methods for investigating and testing materials-1.2

Question 1

how is flammability tested in a workshop?

Answer 1

-use cut fabric samples and paper fuses
-light the fuse and use a stopwatch to time how long it takes for the flame to reach the wire marker
-record the time and other factors such as what happens when the flame comes in contact with the fabric

Question 2

how is crease resistance tested in a workshop?

Answer 2

-the fabric is folded in half and placed between two pieces of paper under a weight
-place the fabric sample on a measuring block resting on a pin and leave it to recover for 5 mins and then calculate the distance between it’s two ends on the horizontal scale
-record the result and repeat with other fabrics being tested

Question 3

how is shrink resistance tested in a workshop?

Answer 3

-sew coloured cross stitches or use a permanent pen to mark a 10cm square
-keep a control sample to compare with the other samples after they are washed at different temperatures and levels of washing machine agitation
-dry and iron the samples
-work out the percentage shrinkage- change in shrinkage / original length all x100

Question 4

how is colour fastness tested in a workshop?

Answer 4

-samples are sewn onto white fabric and washed for a specific amount of time at a specific temperature
-the dried samples are compared to a control sample and the white fabric is checked for staining

Question 5

how is strength tested in a workshop?

Answer 5

• it’s impossible to achieve the larger forces needed to break the fabric using basic tools and equipment.
  -prepare same sized samples and make a small cut at the warp and weft and bias edges
  -tear the samples along the cut to see which tears easily and which fabric requires more force

Question 6

what is pilling?

Answer 6

the formation of little balls of fibres (pills) that form on the surface of the fabric as a result of friction and wear

Question 7

how is pilling tested in a workshop?

Answer 7

-fabric samples are stapled onto a wooden block
-glass paper is stapled onto a smaller wooden block
-the glass paper block is rubbed over the surface of the fabric to stimulate wear
-the number of passes required for pills to form on the surface of the fabric is recorded

Question 8

where are industrial tests usually carried out and with what?

Answer 8

in laboratories in controlled conditions using specialist-testing machinery and standardised test pieces of materials

Question 9

what is the first industrial flammability test?

Answer 9

• a fabric sample is held vertically in a metal frame
• a small bunsen burner flame is applied until it catches fire
  -if the fabric burns for more than one second, the test is complete
  -the time and other observations are recorded (e.g whether burn marks are left)

Question 10

what is the second industrial flammability test?

Answer 10

the flame spread and flame behaviour test- used on fabrics that have low flammability

• a small flame is applied to a fabric sample and removed after 10 seconds
  -the duration of the flame and afterglow are timed and any debris is recorded
  -the size of the hole burned into the fabric is measured and recorded

Question 11

what is the third industrial flammability test?

Answer 11

rate of flame spread:

-large sample of fabric is placed in a metal frame
-cotton trip threads are attached to timers and placed horizontally
-a small flame is applied and removed after 10 seconds
-as each cotton trip thread is burnt through, it’s timer will stop- showing the burn distance and the burn rate to be calculated

Question 12

how is shrink resistance industrially tested?

Answer 12

• a fabric sample is overlocked to prevent fraying
  -a pen is used to mark reference points on the fabric
  -the fabric samples are washed with pieces of polyester fabric to replicate a normal wash load
  -samples are dried
  -if the results of re-measuring between reference points show a change has occurred, a percentage change is calculated
  -fabric shrinkage is shown as a negative percentage
  -fabric stretch is shown by a positive percentage

Question 13

what is the first colour fastness industrial test?

Answer 13

-samples are cut to an agreed size
-each sample is placed in a white fabric ‘envelope’ and washed for a set time and temperature
-the dried samples are compared to the control sample
-changes in colour and staining of the envelope fabric are assessed using grey scales. the best grade is five and the worst grade is 1

Question 14

what is the second colour fastness industrial test?

Answer 14

-samples are cut to an agreed size
-a multi-fibre swatch is sewn to the sample
-accelerated washing (washing which replicates five or more home washes) is done in canisters placed in a machine called a launderometer
-grey scale cards and the control sample are used to evaluate changes in shade, and the extent of staining on different fibres

Question 15

what is a multi-fibre swatch?

Answer 15

a band of woven fabric that is made of multiple fibres and is used to assess the colour transfer of materials.

Question 16

what is colour fastness?

Answer 16

the ability of a fibre or fabric to retain dye during manufacturing processes and when washed or exposed to sunlight

Question 17

what are grey scale cards?

Answer 17

cards that are used to show differences in colour intensity when comparing control samples with samples exposed to washing and UV light

Question 18

what is the third industrial test for light fastness?

Answer 18

-samples are cut to an agreed size
-2/3 of each sample are enclosed in an opaque cover
-the uncovered area of the sample is exposed to intense artificial light generated by a xenon arc lamp
-the light is filtered to replicate the intensity of natural daylight through glass
-the area of the exposed sample is compared with the covered part using the grey scale cards

Question 19

what is the strip test?

Answer 19

a test for tensile strength for woven fabrics

Question 20

how do you do the industrial strip test?

Answer 20

-rectangular fabric samples are cut in a direction parallel to the warp and weft
-to ensure all the yarns in the sample run along it’s entire length, the width of each sample is reduced to 5cm by raveling (removing) yarn from both edges
-the sample is stretched and the distance travelled is plotted which gives information like maximum load and final breaking point
-the test is repeated with samples cut in the warp and weft directions

Question 21

what is the bursting test?

Answer 21

strength test for knitted fabrics

Question 22

how is the bursting test done?

Answer 22

• a circle of knitted fabric is clamped over a rubber diaphragm
  -air or water is pumped under pressure into a chamber below the sample fabric and rubber diaphragm
  -the pressure is applied radially and is increased until the knitted fabric bursts
  -the pressure needed to rupture (burst) the fabric is called it’s bursting strength

Question 23

what machine tests for abrasion and pilling?

Answer 23

the martindale machine

Question 24

how is the pilling test done?

Answer 24

-circular samples of the test fabrics are clamped onto one of the martindales machines four disks and a weight is put on each disk
-the test samples are rubbed against an abrasive fabric
-the machine controls and records the number of rubbing cycles
-the test samples are examined at regular intervals for the presence of wear leading to pilling
-once done, the samples are compared in a light box with the control sample