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Test method for testing the thermal protection performance of fire-resistant clothing with burning dummy

Release time: 2015-08-12 10:36

Firefighters participating in emergency rescue often need to face a variety of thermal threats such as high temperature and flames. Operators must wear fire protection clothing to protect the human body from thermal injury [1-2]
. Different use environments have different heat sources that cause harm to the human body and different ways of transferring heat. Therefore, fire protection clothing needs to have a variety of thermal protection properties such as flame retardancy, heat insulation, and integrity [3-4]
. In the development of fire protection clothing, how to accurately and comprehensively test and evaluate the thermal protection performance of clothing is an important foundation to promote the research and application of fire protection clothing. At present, scholars at home and abroad have done a lot of research on test methods and prediction models of thermal protection performance of fire protection clothing [5-7]. Although traditional textile flame retardant experiments and TPP experiments can evaluate the thermal protection performance of fabrics, they cannot reflect clothing and clothing. The fire resistance of the package as a whole and the degree of protection that can be provided to the wearer, because it ignores the cutting, design and other additional functions of the garment manufacturing process [8-9]
. An objective and comprehensive evaluation of thermal protective clothing should be as realistic as possible to simulate the actual situation of the human body wearing protective clothing in the fire field [10]
. The burning dummy test method uses dummy placed in a fire environment that can control the heat flow, burning time and flame distribution, and predicts the position and extent of human skin to reach second and third degree burns, thereby assessing the overall thermal protection performance of the garment . Its biggest feature is that it can quickly, accurately and repeatably simulate the heat exchange between human body, clothing and environment under flash fire conditions [11]. As early as the 1960s, foreign countries have used combustion dummy to evaluate various thermal protective clothing. In China, the development of the combustion dummy system is relatively late. For many years, vertical combustion method and TPP test method have been used to evaluate the thermal protection of fabrics. Performance has restricted the research and development of thermal protective clothing in China to some extent.
Civil fire protection clothing plays an important role in national fire safety, and excellent thermal protection performance is one of its most important functions. Based on the Donghua Fireman's combustion dummy system of the Functional Protective Clothing Research Center of Donghua University, this article evaluates the overall thermal protection performance of civil fire protection clothing, and analyzes other factors besides fabrics such as clothing design and structure, The influence of the heat shrinkage deformation of the clothing surface on the thermal protection performance is to explore some relevant factors that affect the thermal protection effectiveness of fire protection clothing, and to provide a basis for the optimal design of fire protection clothing.

1 Experiment 1.1 Samples The test clothing used in this experiment is three sets of civil fireproof clothing of the same model and material produced by an enterprise. The garment is a long coat, stand collar,
With cuffs, reflective straps are designed on the chest and back for easy identification, and safety belts are attached on the upper back for escape. The outer fabric of the fire protection clothing is aramid 1313, the thermal insulation layer uses thermal insulation cotton, and the TPP value of the fabric combination is 33.8, which is greater than the thermal protection value specified by industry standards. The finished product specifications of the three sets of fire protection clothing are shown in Table 1.
1.2 Experimental method The test instrument is the “Donghua Fireman” combustion dummy system of the Functional Protective Clothing Research Center of Donghua University. The system fully meets ISO 13506,
Relevant technical indicators for evaluation of combustion dummy systems such as ASTMF 1930. The dummy's body size adopts the standard Chinese adult male body size, with 135 heat flow sensors installed throughout the body, covering the trunk, head, hands, and feet. It can be used not only for the evaluation of thermal protective clothing, but also for helmets,
The need for evaluation of a complete set of thermal protection equipment such as gloves and fire boots; In addition, the burning dummy is also equipped with joints such as shoulders, elbows, hips, knees and ankles, as well as rotation and sliding systems, which can simulate various postures and activities of the human body [12]

In the experiment, a fire dummy wearing a fireproof clothing was placed in a laboratory simulated combustion environment and exposed for a certain period of time. 135 thermal sensors distributed on the dummy were used to measure and calculate the conduction to the body surface through the measured clothing. Heat and temperature, to predict the situation of human burns, and evaluate the thermal protection performance of clothing. The test conditions for the three sets of fire protection clothing are shown in Table 2. Before the experiment, the average heat flow was calibrated to reach 84 ± 2kw / m2, and the standard deviation was controlled within 21kw / m2. In the experiment, the burning process was recorded by video, and the real-time change of clothing was observed during the burning process. The dress burning test scene is shown in Figure 1.
In order to quantify the apparent change of clothing after burning, the dimensions of key parts such as collar, body, sleeves of fire protection clothing before and after burning were measured with a soft ruler, and a 5mm diameter circular stamp was stamped on the clothing corresponding to the dummy heat flow sensor. . The seal has four directions: vertical, horizontal, left oblique, and right oblique. After measuring the length change of the imprint in each direction after burning, the shrinkage of the clothing in all directions can be obtained. The calculation method of the shrinkage α is as follows: α = (L-L1) / L × 100% (1) where: L is the length of the mark before combustion, cm; L1 is the length of the mark after combustion, cm.

2 Results and discussion 2.1 Skin burn degree evaluation results The test results of the burning dummy showed that wearing the No. 1 and No. 2 fireproof clothing did not reach the burn level on the dummy surface, while wearing No. 3 fireproof clothing, the dummy surface appeared relatively The distribution of large-scale and large-scale burns is shown in Figure 2. The total surface area of the dummy was 1.816m2. When wearing No. 3 clothing, the ratio of total burn area on the surface of the dummy was 62.6%, of which the area ratio of third-degree burns was 28.0% and the area ratio of second-degree burns was 34.6%. (First-degree burns are not included in the burn area statistics). The most severe burns were concentrated in the buttocks, chest and back, thighs, calves, and head. In addition, there was almost no burn on the knee joint covered by the overlapping part of the fireproof clothing hem and the foot cover. Comparing the test conditions of the three sets of clothing, the No. 3 fireproof clothing burned for 6 s in the environment where 12 flamethrowers worked together, and the burning time and flame area were significantly larger than those of No. 1 and No. 2 clothing. In addition, the wide hem allowed the flame to quickly penetrate into the clothing, and the flame continued to burn for nearly 10 seconds before the flame extinguished on the inner surface of the clothing with relatively poor flame retardancy, which caused the body surface of the burning dummy to wear a fireproof clothing No. 3 in the experiment. Major burns. After the hem of No. 1 and No. 2 fire protection clothing was reduced by using provincial roads, the flames did not penetrate into the fire protection clothing, and the fire protection clothing did not continue to burn. Therefore, reducing the openings in key parts of clothing and improving the flame retardant properties of the inner material of the clothing are more conducive to improving its thermal protection efficiency. In addition, in the experiment, the continued burning and melting of the reflective tape on the chest of the garment were observed. Although the garment met the relevant requirements in the TPP test, the performance of the reflective tape was not reflected. This also shows that the thermal protection performance of clothing is not only related to the performance of the fabric, the clothing style and structure design, clothing accessories and accessories such as buttons, velcro, reflective tape, and the use of clothing environment is also important to the overall thermal protection performance of protective clothing.
2.2 Heat shrinkage deformation of clothing No. 3 clothing had obvious shrinkage after burning experiments, and holes appeared in many places, exposing the heat insulation layer. Since the No. 3 fire-resistant clothing was severely damaged after burning, it was impossible to accurately measure the size of the key parts of the clothing after the combustion experiment. Therefore, when analyzing the shrinkage and deformation of the surface of the clothing after the combustion, the No. 1 and No. 2 fire-resistant clothing were mainly used. According to Table 3, for No. 1 and No. 2 clothing, the shrinkage of each part of the body after burning is generally greater than the shrinkage of each part of the sleeve. The most contracted part of the body is the hip width, which is about 11 cm on average, followed by the waist width, and the contraction gradually decreases from the hip to the chest. In addition, the total length of the body in the longitudinal direction of the shrinkage is also large, reaching about 7cm. When wearing No. 1 clothing, the shrinkage of the outer collar reached 8 cm, which was significantly larger than that of No. 2 clothing's collar. This may be related to the experiment that the No. 1 fireproof clothing was equipped with a fireproof mask. When wearing the No. 1 fireproof clothing, the neck collar must closely fit the outer wall of the mask, so that the area of the collar collar in contact with the flame in the combustion experiment will increase. The variance analysis of the size shrinkage of key parts of the No. 1 and No. 2 garments found that there was no significant difference between them. P> 0.05. The No. 1 and No. 2 garments are two garments of the same material, style and size. The difference in the shrinkage rate of the clothing is not significant, which indicates that the heat source distribution is the same between the two combustions, and the experimental results are stable and repeatable.
According to formula (1), calculate the shrinkage rate of each seal on the garment in the four directions of vertical, horizontal, oblique, and right oblique, and then take the average value to obtain the shrinkage rate of the corresponding sensor site on the garment. Its distribution is shown in Figure 3. Show. It can be seen that the frontal shrinkage rate is more than 5% more than the back, and the severely deformed part of the front is lower than the back. The main deformation area on the front is 3cm from the hip line to the knee, and the main deformation area on the back is the chest line. About 3cm below the hip line, this may be related to the distribution of the air layer under the clothing and the amount of heat flow obtained at the part when the burning dummy is standing. Both sides of the garment have the greatest contraction in the abdomen and hips, with a contraction rate between 15% and 20%. Taking the deformation of the seal on the abdomen and hip of the left piece of clothing as an example, the deformation rate of the seal in all directions is obtained, as shown in Table 4. According to the statistical analysis results of SPSS16.0, there is no significant difference in the deformation rate of the same seal part in the horizontal, vertical and oblique directions, p> 0.05. It shows that for this experimental clothing, the same part shrinks evenly in different directions.
In summary, in the burning dummy test, the main deformation range of No. 1 and No. 2 fire protection clothing was from the chest to the knee area, and the most severely deformed part was the abdominal hip. Deformation not only affects the structural size of the garment but also destroys the integrity of the garment and reduces the protective ability of the garment to the human body. When the garment continues to be exposed to flames, the probability of burns in the area from the chest to the knee of the dummy will increase significantly, so the shrinkage and deformation of the garment surface will also affect the thermal protection performance of the garment to a certain extent.

Conclusion In this paper, the overall thermal protection performance of civil fireproof clothing was evaluated using a combustion dummy. The results show that the thermal protection performance of clothing is not only determined by the thermal protection performance of the fabric, but also closely related to the style and structure design of the clothing, the performance of the accessories and the environment in which the clothing is used. When wearing No. 3 clothing, the total burn area of the dummy reached 62.6%, and the second and third degree burns were concentrated in the abdomen, hips, back and thighs. After closing the hem of No. 1 and No. 2 clothing, the flame did not penetrate into the inside of the clothing and caused continuous burning. Reducing the openings in key parts of clothing is more conducive to improving the thermal protection performance of clothing.
The combustion dummy can be used to quantitatively evaluate the overall thermal protection performance of clothing, predict the location and extent of human skin's second and third degree burns, and the shrinkage deformation of the clothing surface can also reflect the thermal protection effectiveness of clothing to a certain extent. Although the surface of the dummy was not predicted to be burned in the clothing test No. 1 and No. 2, the area from the chest to the knee showed a large shrinkage deformation, and the abdomen and hips even reached 15% to 20%. To explore the thermal shrinkage mechanism of clothing surface under high temperature and its influence on thermal protection performance is of great significance for the research of clothing thermal protection performance.


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