Methods For Investigating And Testing Materials Flashcards
Material testing
Used to help select the most appropriate fabric for a product.
When setting up tests the process and parameters must be consistently fair
Types of simple workshop tests
Flammability, creased assistance, shrink resistance, colour fastness, strength, piling.
Simple workshop test: flammability
Use are precisely cut fabric samples and paper fuses
Like 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 predetermined observations such as what happens when the flame comes into contact with the fabric
Simple workshop test: crease resistance
The fabric is folded in half and placed between pieces of paper under the weight
After placing the fabric sample on the measuring block leave it to recover for five minutes then calculate the distance between the two ends on the horizontal scale
Record the results and repeat with other fabrics being tested
Simple workshop tests: shrink resistance
Sew coloured cross-stitches are use a permanent pen to mark an exact 10 cm square
Retain a control sample and wash the remaining samples at different temperatures and levels of washing machine agitations
Dry and iron the samples
Work out the percentage shrinkage for example: length between A and B before washing, and then length between A and B after washing, then calculate the percentage shrinkage (length before minus length after divided by original length x by 100)
Simple workshop test: colourfastness
Important factors affecting colourfastness are washing and exposure to sunlight
Samples are sewn onto white fabric and washed for a predetermined time at an agreed temperature. The dried samples are compared to a control sample and the white fabric is checked for staining.
A prolonged period of time is needed and light at 10:30 cannot be controlled in the same way as in a laboratory
Simple workshop test: strength
Strength is difficult to replicate in workshops. It is impossible to achieve the large forces needed to break a fabric using basic tools and experiments.
Prepare same-sized samples
Make a small cut at the warp, weft and bias edges
Tear the samples along with the cut to see which tears easily and which fabric requires more force
Simple workshop test: pilling
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 pilling to start forming on the surface of fabric is recorded
Industrial tests types
Flammability, crease resistance, shrink resistance, colourfastness, strength, pilling
Industrial test: flammability - test 1 minimum flame application time to cause ignition
The prepared fabric sample is held vertically in a metal frame
A small flame from a Bunsen burner is applied for two seconds, then three, four, six, eight and ten seconds until it catches fire
The test is complete if the fabric burns for more than one second
The time and any other predetermined observations are recorded
Industrial test: flammability - test 2 Flame spread and flame behaviour
This test is used on fabrics that have low flammability
A small flame is applied to a prepared fabric sample and removed after ten 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
Industrial test: flammability - test 3 rate of flame spread
A larger sample of fabric is placed in a metal frame
Cotton trip threads, attached to timers, are placed horizontally
A small flame is applied and then removed after 10 seconds
As each cotton trip thread is burnt through, it’s timer will stop, showing the burn distance and allowing the burning rate to be calculated
Industrial test: crease resistance
Standard test pieces are cut from wrinkle-three fabric
Samples are kept in standard room conditions to ensure the fabric temperature and humidity is identical
A sample is folded in half and compressed under a load for a specified time
The load is removed and one end of the creased sample is clamped onto the instrument. The other end is allowed to fall free
The dial of the instrument is rotated to keep the free edge of the sample in line with a knife edge
At the end of the time allowed for recovery, the recovery angle is recorded from the engraved scale
The larger the angle of recovery the better the crease resistance
Industrial test: shrink resistance
The fabric sample is overlocked to prevent fraying
Permanent ink is used to mark precise reference points on the fabric
The prepared fabric samples are washed with pieces of polyester fabric to replicate a normal wash load
The samples are dried using all available options
If the results of re-measuring between the reference points show a change has occurred, the formula used in workshop test is applied to calculate the percentage change
Fabric shrinkage is shown as a negative percentage. Fabric stretch, as a result of the test, is shown as a positive percentage.
Industrial test: colour fastness - test 1 wash fastness
Samples are cut to an agreed size
Each sample is secured in a white fabric ‘envelope’ and washed for a set time at an agreed temperature
The dried samples are compared to the control sample. Changes in colour and the staining of the ‘envelope’ fabric are assessed using grey scales. The best grade is five and the worst grade is one
