5.5 Color Fastness to perspiration
5.5 Color Fastness to perspiration
As we all know, the composition of human sweat is complex, the main component of which is salt, of which the amount varies from person to person. Sweat is acidic and alkaline. The short-term contact between textiles and sweat may have little effect on its Color Fastness, but long-term contact with the skin and sweat will have a greater impact on certain dyes. Clothing with unqualified Color Fastness is likely to cause dyes to transfer from textiles to human skin through sweat. The human body may absorb dye molecules and heavy metal ions through the skin, and this would endanger health.
5.5.1 Comparison of test methods for Color Fastness to perspiration
5.5.2 Examples of testing methods for textile sweat resistance
Use artificial sweat to simulate the condition of sweating to test textiles.
First, cut a certain number of 4mmX10mm test samples according to the project requirements, then sew the lining according to the sample type, and then put them into the petri dish, as shown in the following figure:
Then add the freshly prepared sweat stain solution (Figure 3, Figure 4) and soak for 30 minutes (Figure 5) (Human sweat has a complex composition, sweat is acidic and alkaline, and dyes in textiles are not acid-resistant while some are not alkali-resistant. Under the same conditions, artificial sweat with different acid and alkali levels needs to be tested separately).
After the soaking is completed, take out and scrape off the excess sweat, and sandwich it between the two sample plates. Use the same procedure to combine the samples and stack them together. After stacking them, place them between the sweat rack and the spring pressure plate, put a weight on the spring pressure plate (as shown in Figure 6) and take it away, pour out the excess sweat to form a combined test body.
Put the combined test body in a constant temperature oven for some time (Figure 7).
After taking it out, use the discoloration/staining gray card to evaluate the discoloration of the sample and the staining of the lining fabric (Figure 8).
5.5.3 How to improve the Color Fastness to perspiration? Examples of techniques for improving the Color Fastness of nylon fabric to perspiration
Weak acid dyes are mostly used in nylon printing and dyeing. It’s important to note that dyes and fibers are mainly combined with van der Waals forces and hydrogen bonds, which accommodates poor Color Fastness. Although the commercially available acid dye fixing agents can improve the Color Fastness to soaping and rubbing, it still lacks effective perspiration fastness fixing agent. Although the Color Fastness to acidic perspiration can be improved through sufficient soaping, dye selection, optimization of the fixation process and the development of new fixing agents or fastness enhancers, the Color Fastness to alkaline perspiration is still poor.
The improver of the Color Fastness to perspiration of acid dyes is still mainly the polyamide fixing agent that is a quaternary ammonium salt. The polyamine compound and dicyandiamide polycondensation reaction are mostly used to prepare the formaldehyde-free polyamide fixing agent, such as perspiration fastness Agent SF-30A, a polycationic fixing agent. Although the quaternary ammonium salt type polyamide fixing agent can significantly improve the perspiration fastness of acid dyes, it will significantly reduce the fabric’s rubbing fastness.
The purpose of this research is not to reduce the Color Fastness to rubbing, but to correspondingly improve the Color Fastness to the sweat of the quaternary ammonium salt type polyamide fixing agent. The test firstly measured the color fixation effect of perspiration fastness agent SF-30A, and then investigated the effect of perspiration fastness agent SF-30A and wet friction enhancer HS-222, adhesive SD-20B, and acrylate monomer comprehensive treatment on nylon Improved Color Fastness to rubbing and Color Fastness to perspiration of printed fabrics.
Fabric 380T nylon spun printed fabric, 20D/20D, areal density 35g/m2.
Perspiration fastness agent SF-30A (quaternary ammonium salt type polyamide, 30% solid content, self-made), adhesive SD-20B (copolymer of butyl acrylate and acrylic acid monomers, solid content 24%, Homemade), wet friction enhancer HS-222 industrial grade, chemical agent FMEE, ammonium persulfate and other additives.
1.2 Test method
1.2.1 Dipping finishing process
(1) Process flow
Nylon fabric → impregnation finishing liquid → centrifugal dehydration → drying → high-temperature baking → finished product
(2) Finishing fluid prescription/% (omf)
Perspiration fastness agent SF-30A x
Wet friction enhancer HS-222 y
Adhesive SD-20B z
(3) Sorting conditions
pH value 4.5~5.5 (adjusted by acetic acid), bath ratio 1:20, immersion at room temperature for 20 minutes, and baking at 160°C for 3 minutes.
1.2.2 Padding finishing process
(1) Process flow
Nylon fabric → padding finishing liquid → drying → high temperature steaming → drying → finished product
(2) Monomer emulsion
Mix 3% acrylate monomer, 0.75% emulsifier FMEE and 0.15% ammonium persulfate for high-shear emulsification. The emulsification time is 30min to prepare a monomer emulsion.
(3) Composition of finishing fluid
Add 4% perspiration fastness agent SF-30A to the above monomer emulsion, and adjust the pH value to 4.5-5.5 with acetic acid.
(4) Sorting conditions
Room temperature, double-dipping and two rollings, rolling rate 90%; high temperature steaming, humidity 40%, temperature 160℃, time 5 min.
1.3 Test method
(1) Color Fastness to rubbing
Test according to GB/T3920-2008 “Textile Color Fastness test Color Fastness to rubbing,” and according to GB/T251-2008, “Textile Color Fastness test grayscale for staining evaluation” rating.
(2) Color Fastness to perspiration
According to GB/T3922-2013, “Textile Color Fastness test Color Fastness to perspiration” test, according to GB/T251-2008 “Textile Color Fastness test evaluation staining grayscale” rating.
- Results and discussion
2.1 The influence of perspiration fastness agent on the Color Fastness of nylon
Nylon printed fabric adopts the impregnation finishing process in section 1.2.1. The mass fraction of perspiration fastness agent SF-30A on the Color Fastness to rubbing and Color Fastness to perspiration is shown in Table 1.
Table 1 The influence of mass fraction of perspiration fastness agent SF-30A on Color Fastness.
It can be seen from Table 1 that nylon printed fabrics have excellent dry and wet rubbing fastness and wool staining fastness to alkaline sweat, but the staining fastness of nylon to alkaline perspiration is poor; only Grade 2 to 3. After finishing with perspiration fastness agent SF-30A, it has no effect on dry rubbing fastness and alkaline perspiration Color Fastness of wool, which is still 4~5. However, it has obvious improvement to alkaline perspiration fastness nylon staining and increases with the increase of the mass fraction of SF-30A. The highest can be increased by 1.5 to 4, but it will cause the drop in the wet rubbing fastness in the warp and weft directions, and the drop in the wet rubbing fastness with the SF-30A finishing agent is related to the amount of SF-30A. When the mass fraction of SF-30A is 4%, the wet rubbing fastness will drop by two levels at most. This is because SF-30A finishing agent is a cationic polyamide quaternary ammonium salt with a good affinity with nylon and anionic acid dyes, and can form a film on the fiber surface. It also has good Color Fastness to alkaline perspiration. Therefore, it can improve the perspiration fastness to nylon staining, and does not affect the dry rubbing fastness and alkaline perspiration staining fastness of wool. The electrostatic interaction between cationic polyamide and acid dyes can reduce the resolution of acid dyes on the fabric in an alkaline medium. Still, it will cause acid dyes’ migration to the fiber surface when wet, that is, while improving the fastness of acid dyes to perspiration Reduced wet rubbing fastness. The acid dye used for fabric printing has excellent alkaline perspiration Color Fastness to wool.
2.2 The influence of perspiration fastness agent and wet friction enhancer
To improve the rubbing fastness of nylon printed fabric treated with perspiration fastness agent SF-30A, the finishing process in section 1.2.1 is adopted. The total mass fraction of the fixed finishing agent is 8%. The perspiration fastness agent is SF-30A. The enhancer HS-222 was mixed according to different mass ratios, and the influence of the two mass ratios on the Color Fastness of the fabric to rubbing and perspiration was investigated (Table 2).
Table 2 The influence of the mass ratio of perspiration fastness agent SF-30A and wet grinding enhancer HS-222 on the Color Fastness of fabrics
It can be seen from Table 2 that the perspiration fastness agent SF-30A and the wet friction enhancer HS-222 used in the same bath do not affect the wool staining and dry rubbing fastness of the nylon printed fabric; it is fast to alkaline perspiration, and the degree of nylon staining has been improved up to 2 levels; but the wet rubbing fastness still decreased, up to 1.5 levels. Comparison of Table 1 and Table 2 shows that when the amount of perspiration fastness agent SF-30A is the same, adding wet friction enhancer HS-222 is beneficial to improve the alkaline perspiration fastness, but it cannot improve the wet friction fastness. This may be because the wet friction enhancer HS-222 with crosslinking film-forming properties can improve the interaction between the polyamide cationic quaternary ammonium salt and the fiber, and improve the fastness to alkaline perspiration of the fixing agent. However, it will still cause the dye to migrate to the fiber surface in the wet state due to the water solubility.
2.3 The influence of perspiration fastness agent and adhesive
To improve the combination fastness of perspiration fastness agent SF-30A and nylon fiber, the finishing process in section 1.2.1 is adopted, and the total mass fraction of the fixed finishing agent is 8%. The perspiration fastness agent SF-30A and adhesive SD-20B in different mass ratios, were mixed to investigate the influence of the two mass ratios on the Color Fastness to rubbing and Color Fastness to perspiration. See Table 3.
Table 3 The influence of the mass ratio of perspiration fastness agent SF-30A and adhesive SD-20B on fabric Color Fastness
It can be seen from Table 3 that the use of the perspiration fastness agent SF-30A and the adhesive SD-20B in the same bath does not affect the wool staining fastness to alkaline perspiration and dry rubbing fastness of nylon printed fabric; it does not affect the nylon staining fastness to alkaline perspiration. The Color Fastness is improvable by 1.5 grades, and the impact on the wet rubbing fastness is small. When the mass fraction of the adhesive SD-20B reaches 6%, the wet rubbing fastness will not decrease. This is because the electrostatic effect of anionic SD-20B and cationic SF-30A can greatly develop the finishing agent’s binding fastness to the fiber, prevent the migration of acid dyes to the surface in the wet state, and ultimately improve the finishing agent’s resistance to alkali and sweat. However, it is relatively easy to gather during use and form a fixed stain. For this reason, although the use of nonionic surfactants to add O emulsification is beneficial to prevent aggregation, it is not good for improving the Color Fastness of alkaline perspiration nylon. Therefore, this method is still worthy of further discussion.
2.4 The influence of micro-polymerization of acrylic monomers
Acrylic adhesive is beneficial to improve nylon printed fabrics’ perspiration fastness and prevent the wet rubbing fastness from being reduced. Therefore, the emulsion of 18 acrylic monomers was selected to be finished in the same bath with the perspiration fastness agent SF-30A (according to 1.2.2. Section padding finishing process) to investigate the influence of different acrylate monomer polymerization on the rubbing fastness and perspiration fastness of the fabric. The results are shown in Table 4.
Table 4 The effect of acrylate monomer polymerization on the Color Fastness of fabrics
It can be seen from Table 4 that compared with the unfinished or single-perspiration fastness agent SF-30A, there is polymerization of acrylic monomers, (1) dry rubbing fastness and alkaline perspiration wool staining fastness, except for some single The body (ID-MA, TMPTMA, PEG200DMA, PEG400DMA, TMP3EOTA, DEGDMA, TEGDMA) is reduced by 0.5 level, and the Color Fastness of other monomers remain unchanged;
(2) The staining fastness of alkaline perspiration nylon is improved by 1.5 to 2.0 grades than that of unfinished fabrics, and 0.5 to 1.0 grades higher than that of SF-30A finishing alone;
(3) The wet rubbing fastness is 0.5~2.0 grade lower than that of unfinished fabrics. Except for some monomers (PHEMA, PEG400DMA and Di-TMPTA), the decrease is smaller than that of SF-30A finishing alone;
(4) Nylon fabric finished with BPA2EODMA, Di-TMPTA monomer and perspiration fastness agent SF-30A: Its alkaline perspiration fastness reached 4~5 grades, improved by two grades, and dry rubbing fastness remained unchanged at grade 4~5, but the wet rubbing fastness is slightly reduced, reaching Grade 4.
Acrylic monomers can undergo self-polymerization under initiators’ action and form a film on the surface of the fiber. Still, the nature of the film or the interaction with the perspiration fastness agent SF-30A and the fiber will affect the Color Fastness. This is because:
1) When finishing agent SF-30A exists alone, its fixing mechanism depends on ionic bond and film-forming properties. When the finishing agent SF-30A film formed on the fiber’s surface, it had better alkali resistance, it can prevent the dye from being in an alkaline medium. Analysis, reduce the re-staining (staining) of the fiber, improve the fastness to alkaline sweat, and also improve the fastness to dry rubbing. However, when the film formed by the finishing agent has good swelling properties, it will accelerate the resolution of the dye due to wet rubbing and reduce the wet rubbing fastness.
2) The structure of acrylate monomers contains vinyl groups, and polymerization reaction occurs under the initiation of ammonium persulfate. Acrylates can polymerize into polymers by themselves and form covalent interactions with fibers, finishing agent SF-30A, etc. It can improve its fastness to fiber and reduce the hydrophilicity and swelling of the SF-30A membrane. Therefore, the graft copolymerization of acrylic monomers on the fibers acts as a crosslinking agent, improving the wet rubbing fastness.
3) Due to the graft copolymerization of acrylate, the properties of finishing agent SF-30A and the fastness to the fiber are changed. This is related to the properties of acrylate monomers, such as Di-TMPTA monomers with four vinyl groups and BPA2EODMA monomers with bisphenol-A structure. Due to the increase in monomer reactivity or the introduction of the benzene ring structure, they can not only increase. It greatly improves the alkaline perspiration fastness and can also maintain excellent dry and wet rubbing fastness.
- The influence of monomer and Color Fastness additives on the Color Fastness of nylon fabric to perspiration:
(1) Cationic perspiration fastness agent SF-30A can improve the perspiration fastness of acid dyes, but it will reduce the rubbing fastness of dyes. When perspiration fastness agent SF-30A and wet friction enhancer HS-222 are finished in the same bath, it can inhibit the decrease of nylon printed fabric’s friction fastness.
(2) Cationic perspiration fastness agent SF-30A and anionic binder SD-20B are treated in the same bath, which can not only improve the perspiration fastness of acid dyes, but also have little effect on the rubbing fastness of nylon printed fabrics, but there is a tendency to aggregate insufficiently.
(3) The polymerization of acrylate monomers is beneficial to improve the rubbing fastness, but it is related to the monomer self-polymer properties. When choosing Di-TMPTA monomer with four vinyl groups or BPA2EODMA monomer with bisphenol-A structure and perspiration fastness agent SF-30A in the same bath, the nylon printed fabric has ideal Color Fastness, and alkaline perspiration is fast. The Color Fastness degree is 4~5, while the rubbing fastness is up to 4.