Technical points: Cotton/ammonia core-spun yarn elastic fabric has the advantages of cotton fiber and the high elasticity of spandex, making the fabric have a good deformation recovery angle, breathable, moisture permeable, and soft to the touch. However, because the product contains spandex, improper use of alkali, hypochlorite, etc. in pre-treatment or improper process control such as mercerization and shaping will have a negative impact on the spandex elastic fiber, causing the cotton/spandex (weft) elastic fabric to lose style. Therefore, the following points should be mastered in the pre-treatment process to reduce misunderstandings in production.
1 The effect of alkali on spandex elastic fiber Influence.
Spandex suffered little strong damage when boiled with 40g/L NaOH for 1h, 2h, and 3h under normal pressure conditions, and the elastic recovery rate was above 97%. On the open-width scouring machine, 60g/L NaOH was used for two dips and two rollings, steamed at 102°C for 60 minutes, and the elastic recovery rate was still 96%. Using 50g/L NaOH, 10-11g/LH2O2 and other cold rolling stacks for 18 hours, the elastic recovery rate was 98%, indicating that there was little strong damage during cold rolling stacks. If hot rolling, coiling, and steaming are used for 3 hours, the elastic recovery rate is only about 3%, indicating that the elasticity damage is greater when hot rolling and steaming are used, and it should not be used.
2 Effect of hypochlorite on spandex elastic fiber .
In tests on spandex elastic fabrics under different concentrations of sodium hypochlorite and under different time conditions, it was found that the sodium hypochlorite concentration was 4g/L, the time was about 1 hour, and the elastic recovery rate was about 96%. , the concentration of sodium hypochlorite is greater than 4g/L, and the time is more than 1 hour, the elasticity of the spandex is significantly reduced.
3 Effect of mercerized alkali concentration on spandex elasticity.
When the alkali concentration is 150-230g/L, the elasticity of spandex is not greatly damaged; however, the application depends on the thickness of the fabric. The alkali concentration for mercerization of thin fabrics should be lower, and for heavy fabrics, the alkali concentration should be lower. The alkali concentration shall not exceed 230g/L.
4 Effect of heat setting on the elasticity of spandex.
After testing, the spandex elasticity has little effect when the heat setting temperature is 160°C. The setting time should be determined according to the thickness of the fabric. The setting time for thin fabrics (such as stretch poplin) is generally within 30s, for medium-thick fabrics is generally 40s, and for thick twill fabrics, the setting time does not exceed 60s. Based on the above tests, different processes can be adopted according to the factory equipment and the process conditions can be controlled before the pre-treatment process can be reasonably formulated. </p
