vinyl 
tris(2-methoxyethoxy)silane, and 3-(trimethoxysilyl)propyl methacrylate. 
Polymers bearing hydrolyzable functionality arc preferred. An acidic or 
basic catalyst may be used to accelerate the water cure of these 
compositions. Strong acid catalysts are preferred. 
Also included as presently more preferred resins in the instant invention 
are alkoxysilane terminated resins, i.e., prepolymers or oligomers, having 
a number average molecular weight of about 400-10,000, preferably about 
500-3,000. A polymer forms upon contacting the alkoxysilane terminated 
prepolymer with water as a result of condensation of molecules of this 
prepolymer with other molecules of the same prepolymer. Each molecule of 
the prepolymer or oligomer contains at least one hydrolyzable terminal 
alkoxysilane group. Compounds of Formula I useful in the resin 
compositions of the present invention may contain one to six terminal 
alkoxysilane groups per 5 molecule. Preferably, the alkoxysilane 
terminated resin is a urethane-based resin, i.e., a prepolymer containing 
--NH--C(O)--O--group(s), or a urea resin, i.e., a prepolymer containing 
##STR3## 
group(s), or a resin containing both urea and urethane groups. More 
preferably, the resin is urea/urethane-based. 
The water-reactive alkoxysilane terminated resin having at least one 
hydrolyzable terminal alkoxysilane group per molecule is preferably a 
compound of the formula (Formula I): 
##STR4## 
wherein: 
Q is a polyol residue; 
W is --NH--C(O)--X(R.sup.2.sub.2-n-q)-- or --X--C(O)--NH--; 
X is 
##STR5## 
--O--, or --S--; 
Y is 
##STR6## 
--O--, --S--, carbamylthio (--S--C(O)--NH--), carbamate (--O--C(O)--NH--), 
or substituted or N-substituted ureido (--N(C(O)--NH--) --); 
R.sup.1 is a substituted or unsubstituted divalent bridging C.sub.1 
-C.sub.100 hydrocarbon group, optionally interrupted in the backbone by 
1-50 nonperoxide --O--, --C(O)--, --S--, --SO.sub.2 --, --NR.sup.6 --, 
amide (--C(O)--NH--), ureido (--NH--C(O)--NH--), carbamate 
(--O--C(O)--NH--), carbamylthio (--S--C(O)--NH--), unsubstituted or 
N-substituted allophonate (--NH--C(O)--N(C(O)--O--)--), unsubstituted or 
N-substituted biuret (--NH--C(O)--N(C(O)--NH)--), and N-substituted 
isocyanurate groups; 
R.sup.2 call be present or absent, and is selected from the group 
consisting of H and a substituted or unsubstituted C.sub.1 -C.sub.20 
hydrocarbon group, optionally interrupted in the backbone by 1-10 
nonperoxide --O--, --C(O)--, --S--, --SO.sub.2 --, or --NR.sup.6 -- 
groups; 
R.sup.3 is a substituted or unsubstituted divalent bridging C.sub.1 
-C.sub.20 hydrocarbon group, optionally interrupted in the backbone by 1-5 
nonperoxide --O--, --C(O)--, --S--, --SO.sub.2 --, or --NR.sup.6 -- 
groups; 
R.sup.4 is a C.sub.1 -C.sub.6 hydrocarbon group or --N.dbd.C(R.sup.7).sub.2 
; 
each R.sup.5 and R.sup.7 is independently a C.sub.1 -C.sub.6 hydrocarbon 
group; 
R.sup.6 is a H or a C.sub.1 -C.sub.6 hydrocarbon group; 
n=1-2 and q=0-1, with the proviso that when X is N, n+q=1, and when X is S 
or O, n+q=2; 
u=the functionality of the polyol residue=0-6, with the proviso that when 
u=0, the compound of Formula I is 
##STR7## 
m=2-3; and 
z=1-3. 
It is to be understood that each "R.sup.3 --Si(R.sup.5).sub.3-m 
(OR.sup.4).sub.m " moiety can be the same or different. When used in 
Formula I, the Y and R.sup.1 groups that are not symmetric, e.g., amide 
(--C(O)--NH--) and carbamylthio (--S--C(O)--NH--) groups, are not limited 
to being bound to adjacent groups in the manner in which these groups are 
represented herein. That is, for example, if R.sup.1 is carbamate 
(represented as --O--C(O)--NH--), it can be bound to Y and W in either of 
two manners: --Y--O--C(O)--NH--W-- and --W--O--C(O)--NH--Y--. 
Herein, when it is said that "each" R.sup.5 and R.sup.7 is "independently" 
some substituent group, it is meant that generally there is no requirement 
that all R.sup.5 groups be the same, nor is there a requirement that all 
R.sup.7 groups be the same. As used herein, "substituted" means that one 
or more hydrogen atoms are replaced by a functional group that is 
nonreactive, e.g., to hydrolysis and/or condensation and noninterfering 
with the formation of the cured polymer. 
In preferred materials R.sup.1 is selected from the group consisting of a 
substituted or unsubstituted C.sub.1 -C.sub.200 alkyl, a substituted or 
unsubstituted C.sub.1 -C.sub.200 acyl, and groups of up to 50 multiples of 
a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.7 -C.sub.20 aralkyl, and a C.sub.6 
-C.sub.18 aryl. By this, it is meant that R.sup.1 can be a long chain 
containing, for example, up to 50 repeating C.sub.6 -C.sub.18 aryl groups. 
More preferably, R.sup.1 is selected from the group consisting of a 
substituted or unsubstituted C.sub.1 -C.sub.100 alkyl, a substituted or 
unsubstituted C.sub.1 -C.sub.100 acyl, and groups of up to 30 multiples of 
a C.sub.5 -C.sub.8 cycloalkyl, and a C.sub.6 -C.sub.10 aryl. Most 
preferably, R.sup.1 is selected from the group consisting of a C.sub.1 
-C.sub.20 alkyl, a C.sub.1 -C.sub.8 acyl, and groups of up to 5 multiples 
of a C.sub.5 -C.sub.8 cycloalkyl, and a C.sub.6 -C.sub.10 aryl. In each of 
the preferred R.sup.1 groups, the backbone is optionally interrupted by 
1-20 nonperoxide --O--, --C(O)--, --S--, --SO.sub.2 --, --NR.sup.6 --, 
amide, ureido, carbamate, carbamylthio, allophonate, biuret, and 
isocyanurate groups. 
In each of the more preferred R.sup.1 groups, the backbone is optionally 
interrupted by 1-10 nonperoxide --O--, --C(O)--, --S--, --SO.sub.2 --, 
--NR.sup.6 --, amide, ureido, carbamate, carbamylthio, allophonate, 
biuret, and isocyanurate groups. In each of the most preferred R.sup.1 
groups, the backbone of each of the R.sup.1 groups is not interrupted by 
any of these groups. 
In preferred materials, each of R.sup.2 and R.sup.3 is independently 
selected from the group consisting of a substituted or unsubstituted 
C.sub.1 -C.sub.20 alkyl, a substituted or unsubstituted C.sub.2 -C.sub.18 
alkenyl, and groups of up to 10 multiples of a C.sub.3 -C.sub.18 
cycloalkyl and a C.sub.6 -C.sub.18 aryl. More preferably, each R.sup.2 and 
R.sup.3 is independently selected from the group consisting of a 
substituted or unsubstituted C.sub.1 -C.sub.10 alkyl, a substituted or 
unsubstituted C.sub.2 -C.sub.10 alkenyl, a C.sub.5 -C.sub.8 cycloalkyl, 
and a C.sub.6 -C.sub.10 aryl. Most preferably, each R.sup.2 and R.sup.3 is 
independently selected from the group consisting of a C.sub.1 -C.sub.6 
alkyl, a C.sub.2 alkenyl, a C.sub.5 -C.sub.8 cycloalkyl, and a C.sub.6 
aryl. In each of the preferred R.sup.2 and R.sup.3 groups, the backbone is 
optionally interrupted by 1-5 nonperoxide --O--, -- C(O)--, --S--, 
--SO.sub.2 --, and --NR.sup.6 -- groups. In optimal resins, the backbone 
of each of the R.sup.2 and R.sup.3 groups is not interrupted by any of 
these groups. 
In preferred materials, each of R.sup.4, R.sup.5, R.sup.6, and R.sup.7 is 
independently a C.sub.1 -C.sub.6 alkyl group. More preferably, each is a 
C.sub.1 -C.sub.3 alkyl group. A single prepolymer according to Formula I 
can be used in the resin composition of the present invention. 
Alternatively, a mixture of several different prepolymers according to 
Formula I can be used in the resin composition. 
Optionally, the scrims of the present invention are coated with a resin 
which incorporates microfiber fillers. These preferred orthopedic bandages 
enjoy many benefits, for example, resins which incorporate microfiber 
fillers exhibit: a dramatic increase in strength when coated on the 
backings of the present invention; an increased "early strength" upon 
curing; an improved durability and increased modulus; better 
layer-to-layer lamination strength; a lower exotherm upon setting; and a 
lower effective resin cost compared to resins which do not incorporate 
such microfiber fillers. In addition, resin suspensions employing the 
microfiber fillers of the present invention exhibit generally very little 
increase in resin viscosity--thereby ensuring easy unwind of the casting 
bandage and good handling properties such as drapability. Suitable 
microfibers for use in the present invention include those microfiber 
fillers disclosed in U.S. patent application Ser. No. 08/008,755 which is 
herein incorporated by reference. 
In addition to the application of the present invention to the field of 
orthopedic casting tapes, other uses may include wrapping and/or joining 
pipes, cables or the like; patching or bridging gaps to provide a surface 
for filling and repairs; etc. 
The following examples are offered to aid in understanding of the present 
invention and are not to be construed as limiting the scope thereof. 
Unless otherwise indicated, all parts and percentages are by weight. 
EXAMPLE 1 
Three samples of fiberglass knit (82.5 mm wide and approximately 61 m long) 
prepared according to the example of U.S. Pat. No. 4,609,578 (which is 
herein incorporated by reference) were loosely rolled up on a 76 mm 
diameter core. The cores were removed and the tape placed in individual 4 
liter mason jars containing the following solutions: 
TABLE 1A 
______________________________________ 
Component Run 1 Run 2 Run 3 
______________________________________ 
Water (60.degree. C.) 
2300 gm 2200 2340 
Alconox Detergent.sup.1 
-- 18.8 -- 
Steol CA-460.sup.2 
-- -- 22.0 
Fiberglass 204 200 207 
______________________________________ 
.sup.1 Available from VWR Scientific, San Francisco, CA 
.sup.2 An ionic polyethoxylated surfactant available from Stepan Company, 
Northfield, IL. 
The contents of each jar were heated, without agitation, to 79.degree. C. 
The jars were then sealed and placed on a mechanical shaker for 15 
minutes. The solutions were decanted off and the tape rinsed with 3 
volumes of hot (60.degree. C.) water. The tape was untangled and gently 
rewound by hand onto a 76 mm diameter core. The core was removed and the 
tape placed in an aluminum pan and dried in a 65.degree. C. recirculated 
oven for 12 hours. 
Portions of the fabrics were resized in order to evaluate the extensibility 
characteristics. The fabrics were resized by immersing the material in a 
1% aqueous solution of Ultra Downy fabric softener (available from Proctor 
and Gamble, Cincinnati, Ohio). The initial weight and wet weights are 
given below in Table 1b. 
TABLE 1B 
______________________________________ 
Run Dry Weight Wet Weight 
______________________________________ 
1 29.05 gm 41.6 
2 24.2 36.4 
3 43.75 64.7 
______________________________________ 
The tapes were tested for extensibility (% stretch) under a 22.2N load. The 
mean values were calculated for several trials (n=3 for Runs 1-3; n=4 for 
control) and appear in Table 1c. 
TABLE 1C 
______________________________________ 
Run Wet treatment 
Mean % stretch 
______________________________________ 
Control none 25.5 
1 water 46.0 
2 Alconox 47.8 
3 Steol CA-460 
51.8 
______________________________________ 
The above data indicates that addition of a detergent helps to achieve 
greater compaction. 
EXAMPLE 2 
Integrity of Heat Set Wet Compacted Fabrics: 
A portion of the fabric of Run 2 from Example 1 was desized in roll form 
using the following temperature profile: heat up from 24.degree. C. to 
427.degree. C. in 1 hour; hold at 427.degree. C. for 7 hours; and then 
cool down from 427.degree. C. to 24.degree. C. in 1 hour. 
A portion of the sample was then resized as described in Example 1. A 
control sample of fabric which was not compacted was also heat set and 
resized. The fabrics were tested for extensibility as described in Example 
1. The mean values (% stretch) were calculated for three trials and appear 
in Table 2a. 
TABLE 2A 
______________________________________ 
Run Sample Treatment Mean 
______________________________________ 
1 Control none 31.0 
2 Run 2, Ex. 1 Alconox/Heat Set 
49.3 
______________________________________ 
The integrity of the fabrics was measured by determining their tensile 
strength. Portions of each fabric (178 mm sections) were first marked off 
and placed in the standard jaws of an Instron tensile tester Model 1122 
having a jaw separation of 178 min. The marks were aligned with the tip of 
each jaw. The tape was extended at a rate of 127 mm/min until failure. The 
strain at specific stress levels is given below in Table 2b along with the 
peak stress (tensile strength) for each fabric. The integrity of the 
fabric from run 3 of Example 1 which was either resized and not heat set 
or not resized and not heat set was also determined. The mean values of 5 
samples are reported below in Table 2b. 
TABLE 2B 
__________________________________________________________________________ 
Treatment % Strain at Tensile 
Run 
Sample 
Heat Set 
Resized 
4.45 N 
13.3 N 
22.2 N 
Strength (N) 
__________________________________________________________________________ 
1 Control 
yes yes 25.0 
32.9 
35.1 
148.6 
2 Rn 2, Ex 1 
yes yes 41.5 
53.0 
56.0 
66.7 
3 Rn 3, Ex 1 
no yes 40.0 
51.1 
53.8 
71.6 
4 Rn 3, Ex 1 
no no 6.1 43.8 
49.0 
89.4 
__________________________________________________________________________ 
As is demonstrated in the above table the compacting process has 
dramatically increased the extensibility of the fabric. Furthermore, the 
heat setting process was performed without loss of extensibility. 
Comparing runs 2 and 3 indicates that the heat setting process resulted in 
only a very minor decrease in the web integrity. Comparing run 1 to runs 2 
and 3 appears to indicate that the compacting process results in a 
decrease in web integrity. This is probably a result of the rather 
vigorous shaking the samples were subjected to which resulted in visible 
fiber bundle damage. Less severe vibration such as agitation or ultrasonic 
vibration should alleviate this problem. Notably, the web integrity is 
still very high for these samples. It is also worth noting that run 4 
which was not resized had a very different stress/strain profile. Without 
sizing the tape was "stabilized" and pulling out the stretch imparted by 
the compacting process was difficult. Even at a total load of 4.4N the 
tape only elongated 6%. 
EXAMPLE 3 
Ultrasonic Compaction 
Two "marks" 152 mm apart were positioned on the center section of a 254 mm 
long by 76 mm wide piece of the fiberglass fabric of Example 1. The marked 
tape was immersed for 3 minutes in an ultrasonic cleaner (available from 
Leco as Model MEII) filled with a 0.75% by weight solution of Alconox in 
water at 45.degree. C. After this time the 152 mm marked section measured 
only 139 mm. After an additional 3 minutes in the bath the fabric was 
removed and rinsed in 45.degree. C. tap water. The marked section now 
measured only 133 mm (the fabric has been compacted by 12.5%). Since the 
initial uncompacted fabric had an extensibility of about 25.5% the 
compacted fabric of this example would have a total extensibility of about 
43.4%. 
Various modifications and alterations of this invention will be apparent to 
those skilled in the art without departing from the scope and spirit of 
this invention, and it should be understood that this invention is not 
limited to the illustrative embodiments set forth herein.