Analysis of common problems that textile fabrics fail to test and how to solve and improve them. There are two common aspects of testing items. One is a physical item and the other is a chemical item. The chemical item is also what we call environmentally harmful substances. Let's first understand a piece of data. These data have also been compared between its and bv in the three major testing institutions, which are basically consistent with the situation we encountered.
1. Torsion Torsion refers to the internal stress of the fabric itself, and the degree of deformation after washing is also twisted.
Skew test method ac–bd/ac+bd (2) positive value left oblique, negative value right oblique
Weaving reason: the more reasonable the fabric specification is, the less likely it is to produce skew, the finer the yarn count, the easier it is to produce skew.
Improvement plan: When determining whether a fabric can meet the standard skew, we can calculate the torsion according to the s skew and z skew by setting the front version, and then adjust it by setting the beating-up slash angle. The second twist is that the trousers do not twist legs. This is for the trousers. It is also necessary to test whether the fabric is twisted first. If so, you need to make the fabric slanted first, and then twist it back when you wash it.
2. Light fastness
National standard European standard 8-level system, level 1 is the worst, level 8 is the best, American standard is level 5, level 1 is the worst and level 5 is the best
1) Unqualified factors
The structure of the fabric
The molecular structure of the dye (the most critical dye)
Color matching with dyes with different light fastnesses
Some auxiliaries treated on the fabric will affect the light fastness (such as fixing agent softener)
Most of the fluorescent colors are generally poor at about 2 levels, and many paper printing colors are poor at about 2-3 levels. The color is sensitive, and the light fastness is poor, such as gray-green, etc.
2) How to improve
Choosing the right dye
Develop and implement reasonable dyeing process conditions, the pre-treatment is sufficient to make the fabric dyed and evenly dyed, and the color is fully fixed; soaping and washing after dyeing, fully removing the floating color, and using a light fastness enhancer
3. Pilling performance
There are four conventional methods for pilling: Martindale 2000 box pilling, random round trajectory, and the results measured by different test methods will be different.
Pilling process
Fuzzing: The fiber ends are drawn from the fabric due to friction to produce long pile; the single filaments in the filament are broken and hooked out to form a loop
Pilling: The fibers that have not fallen off are entangled with each other, and the more entangled, the tighter, and finally form small pellet
the reason
Fiber properties: high fiber strength, high elongation, especially fatigue-resistant fiber easy to fluff and pilling
Yarn structure: When the yarn twist is large, the large fibers in the yarn are tightly bound, the fibers are not easy to be drawn out, and it is not easy to pilling
Fabric structure: plain weave fabric is the least prone to pilling, satin weave fabric is the easiest to pilling, knitted fabric is easier to pilling than woven fabric
Improvement skills: Choosing a yarn with good twist and less hairy feel is not easy to pilling. The tighter the fabric, the less likely it is to pilling. Appropriate singeing, shearing and bristling treatment can reduce the pilling performance of the fabric. Excessive softness has a certain untwisting effect and will increase the risk of pilling. Enzyme treatment and anti-pilling finishing can improve the anti-pilling performance to a certain extent.
4. Color fastness to bleaching and non-chlorine bleaching
1) Unqualified factors
Active chlorine reacts with the dye, causing the dye to undergo oxidative decomposition;
The peroxide reacts with the dye matrix to change or fade the dye, or damage the bond between the dye and the fiber.
The color fastness of dyes to chlorine bleaching and non-chlorine bleaching is related to the structure of the dye, and the general reactive dyes are generally poor.
2) How to improve
Select dyes reasonably, and choose dyes with chlorine bleaching resistance and non-chlorine bleaching structure; (reactive dyes are generally inferior, and vat dyes are the best)
Fully scouring before dyeing, and washing after dyeing, strive to remove impurities and keep the fabric neutral, because the presence of impurities and acid and alkali will accelerate the decomposition of the dye under the conditions of chlorine bleaching and non-chlorine bleaching;
Use chlorine-resistant fixing agent to improve the chlorine resistance of dyes and strengthen the combination of dyes and fibers;
Chlorine bleaching fixatives have increased the requirements of the American standard by about one level, and the Japanese standard requirements can be achieved by level 4. It is mainly related to the different test methods and effective chlorine concentration.
5. The color fastness of denim fabric to ozone
1) Unqualified factors
Denim is generally dyed with indigo dye. Indigo dye is decomposed into isatin under the action of strong oxidizing agent, and ozone has a strong oxidizing effect.
Isatin should be red, but the phenomenon seen in the actual test is more yellowish, which is related to the purity of the dye used, other chemicals added in the dyeing process, the fabric and the finishing process
2) How to improve
Choose a dye with a structure resistant to ozone oxidation
Antioxidant and anti-yellowing additives
Environmental protection project
Formaldehyde problem
There are many sources of formaldehyde problems, such as fixing agents Y and M, some softeners, waterproofing agents, adhesives, stiff resins, etc. Some have formaldehyde. At the same time, the migration of formaldehyde in the air will also cause excessive formaldehyde on the fabric, but these can be avoided, because with the promotion of environmental protection concepts, most of the dye additives have already eliminated formaldehyde.
But now I will introduce two processes that cannot avoid the formaldehyde problem.
One is that the non-iron finishing (resin finishing) additives will decompose formaldehyde when setting the shape, causing the formaldehyde content to exceed the standard.
The second is the permanent flame-retardant process of cotton, and the additives also contain formaldehyde, which will cause a large amount of formaldehyde to exceed the standard. Last year, a company developed a formaldehyde-free permanent flame-retardant process for the first time in the world. It has not been widely promoted, and the process is not particularly mature.
At the same time, these processes also need to pay special attention to the formaldehyde problem: when the hand feel is stiff, the color fixing agent is selected for the glue selection with the aldehyde fixing agent flocking process, and even the pigment printing also needs to choose the adhesive.
2. APEO exceeds the standard
APEO, as a chemical indicator, is strictly restricted by some countries, especially European countries. Now let’s take a look at how this substance gets onto our fabrics. First, some scouring agents and penetrants used in the pre-treatment of fabric dyeing, detergents and leveling agents in printing and dyeing, and emulsifiers in softeners in post-finishing may be the source of apeo substances. Since a large number of TX and NP series surfactants have been used as raw materials for additives in the past few years, it is difficult to prevent them. The only way is for printing and dyeing factories to insist on using environmentally friendly additives and strictly prohibit the use of additives containing APEO into the factory. It will be more secure if you choose Demei Chuanhua listed company or Rudolf Huntsman Japan Nikka additives
3. Excessive heavy metal ions
Metal ions such as chromium and antimony are strictly tested in products exported to Europe. If they exceed the standard, they will have serious consequences like formaldehyde. There are fewer metal ions in the additives, but some additives can cause exceeding standards, such as flame retardants. Antimony trioxide emulsion contains a large amount of mercury. When mordant dyes are used in wool spinning, the mordant dye used is potassium dichromate or sodium dichromate or sodium chromate. Cr6+ will exceed the standard. The origin of antimony is cloth slurry, embryo The cloth itself contains some moisture wicking additives
4. pcp (organochlorine carrier) is an important anti-mildew and preservative, which is convenient for storage. It is generally present in the leveling agent and repair agent used in dyeing. The carrier dye used in dyeing polyester and wool blended polyester may contain
5. Azo was previously an important dye intermediate, which existed in dyes. Now, most dye companies have eliminated azo dyes, and occasionally they exist in some off-brand dyes. It is necessary to pay attention to woolen dyed yarn fibers (Yuyao area). Sometimes there is the problem of azo exceeding the standard. It is recommended to test first, and then buy back to production after passing the test.
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