my country is a large grassland country, with the second largest grassland area in the world. Pastoral areas are the main areas inhabited by ethnic minorities in my country. There are 40 ethnic minorities including Mongolian, Tibetan, Uyghur, Hui, Manchu, Korean, Kazakh, and Kirk, with a total population of 50.52 million [1].
Since ancient times, the vast number of herdsmen have “lived in pursuit of water and grass”, and tents are a common residence for herdsmen. Since the tent is generally in a wild camping state during use, it needs to withstand the sun and rain, and the tarpaulin is the main part of the tent. Therefore, how to improve the waterproof performance of the tent tarpaulin in pastoral areas and reduce the cost of the tarpaulin is obvious. is particularly important [2]. However, there is currently almost no research on nomadic tents at home and abroad, and there are no reports on the waterproof performance of nomadic tent tarpaulins.
With the development of tent tarpaulins to this day, the waterproof effect is mainly achieved through the use of coating technology, which is mainly to evenly coat a layer of polymer compounds that can form a thin film on the surface of the fabric, because it can not only give the fabric various functions, but also It gives the fabric a unique style, feel and appearance, and can greatly increase the added value of the product. Its effect is difficult to achieve by ordinary printing and dyeing finishing. At present, tent fabrics are the most consumed type of industrial coated fabrics. Coating agents are mainly classified according to their chemical structure: polyacrylate (PA), polyurethane (PU), polyvinyl chloride (PVC), silicone, synthetic rubber, as well as fluorine-containing, polyamide, poly Ethylene, polypropylene and proteins [3-4]. Table 1 shows a comparison of the performance of four commonly used coating agents.
Table 1 Performance comparison of commonly used coating agents
Polytetrafluoroethylene is the only resin that combines three functions: waterproof, oil-repellent and anti-fouling. It is heat-resistant and resistant
It has good oxidation and weather resistance, no mildew, good elasticity, and no sticking phenomenon. It is an ideal coating agent, but it is expensive
The grid is very high, which limits its use. In order to make the tent tarpaulin have good waterproof performance, this article plans to use different finishing processes and fluorine-containing water-repellent finishing agents to finish the tent fabric, and test its performance. In order to develop a nomadic product with excellent waterproof performance and reasonable cost, Tent tarpaulin provides the basis.
2 Experimental part
2.1Experimental materials
Finishing agent: fluorine-containing water-repellent finishing agent; cross-linking agent: melamine and glyoxal. The function of the cross-linking agent in the experiment is to react with the fluorine-containing water-repellent finishing agent to form a three-dimensional network structure on the surface of the fiber, making the water-repellent agent The shedding is hindered, improving the finishing effect and washability of the fabric.
Catalyst: glacial acetic acid, analytical grade.
2.2 Test steps
Water repellent function finishing (oil removal and bleaching → dyeing → drying cloth → padding with resin → drying → padding → baking and shaping → cooling → discharging cloth → rolling) → sample testing.
2.3 Experimental instruments and test methods
2.3.1 Experimental instruments
5101-3E electric blast drying oven; MP502B electronic balance; 55YH stainless steel constant temperature water bath; YG812N fabric water permeability tester; beaker; measuring cylinder.
2.3.2 Test method
(1) Hydrostatic pressure resistance test
Sample chuck area: l00cm2, water pressure rising rate: l000Pa/min~20000Pa/min digital setting.
Preparation work before the test: Before doing the pressure boosting, constant pressure timing, constant pressure timing, and flexural relaxation experiments, measure
Before testing, you need to fill the lower chuck with water, clamp the sample, and press the ← key to enter the calibration state and clear it.
There are 5 working modes of this instrument: 1) pressurization method; 2) constant pressure timing method; 3) constant pressure timing method; 4) flexure relaxation method; 5) water leakage method (constant speed). This experiment uses the boosting method: After the test is ready, enter the method selection in the settings and set the rising rate. Press the start button to start the test. When the third drop of water appears on the sample, press the stop button. The instrument will automatically save the test data. After the test is completed, the piston will automatically return.
3 Results and discussion
There are many factors that affect the waterproof performance of organic fluorine-finished fabrics, such as yarn properties, thickness, fabric density, tightness, thickness, gray fabric pre-treatment process, finishing agent, additive performance, dosage, pH, rolling residue rate, processing flow, temperature , time, etc. Based on a large amount of domestic and foreign data, the researchers of this project carried out a series of process tests focusing on seven major factors, including fabric tightness, gray fabric pre-treatment process, finishing agent, pH, additive formula, padding process, and rolling residue rate. , and tested and analyzed the reasons for water repellency.
3.1 The influence of fabric tightness on waterproof performance
The tightness of the fabric is the basis for waterproofing, and a loose structure is obviously difficult to achieve effective waterproofing. Three kinds of ordinary T/3×3 gray fabrics and special T/3×3 gray fabrics (sample 4#) were tested using the common organic fluorine finishing process. The results are shown in Table 2.
Table 2 Fabric tightness and hydrostatic pressure test results
As can be seen from Table 2, there is a significant relationship between fabric tightness and waterproof performance. The higher the tightness, the better the waterproof performance. However, in actual production, due to limitations of equipment conditions, it is impossible to increase the weaving tightness without limit. The tightness of the 4# sample we specially tried to weave is close to the equipment limit, but the hydrostatic pressure index is still far from the new tent fabric standards in pastoral areas. However, it is different from the commercially available organic fluorine tarpaulin index (based on 3.45kPa, the same below) ), an increase of 18.8%.
3.2 The influence of gray fabric pre-treatment process on waterproof propertiesThe influence of ��
Although the new tents in pastoral areas are made of white fabric and the dyeing process can be omitted, due to the unavoidable oil stains and stains on the green tent, the degreasing and bleaching processes cannot be omitted. During the production process, it was found that when gray fabrics of the same specification are waterproofed, the waterproof effect of dyed fabrics is generally better than that of bleached fabrics. Therefore, a special T/3×3 gray cloth was used (this gray cloth will be used in future tests and will not be repeated again), and 3 sets of process plans were determined for testing, which are:
Plan 1#: Ordinary 95℃ hydrogen peroxide bleaching + organic fluorine finishing;
Plan 2#: 130℃ high temperature dyeing + organic fluorine finishing;
Plan #3: 130℃ high temperature bleaching + organic fluorine finishing.
The test results are: the 1# scheme sample has a hydrostatic pressure of 4.1kPa; the 2# scheme sample has a hydrostatic pressure of 4.54kPa; the 3# scheme sample has a hydrostatic pressure of 4.43kPa.
It can be seen that the hydrostatic pressure index of scheme 3# is 8% higher than that of scheme 1#. Analyzing the reason, it is estimated that the fibers of the gray fabric are redistributed under the action of high-temperature water bath, and the structure becomes tighter and more uniform, thus improving the waterproof effect.
3.3 The impact of organic fluorine finishing agents on waterproof performance
When different types of organic fluorine finishing agents are used to treat fabrics, the waterproof indicators vary greatly. In this study, a total of 5 batches of organic fluorine (owned by Lianzhuang) produced by different manufacturers at home and abroad were purchased for comparative testing. The test results are shown in Figure 1.
It should be noted that 1#, 2#, and 3# are domestic organic fluorine finishing agents, while 4# and 5# are imported organic fluorine finishing agents. According to test data, the imported finishing effect is significantly better than that of domestically produced ones, but ordinary processes still fail to meet the standards for new tent fabrics in pastoral areas. Therefore, 4# was selected to proceed to the next test.
3.4 Relationship between pH and hydrostatic pressure of organic fluorine finishing fluid
With other conditions unchanged, we prepared organic fluorine finishing solutions with different pH levels for testing. The test results are shown in Figure 2.
According to information, organic fluorine molecules generally consist of four parts: fluorocarbon chain links, buffer chain links, polymer chain links, and other modified groups. The strong polarity of the fluorine-carbon bond will reduce the stability of the entire molecule, and the stability of the monomer is improved by connecting the buffer links to the main chain. Under acidic conditions, the second component is affected, stabilizing its buffer link. If it is under alkaline conditions or not very acidic, its buffer links will be destroyed, the monomer will be unstable, and the waterproofing effect will become worse. The test results in Figure 2 verify this theory: the higher the pH value, the lower the hydrostatic pressure index; the lower the pH value, the higher the hydrostatic pressure index; as the pH value continues to decrease, the increase in the hydrostatic pressure index slows down.
3.5 Research on the formula of organic fluorine finishing fluid
By taking many of the above measures, the hydrostatic pressure index has been increased to 5.41kPa, which is 56.8% higher than that of ordinary organic fluorine tarpaulins. However, the impact of a single measure on the waterproof index is limited. Therefore, we try to focus on the formulation of organic fluorine finishing fluids in order to There has been a breakthrough in waterproof indicators.
First, using the above-mentioned 4#, stiffening agent, antistatic agent, and weak acid as the basic formula, five different types of resins A, B, C, D, and E were added for testing. The results are shown in Table 3.
Table 3 Hydrostatic pressure values of fabrics finished with different resins
It can be seen from the above table that adding type A, B, and C resin not only did not improve the waterproof performance of the fabric, but made it worse; adding type D resin had little effect on the waterproof index; adding type E resin increased the hydrostatic pressure index by 6.5%. . Therefore, the following four sets of plans were formulated for further testing of E-type resin alone. The results are shown in Table 4.
Plan 1#: basic formula + E-type resin + cross-linking agent A;
Plan 2#: basic formula + E-type resin + cross-linking agent A + catalyst;
Plan 3#: basic formula + E-type resin + cross-linking agent B;
Plan 4#: basic formula + E-type resin + cross-linking agent B + catalyst.
Table 4 Effects of cross-linking agents and catalysts on waterproof performance
It can be seen from Table 4 that cross-linking agent A has no significant impact on waterproof performance (the same regardless of adding a catalyst), cross-linking agent B can slightly improve the waterproof performance, and after adding a catalyst, the waterproof index is significantly improved. On this basis, the formula proportion was adjusted, and the hydrostatic pressure index was basically stable at around 6.1kPa, which has exceeded the standard requirements for new tent fabrics in pastoral areas.
3.6 The impact of rolling residue rate and padding process on waterproof indicators
Considering that there will be certain fluctuations in the actual production process, we decided to further find ways to improve the waterproof performance of the fabric. In terms of padding process, it can be divided into one-step method and two-step method. The so-called one-step method means that organic fluorine finishing agents, resins, stiffening agents and other additives are padded and dried in the same bath. This method is commonly used by enterprises; the two-step method means that finishing agents and additives are padded in order. ,drying. In order to explore the impact of these two processes on the waterproof performance of fabrics, a two-step process was developed based on the above 4# solution formula:
The first step: resin + cross-linking agent + catalyst + stiffening agent, padding and drying;
The second step: + antistatic agent + weak acid, padding, drying, and baking.
The hydrostatic pressure of the one-step sample is only 5.95kPa, while the hydrostatic pressure of the two-step sample reaches 6.49kPa. It can be seen that the two-step process can significantly improve the waterproof performance of the fabric. Because this process can make the organic fluorine finishing agent molecular groups more completely cover the surface of the fabric fiber, thus improving the waterproof effect of the fabric.
We have also conducted some explorations regarding the rolling residue rate, a process parameter that has not been taken seriously in the past. The test results are shown in Figure 3.
It can be seen from Figure 3 that the higher the rolling reduction ratio, the better the hydrostatic pressure index, and the stability of the measured data is better. The analysis reason is: under the condition of high rolling ratio, it is more conducive for the organic fluorine finishing agent, resin, and additives to be evenly distributed and fully reacted on the surface of the fabric fiber, thus improving the waterproof performance. However, considering the issue of energy consumption, this paper did not conduct experiments with higher rolling residue rates.
4Conclusion
Through the above series of process measures, the following conclusions can be drawn to improve the waterproofing effect of organic fluorine tarps:
1) High-density fabric is the basis for improving waterproof performance, and higher warp and weft tightness must be used;
2) High-temperature bleaching process is more effective than ordinary bleaching process;
3) The imported effect is better than that of domestic products, so it is recommended to choose it;
4) A lower pH value of organic fluorine finishing solution can improve the waterproof index;
5) The formula of finishing fluid is the key to improving waterproof performance, and it is advisable to select the best solution through repeated trials;
6) The two-step process and high rolling residue rate can effectively improve the waterproof performance.
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