Question

The properties of acrylic fibre

Answer 1

Acrylic fibre is the most popular among the synthetic fibres. It contains about 85% acrylonitrile units. It is generated from hydrogen, cyanide, acetylene and petroleum.


The main properties of acrylic fibres may be described as follows:

Length
The length of the acrylic fibre can be controlled. That means, it may be in filament or staple form.

Fineness
Fineness of this fibre is also controllable. The filament yarns are made 75 to 200 denier ranges while staple fibres are made 2 and 3 denier cut into 1.5”, 2”, 3” and 4” length.

Strength and Extension
It is fairly strong fibre. Its tenacity is 5 gm per denier in dry state and 4.8 gm per denier in wet state. Extension at break is 15%. Good recovery from deformation.

Elasticity
It has an elastic recovery of 85% after 4% extension when the load is extremely released.

Cross-sectional shape
Normally round but cross-section of this fibre could be varied.

Appearance
It is about 30% bulkier than wool. Regarding insulating warmth, it has about 20% greater insulating power than wool.

Effects of chemical
Acid: It has good resistance to mineral acid.
Alkali: The resistance to weak alkali is fairly good but hot strong alkali damages this fibre.
Solvent: It has excellent resistance to common solvents, oils, greases, and natural salts.
Water: moisture regain of this fibre varies from 1.5% to 3%. Easy to wash and quick drying.
Effect of heat and sunlight
This fiber has very good thermal stability. Safe ironing temperature is at 1600C. At 230 – 2350C acrylic sticks with the iron i.e. melting occurs. High temperature may sometime causes yellowing of this fibre.

Effect of Biological agents
This fibre is unaffected by mildew, moulds, larves and insects.

End use
100% acrylic is used mainly in sweater, jersey, knit outer wear fabric and blankets. It is used as a blend component with cotton, viscose, wool etc. It has good warmth and recovery property. It is also used for making carpet due to good resiliency property.

Physical Properties of Acrylic: Acrylic fiber has some physical properties. Here, I have given some physical properties of acrylic.

Tenacity: 2 – 4.2 gm/den
Density: 1.16 gm/c.c
Elongation at break: 20 to 55%
Elasticity: Good
Moisture Regain (MR%): 1 – 2.5%
Resiliency: Good
Melting point: 2300C
Ability to protest friction: Good
Color: White or grey white
Light reflection ability: Good
Ability to protest heat: It can protest up to 1500C temperature.
Lusture: Bright to light


Chemical Properties of Acrylic: Chemical properties of acrylic fibers are given below.

Acids: Acrylic has enough ability against acidic action.
Basic: Strong alkali damages the fiber.
Effect of bleaching: It is safe to bleach acrylic fiber.
Organic solvent: Organic solvents do not cause harm to the acrylic fiber.
Protection ability against mildew: Excellent
Protection ability against insects: Insect does not affect acrylic fiber.
Dyes: Acid dyes and Basic dyes are suitable to dye acrylic fiber.
Acrylic fibers are widely used in textile industry.

other properties are:

1. Acrylic has a warm and dry hand like wool. Its density is 1.17 g/cc as compared to 1.32 g/cc of wool. It is about 30% bulkier than wool. It has about 20% greater insulating power than wool.
2. Acrylic has a moisture regain of 1.5-2% at 65% RH and 70 deg F.
3. It has a tenacity of 5 gpd in dry state and 4-8 gpd in wet state.
4. Breaking elongation is 15% ( both states)
5. It has a elastic recovery of 85% after 4% extension when the load is released immediately.
6. It has a good thermal stability. When exposed to temperatures above 175 deg C for prolonged periods some discolouration takes place.
7. Acrylic shrinks by about 1.5% when treated with boiling water for 30 min.
8. It has a good resistance to mineral acids. The resistance to weak alkalies is fairly good, while hot strong alkalies rapidly attack acrylic.
9. Moths, Mildew and insects do not attack Acrylic.
10. It has an outstanding stability towards commonly bleaching agents.