The influence of dyeing and finishing process on the flame retardant finishing effect of knitted fabrics
The influence of dyeing and finishing process on the fire-proof finishing effect of knitted fabrics. Knitted fabrics were selected to examine the effect of fire-proof finishing. Different printing and dyeing methods such as bleaching, coloring and some chemical additives used for bleaching and dyeing finishing were mainly studied. The influence of finishing technology on the flammability of fabrics. In the test, the BS5438 vertical combustion performance test method was used to test the flammability level of the finished fabric. The test results of this method are particularly close to the actual burning behavior of the fabric. The SPSS program was used to conduct statistical analysis and evaluation of the test results, accurately describing how and to what extent chemical parameters affect the burning behavior of knitted fabrics.
According to statistics, in general household fires, cloth, wood products and paper are usually the first to be ignited, accounting for 63% of the causes of fires and 70% of the burning materials. Fabrics are simple to burn. Usually the first thing to be ignited is cotton fabrics (90.6%), followed by furniture fillings and mattresses (6%), decorative fabrics (1.7%) and other decorative fabrics (1.7%), etc. .
Measures such as adopting materials with poor combustion properties, strengthening the testing of raw materials and finished products, and improving relevant laws and regulations will help reduce property losses and even casualties caused by fabrics. However, because these plans either limit people’s choices and aesthetics, or impose a heavy economic burden on people, they are difficult to be accepted by the general public.
From this point of view, it is very important to clarify how the fiber and fabric structure affects the final combustion performance of the product to guide production. By manipulating the finishing process, it is possible to produce an end product with suitable physical and combustion properties. In previous research work, we have attempted to precisely characterize the influence of knitted fabric properties on their fire resistance. Through research, we analyzed the impact of the finishing process of knitted fabrics on their fire resistance to reveal the role of physical and chemical parameters in the finishing process on the fire resistance of the product.
The flammability of fabrics depends on various factors, such as fiber composition, fabric structure, oxygen concentration, and environmental conditions (humidity, temperature, air flow speed, etc.), but the finishing agent on the fabric has The influence of combustion performance cannot be ignored either. These finishing agents can affect the burning behavior of fabrics by catalyzing the fabric to produce flammable substances, interfering with the fire retardant system, or indirectly interacting with residual coloring additives and printing adhesives on the fabric. It is known that hard water substances deposited on fabrics during the laundering process, especially for products washed with phosphorus-free detergents, can increase the flammability of certain materials and prevent the action of fire retardants. As far as the post-printing and dyeing finishing process of fabrics is concerned, early studies have shown that acidic, vat and direct dyes and acidic fluorescent whitening agents can all improve the LOI value of fabrics; on the other hand, the impact of reactive dyes on the LOI value of fabrics is strong But it depends on the application. Therefore, it is possible to improve the LOI value of the fabric by introducing nitrogen, sulfur and halogen-containing groups or introducing metal ions such as copper and cobalt into the coloring formula. These substances also help to prevent thermal decomposition of the fabric. Generate flammable and explosive gases. Research shows that disperse dyes, especially nitrogen-containing disperse dyes, may have a particularly significant inhibitory effect on the flammability of polyester fabrics. In addition, cleaning aids such as bleaching, cleaning and softening are generally flammable. If these chemicals still remain on the fabric after cleaning, the flammability of the fabric will be enhanced.
In this context, it is reasonable to assume that the flammability potential of workwear fabrics depends greatly on the printing and dyeing process. Early related research was based on a finishing base fabric and examined its impact on the flammability of the material. In this study, we used carefully selected knitted fabrics; in previous studies, we have studied the impact of the physical parameters of these knitted fabrics on their fire resistance to measure various printing and dyeing processes and printing and dyeing auxiliaries. The degree of influence of the agent on the burning characteristics of fabrics. In this way, it is possible to evaluate the impact of all possible dyeing and printing finishes on the burning characteristics of a certain fabric.
Test All fabrics are original color cotton without dyeing, finishing or finishing. After scouring, these fabrics are then treated with different printing and dyeing finishing processes. The treated fabrics are rinsed in cold water and dried naturally. Chemicals and Test Methods Bleaching. Pure cotton 19.4tex single-jersey knitted fabric was bleached with 0.2%, 0.4% and 0.6% hydrogen peroxide (Merc, 50%).
Full fluorescence and whitening. We chose two fluorescent brighteners, Unitex 2BT (Setas Chemical Company) and anionic, reactive Techowhite NABF Flussig (Toran Kimya Co., Textil Color AG) to study the effect of fluorescent brighteners on the fire resistance of knitted fabrics. These two fluorescent whitening agents are both stilbene structure derivatives, and the dosages used in the bleaching-whitening bath are 0.05, 0.1% and 0.2% respectively. When the concentration of the whitening agent changes, the concentration of hydrogen peroxide is fixed at 0.4%. Reactive dye coloring: RemazolNavyRGBgran 150% reactive dye (Dystar Co., BASF), which is especially suitable for cotton and viscose fibers, is used to color cotton and viscose fabrics at concentrations of 0.5%, 1%, and 2% respectively. Colored with disperse dyes. Polyester single knitted fabrics were colored with disperse dye DispersolNavyC-VSE (Dystar Co., BASF). The dye concentrations were 0.5%, 1% and 2% respectively.
Soft finishing. Softening finishing can make the fabric soft, give the fabric a smooth feel, and improve the sewability of the fabric. In production, commonly used softeners are anionic, quaternary ammonium salts and non-quaternary ammonium salts, cationic, nonionic and neutral softeners. This study adopted cationic KF94, nonionic WF95 (Setas Chemical Co.), microemulsion SoftyconMES silicone (ToranKimyaCo., TextilColorAG), cationic HagesoftKD, nonionic HagesoftNT (Lefateks Chemical Co., THORGmbH) and amphoteric SoftyconPWSK ( Softeners such as Toran Kimya Co., Textil Color AG) are available in five different concentration levels (silicone softeners: 1%, 1.5%, 2%, 2.5% and 3%; other softeners: 1%, 2%, 3%, 4% and 5%) applied to cotton fabric bleaching baths.
Defoaming agent. Five different concentrations (0.1g/L, 0.2g/L, 0.3g/L, 0.4g/L and 0.5g/L) of weakly amphoteric TCEntshaeumerTSR-K defoaming were added to the bleach bath (0.4%H2O2). agent (Toran Kimya Co., Textil ColorAG) to study the effect of defoaming agents on the fire resistance of fabrics. Anti-pilling agent. ToracallASW-1 acid cellulase (ToranKimyaCo., TextilColorAG) was selected to study the effect of enzyme application on the flammability of fabrics. Anti-pilling agents are used at concentration levels of: 0.5%, 1%, 1.5%, 2% and 2.5%. All finishing touches the fabric undergoes are performed using an Ahiba experimental coloring machine with a production bath ratio of 1:20. The finishing prescription and post-treatment process of fabric printing and dyeing are shown in Table 2. The flammability of each sample was tested four times in parallel, and a total of 297 tests were conducted to evaluate the finishing effect.
Since the vertical burning test method is closer to the actual situation of people wearing work clothes, we adopted the BS5438 burning performance vertical testing method to test the flammability of finished fabrics. Before testing, the sample was equilibrated for 24 hours at a temperature of 20°C ± 2°C and a relative humidity of 65% ± 2%. The test measured the ignition time of all samples and the time required for the flame to spread 60cm. The flame spread speed (R, mm/s) was also tested at the same time as the carbonization length and burning time.
We conducted variance analysis on the test results to reveal the importance of the finishing process; we used regression analysis to study the correlation between the finishing process and the flammability of the finished fabric. The importance of process variables (such as bleaching, coloring, etc.) changes with different significance levels (such as 0.05, 0.01).
Test results Bleaching. From the multivariate regression analysis (flame propagation speed F=25.8, R2=79.9%, sig.＜＜0.01), it is known that the bleaching process significantly affects the combustion characteristics of the fabric. As the peroxide content increases, the flame propagation speed of the fabric increases significantly. This may be due to the fact that the dirt and inorganic salts on the fabric have been removed and the bleached cotton fabric contains some flammable substances. When the dosage of hydrogen peroxide is 0.4% and 0.6%, the fabric has a large burning rate
It can also be seen from the results of multivariate regression analysis (R2=96%, sig.<<0.01) that the ignition time of the fabric is also significantly affected by the bleaching process. When the dosage of hydrogen peroxide is 0.2%, the ignition time of the fabric is shortened by 1.5 seconds. The fluorescence is completely whitened. Variance analysis and regression analysis (for Uvitex: R2=21%, sig.=0.074; for Techowhite: R2=0.3%, sig.=0.876). The results show that within the test dosage range of fluorescent whitening agent, its dosage has a significant impact on knitted fabrics. There is no obvious effect on the flame propagation speed and ignition time of the object. We believe that this may be affected by the hydrogen peroxide in the bleaching bath.
Multiple regression analysis of reactive dye coloring (for cotton fabric: R2=96.6%, sig.＜＜0.01; for viscose fabric: R2=0.37%, sig.=0.781) shows that the flame propagation speed of the fabric greatly increases Affected by dye concentration. The increase in dye concentration causes the flame to spread faster on cotton fabrics; however, this phenomenon is not obvious for viscose fabrics. We believe that the impact of reactive dyes on the flammability of cotton fabrics may be due to the removal of part of the chemical additives during coloring and finishing, rather than due to refining. The caustic soda concentration should be increased in the bath to increase color depth.
Coloring with disperse dyes. The research results show that at the disperse dye concentration we selected, the ignition time of polyester fabric is not affected by the dye concentration. All samples can be ignited within 2 seconds, no different from undyed polyester fabrics. However, the propagation speed of flames on fabrics increases significantly with the increase in dye dosage (R2=79.1%, F=24.59). The relationship between dye concentration and the flammability of knitted fabrics is obtained. Interestingly, the samples with 1.5% and 2% dye content had the same flame propagation speed. This phenomenon confirms previous research results.
Soft finishing. The study found that within the concentration range we selected, the softener had no effect on the ignition time of the fabric; however, the results of the multivariate regression analysis showed that the softener had a significant impact on the propagation speed of the flame on the fabric. When weak cationic microemulsion silicone softeners and non-ionic softeners are used, the fabric has a fast flame propagation speed; non-ionic silicone softeners can give the fabric a low flame propagation speed.
All softeners will cause the flame propagation speed of the fabric to increase dramatically, and the burning rate of the fabric will increase from 18mm/s to 20mm/s to 35mm/s to 42mm/s. This is because the softener itself contains fatty acid condensates or fatty acid derivatives, making it a flammable material.
The impact of defoaming agents. Any chemical that can change the surface properties of an object system to make it less likely to foam isKnown as defoaming agents, these chemicals are often used in printing and dyeing finishing baths and printing pastes for fabrics. The regression analysis of the flame propagation rate (R2=79.2%, F=40) shows that the use of defoaming agent has a significant impact on the flammability of the fabric; regardless of the concentration of the defoaming agent, the ignition time of the fabric is 3s. As the amount of defoamer increases, the burning rate of the fabric increases significantly; moreover, regardless of the amount of defoaming agent, the burning rate of the fabric is high (R>30mm/s). The actual effectiveness of defoaming agents in this regard depends on the flammable fatty acid esters, fatty acid salts and high molecular weight hydrocarbons in them.
The effect of anti-pilling agents. The combustion performance test and statistical analysis results of the fabric (R2=74.9%, F=31.41) both show that with the increase in the amount of anti-pilling agent, the burning rate of the fabric also increases significantly. When its dosage exceeds 1%, the anti-pilling agent makes the fabric’s burning rate reach 35mm/s. On the other hand, the ignition time of the fabric did not change with the amount of anti-pilling agent. Conclusion In this study, we investigated the effect of printing and dyeing processes on the fire performance of knitted fabrics. It mainly reports on the printing and dyeing process (hydrogen peroxide bleaching, fluorescent whitening treatment, reactive dye and disperse dye coloring, etc.) and printing and dyeing auxiliaries commonly used in the dyeing and finishing of knitted fabrics (softeners, defoaming agents, anti-pilling finishing agents) etc.) on the fire resistance of knitted fabrics. The test adopted the vertical combustion performance test method to test the flammability level of 297 samples after printing and dyeing; and used the SPSS program to conduct variance and multivariate regression analysis and evaluation of the test results.
It can be seen from the research results that the printing and dyeing finishing process of knitted fabrics can significantly affect their flammability, especially their burning speed. As the amount of hydrogen peroxide increases, the burning speed of the fabric can increase from 12mm/s to 20mm/s~22mm/s. However, what is different from the previous research results – “When the dosage of fluorescent whitening agent is higher, the LOI value of the fabric is also higher” is: this study found that the change in concentration of fluorescent whitening agent will not be obvious. Affects the burning characteristics of bleached knitted fabrics. Reactive dyes can significantly accelerate the spread of flames on cotton fabrics. We believe that this change in the burning behavior of the fabric does not depend on the concentration of the reactive dye, but on the increase in the concentration of caustic soda in the dye bath. The burning speed of polyester knitted fabrics dyed with disperse dyes is increased by 100%, from 5.5mm/s to 10mm/s. This shows that disperse dyes have a particularly important impact on the flammability of polyester fabrics.
Both silicones and softeners can increase the burning speed of bleached fabrics by 50%. Similar to softeners, defoaming agents can also increase the burning speed of bleached fabrics by 60% to 70%. When anti-pilling agents are applied to pure cotton knitted fabrics, even a small concentration will increase the flammability of the fabric by 50% to 70%, which may be caused by damage to the fibers by the anti-pilling agents. The burning rate of fabrics caused by softeners, silicones, defoaming agents and anti-pilling finishing agents is significantly increased, suggesting that we should use less of these additives or use more of those materials with lower flammability.
Another important conclusion drawn from this study is: in the lower finishing agent concentration range, the ignition time of the fabric can be reduced by 1s to 2s; then, regardless of the finishing agent concentration, this value no longer change. It can be seen that a lower dosage of finishing agent will significantly reduce the fire resistance of the fabric; when the concentration of finishing agent is higher, its impact on the ignition time of the fabric will be smaller.
AAADF3RSEGDTHIU
Extendedreading:https://www.yingjietex.com/product/1600D-Polyester-DOBBY-YARN-OXFORD-Fabric.html
