Practical Textile 
Cationic polyester is cationic dyeable polyester. It is a special type of polyester that can be dyed at only 100⁰C temperature with cationic dyestuffs. Whereas ordinary polyester is dyed at 130⁰C. This is to get better strength and sustainability.
Some special fibers like silk and wool can not be dyed at 130⁰C temperature. Because they can lose their strength and recover at this high temperature and pressure. For this purpose, we can use this cationic durable polyester to make them blend.
The abbreviation of cationic polyester is CDP or PBT. At the factory level, it is also called CD yearn.
If we Blend:
Silk + Normal Polyester = Dyeing with 130⁰C Result: Silk damage (Strength)
Silk + CDP = Dyeing with only 100⁰C Result: Silk has its strength and recovery.
So that at the last, We can say that this is cationic polyester.
Mechanism of Cationic polyester/Why Cationic polyester can dye at 100⁰C:
Normal polyester (PET):
- Hydrophobic
- Higher crystalline So that there is no gap inside the fiber structure.
- It has no ability to combine with acid, basic or direct dyes.
- The molecular chain structure is tight.
- Not possible to inter the dye molecule into the fiber structure.
- It only creates a hydrogen bond with dispersed dye at high temperatures and pressure.
Because of its higher crystallinity and tight molecular structure, it has no swelling and dye absorption properties like cotton fiber. So that it needs a higher temperature (Upper than 130) and pressure to open the molecular structure and to create amarpass region. In this condition, the dye molecules can enter the fiber structure and create a hydrogen bond.
Cationic Polyester:
Polyester chip + dimethyl isophthalate (with polarity-based SO3Na) = Cationic Polyester
So that has-
- Lower crystalline properties than PET.
- The molecular chain structure is looser than PET.
- Higher absorption property.
- Hither hygroscopicity.
As a result, the dye molecule can easily enter the fiber molecule at a low temperature and pressure than PET. So that it can be dyed at 100⁰C.
So that at the last, We can say that this is cationic polyester. and it can be dyed at 100⁰C.
Frequently Asked Questions:
1. What is the cationic polyester fabric?
The cationic polyester fabric is a fabric made with CDP yearn. It can also be blended with different fibers. This fabric dyeing with cationic dyestuff.
2. What is cationic polyester Interlock fabric?
Interlock fabric made of CDP yarn is cationic polyester interlock fabric.
3. Is the cationic polyester dyeing process is power and energy-consuming process?
Yes, the cationic dyeing process is a more power and energy-consuming process than the ordinary polyester dyeing process. Normal polyester needs 130⁰C whereas cationic polyester needs only 100⁰C. So it consumes around 30% of power and energy.
Research link:
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[…] The cationic polyester (CDP) dyeing process is the special dyeing process by which cationic dyeable polyester is dyed with cationic dyestuff at 100⁰C temperature. Whereas normal polyester (PET) is dyed at 130⁰C temperature. […]