# GATE (TF) Textile 2018 Question Paper Solution | GATE/2018/TF/34

###### Question 34 (Textile Technology & Fibre Science)

Match the test in Group I with fabric property in Group II.

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### How do you measure permeability of fabric?

Water vapor permeability is an important property of fabric that determines its breathability and comfort. There are several methods for measuring the water vapor permeability of fabric, including the cup method, the sweating guarded hotplate method, and the modified inverted cup method. Here’s an overview of the modified inverted cup method:
Materials:
Fabric sample
Weighing scale
Cylindrical vessel (with diameter of 120 mm and height of 80 mm)
Glass or plastic tube (with a diameter of 12 mm and length of 120 mm)
Rubber stopper (with a hole to accommodate the tube)
Deionized water
Procedure:
Cut a circular fabric sample with a diameter of approximately 120 mm.
Weigh the fabric sample and record the weight.
Fill the cylindrical vessel with deionized water to a depth of approximately 20 mm.
Insert the glass or plastic tube through the rubber stopper and place the stopper at the bottom of the vessel.
Place the fabric sample over the vessel and secure it in place with the help of the rubber stopper.
Weigh the assembly (vessel + fabric + stopper + tube) and record the weight.
Place the assembly in a conditioning chamber maintained at a temperature of 25 ± 1°C and a relative humidity of 50 ± 5% for 24 hours.
Remove the assembly from the conditioning chamber and weigh it again to determine the weight gain due to the absorption of water vapor by the fabric.
Calculate the water vapor permeability of the fabric using the following formula:
WVP = (m/t) x (L/A)
where WVP is the water vapor permeability in g/m2/h, m is the mass of water evaporated (g), t is the time in hours, L is the thickness of the fabric sample in m, and A is the exposed surface area of the fabric sample in m2.
The modified inverted cup method provides a reliable and reproducible measure of water vapor permeability of fabrics. It is commonly used in the textile industry to evaluate the performance of fabrics for various applications, including sportswear, outdoor apparel, and medical textiles.

### What are the methods of fabric stiffness?

Fabric stiffness is a measure of the resistance of a fabric to bending, folding or draping. It is an important characteristic for fabrics used in certain applications, such as industrial fabrics, tents, and upholstery. There are several methods used to measure fabric stiffness. Here are some of the most common methods:

Shirley stiffness tester: This is a mechanical instrument that measures the resistance of a fabric to bending. A rectangular fabric sample is clamped between two parallel plates and a weight is applied to the center of the sample. The deflection of the sample is measured and used to calculate the bending stiffness of the fabric.

Cantilever test: In this method, a fabric sample is clamped at one end and allowed to hang freely. The deflection of the fabric under its own weight is measured and used to calculate the bending stiffness of the fabric.

Kawabata Evaluation System (KES): This is a comprehensive system for evaluating the mechanical properties of fabrics, including stiffness. The KES measures the bending, shearing, and compression properties of the fabric and provides a stiffness index that represents the fabric’s overall stiffness.

Circular Bend Test: This method measures the ability of a fabric to recover from a curved shape. A fabric sample is bent around a cylindrical mandrel of a specific diameter, and the angle of curvature is measured. The fabric is then released and the angle of recovery is measured. The difference between the two angles is used to calculate the stiffness of the fabric.

Handle-O-Meter: This is an instrument used to measure the stiffness, smoothness, and softness of fabrics. A fabric sample is clamped between two plates and a weight is applied to the center of the sample. The sample is then pulled through a slot and the force required to do so is measured. This force is used to calculate the stiffness of the fabric.
These methods are widely used in the textile industry to evaluate the stiffness of fabrics and to ensure that they meet the requirements for specific applications.

### What is a spray rating test fabric?

A spray rating test is a test used to determine the water resistance of fabrics. It measures the ability of a fabric to resist penetration by water under a specific pressure. The test involves spraying water onto a fabric sample at a constant rate and pressure and then visually inspecting the sample for any signs of water penetration or wetting.
The spray rating test is commonly used in the textile industry to evaluate the water resistance of fabrics used in applications such as rainwear, outdoor apparel, and tents. The test is typically performed using a spray rating tester, which consists of a water spray nozzle, a sample holder, and a standardized water pressure and flow rate.
During the test, the fabric sample is placed on a flat surface and the spray nozzle is positioned at a specific distance and angle from the sample. Water is sprayed onto the fabric at a constant rate and pressure for a specified period of time, typically 2-5 minutes. The sample is then visually inspected for any signs of water penetration or wetting, and a spray rating is assigned based on a standardized scale, typically ranging from 0 to 5, with higher numbers indicating greater water resistance.
A spray rating of 0 indicates that the fabric immediately wets out and allows water to penetrate through, while a rating of 5 indicates that the fabric remains completely dry and does not allow any water to penetrate through. Spray ratings between 1 and 4 indicate varying degrees of water resistance, with a rating of 4 indicating good water resistance and a rating of 1 indicating poor water resistance. The spray rating test is an important tool for assessing the water resistance of fabrics and ensuring that they meet the requirements for specific applications.

### What is the test method for hydrostatic pressure?

The hydrostatic pressure test is a commonly used method for determining the water resistance of fabrics. The test involves measuring the amount of water pressure required to force water through a fabric sample.
Here are the general steps for conducting the hydrostatic pressure test for fabric:

1.Cut a circular sample of the fabric to be tested with a diameter of at least 100 mm.
2.Mount the fabric sample over the opening of a test cell.
3.Fill the test cell with distilled water, ensuring that the water level is at least 20 mm above the surface of the fabric sample.
4.Clamp the test cell onto the test head of a hydrostatic pressure tester.
5.Increase the water pressure inside the test cell at a rate of approximately 60 mm/min until water droplets are observed on the underside of the fabric or water starts to penetrate through the fabric.
6.Record the pressure at which water droplets appear or water starts to penetrate through the fabric. This pressure is referred to as the hydrostatic pressure or water resistance of the fabric.
The hydrostatic pressure test is typically performed in accordance with standard test methods such as AATCC 127 or ISO 811. These test methods provide specific details on the equipment to be used, the preparation of test samples, and the testing procedures.