Water Repellency Test | Bundesmann Water Repellency Test

Bundesmann Water Repellency Test

The Bundesmann test aims to produce the effect of a rainstorm on a fabric in the laboratory. Water repellency test is done by Bundesmann test.   In the test shown in Fig. the fabric is subjected to a shower of water from a head fitted with a large number of standard nozzles. During the shower the back of the fabric is rubbed by a special mechanism which is intended to simulate the flexing effect which takes place when the fabric is worn. 

The Bundesmann shower test.

The method is not currently a British standard because considerable variation has been found between different machines, although when tests are carried out on the same machine the variability can be reduced to acceptable levels. 

In the test four specimens are mounted over cups in which a spring loaded wiper rubs the back of the cloth while the whole cup assembly slowly rotates. They are subjected for l0 min to a heavy shower whose rate has been adjusted so as to deliver 65ml of water per minute to each cup. The water flow is maintained at 2O0C and between pH 6 and 8. Because of the large amount of water consumed the equipment has to be connected to the mains water supply which leads to difficulties in keeping the water temperature constant. The shower is calculated to have a kinetic energy 5.8 times that of a cloudburst, 90 times that for heavy rain, 480 times that for moderate rain and 21,000 times that for light rain.

Two fabric parameters are determined from the test:
1 Penetration of water through the fabric: the water collected in the cups is measured to the nearest ml.
2 Absorption of water by the fabric: in order to do this the specimen is weighed before the test and then after the shower. To remove excess water the fabric is shaken ten times using a mechanical shaker and then weighed in an airtight container: 

In each case the mean of four values is calculated.

What is Pilling Formation on Fabric? | Pilling Resistance Test |Working Procedure of Pilling Resistance Test

Pilling
Pilling is a condition that arises in wear due to the formation of little ‘pills’ of entangled fibre clinging to the fabric surface giving it an unsightly appearance. Pills are formed by a rubbing action on loose fibres which are present on the fabric surface. Pilling was originally a fault found mainly in knitted woollen goods made from soft twisted yarns. The introduction of man-made fibres into clothing has aggravated its seriousness. The explanation for this is that these fibres are stronger than wool so that the pills remain attached to the fabric surface rather than breaking away as would be the case with wool. Figure 7.3 shows a pill on a cotton/polyester fabric.

The initial effect of abrasion on the surface of a fabric is the formation of fuzz as the result of two processes, the brushing up of free fibre ends not enclosed within the yarn structure and the conversion of fibre loops into free fibre ends by the pulling out of one of the two ends of the loop. Gintis and Mead consider that the fuzz formation must reach a critical height, which is dependent on fibre characteristics, before pill formation can occur.

Pilling Resistance Test:
Purpose and Scope:
This method is intended for the determination of the resistance of textiles of all kinds in all forms to the action of an applied resistive force. This causes pilling in the tested fabrics

Apparatus:
· Pilling tester
· Metal plates 4 inch diameter and 1 inch thick
· Standard for assessing the pilling grade

Working Procedure:
A piece of fabric measuring 10×10 inch is sewn to a firm fit when placed round a rubber tube. The out end of the fabrics is covered by cellophane tape and metal plates are placed on the tester .Run the tester for 300 cycles. Remove the sample and compare the sample with standard scale. 

Standard
Pilling Standard:              3-4 gray scale matching 

What is Air Permeability | Air Permeability Test

Air Permeability

The air permeability of a fabric is a measure of how well it allows the passage of air through it. The ease or otherwise of passage of air is of importance for a number of fabric end uses such as industrial filters, tents, sailcloths, parachutes, raincoat materials, shirtings, downproof fabrics and airbags.

Air permeability is defined as the volume of air in millilitres which is passed in one second through 10Os mm2 of the fabric at a pressure difference of 10mm head of water.

In the British Standard test the airflow through a given area of fabric is measured at a constant pressure drop across the fabric of 10mm head of water. The specimen is clamped over the air inlet of the apparatus with the use of rubber gaskets and air is sucked through it by means of a pump as shown in Fig.A. The air valve is adjusted to give a pressure drop across the fabric of 10mm head of water and the air flow is then measured using a flow meter.

Five specimens are used each with a test area of 508mm2 (25.4mm diameter) and the mean air flow in ml per second is calculated from the five results. From this the air permeability can be calculated in ml per 100mm2 per second.

The reciprocal of air permeability, air resistance, can be defined as the time in seconds for ImI of air to pass through 100s mm2 of fabric under a pressure head of 10mm of water. The advantage of using air resistance instead of air permeability to characterize a fabric is that in an assembly of a number of fabrics, the total air resistance is then the sum of the individual air resistances. 

 

Fig(A) : The air permeability test

To obtain accurate results in the test, edge leakage around the specimen has to be prevented by using a guard ring or similar device (for example, efficient clamping). The pressure drop across the guard ring is measured by a separate pressure gauge. Air that is drawn through the guard ring does not pass through the flowmeter. The pressure drops across the guard ring and test area are equalised in order that no air can pass either way through the edge of the specimen. A guard ring of three times the size of the test area is considered sufficient.

Bursting Strength Test | Diaphragm of Bursting Test

Bursting Strength

Tensile strength tests are generally used for woven fabrics where there are definite warp and weft directions in which the strength can be measured. However, certain fabrics such as knitted materials, lace or non-wovens do not have such distinct directions where the strength is at a maximum. Bursting strength is an alternative method of measuring strength in which the material is stressed in all directions at the same time and is therefore more suitable for such materials. There are also fabrics which are simultaneously stressed in all directions during service, such as parachute fabrics, filters, sacks and nets, where it may be important to stress them in a realistic manner. A fabric is more likely to fail by bursting in service than it is to break by a straight tensile fracture as this is the type of stress that is present at the elbows and knees of clothing.

When a fabric fails during a bursting strength test it does so across the direction which has the lowest breaking extension. This is because when stressed in this way all the directions in the fabric undergo the same extension so that the fabric direction with the lowest extension at break is theone that will fail first. This is not necessarily the direction with the lowest strength.

Diaphragm of Bursting Test
The British Standard describes a test in which the fabric to be tested is clamped over a rubber diaphragm by means of an annular clamping ring and an increasing fluid pressure is applied to the underside of the diaphragm until the specimen bursts. The operating fluid may be a liquid or a gas.

Two sizes of specimen are in use, the area of the specimen under stress being either 30mm diameter or 113mm in diameter. The specimens with the larger diameter fail at lower pressures (approximately one-fifth of the 30mm diameter value). However, there is no direct comparison of the results obtained from the different sizes. The standard requires ten specimens to be tested.

Bursting Strength Test

In the test the fabric sample is clamped over the rubber diaphragm and the pressure in the fluid increased at such a rate that the specimen bursts within 20 ± 3 s. The extension of the diaphragm is recorded and another test is carried out without a specimen present. The pressure to do this is noted and then deducted from the earlier reading.

The following measurements are reported:

• Mean bursting strength kN/m2 
• Mean bursting distension mm
• Liquid
• Piston
• Rubber
• diaphragm
• Specimen
• Clamp

The US Standard is similar using an aperture of 1.22 ± 0.3 in (31 ± 0.75mm) the design of equipment being such that the pressure to inflate the diaphragm alone is obtained by removing the specimen after bursting. The test requires ten samples if the variability of the bursting strength is not known.

The disadvantage of the diaphragm type bursting test is the limit to the extension that can be given to the sample owing to the fact that the rubber diaphragm has to stretch to the same amount. Knitted fabrics, for which the method is intended, often have a very high extension. 

Water Resistance, Water Resistancy | Determination of Water Resistanceby Shirley Hydrostatic Head Tester

Name of the Experiment: Determination of water resistance by Shirley Hydrostatic Head tester.

Introduction:
The merit of a fabric intended for rainwear, wagon covers or tents is judged, amongst other properties, by its ability to keep water out; conversely, when intended for hose pipes or canvas buckets, to keep water in. In another direction, some fabrics must exhibit the ability to absorb water rapidly, toweling being an obvious example. So there is a relation between water and textile materials which is very necessary for their end use.
 
Objective:
To measure the water resistance of the given fabric.
 
Theory:
Water resistance is the force or pressure of water which it applied on textile material to keep out though it and the determination of this required pressure or force is very important for particular use of a fabric. Shirley Hydrostatic Head tester is used to determine this pressure of water. In this instrument the specimen holder consists a double-chambered cell; the internal diameter of the inner chamber is 5 cm. Circular specimens are clamped between rubber gaskets over the orifice. Compressed air enters the outer chamber through a tube B and displaced the distilled water contained in the chamber through communicating passages into the inner chamber, thereby forcing water up against the specimen. The clamp is provided with a skirt which prevents air from leaking continuously across the test specimen from inner to outer chamber or to the atmosphere. The tube is connected to a manometer and the pressure of water against the fabric is, for all practical purposes, the pressure shown on the adjustable scale mounted on one arm of the manometer tube. The air supply for the test is drawn from a reservoir of about 3 l capacity which is itself fed through a flow control device from a source which may vary between 4 and 20 in/lb2. The flow control device is so designed that once it has been set to give the required rate of increase of pressure of 10 cm of water per minute, the rate of loading will be within the specified limits of 10+/-0.5 cm/min up to the limit of the instrument. The maximum head attainable is 150 cm of water.

Spray tester

Apparatus:

1. Crease recovery tester
2. Water
3. Template
4. Canvas fabric.

Sample:
Spherical canvas fabric.
Size:       6 cm diameter.
 
Atmosphere:
Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.
 
M/c specification:
Name: Shirley Hydrostatic Head tester
Brand: NEGRETTI & ZAMBRA, made in England. 

Capacity: 0-150 cm.  

Working Procedure:

1. Circular specimens of 6 cm diameter are cut very carefully with as little handling of the fabric as possible.
2. The test cell is rinsed with distilled water and filled up to approximately 0.3 cm of the top.
3. The inner rubber gasket is thoroughly dried by wiping with a clean absorbent cloth and a test specimen is laid over the orifice.
4. The dried clamp is placed in position and screwed down.
5. The switch is turned to ‘Head’ position to start the compressor and then turned to ‘Test’ position.
6. The pressure under the specimen is increased at a specified rate and until water appears minimum at the three places on the fabric, the switch will not be turned to ‘Head’ position.
7. As soon as three drops of water appear on the fabric the reading is taken from the dial.
8. In this way at least 10 readings are taken from 10 specimens and average pressure is then calculated.

Data:

S/n	Pressure in cm	Average pressure
1	28	30.8
2	30
3	34
4	29
5	33

Table: Pressures found from the test.

Result:
The water resistance of the sample fabric is 30.8 cm water pressure. As a result fabric will be water repellent.

Remark:
According to the type of fabric the resistance of fabric varies between 0 -150 cm. The sample of the fabric is a canvas cloth and its water resistance is 30.8 cm. So it may say that the fabrics resistant to water is enough for its end uses.

Water Repellency, Water Repellent | Determination of Water Repellencyby Spray Tester

Name of the Experiment: Determination of water repellency by Spray tester.

Introduction:
The merit of a fabric intended for rainwear, wagon covers or tents is judged, amongst other properties, by its ability to keep water out; conversely, when intended for hose pipes or canvas buckets, to keep water in. In another direction, some fabrics must exhibit the ability to absorb water rapidly, toweling being an obvious example. So there is a relation between water and textile materials which is very necessary for their end use.

Objective:
To measure water repellency of a given fabric.

Theory:
Water repellent is a state characterized by the non-spreading of water globules on a textile material. This term is not normally applied to a water-repellent finish impervious to air. This is generally referred to as water proof. It is generally done by treated fabric with fat, wax, rubber etc. This addition may be in form of physical film or coating or physical combination. The feature of a waterproof fabric is the low degree of air permeability. Spray tester is such an instrument which measures the water repellency of a fabric. In this test a small amount of shower is produced by pouring water through a spray nozzle. The water falls on to the specimen which is mounted over a 6 in. diameter embroidery hoop and fixed at an angle of 45 degrees. To carry out the test, 250 cm3 of water at 70oF are poured steadily into the funnel. The American Association of Textile Chemists and Colorists recommend the use of a chart of photographs against which the actual fabric appearance is compared. 

The ratings are as follows:

Rating                Description
100                     No sticking or wetting of the upper surface.
90                       Slight random sticking or wetting of the upper surface.
80                       Wetting of upper surface at spray points.
70                       Partial wetting of whole of upper surface.
50                       Complete wetting of whole of upper surface.
0                        Complete wetting of whole of upper and lower surfaces.

Apparatus:
1. Spray tester
2. Water
3. Fabric

Sample:
100% cotton, polyester, umbrella, parachute cloth.

Atmosphere:
Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

M/c specification:
Name: Spray tester
Brand: DAIEI KAGAKUSEHCI SEISAKUSHO LTD., Kyoto Japan.
Template: 50 cm circumference.

Working Procedure:
1. The sample fabric is mounted on the embroidery hoop and fixed on the instrument at 45o.
2. Now the beaker is filled with 250 cc water and poured on the funnel.
3. The water is showered through spray nozzle on the fabric.
4.After spraying has finished the sample holder is removed and the surplus water removed by tapping the frame 6 times against a solid object, with the face of the sample facing the solid object.
5. The water repellency is assessed from the spray rating chart.
6. 5 tests should be made and the nearest rating assigned to each, since no interpolation is allowed, i.e. a rating for a specimen cannot be 75.
7. The mean of the 5 ratings is taken as the result.

Data:

S/n	Type of fabric	Spray rating
1	100% cotton	0
2	Polyester	0
3	Umbrella	70
4	Parachute	100

Table: Ratings found for different fabrics.

Result:
Water repellency of a 100% cotton fabric is 0.
Water repellency of a polyester fabric is 0.
Water repellency of a umbrella fabric is 70.
Water repellency of a parachute fabric is 100.

Remark:
According to the type of fabric water repellency varies from 0-100. From the experiment we can understand this. It is mainly selected depending on the end use of fabrics.

Determination of Light Fabric Strength by Vertical Strength Tester

Figure: The pendulum lever principle

Name of the Experiment: Determination of light fabric strength by vertical Strength Tester with pendulum lever principle.

Introduction:
The strength of a fabric gives us an idea how much load we can apply on it and it is very important for fabric. The strength of the fabric is very necessary for it because if the fabric strength is not good then it will break with excessive tensile force and thus the dresses produced may tear with the outside force. The strength of a fabric varies with EPI, PPI, and Count variation. The strength of the fabric also varies if the length and width of the fabric to be tested is changed. The strength of the fabric also depends on the construction of the fabric. A plain fabric is stronger than a twill fabric if made from yarn of same count.

The m/c used here is a vertical strength tester .Therefore, the experiment has two objects:

1. To find out the strength of the fabric.
2. To be precise in testing.

Theory:
Strength is a measure of the steady force necessary to break a material and is measured in pound. The m/c works in Pendulum lever principle with constant rate of extension.
Assuming the specimen to be extensible and an absence of any dynamic effects, we get from the figure:
Fr = Mgr = MgRsinq

As the value of M,g,R and r are constant, therefore
F µ sin q.
According to the applied force the m/c dial gives us the strength in lb on the basis of this q.
Apparatus:
1. Cotton fabric
2. Fabric strength tester
3. Scissors

M/c specification:

1. The Fabric Strength Tester
2. Goodbrand & Co. Ltd.
3. Capacity: 250lb

Testing atmosphere:
Temperature – 29oC and relative humidity – 76%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

Sample:
Size – 8inch X 2inch.
No. of sample – 20 (For warp way-10, For weft way-10).

Working procedure:
1.At first 12inch × 2inch fabric was cut out from a big piece of fabric. The excess amount of fabric was cut because the two jaws will require at least 2inch each to grip the fabric. Thus 10 samples were cut down for testing.
2.Now, the first sample is fixed with the upper jaw J1 and the lower jaw J2.
3.The m/c is started and observed the dial until the sample is torn out.
4.When the sample is torn out the m/c is stopped and the reading is taken.
5.By this way the others’ reading are taken.
6.At last average and CV% are calculated.

Data:

Warp way:

Reading	Fabric strength (lbs)	Avg strength (lbs)	SD	CV%
1	80	82.3	3.23	3.92
2	87
3	86
4	78
5	80

        
Weft way:

Reading	Fabric strength (lbs)	Avg strength (lbs)	SD%	CV%
1	71	70.4	2.9	4.24
2	64
3	69
4	72
5	74

Calculation:

Result:

The warp way fabric strength= 82.3 lbs
The weft way fabric strength= 70.4 lbs
The CV% for warp way fabric strength=3.92%
The CV% for weft way fabric strength=4.24%

Remark:
The strength of a fabric varies with (1) EPI variation,(2) PPI variation, (3) Count variation. The strength of the fabric also varies if the length and width of the fabric to be tested is changed. If we take a sample which size is 3inch×6inch and another sample size 2inch×6inch then the strength of the first sample will be greater than the second one. Thus if we increase the length of the second sample then the strength of the second sample will be decreased. The strength of the fabric also depends on the construction of the fabric.