Answer: The following are the factors, a) Form of the material b) Amount of the material available c) Nature of the test d) Type of testing instrument e) Information required f) Degree of accuracy required

Answer: The difference between biased sampling and random sampling is, i) In random sampling every individual have a chance to include in the test sample than in biased sampling. ii) The test results may be repeated in the case of biased sampling, but in the case of random sample repetition is quite impossible. Causes of bias during sampling: a) Bias due to physical characteristic like longer fibers are always has greater chance to select than shorter fibers. b) Position relative to the person like lab technician taking samples from bobbin case repeatedly from top layer. c) Subconscious bias like person intensely choosing good material from bulk available for sampling.

Answer: a)In sample the ratio of proportion of 10 mm, 20 mm, and 30 mm will be 1: 2: 3. b) Removal of length biased sample will change the proportion of fibers in the remaining bulk as longer fibers will be removed at higher proportion. c) In the earlier figure chance of fiber crossing the lines A and B is proportion to its length. If by some way the fibers crossing this area (between A & B are selected) then the longer fibers will preferentially selected.(refer diagram in the section Sampling------->Fiber Sampling from Combed Sliver/Roving/Yarns) d)In the earlier figure chance of fiber crossing the lines A and B is proportion to its length. If by some way the fibers crossing this area (between A & B are selected) then the longer fibers will preferentially selected. (refer diagram in the section Sampling-------> Fiber Sampling from Combed Sliver/Roving/Yarns)

Answer: While cutting sample from fabric for yarn count, the strip should be taken out from various places in the fabric. Because taking sample from same course will lead bias in the sample.(Ref. figure: Sampling--------->Yarn and fabric sampling) During twist measuring of yarn, there should be gap of about 1 yard between consecutive samples. This is because to avoid error in twist level caused untwist in the sample next to the tested material.

Answer: The fiber length measurement is the one of the prime most factors for staple fiber like cotton, wool, and other natural fibers. (Fiber length of man-made cut staple is also important while work with natural fibers) The fiber length property is useful to decide machine setting in spinning (drafting zone setting), to calculate the combing efficiency and to study the breakage rate during processing.

Answer: Effective Length: Photo Electric stapler x 1.1 In this instrument, while sample of fiber fringe advanced inside of the instrument, two maximum density gradient point will be there and this distance is staple length(max. deflection of galvanometer in opposite direction)

Answer: Photo electric cells are used to measure the fiber length. A light source illuminates the fringes and the amount of light penetrating through the fringes measured electronically. At the start of the measurement the fringes are scanned across the densest region, i.e. near the comb teeth, and the light which penetrates will be a minimum. At the fiber ends, more and more light will be fall on the photo electric cells. The Servo-Fibrograph automatically records the change in the amount of light reaching the cells, not in the terms of intensity of illumination but as a special form of frequency distribution. This graph will be analyzed further for length. Ref: Fiber Length --> Measurement of Individual Fiber Length: Cotton Fiber Length --> H.Photoelectric Method (FibroGraph)

Answer: Refer: Sample length -----> Wool fiber Length

Answer: The minimum no. of fibers required in the yarn cross section is 30. If less than this in the yarn cross section means it is weak place. Also the yarn will have more Index of irregularity (like more Uster CV %).The yarn performance in further stages also will be poor.

Answer: The number of fibers in the yarn cross section will get increase, and this intern will give less mass variation (CV %), higher strength, good cover factor in the fabric, etc.

Answer: Refer: Fiber fineness ----->Method of Measurement ---->(c) By Microscope

Answer: The surface area of the fibers will increase with the increase of fineness of fibers; it is due to no. of fibers will be more in particular region than coarser fiber.

Answer: Refer: Fiber fineness -----> Method of Measurement ----> (f) Light Scattering Method

Answer: Refer: Fiber fineness ---> Method of Measurement ---> (c) By Microscope

Answer: Refer: Fiber fineness ---> Method of Measurement ---> (f) Light Scattering Method

Answer: Relative Humidity: The ratio of the absolute humidity of the air to that of air saturated with water vapor at the same temperature and pressure, expressed as a percentage. For diagram Refer: Moisture Textiles ---> Atmospheric condition and Relative Humidity ---> Moisture content By increasing the RH% in the atmosphere the moisture regains of textile fiber will be increase (shown in fig)

Answer: Refer: Moisture Textile ---> Measurement of moisture ---> 1) by Oven Dry weight method

Answer: Scouring process will remove the wax and oil contents in the yarn so scoured cotton will gain more moisture from atmosphere than raw cotton.

Answer: Fibres protruding out from the main body of the yarn are called hairiness. The number of hairs exceeding 3mm in length as a percentage of the total number of hairs is found to be linearly related to the count of the yarn, i.e. there are more hairs in a fine yarn than a coarse one of the same type. Advantages: It helps to produce Flannel type fabrics. It will increase the thermal resistance of the fabrics; it is due to air entrapped in between the hairs. Disadvantages: It causes problems in printing. Fine designs are not made possible. Machine parts life is reduced.

Answer: In filament yarns, hairiness occurs due to weak monofilaments, inadequate finish, rough surfaces, loose running monofilaments which break at subsequent process. (Due to loose run, denier is reduced hence weaken yarn)

Answer: All the three instruments are based on light principle only. But in the case of Shirley Hairiness tester & Zweigle -G565 both measuring hairiness based on set length on the instrument like Hairiness count of various hairs 1, 2, 3, 4, 6, 8, 10, 12,15,18,21, and 25 mm. But Uster Tester monitoring only total hairiness, but using the Uster evenness data collection system can monitor changes in hairiness along the yarn by means of a diagram, spectrogram, CV of hairiness, and mean hairiness in a manner similar to that used in evenness testing.

Answer: Random variation means variation occurs in the textile material in indefinite order. Example: Neps caused by immature fibres and long thick places in the yarn. Periodic variation means variation occurs in the textile material in definite fashion. Example: Thick and thin place caused problematic roll and cots in the drafting zone.

Answer: Refer: Evenness ---> Effects of irregularity ----> Variance length curve

Answer: The yarn has to be wound on black boards with help of suitable mechanical device and compare with the standard yarn appearance board for Grade (ASTM standard Yarn Appearance board). Yarn Grade C = some larger neps and smaller neps, fuzziness, foreign maters more than B, more rough appearance than B.

Answer: Refer: Evenness ---> Method of measuring yarn evenness ---> 3. By Measuring Variation In Thickness Under Compression

Answer: The spectrogram is amplitude of periodic mass variation plotted against the wave length. With help of this diagram we can trace the likely cause of imperfections or faults in the yarn, i.e. to find out the faulty parts of the machine.

Answer: The optical method is measuring the diameter variation but the capacitance method measuring the mass variation per unit length. So measuring mass variation is best suitable method for measuring yarn Unevenness. Simply, optical method is claimed to be nearer to the human eye in the way that it sees faults, the capacitance methods it feels the faults. Refer: Evenness ---> Method of measuring yarn evenness ---> 6) Optical method (IR Method): Zweigle G580

Answer: As per the Uster Classimat II the following are the objectionable faults, Short Thick faults A4, B4, C3, C4, D3, D4 are objectionable faults. In stricter norms faults under A3, B3, C2, D2 are also considered as objectionable. Long thick Faults E & G are objectionable. Thin faults H2, I1 & I2 are more critical. Normally these faults will be cleared in winding process. If it is presents in the yarn, the warping and further performance will be poor, also it will lead bad fabric appearance.

Answer: Refer: Evenness ---> Method of measuring yarn evenness ---> 7. Yarn faults classification (Capacitance method)

Answer: Breaking load means the load at which the specimen breaks, usually expressed in grams weight or pounds weight. But Tenacity (specific strength) of material is the mass stress at break; the unit is gram/tex or gram/denier. Dividing the breaking load by denier or tex of the fiber we will get tenacity value. RKM means breaking resistance in Kilometer i.e. the length of the specimen which will just break under its own weight when hung vertically.

Answer: 1. CRE: Rate of increase of specimen length is uniform with time (the load measuring mechanism moves a negligible distance). 2. CRL: Rate of increase of the load is uniform with time and rate of extension is dependent on the load-elongation characteristics of the specimen.

Answer: Breaking length = (400 * 1000) / (20 * 1000) = 20 km

Answer: If the length of test specimen increases, means the pobability of weak links are more than compared to short length of specimen, so the breaking load will get decrease when increasing the specimen length.

Answer: Refer: Tensile Testing ---> Principle of Tensile Testing ---> (b) Stelometer

Answer: Refer: Tensile Testing ---> Principle of Tensile testing ---> g) Strain Gauge principle

Answer: In this Grab Tensile test, there is a certain amount of assistance from yarns adjacent to the central stressed area so that the strength measured is higher than frayed strip test.

Answer: The loose weave fabric will have more tearing strength than high sett fabric. It is because of loose weave fabric allows the threads to group better than high sett weave, so loose weave exhibit better resistance to tearing than plain weave.

Answer: Bursting strength is a method of measuring strength in which the material is stressed in all the directions at the same time and is therefore more suitable for materials such as knitted fabrics, lace or non-woven. Fabrics used in parachute, filters, sacks and nets are simultaneously stressed in all the directions during service. In service, a fabric is more likely to fail by bursting than by a straight tensile fracture.

Answer: a) Diaphragm bursting test is not suitable for highly stretchable fabrics. b) Errors due to diaphragm expansion. c)This test can be performed using an attachment on a standard tensile testing m/c. d)25 mm diameter ball is pushed through the stretched fabric and force required is recorded. e)In diaphragm pressure is measured, but here force is measured. f)No limit to the amount that a sample can be extended. g)The load cell operates in compression mode.

Answer: In the ICI pilling test the fabric will undergo tumbling action while in the case of Martindale abrasion test the fabric sample will undergo multidirectional action against the emery cloth. So the test condition in Martindale is widely acceptable than ICI pilling.

Answer: The evaluation is made by a) Weight loss: Size of specimen depends on gsm. After abrasion the specimen is taken out and any loose debris are removed and then weighed. % loss in wt. is calculated. b) Grab Tensile Test: Grab tensile strength will be carried out before and after test. And the loss of strength will be calculated.

Answer: The Drape co-efficient is the ratio of the projected area of the draped specimen to its undraped area, after deduction of the area of the supporting disk. Drape value is useful to judge the fabric fit to the body contours. Higher the value is less fit to the contour of the body & vice-versa.

Answer: a)Stage 1: Individual protruding surface fibres are compressed (by bending) [Elastic Deformation] b) Stage 2: Inter yarn or inter fiber friction resist the slippage [Plastic Deformation] c) Stage 3: Lateral compression of the fibres themselves [Elastic Deformation]

Answer: Refer: Fabric Comfort ---> Important fabric properties for maintaining Thermal comfort ---> Air Permeability

Answer: The thermal insulation of the double layer fabric will be greater than 2T, because between the fabrics layer there will be air gap. The air presence in the gap will increase the thermal insulation.

Answer: If the fabric thickness increases means thermal conductivity will get decrease. Thermal resistance will increase by increasing the fabric porosity.