Textile stiffener is an organic polymer substance that improves the appearance of fabric, increases the elasticity and heaviness of fabric, and gives it a stiff feel. It is an important part of the finishing auxiliaries. The treated fabric can be widely used in decorative fabrics, especially curtain fabric, bag fabric and warp knitted fabric production. It is also used in the production of interlining (fusible interlining and resin interlining).
In western developed countries, emulsion polyacrylate compounds due to its low price, convenient synthesis, stable performance and other advantages in the textile printing and dyeing industry has been widely used. Commonly used stiffener are: melamine resin, urea-formaldehyde resin, polyacrylate, polyvinyl acetate, polyvinyl alcohol and starch, and their modified products.
Advantages and disadvantages of stiffeners
After finishing the fabric stiffness, shrinkage, elasticity, feel are better, especially for synthetic fiber stiffness effect is good.
After finishing, the fabric is easy to absorb moisture, hardness and stiffness decline, yellowing and strength decline,release of free formaldehyde, etc. Finishing agent storage stability is poor.
After finishing, the fabric has better stiffness and lower raw material cost.
After finishing, the fabric has poor elasticity, rough handfeel, large shrinkage, poor washing resistance and release of free formaldehyde. Poor storage stability of finishing agent.
Polyacrylates and polyvinyl acetates
It has the characteristics of light resistance, aging resistance and no yellowing. Easy to synthesize, good storage stability, does not produce free formaldehyde. Stiffening effect is good, especially for cellulose fiber fabric stiffening finishing.
The same amount of finishing agent, the hardening effect on synthetic fabrics is inferior to melamine resin. After finishing, the fabric lacks elasticity and thick feeling. Polyvinyl acetate is brittle and has poor frost resistance.
It has good rheology and can form a film with high strength, which has good stiffening effect on cellulose fabric.
It is difficult to degrade under natural environment and can form a large amount of foam in water. Finishing agent in the fabric after the heat is easy to soften and bleed, poor washability.
It is easy to get raw material, low price, non-corrosive, easy to use, biodegradable, and can make the fabric have a good stiffening effect.
After finishing, the stiffness of the fabric decreases with moisture, and it is easy to deteriorate and become moldy. Poor washing resistance, rough hand feel, and poor elasticity.
Process key points
The roasting process has a greater impact on the formaldehyde on the fabric surface and the stiffness of the fabric after finishing. With the increase of roasting time and roasting temperature, the stiffness increases and the formaldehyde content on the fabric surface decreases significantly. When the processing process is controlled at 200°C×60s, the formaldehyde on the fabric can reach below 75ppm.
This is because with the enhancement of the drying process, the crosslinking of the stiffener is more adequate, so the stiffness of the fabric after finishing increases. On the other hand, the formaldehyde on the finishing fabric is easy to volatilize under high temperature conditions, resulting in low formaldehyde on the final fabric.
There is a reversible equilibrium reaction between the stiffening agent and formaldehyde. With the change of external environment (such as: temperature, humidity, pH, etc.), formaldehyde will be separated out continuously. After the finishing of the initial fabric sample formaldehyde is low, with the extension of storage time formaldehyde gradually increased. When the storage time reaches 10-12 days, cloth formaldehyde basic stabilization.
If stored in an airtight environment, the formaldehyde released will accumulate more and more, there will be a pungent and harsh feeling. It is recommended that the fabric after finishing with hardening resin should be stored in a place with good ventilation.
Applicable conditions of each type of stiffener
- Cotton fabric after finishing stiffness: polyvinyl alcohol > polyacrylate > starch > melamine resin.
- Polyester fabric after finishing stiffness: polyvinyl alcohol > starch > melamine resin > polyacrylate.
- Washing fastness: polyacrylate > polyvinyl alcohol > melamine resin > starch.
- Polyvinyl alcohol in cotton and polyester fabrics after finishing stiffness are larger, but the feel is rougher. In polyester fabric is not as elastic as melamine resin, washing fastness is second only to polyacrylate. Starch finishing fabric stiffness is good, second only to polyvinyl alcohol, but the washing fastness is very poor.
- Melamine resin finishing polyester fabric, stiffness effect is relatively good, and thick feeling and elasticity are better. But in the cotton finishing effect is not ideal, and after finishing the fabric will release formaldehyde. Polyacrylate in cotton on the stiff finishing effect is better, in polyester fabric finishing effect is not ideal, but the washing fastness is the best.
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