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Showing posts with label Testing & Quality Control-I. Show all posts
Showing posts with label Testing & Quality Control-I. Show all posts

Saturday, 12 September 2020

Fabric Strength | Tensile Strength | Tearing Strength | Bursting strength

Tensile strength testing: This is referred to as a strength test where the load is applied along the direction of the test sample. Tensile strength test of fabric is divided into two groups-
1. Strip test and
2. Grab test.

👉Strip strength test:
i. Five fabric samples are extended in a direction parallel to the warp and five parallel to the weft.
ii. The specimens are cut to a size of 2.5 inches in width and then removing threads from both edges until the width has been reduced to 2 inches. 
iii. The test length should be 8 inches between the jaws and so enough extra length must be allowed for gripping in the jaws.
iv. Under optimum conditions, the specimen will be mounted centrally. Security gripped along the full width to prevent slipping.
v. The load is applied uniformly across the full specimen width till the specimen tear out.
vi. If a test specimen breaks within 0.25 inch of the line of contact of either of the pairs of jaws at a load less than the average of normal breaks, the result should not be used in the calculation. 

Tensile strength testing|Strip strength test|Texpedia
Figure: An apparatus for fabric tensile strength test.

Friday, 11 September 2020

Crease Resistance & Recovery | Shirley Crease recovery tester

The crease is a fabric defect evidenced by a break line or mark or folds in a fabric generally caused by a sharp fold. Crease appears when the fabric is distorted in such a manner that part of it is stretched beyond its elastic recovery.  During creasing the upper surface of fabric goes on extension and lower surface goes on compression.

Crease Resistance: The resistance to creasing of textile material during use is known as crease resistance. Amongst the textile materials, the decreasing order of crease resistance is wool, silk, acetate rayon, viscose, rayon, cuprammonium rayon, cotton, flax etc.
Crease recovery: It is the property of a textile material by which it can return to its former shape after being creased. The measure of crease resistance is specified quantitatively in terms of crease recovery angle. The crease recovery of fabric can be increased by resin treatment.

Wednesday, 26 August 2020

Transmission Electron Microscope | TEM

Working Principles:
A transmission electron microscope fires a beam of electrons through a specimen to produce a magnified image of an object.
TEM working flows.

Tuesday, 25 August 2020

Scanning Electron Microscope | SEM

Working Principles: Produces images of a sample by scanning the surface with a focused beam of electrons. Electrons from the beam hit the surface of the sample and bounce off it as the secondary electron, backscattered electron etc. A detector registers these scattered electrons and turns them into a picture.
SEM Working flows.

Monday, 24 August 2020

X-RAY Powder Diffractometer | XRD

Working Principles:

X-rays are collimated and directed onto the sample. As the sample and detector are rotated, the intensity of the reflected X-rays is recorded. When the geometry of the incident X-rays impinging the sample satisfies the Bragg Equation, constructive interference and a peak in intensity occur. A detector records and processes this X-ray signal and converts the signal to a count rate which is then output to a device such as a printer or a computer monitor. Every crystalline substance gives a pattern; the same substance always gives the same pattern, and in a mixture of substances each produces its pattern independently of the others. The X-ray diffraction pattern of a pure substance is, therefore, like the fingerprint of the substance.


Textile testing | Crease resistance & recovery | Measuring crease recovery

To evaluate how something works under certain established methods or test standardsTextile testing is to check its properties under certain conditions in a standard environment prescribed as per Test standards. 

Main steps for textile testing:
  1. Checking raw materials
  2. Monitoring production
  3. Assessing the final product
  4. Investigation of faulty material
  5. Product development and research

Different fabric tests:
  1. Dimensional Characteristics- A) Length, B) Width, C) Thickness
  2. Threads/Inch – EPI, PPI, CPI, WPI
  3. Count- Warp & Weft
  4. Weight,
  5. Crimp%,
  6. Strength,
  7. Abrasion & Pilling,
  8. Handle a) Stiffness, b) Drape, c) Crease Resistance & crease recovery,
  9. Flame Retardancy,
  10. Water repellency

Sunday, 23 August 2020

Thermogravimetric Analyzer | TGA

Thermogravimetric Analyser (TGA) measures weight changes in a material as a function of temperature (or time) under a controlled atmosphere. Its principle uses include measurement of a material’s thermal stability, filler content in polymers, moisture and solvent content, and the percent composition of components in a compound.

Construction
The thermogravimetric analysis instrument usually consists of a high-precision balance and sample pan. The pan holds the sample material and is located in a furnace or oven that is heated or cooled during the experiment. A thermocouple is used to accurately control and measure the temperature within the oven. The mass of the sample is constantly monitored during the analysis. An inert or reactive gas may be used to purge and control the environment. 


Thermogravimetric Analyzer | TGA


Principle of Operation
A TGA analysis is performed by gradually raising the temperature of a sample in a furnace as its weight is measured on an analytical balance that remains outside of the furnace.

Saturday, 22 August 2020

Differential Scanning Calorimetry | DSC

Differential Scanning Calorimetry (DSC) is a thermal analysis technique in which the heat flow into or out of a sample is measured as a function of temperature or time, while the sample is exposed to a controlled temperature program. It is a very powerful technique to evaluate material properties such as glass transition temperature, melting, crystallisation, specific heat capacity, cure process, purity, oxidation behaviour, and thermal stability.

Construction
There are two pans. In one pan, the sample pan, you put your polymer sample. The other one is the reference pan. You leave it empty. Each pan sits on top of a heater. Then you tell the nifty computer to turn on the heaters. So the computer turns on the heaters and tells it to heat the two pans at a specific rate, usually something like 10ºC per minute. The computer makes absolutely sure that the heating rate stays exactly the same throughout the experiment.

Differential Scanning Calorimetry | DSC

Friday, 21 August 2020

Fourier Transmission Infra-Red | FTIR

Fourier Transform-Infrared Spectroscopy (FTIR) is an analytical technique used to identify organic (and in some cases inorganic) materials. This technique measures the absorption of infrared radiation by the sample material versus wavelength. The sample’s absorbance of the infrared light’s energy at various wavelengths is measured to determine the material’s molecular composition and structure.

How FTIR Works:
A simple device called an interferometer is used to identify samples by producing an optical signal with all the IR frequencies encoded into it. The signal can be measured quickly. Then, the signal is decoded by applying a mathematical technique known as Fourier transformation. This computer-generated process then produces a mapping of the spectral information. The resulting graph is the spectrum which is then searched against reference libraries for identification.

With the microscope attachment, samples as small as 20 microns can be analyzed. This allows quick and cost effective identification of unknown particles, residues, films or fibers. FTIR can also measure levels of oxidation in some polymers or degrees of cure in other polymers as well as quantifying contaminants or additives in materials.

Testing Process:
👉Step 1: Place sample in FTIR spectrometer. The spectrometer directs beams of IR at the sample and measures (1) how much of the beam and (2) at which frequencies the sample absorbs the infrared light. The sample needs to be thin enough for the infrared light to transmit through, or a thin slice of the material must be removed. Reflectance techniques can be used on some samples and no damage is done to the sample. Samples conducive to reflectance are residues, stains or films on a fairly flat reflective surface or somewhat pliable materials that are thin enough to fit under the microscope using the attenuated total reflectance attachment to the microscope.

👉Step 2: The reference database houses thousands of spectra, so samples can be identified. The molecular identities can be determined through this process.

Thursday, 20 August 2020

RAMAN Spectroscope

Raman spectroscope is one of the popular characterisation tools for textile testing especially textile materials characterisation. 

Working Principles: It is based upon the interaction of light with the chemical bonds within a material. Raman is a light scattering technique, whereby a molecule scatters incident light from a high-intensity laser light source. Most of the scattered light is at the same wavelength (or colour) as the laser source and does not provide useful information – this is called Rayleigh Scatter. However, a small amount of light (typically 0.0000001%) is scattered at different wavelengths (or colours), which depend on the chemical structure of the analyte – this is called Raman Scatter.


Applications:

- Vibrational, rotational and other states in molecules,
- Chemical composition and structure of samples,
- Whether solid, liquid, gas, gel or powder.

Graph: A Raman spectrum features a number of peaks, showing the intensity and wavelength position of the Raman scattered light. Each peak corresponds to a specific molecular bond vibration, including individual bonds such as C-C, C=C, N-O, C-H etc.

Tuesday, 18 August 2020

What are the Test Standards?

Textile testing is done to ensure a certain level of quality and to do so different types of pieces of equipment, principles or methods can be applied. But it is essential to follow a prescribed and well-recognized methods to get valid and reliable test results. You cannot execute any test as your wish or convenience. You have to maintain a standard testing environment to conduct the testing for instance temperature, pressure, relative humidity etc. should be maintained carefully. Otherwise, there arises the question of data validity and the generated test data will not be accepted to the research society. Various national and international organizations have established standards for textile testing. Some of the organizations involved in developing textile testing standards are as follows:

- AATCC - American Association of Textile Chemists and Colorists
- ASTM - American Society for Testing and Materials
- ANSI - American National Standards Institute
- ISO - International Organization for Standardization
- BSI - British Standards Institute 
- BIS - Bureau of Indian Standards 
- BS EN - British Standard European Norm 
- IS - Indian Standards

Reference: A Practical Guide to Textile Testing by K. Amutha (Woodhead Publishing)

Monday, 17 August 2020

What is sampling? | Why sampling? | Types of sample

The true representative of the bulk or population is termed as a sample and the process of selecting a sample is called the sampling process. Sampling for textile testing can be in-
  • Fibre stage 
  • Yarn stage 
  • Fabric stage 
  • Garment stage 
Population: All elements, individuals or units that meet the selection criteria for a group to be studied and from which a representative sample is taken for detailed examination. 

Why sampling? 
As the textile is produced in huge quantity, it is impossible to test all the final output from a production process. That is why only representative samples of the material are tested. Proper sampling saves time, cost and labour. Besides, Textile testing is destructive in nature, i.e. the materials used for testing go as waste after testing and hence it is not desirable to test all of the material.

Sunday, 16 August 2020

What is Zoning Sampling Technique?

Zoning technique: When bulk is not homogeneous, a number of sub-samples must be taken at random from different places in the bulk. Question is how much and how many times should be taken from the different position of the bulk of loose fibres like cotton. It certainly depends on the heterogeneity of the bulk/fibre bales. 

A comparatively large sample (2 ozs bulk) is drawn from the bulk and then divided into four parts. 16 small tufts are taken from each part randomly and after that, each tuft is halved four times. Each tuft is halved and one half is discarded at random; the retained half is again divided into two and half of that discarded. This process is repeated until getting 16 wisps from each part. Next, these wisps are combined to form a tuft and each tuft is again divided into four parts. A new tuft is obtained by combining a part of each of four tufts. The sample is mixed again by doubling and drawing and a quarter of the sample is taken out from each tuft to form the final sample. Zoning technique has been graphically illustrated as below-

Saturday, 15 August 2020

What is Textile Testing?

To evaluate how something works under certain established methods or test standards. Textile testing is to check its properties under certain conditions in a standard environment prescribed as per Test standards. 

Types of Testing?
Destructive testing: The testing which breaks the test specimen and goes as waste after testing is called destructive testing. For example, tensile test, compression test, bending test etc. 


Textile Testing

Nondestructive testing: The testing in which test materials do not go as waste after testing is called non-destructive testing method. For example, thermal and electrical conductivity testing.

Why testing?
- To check the quality and suitability of raw material;
- To monitor the production (process control);
- To assess the quality of final product;
- To investigate the faulty materials;
- To set standards or benchmarks;
- For R&D (research and development) purpose;
- For new product development.

Reference: A Practical Guide to Textile Testing by K. Amutha (Woodhead Publishing)

Friday, 14 August 2020

Standard Testing Atmosphere | Related Terms.

Moisture equilibrium: It is the condition reached by a material when it no longer takes up moisture from or gives up moisture to, the surrounding atmosphere. 

Pre-conditioning: To bring a sample or specimen of textile to relatively low moisture content (approximate equilibrium atmosphere with relative humidity between 5% and 25%) before conditioning in a controlled atmosphere for testing. 

Conditioning: To bring a material to moisture equilibrium with a specified atmosphere. Before a textile is tested, it is conditioned by placing it in the atmosphere for testing in such a way that the air flows freely through the textile and keeping it there for the time required to bring it into equilibrium with the atmosphere. 

Thursday, 13 August 2020

Fibre Moisture Measurement | Importance

The moisture content of cotton makes significant changes in the physical properties of cotton and hence moisture content has to be known. High moisture content increases flexibility, toughness, elongation and tensile strength. If the moisture content is too high it causes difficulty in processing due to the tendency of the stock to lap-up on drafting rolls. Low moisture, on the other hand, facilitates cleaning but increases the brittleness of the fibre and results in fibre breakage during ginning, cleaning and mill processing. Low moisture also increases fly waste and may cause manufacturing difficulties due to static electricity.

Reference: A Practical Guide to Textile Testing by K. Amutha (Woodhead Publishing)


Wednesday, 12 August 2020

What is moisture content and moisture regain?

Moisture Regain: Moisture regain is defined as the amount of water (or moisture) expressed as the percentage of oven-dry weight.

Moisture regain, MR = (W / D) × 100%,  where W = weight of moisture; D = Oven dry weight of the sample

Moisture Content: Moisture content is defined as the amount of water expressed as the percentage of the original weight of the sample. 

Moisture content, MC = [W / (W+D)] × 100% 
                                     = MR / [1 + (MR/100)], where W = weight of moisture; D = oven dry weight of sample, W + D = original weight of sample.

Oven-dry weight: It is the weight of the sample after removing all water or moisture by heating in an oven at 105℃ to constant weight. The weight of the water is the difference in the weight of the sample before and after drying. 
Moisture Content & Moisture Regain of fibres

Tuesday, 11 August 2020

The Standard Atmosphere for Textile Testing

The Standard Atmosphere for Textile Testing

Laboratory conditions for testing fibres, yarns and fabrics in which air temperature and relative humidity are maintained at specific levels with established tolerances. Textile materials are used in a number of specific end-use applications that frequently require different testing temperatures and relative humidity. Specific conditioning and testing of textiles for end-product requirements can be carried out using as below-


Standard Atmosphere for testing various materials

Materials
Temperature (℃)
Relative Humidity (%)
Textiles
21±1
65±2
Nonwovens including papers
23±1
50±2
Glass fibre for textile applications
21±1
65±5

Monday, 10 August 2020

How to cut sample from knit and woven fabric?

Fabric samples from warp and weft are taken separately as their properties vary substantially along warp and weft. Identify and mark the warp direction first. Make sure that no two specimens contain the same warp or weft threads. Mark and cut samples at least 2 inches away from the selvedge. Also, make sure not to take samples from creased, wrinkled or damaged portions of the fabric, if any. In the case of knit fabric, samples are taken from different parts of the fabric almost the same way as done for wovens.

How to cut sample from knit and woven fabric?

Sunday, 9 August 2020

Yarn Numbering System | Count

Count: It is a numerical expression of yarn fineness or coarseness and also indicates the relationship between length and weight (the mass per unit length or the length per unit mass) of that yarn. Another term ‘linear density’ is also used to express the yarn fineness or coarseness. We can have an idea about the yarn diameter by yarn count. 

Classification of Count:
1. Direct Count system (weight per unit length)
2. Indirect Count system (length per unit weight)

Direct Count system (weight per unit length): In this system, the weight of a fixed length of yarn is determined and the weight per unit length is the yarn count. The common feature of all direct count systems is the length of yarn fixed, and the weight of yarn varies according to its fineness. The following formula is used to calculate the yarn count: 

N= W / L

where, 
N = Yarn count or numbering system 
W = Weight of the sample at the official regain in the unit of the system 
L= Length of the sample

Botanical Names of Cotton Fibre

1. Gossypium Herbaceum:  - Fibre length: 20mm – 26mm  - Producing country: India, China, Bangladesh  3. Gossypium Arboreum: - F...