Preparation and Physicochemical Properties of Flame Retardant Nonwovens

According to the factors affecting the combustion process, combustion principle and combustion performance of the polymer, the basic principle of flame retardant of nonwoven fabric can be divided into three types: condensed phase flame retardant, gas phase flame retardant and melt blocking flame retardant. Regardless of the kind of flame-retardant non-woven products, it is necessary to select the appropriate non-woven fabrics according to the nature of the products themselves, in order to achieve the best use of materials, and expand the use space and value space of various flame-retardant nonwoven fabrics. It is bigger.

Experimental operation yields key data

In general, the combustion process of polymer materials for industrial use is that thermal decomposition of polymer materials under the action of fire sources generates flammable substances (free radicals) under the action of heat and air, and flammable substances are burned and oxidized in flames. (Generating oxygen-containing free radicals), releasing a large amount of heat energy, which further promotes thermal cracking of the polymer material, and thus circulates until the combustion is completed.

Raw materials and equipment

The equipment involved in this paper includes: tensile strength meter (provided by Nantong Hongda Experimental Instrument Co., Ltd., model HD026N); limiting oxygen index tester (provided by Atsfaar, Italy); vertical burning tester (available from Atlas, UK, model 17621).

Limiting oxygen index determination experiment

Draw a line 50mm away from the ignition end on the wide surface of the sample; mount the sample vertically on the sample holder, and the distance from the upper end of the sample to the top of the tube is not less than 100mm; adjust the flow valve to mix the oxygen and nitrogen flowing into the combustion tube. The gas reaches the required oxygen concentration, and the gas flow rate in the combustion cylinder is (4 ± 1) cm3 / s; the combustion cylinder is cleaned with gas, and then the top of the sample is ignited with an igniter, and immediately after the ignition, the timing is started. Repeat 3 times.

Washing resistance test

Two samples of 120 mm × 50 mm size were cut out from all the samples, and they were divided into two groups for testing. Take one of the samples in a large beaker filled with clean water, wash each time with a cloth sample, dry and mark the washed cloth sample, and make it together with the unwashed cloth sample. Limiting oxygen index comparison test.

Data analysis to determine the best process

Polypropylene spunbonded fabric and SMS composite fabric, the limiting oxygen index of these two types of flame-retardant masterbatch-added nonwoven fabrics is significantly lower than the limiting oxygen index of spunlace and PVA flame retardant nonwoven fabrics. There is a difference in the evaluation of the flame retardant effect level.

This is because in the production process, the flame-retardant masterbatch is melt-spun with the main section in a ratio of 1:25, in order to achieve better fusion of the flame-retardant masterbatch with the main section in the subsequent production, and to exert flame retardant Therefore, it is necessary to remove the flame retardant component decabromobiphenyl Sb2O3 in the flame-retardant masterbatch production process, and to add the dispersant polyethylene wax and the carrier. Thus the amount of flame retardant in the cloth will be greatly reduced. In addition, after the finishing modified modified flame-retardant nonwoven fabric is finished, the flame retardant component adheres to the surface of the fiber, and when it is in contact with the flame, the flame retardant coats the fiber, and the insulating heat source and the fiber can be directly contacted. Thereby greatly improving the flame retardant effect.

It can be seen that the post-finishing modified flame-retardant nonwoven fabric is superior to the flame-retardant functional masterbatch-added nonwoven fabric in flame retardancy. Since the modified fiber nonwoven fabric is directly made of modified flame retardant fiber, and has not undergone subsequent flame retardant processing, finishing and the like, the flame retardant property mainly depends on the flame retardant property of the fiber itself.

Table 2 Limit oxygen index test data after washing

It can be seen from the data in the above table that the swatches of No. 1, No. 3 and No. 4 belong to the flame-retardant masterbatch masterbatch nonwoven fabric, and the flame retardant properties of the fabric are not greatly changed after washing with water. This is due to the addition of functional masterbatch during the spinning process. The masterbatch is not adhered, but is well "fused" into the fiber. General cleaning does not affect their flame retardant properties. No. 2 swatches are not flame retardant by themselves, and no experimental comparison is made here. The limiting oxygen index of No. 5 and No. 6 swatches before cleaning is 35.1 and 37.3, respectively, which belong to B1 grade and have good flame retardancy. However, after cleaning, the limiting oxygen index fell to 19.1 and 19.3, ignited in the air, and lost the original flame retardancy, indicating the washing fastness of the flame retardant nonwoven fabric after finishing the two flame retardants. difference.

It should be noted that during the water washing process, PVA has a good water solubility and can be quickly dissolved in water. Even if the solution is evaporated, it is difficult to ensure that the PVA component can be completely removed. The composition and the precipitate have been unable to maintain the quantitative and structure of the original swatch, and the comparative test of the precipitate will not achieve the desired effect. Therefore, in this test, the PVA finishing nonwoven fabric was not tested and analyzed. The modified fiber flame-retardant cloth mainly has the flame retardant property of the modified fiber itself, and the water washing does not change the physical and chemical properties of the material itself, and therefore, the flame retardant property thereof has not changed.

In the vertical burning performance test, the No.1, No.3 and No.4 swatches are all flame-retardant masterbatch-added non-woven fabrics, and no flame is generated during the ignition for 12s. The experimental material is polypropylene fiber, and black smoke is generated during the combustion process, which is determined by its own properties. At the same time, during the heating process, the surface of the fabric shrinks due to heat, resulting in damage to the fabric surface and droplets. According to the above-mentioned melt-blocking flame-retardant mechanism, this is due to the flame retardant effect of the flame-retardant masterbatch in the polypropylene flame-retardant nonwoven fabric, which is from the burning phenomenon of the No. 2 swatch. It can be verified that the No. 2 swatch is also accompanied by black smoke generation, but no droplets are generated until the burnout, and the flame spreads on the cloth surface at a relatively fast speed.

No. 5, 6, and 8 swatches were produced without flames during the 12 s fire. The heated cloth surface is gradually carbonized, the carbonization area is small, and there is no spreading phenomenon. From the perspective of the length of damage and the damaged area of ​​the fabric, it is still better than the flame-retardant masterbatch nonwoven fabric in the flame retardant performance of the flame-retardant finishing nonwoven fabric. This is because the flame retardant component in the flame-retardant finishing cloth exists in the form of adhering to the surface of the fiber, and the resistance of the finishing flame-retardant nonwoven fabric is compared with the flame retardant component in the flame-retardant functional masterbatch nonwoven fabric. The fuel content is also high. In the combustion process, the flame retardant component of the flame-retarded and finished nonwoven fabric is directly in contact with the heat source, and the heat source is separated from the fiber, so that the flame retardant effect is more remarkable. However, the No. 7 swatch, which has not been subjected to flame retardant treatment, burns more quickly and has a larger damage area. The above experimental results again demonstrate that the flame retardant performance of the flame retardant finishing nonwoven fabric is superior to that of the flame retardant functional masterbatch nonwoven fabric, and the flame retardant finishing nonwoven fabric has significant advantages in flame retardancy. (Author Wang Minmin, graduate student of Nonwoven Materials and Engineering, Tianjin Polytechnic University, is currently a technician in Zhejiang Guangji Medical Nonwoven Products Co., Ltd.: Ren Yuanlin, Associate Professor, Department of Textile Science, Tianjin Polytechnic University)