Analysis of advantages and disadvantages of various stiffeners and control of key points in process

2020-11-24

Times

In western developed countries, emulsion polyacrylate has been widely used in textile printing and dyeing industry because of its low price, convenient synthesis and stable performance. Commonly used stiffening agents include melamine resin, urea-formaldehyde resin, polyacrylate, polyvinyl acetate, polyvinyl alcohol, starch and their modified products

Advantages and disadvantages of various stiffeners

name	advantage	disadvantage
melamine resin	The finished fabric has good stiffness, shrinkage, elasticity and hand feeling, especially for synthetic fibers.	After finishing, the fabric is easy to absorb moisture, stiffness decreases, yellowing and strength decreases, and free formaldehyde is released The storage stability of finishing agent is poor.
Lauxite	The finished fabric has better stiffness and lower raw material cost.	The finished fabric has poor elasticity, rough hand feeling, large shrinkage, poor washing resistance and free formaldehyde release, etc. The finishing agent has poor storage stability.
Polyacrylate and polyvinyl acetate	It has the characteristics of light resistance, aging resistance, no yellowing, convenient synthesis, good storage stability and no free formaldehyde; Good stiffening effect, especially suitable for stiffening finishing of cellulose fiber fabrics.	When the amount of finishing agent is the same, the stiffness of synthetic fiber fabric is not as good as that of melamine resin, and the finished fabric lacks elasticity and thick feeling. Polyvinyl acetate is brittle and has poor frost resistance.
polyvinyl alcohol (PVA)	It has good rheological property, can form a film with high strength, and has good stiffness finishing effect on cellulose fabric.	It is difficult to degrade in natural environment and can form a large number of foams in water; Finishing agent is easy to soften and ooze when heated on fabrics, and has poor washing resistance.
Modified starch	The fabric has the advantages of easily available raw materials, low price, no corrosion, convenient use and biodegradability, and can make the fabric have better stiffness effect.	After finishing, the stiffness of the fabric decreases after being affected with moisture, which is easy to deteriorate and mildew, and has poor washing resistance, rough hand feeling and poor elasticity.

Key points of process

The baking process has great influence on the formaldehyde on the cloth and the stiffness of the finished fabric. With the increase of baking time and temperature, the stiffness increases and the formaldehyde content on the cloth decreases obviously. When the processing technology is controlled at 2O0℃×60s, the formaldehyde on the cloth can reach below 75ppm.

This is because with the strengthening of baking process, the crosslinking of stiffening agent is more sufficient, so the stiffness of finished cloth increases; On the other hand, formaldehyde on the finished cloth is volatile at high temperature, which leads to lower formaldehyde on the final cloth.

There is a reversible equilibrium reaction between stiffening finishing agent and formaldehyde. With the change of external environment (such as temperature, humidity, pH, etc.), formaldehyde will be separated continuously. After finishing, the formaldehyde on the cloth surface was low at the initial stage, and increased gradually with the extension of storage time. After the storage time reached 10 ~ 12 days, the formaldehyde on the cloth surface basically tended to be stable.

If stored in a closed environment, the released formaldehyde will accumulate more and more, and it will have a pungent and dazzling feeling. It is suggested that the fabrics treated with stiff resin should be stored in a well ventilated place.

Applicable conditions of various stiffeners

1. Stiffness of cotton fabric after finishing: polyvinyl alcohol > polyacrylate > starch > melamine resin;

2. Stiffness of polyester fabric after finishing: polyvinyl alcohol > starch > melamine resin > polyacrylate;

3. Washing fastness: polyacrylate > polyvinyl alcohol > melamine resin > starch

4. The stiffness of polyvinyl alcohol after finishing on cotton fabric and polyester fabric is high, but the hand feel is rough. The elasticity of polyvinyl alcohol on polyester fabric is inferior to melamine resin, and the washing fastness is second only to polyacrylate. The stiffness of the fabric after starch finishing is good, second only to polyvinyl alcohol, but the washing fastness is very poor;

5. After finishing polyester fabric with melamine resin, the stiffening effect is better, and the thickness and elasticity are better, but the finishing effect on cotton is not ideal, and the finished fabric will release formaldehyde; Polyacrylate has better stiffness finishing effect on cotton, but not ideal finishing effect on polyester fabric, but the washing fastness is the best.

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