Bonded Fabric

Bonded fabric is a combined structure of fabric that is being created by joining two set of fabric. This attachment of two fabrics can be made with adhesive or thin bonding fabric with low melting point without any major changes of finished fabric thickness. Here a face or shell fabric is joined with backing fabric. Artificial leather products can be a good example of this type of fabric. Bonded fabric also used in design purposes and fabric stabilization.

An aqueous acrylic adhesive is used for joining bonded fabric. A latex adhesive such as, acrylate, a vinyl chloride or vinyl acetate or thermosetting resin also being used for this purpose. This bonding strength between these two layer fabrics is the main thing where the end uses of the finished product depends on.

Fabric Bonding Procedure:
There are two common methods for attaching fabric to fabric.
1. Wet adhesive method
2. Flame foam method

Wet adhesive method:
· An adhesive liquid is applied to the back of the face fabric.
· Face fabric is set on backing fabric and passed together between the heated rollers.
· Thus, the heat fixes the adhesive between two fabrics and makes the bonded fabric.

Flame foam method:
· Here, a thin layer of polyurethane foam is used to attach two set of fabrics
· First, polyurethane foam is melted a little by passing it over a fire/heat.
· Then this melted foam is set between two layers of fabric just like a sandwich.
· After that, when the foam got dries, it attach the two layers of fabric.

Actually the foam in the bonded fabric is so thin (around 0.010 inch). That why, It doesn’t make any significant changes on the thickness of the finished fabric. By this method fabric may got stiffer than the wet-adhesive method. Sometime foam may appear of the surface of the fabric. That’s why it is not better not to use this method with open-weave fabrics.

Advantages
· This bonded fabric is much cheaper in price
· This fabric is machine washable
· Fabric doesn’t crease easily

Crimp based on warp and weft yarn on fabric

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CRIMP
When warp and weft yarns are interlaced in a fabric they follow a WAVE or CORRUGATED configuration, the plane of the weave being substantially perpendicular to that of the fabric. This WAVINESS OF YARN is called CRIMP of yarn and is expressed quantitatively either as a fraction, c or as a percentage, c per cent:

c = (Ly - Lf)/Lf; and, c per cent = (Ly – Lf) x 100/Lf

Where Ly = the un crimped length of the yarn, and, Lf = its extent in the fabric.

The expression c = (Ly – Lf) / Lf may be written as:

c = Ly / (Lf - 1), from which

(1 + c) = Ly / Lf;

where (1 + c) is called the crimp ratio. It is useful in fabric calculations.

MATH: Calculate the length of warp required to weave 160 yds. of cloth if the warp crimp is 12 percent.

We know,
Lf = 160 yd. and c1 percent = 12; so c1 = 0.12, where c1 is fractional warp crimp, and

Ly = Lf (1 + c) = 160 x 1.12 = 179.2 yd.

So, to prepare 160 yds of fabric 179.2 yds of warp is required.

MATH: What length of cloth can be woven from 800 yds of warp if the crimp is 8 percent?

We know
Ly = 800 Yd., and c1 percent = 8, so c1 = 0.08; where c1 is fractional warp crimp, and

Lf =Ly/(1+c) = 800/1.08 = 740.8 yds.

So, 800 yds. of warp will weave 740.8 yd of cloth.

When the shuttle inserts the weft in the open shed, the weft is un crimped, and each pick has a length Ly, which is equal to the width occupied by the warp in the reed. This is called the reed width. When it is beaten up by the reed and incorporated into the cloth at the cloth fell, the weft attempts to crimp under the scissors-like pressure exerted by the warp threads. At this stage, it is prevented from crimping freely by the temples, whose function is to hold out the cloth near the fell to reed width, so as to prevent excessive abrasion of the warp threads near each selvedge by the reed. As the cloth moves forward towards the breast beam, it leaves the temples and is free to contract to a length Lf, called loom-state width. The weft is now crimped. We have three variables, i) reed width, ii) the width of the loom-state cloth, and iii) the weft crimp in the loom-state cloth. If we know two of these variables, the third can be calculated as illustrated by the following examples.

MATH: Calculate the reed width required to give a cloth with a loom-state width of 38”, if the weft crimp in the loom-state cloth is known to be 6 percent.

We know
Lf = 38”, and c2 percent = 6; so c2 = 0.06, where c2 weft crimp, and

Ly = Lf (1 + c) = 38 x 1.06 = 40.28”

which is the required reed width.

MATH: Calculate the loom-state cloth width if the reed width is 60”, and the weft crimp is known to be 9 percent.

We know

Ly = 60” and c2 percent = 9; so c2 = 0.09, where c2 is weft crimp, and

Lf = Ly/ (1+c) = 60/1.09 = 55.05”

which is loom-state cloth width.

MATH: Calculate the weft crimp in the loom-state cloth if the reed width is 44” and the loom-state cloth width is 40”.

We know

Ly = 44”, and Lf = 40”.

Therefore (1+c) = Ly/Lf = 44/40 = 1.10, so c2 = 0.10 and c2 percent = 10

which is the weft crimp.

In any of the above examples we could substitute the width of the finished cloth for that of the loom-state cloth, provided that we also substitute the weft crimp in the finished cloth for that of the in the loom-state cloth. The calculation would be valid, if no unrecoverable shrinkage had occurred during finishing, but not, for example for a milled woolen cloth.

EFFECT OF CRIMP OF YARN ON FABRIC PROPERTIES
a) RESISTANCE TO ABRASION: With the increase of crimp %, the abrasion resistance will also increase
b) SHRINKAGE: With the increase of crimp %, shrinkage of fabric will decrease.
c) FABRIC BEHAVIOUR DURING TENSILETESTING: With the increase of crimp%, breaking load of fabric will also increase.
d) FABRIC COSTING: With the increase of crimp%, fabric costing will also increase. Because crimp decrease the length of yarn as a result more yarn will be needed for fabric manufacture in case of more crimp on yarn.
e) FAULTS IN FABRIC: If there is variation of crimp in the threads then the following faults may be found in fabric; A) Reduction in strength may occur, and B) Stripes will be seen in yarn dyed cotton fabric.
f) FABRIC DESIGN: To achieve satisfactory appearance and required shape in finished fabric control of crimp in warp and weft yarn is necessary..
g) FABRIC STIFFNESS: If crimp is increased then stiffness of fabric will decrease.
h) ABSORBENCY: With the increase of crimp % absorbency of the fabric will increase.
i) DIMENSIONAL STABILITY: Dimensional stability will decrease with the increase of crimp%.
j) FABRIC HANDLE: If crimp is increased then the fabric will be soft in handle.
k) DYE TAKE-UP: With the increase of crimp the take-up percentage of dye-uptake will also increase.

Wish You Good Luck..................................
You Should Interested to read RELATED POST on the topics

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Cover Factor of Fibre, Yarn and Fabric

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CONCEPT OF SIMILAR CLOTH
Fibre or raw materials of the two cloths may be same but they can differ on other factors, such as:-
i) The yarn count may be different.
ii) The ratio of yarn count in warp and weft may differ.
iii) The warp ratio of yarn spacing may differ.
iv) The average of yarn spacing may differ.
v) The weave design may differ.
vi) The amount of twist in yarn may differ.

If there is similarity in COVER FACTOR of two cloths but they differ in such points as mentioned above then they are called similar cloth.

COVER FACTOR
Cover is the degree of evenness of thread spacing. Good cover gives the effect of a uniform plane surface & it can not be obtained with hard twisted yarn. In case of woven fabric cover factor is a number that indicates the extent to which the area of a fabric is covered by warp and weft threads. For any fabric by introducing suitable numerical constants its evaluation can be made in accordance with any system of counting. It is denoted by k.

Mathematically,

        k = d / p;

where, d₁ = Warp dia; d₂ = Weft dia; P₁ = Warp spacing; P₂ = Weft spacing; k₁ = Warp cover factor, and k ₂ = Weft cover factor.

     

So, k₁ = d₁/P₁    &    k₂ = d₂/P₂

Therefore, Fabric Cover Factor =  k₁ + k₂.

The ratio of yarn diameter to yarn spacing, d/p, is a measure of the relative closeness of the yarns in the warp or weft of a woven fabric. This ratio also expresses the fraction of the area of the cloth covered by the warp or weft yarns. We may therefore call it the fractional cover,  i.e.

                      Fractional cover = d / p.

Substituting Peirce’s estimate of yarn diameter, d = 1/28 √N, we have 

d / p= [1/(28√N) x1/p]

 But 1/p = n, where n = threads/in., so

 d / p= n/(28√N) ……………………………… (6)

Now d/p has a value of 1.0 when the yarns are just touching. Peirce multiplied eq.(6) by 28 to eliminate the numerical constant, 28, and defined the result as the ‘coverfactor’, K.

Cover Factor, K  = n /  √N  ……………………………………………..(7)

Because we have multiplied by 28, cover factor as defined in eq.(7) has a value of 28 when the yarns are just touching. The relative yarn spacing corresponding to various cover factors are shown below:

It is usual to calculate separate cover factors for the warp and the weft. Using the suffices 1 and 2 for warp and weft, we have

      Warp Cover Factor, K₁ = n₁ / √N₁ and

      Weft Cover Factor, K₂ = n₂ / √N₂.

The sum of the warp and weft cover factors is known as cloth cover factor, Kc.  It is customary and more informative, however, to state the warp and weft cover factors separately. Just as twist factor enables us to compare the relative hardness of twist in yarns of different counts, so cover factor enables us to compare the relative closeness of the yarns in different fabrics.

Math related to cover factor

Compare the relative closeness of the warp yarns in the following two plain cloths; (a) 16s cotton; 50 ends/in; and (b) 36s cotton; 84 ends/in.

We have the cover factor for cloth (a), K₁ = 50 / √16   = 12.5.

And for cloth (b) cover factor, K₂ = 84 / √36   = 14.0

So the ends are more closely spaced in cloth (b) than in cloth (a)

MATH:- Calculate the warp and weft cover factors for the following fabric: 60 denier nylon x 48s worsted; 96 x 72.

      60 denier = 5315/60 = 88.57s cotton count.

So, K₁ = 96 / √88.57   = 10.2

       40s worsted = 48 x 560/840 = 32s cotton count.

So, K₂ = 72 / √32   = 12.7

GENERAL FORMULA FOR CALCULATING COVER FACTORS

   Indirect systems                                              direct systems.

      K = cn/ √N                                                    K = cn √N

Where N is the yarn number in the particular system.

System                Value of c                          System          Value of c

Cotton                     1.0                                     Denier        0.01375

Worsted                  1.228                                 Tex             0.04126

Linen lea                 1.667                                 lb/spdl        0.2422

MATH: Calculate the cover factor corresponding to 80 threads/in. of 100 denier. 

From the table constant for the denier system is  0.01375.

Therefore, K  = 0.01375 x 80 x √100  = 11.0

MATH: How many threads/in. of 5 tex nylon are required to give the same cover factor as 90 threads/in. of 2/100s cotton?

Since the equivalent singles count of 2 /100s is √50 s.

Therefore,

                            K  = 90/ √50.

So, K = 12.7  = 0.04126 x n √5

 Therefore  the number of threads required

n=12.7/0.04126 x √5 = 138 threads / in.         

Thus required thread/in is 138 of 5 tex to give the same cover factor as 90 threads/in. of 2/100s cotton.

This problem can also be solved with reference to the formula for calculating cover factor.

     5 tex  = 590.5 / 5  = √118 s cotton count.

As before, K  = 12.7  = n/ √118.

Therefore n = 12.7 x   118   = 138 as before.

Wish You Good Luck..................................
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