A method for detecting the melt dripping resistance of chemical fibers

Abstract

The present invention discloses a chemical fiber anti-melting droplet detection method, which ignites the fiber and records the time when the first drop of melt is generated, the number of melt drops and the total mass of the melt drops, and tests the fiber heating bending strength change rate and the sound wave transmission speed change rate, and scores and grades the data obtained by the test. Through the combination of external analysis of ignition performance and internal analysis of heating performance, the fiber can be comprehensively analyzed under ignition conditions and heating conditions, and the direction of ignition of melt drops and heating structure change can be comprehensively evaluated, thereby solving the defect of inconsistent performance evaluation caused by difference in test conditions in the chemical fiber anti-melting droplet detection method; by assigning points and comprehensively evaluating multiple indicators such as the time when the first drop of melt is generated, the number of melt drops, the total mass of melt drops, the bending strength change rate, the sound wave transmission speed change rate, etc., the anti-melting droplet performance of the chemical fiber can be reflected more comprehensively and objectively, thereby avoiding misjudgment of the fiber anti-melting droplet performance due to the one-sidedness of a certain indicator.

Description

Technical Field

[0001] The present invention relates to the technical field of material analysis by means of chemical or physical properties of materials, in particular to a testing and analysis method using a thermal method, and in particular to a chemical fiber anti-melting dripping detection method. Background Art

[0002] Chemical fibers are made by chemically processing natural or synthetic polymers and are a key material category in the textile industry. The chemical fiber production process involves monomer molecules undergoing polycondensation or addition to form long-chain polymers. The molten or dissolved polymer is then extruded through a spinneret, cooled, and stretched to form fibers.

[0003] When chemical fibers are heated, the thermal motion of their internal polymer chains intensifies. If the temperature exceeds the melting point but remains below the decomposition temperature, the fibers first soften into a liquid state, then form droplets due to gravity or surface tension, rather than directly carbonizing or vaporizing.

[0004] Molten droplets carry high temperatures and drip onto the underlying combustibles, creating new combustion points. The probability of ignition by molten droplets is 40% higher than direct flame contact. Molten droplets adhere to the skin, causing deep burns and causing significant harm to the human body in a fire. Testing the anti-molten droplet performance of chemical fibers is of great significance.

[0005] In the existing technology, the anti-melt dripping test is to directly ignite the chemical fiber and observe the melt dripping phenomenon. However, due to the differences in the regulations of different test methods on ignition time, flame height, and sample clamping method, the results are less comparable.

[0006] Therefore, it is necessary to improve the chemical fiber anti-drip detection method in the prior art to solve the above problems. Summary of the Invention

[0007] The present invention overcomes the deficiencies of the prior art and provides a method for detecting chemical fiber anti-melting dripping, aiming to solve the defect of inconsistent performance evaluation caused by differences in test conditions in the prior art chemical fiber anti-melting dripping detection method.

[0008] To achieve the above object, the present invention adopts the following technical solution: a method for detecting anti-drip of chemical fiber, comprising the following steps:

[0009] S1: Set the ignition temperature according to the density of the chemical fiber to ignite the chemical fiber, and record the time when the first droplet is generated, the number of droplets, and the total mass of the droplets;

[0010] S2: Obtaining a heating temperature according to the ignition temperature of S1;

[0011] S3: heating the chemical fiber according to the heating temperature in S2, and measuring the bending strength and acoustic wave transmission velocity of the chemical fiber before and after heating, respectively, to obtain a bending strength change rate and an acoustic wave transmission velocity change rate;

[0012] S4: Score and grade the chemical fiber according to the first droplet generation time, the number of droplets and the total mass of droplets in S1, and the bending strength change rate and the acoustic wave transmission speed change rate in S2.

[0013] In a preferred embodiment of the present invention, the ignition temperature in S1 is positively correlated with the density of the chemical fiber.

[0014] In a preferred embodiment of the present invention, the ignition temperature T i The relationship with the chemical fiber density ρ is:

[0015] , where T d It is the melting point of chemical fiber.

[0016] In a preferred embodiment of the present invention, the heating temperature in S2 is lower than the melting point of the chemical fiber, and the heating temperature is related to the density of the chemical fiber.

[0017] In a preferred embodiment of the present invention, in step S2, obtaining the heating temperature includes: when the chemical fiber density ρ is less than 1.2, the heating temperature Th is: , where T i is the ignition temperature.

[0018] In a preferred embodiment of the present invention, in step S2, obtaining the heating temperature includes: when the chemical fiber density ρ is greater than or equal to 1.2, the heating temperature T h for: , where T i is the ignition temperature.

[0019] In a preferred embodiment of the present invention, the bending strength in S3 is determined according to a three-point bending test and The test was performed using the calculation formula, where F is the maximum load, L is the span, the span is the distance between the load point and the clamping point, b is the fiber width, d is the fiber diameter, the bending strength before heating is σ0, the bending strength after heating is σ1, and the calculation formula for the bending strength change rate Δσ is: .

[0020] In a preferred embodiment of the present invention, the sound wave transmission speed v in S3 is The calculation formula is used for determination, where L0 is the initial spacing, L1 is the modified spacing, the value of the modified spacing is greater than the value of the initial spacing, Δt is the sound wave transmission time at the initial spacing, Δt' is the sound wave transmission time at the modified spacing, the sound wave transmission speed before heating is v0, the sound wave transmission speed after heating is V1, and the calculation formula of the sound wave transmission speed change rate Δv is: , the modified spacing L1 is consistent before and after heating.

[0021] In a preferred embodiment of the present invention, the scoring and grading in S4 include A, B, C and D, and the corresponding numerical ranges are [90, 100], [80, 90), [60, 80), (0, 60), and the weights of the scoring of the time of first droplet generation, the scoring of the number of droplets, the scoring of the total mass of droplets, the scoring of the bending strength change rate and the scoring of the acoustic wave transmission velocity change rate are 0.15, 0.2, 0.15, 0.2 and 0.3 respectively.

[0022] In a preferred embodiment of the present invention, the time for the first droplet to be generated is assigned to S T for , where t is the time when the first droplet is generated, and the number of droplets assigned SN is , where N is the number of droplets, and the fraction Sm of the total mass of the droplets is , where m is the total mass of the droplet, and the bending strength change rate Sσ is The score Sv of the acoustic wave transmission velocity change rate is .

[0023] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0024] (1) The present invention provides a method for detecting the resistance of chemical fiber to droplets, which records the time of the first droplet generation, the number of droplets and the total mass of the droplets after the fiber is ignited, and tests the rate of change of the fiber heating bending strength and the rate of change of the acoustic wave transmission speed. The data obtained from the tests are scored and graded. By combining the external analysis of the ignition performance with the internal analysis of the heating performance, compared with the chemical fiber anti-droplet detection method in the prior art, the fiber can be comprehensively analyzed under the ignition condition and the heating condition, and the direction of the ignition droplet and the heating structure change can be comprehensively evaluated, thereby solving the defect of inconsistent performance evaluation caused by the difference in test conditions in the chemical fiber anti-droplet detection method in the prior art.

[0025] (2) In the present invention, the heating temperature is lower than the melting point of the chemical fiber, and the heating temperature is related to the density of the chemical fiber. By associating the heating temperature with the density, the temperature gradient can be adjusted according to the thermal characteristics of fibers of different densities. Compared with the existing technology, it can simulate the differentiated thermal environment that it may experience in actual applications, so that the thermal response of the fiber can be triggered more accurately during the detection process, thereby more accurately observing and evaluating its anti-melting droplet performance.

[0026] (3) In the present invention, the bending strength is determined by a three-point bending test and in accordance with The calculation formula is used for testing, and the bending strength of chemical fibers before and after heating is accurately determined. Compared with the existing technology, the changes in the mechanical properties of the fibers before and after heating can be accurately obtained, and the degree of change in the mechanical properties of the fibers caused by heating can be intuitively reflected in a quantitative form, providing a specific numerical indicator for evaluating the anti-melt droplet performance, reflecting the anti-melt droplet performance of the fibers.

[0027] (4) In the present invention, the sound wave transmission speed and its rate of change are calculated, and the anti-melt droplet performance of the fiber is evaluated by taking advantage of the fact that the propagation speed of the sound wave in the medium is closely related to the elastic modulus of the medium. Compared with the existing technology, the change of the internal structure of the chemical fiber during the heating process will affect its elastic modulus and crystallinity, and then affect the sound wave transmission speed. It can quantify the microstructural changes of the chemical fiber before and after heating, and highlight the anti-melt droplet performance of the fiber.

[0028] (5) In the present invention, by assigning scores and comprehensively evaluating multiple indicators such as the time when the first drop of molten drop is generated, the number of molten droplets, the total mass of molten droplets, the rate of change of bending strength, and the rate of change of acoustic wave transmission speed, compared with the existing technology, the anti-melt droplet performance of chemical fibers can be reflected more comprehensively and objectively. A single indicator often has limitations, and the combination of multiple indicators can avoid misjudgment of the anti-melt droplet performance of fibers due to the one-sidedness of a certain indicator. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments described in the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts.

[0030] Figure 1 It is a method step diagram of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0033] like Figure 1 As shown, a method for detecting anti-drip of chemical fiber includes the following steps:

[0034] S1: Set the ignition temperature according to the density of the chemical fiber to ignite the chemical fiber, and record the time when the first droplet is generated, the number of droplets, and the total mass of the droplets;

[0035] S2: Obtaining a heating temperature according to the ignition temperature of S1;

[0036] S3: heating the chemical fiber according to the heating temperature in S2, and measuring the bending strength and the acoustic wave transmission speed of the chemical fiber before and after heating, respectively, to obtain the bending strength change rate and the acoustic wave transmission speed change rate; during heating, specifically, another chemical fiber of the same material is taken for heating, and the chemical fiber during heating is consistent with the chemical fiber in the ignition step in S1 in density, fineness and length.

[0037] S4: Score and grade the chemical fiber according to the first droplet generation time, the number of droplets and the total mass of droplets in S1, and the bending strength change rate and the acoustic wave transmission speed change rate in S2.

[0038] A method for detecting the resistance of chemical fibers to droplets is disclosed. The method ignites the fiber and records the time when the first droplet is generated, the number of droplets, and the total mass of the droplets. The rate of change of the fiber's heating bending strength and the rate of change of the acoustic wave transmission speed are tested. The data obtained from the tests are combined for scoring and grading. By combining external analysis of the ignition performance with internal analysis of the heating performance, the fiber can be comprehensively analyzed under ignition conditions and heating conditions, and the direction of the ignition droplet and the change of the heating structure can be comprehensively evaluated, thereby solving the defect of inconsistent performance evaluation caused by differences in test conditions in the chemical fiber resistance to droplet detection method in the prior art.

[0039] The ignition temperature in S1 is positively correlated with the density of chemical fiber. i The relationship with chemical fiber density ρ is:

[0040] , where T d It is the melting point of chemical fiber.

[0041] Setting the ignition temperature relatively low at low density can prevent premature ignition of the fiber during normal use or in low-energy environments, thereby reducing the possibility of accidental fires. As density increases, the ignition temperature setting formula changes accordingly, ensuring appropriate ignition conditions at different densities, preventing ignition at unexpectedly low temperatures and improving safety. Because the ignition temperature is related to parameters such as the melting point, this setting relationship ensures that the fiber can only ignite near its melting point, allowing the fiber to maintain good thermal stability in normal temperature environments and reducing the risk of thermal runaway and spontaneous combustion caused by factors such as temperature fluctuations.

[0042] The heating temperature in S2 is below the melting point of the chemical fiber and is related to its density. This ensures that the fiber does not melt during testing. This allows subsequent flexural strength and acoustic wave transmission velocity tests to accurately reflect the material's performance changes while heated but not melted. Heating the chemical fiber at this temperature involves heating the fiber in a uniform temperature environment for 5 minutes.

[0043] High-density fibers typically have higher molecular chain packing density and stronger intermolecular forces, resulting in faster heat conduction rates but lower thermal expansion coefficients. Low-density fibers exhibit the opposite effect. By correlating heating temperature with density, the temperature gradient can be adjusted to the thermal characteristics of fibers of different densities, simulating the diverse thermal environments they may experience in real-world applications.

[0044] In step S2, obtaining the heating temperature includes: when the chemical fiber density ρ is less than 1.2, the heating temperature Th is: , where T i Is the ignition temperature. When the chemical fiber density ρ is greater than or equal to 1.2, the heating temperature T h for: , where T i The ignition temperature.

[0045] For low-density fibers, this temperature setting provides sufficient energy to enable the fibers to undergo necessary physical or chemical changes during testing, such as proper movement of molecular chains, without overheating. For chemical fibers with a density less than 1.2, the heating temperature setting is different from that of fibers with higher densities. This distinction takes into account the differences in structure and performance of fibers of different densities, as different densities may indicate differences in the fiber's internal microstructure, such as molecular arrangement and crystallinity, which in turn affects its thermal response and physical and chemical changes during heating.

[0046] For high-density fibers, the effect of increased density on heat absorption and transfer is considered. Higher densities may require higher temperatures to achieve uniform heating and the corresponding physical and chemical changes, but this formula provides reasonable limits to avoid quality issues such as fiber degradation and embrittlement caused by excessive temperatures.

[0047] By setting the heating temperature based on key factors such as fiber density and melting point, the thermal response of the fiber can be more precisely triggered during testing, allowing for more accurate observation and evaluation of its anti-melt droplet performance. For example, testing low-density fibers at a relatively low and reasonable temperature can prevent premature or excessive melting of the fiber due to high temperatures, which could obscure its true anti-melt droplet performance. Testing high-density fibers at appropriate temperatures can also accurately reflect their performance under corresponding thermal conditions.

[0048] Heating the fiber at a temperature close to the melting point can more accurately evaluate its anti-melt droplet performance near the critical melting state, and can reflect the performance of the fiber under high temperature conditions that may actually be encountered.

[0049] The flexural strength in S3 is determined by a three-point bending test and in accordance with The test was performed using the calculation formula, where F is the maximum load, L is the span, the span is the distance between the load point and the clamping point, b is the fiber width, d is the fiber diameter, the bending strength before heating is σ0, the bending strength after heating is σ1, and the calculation formula for the bending strength change rate Δσ is: .

[0050] The flexural strength of chemical fibers before and after heating can be measured with high precision, accurately determining the changes in mechanical properties before and after heating, thereby indirectly reflecting their anti-melt dripping performance. This quantitatively and intuitively reflects the degree of change in mechanical properties of the fiber due to heating, providing a specific numerical indicator for evaluating anti-melt dripping performance.

[0051] The standardized three-point bend test method makes the entire testing process standardized and repeatable. Testing by different laboratories or researchers using this setup can yield relatively consistent and comparable results, facilitating the unified evaluation and comparative analysis of the anti-drip performance of chemical fibers.

[0052] By measuring the flexural strength and its rate of change before and after heating, the fiber's anti-melt dripping performance can be inferred from the perspective of changes in mechanical properties. If the flexural strength decreases slightly after heating, it may mean that the fiber structure remains relatively stable when heated, the dripping phenomenon is not obvious, and the anti-melt dripping performance is good; otherwise, the anti-melt dripping performance is poor.

[0053] The calculation formula incorporates multiple parameters related to fiber geometry and stress, comprehensively considering the impact of factors such as the fiber's shape and behavior under stress on its mechanical properties. This comprehensive consideration of multiple parameters more comprehensively reflects the complex stress and thermal conditions that a fiber may encounter in actual use, leading to a more accurate assessment of its anti-drip performance.

[0054] The sound wave transmission speed v in S3 is calculated according to The calculation formula is used for determination, where L0 is the initial spacing, L1 is the modified spacing, the value of the modified spacing is greater than the value of the initial spacing, Δt is the sound wave transmission time at the initial spacing, Δt' is the sound wave transmission time at the modified spacing, the sound wave transmission speed before heating is v0, the sound wave transmission speed after heating is V1, and the calculation formula of the sound wave transmission speed change rate Δv is , the modification spacing L1 before and after heating is consistent.

[0055] By calculating the acoustic wave transmission velocity and its rate of change, it is possible to quantify the microstructural changes in chemical fibers before and after heating. This is because the propagation speed of acoustic waves in a medium is closely related to physical properties such as the elastic modulus of the medium. Changes in the internal structure of chemical fibers during heating affect their elastic modulus and other properties, which in turn affect the acoustic wave transmission velocity. This quantification helps to more accurately assess the physical changes associated with the anti-drip performance of chemical fibers, providing clear, quantifiable indicators for the testing process, reducing errors caused by subjective judgment and improving test accuracy.

[0056] The rate of change of acoustic wave transmission velocity can reflect the movement of molecular segments, changes in crystallinity, and possible defects such as pores within chemical fibers during heating. Fibers with good anti-melting properties have a relatively stable internal structure during heating, resulting in a relatively small rate of change in acoustic wave transmission velocity. Conversely, fibers with poor anti-melting properties experience significant internal structural changes during heating, resulting in a large rate of change in acoustic wave transmission velocity. Therefore, this parameter effectively reflects internal structural changes related to the anti-melting properties of chemical fibers.

[0057] Because there are clear calculation formulas and regulations for relevant physical quantities, when testing in different laboratories or by different operators, as long as the same standard procedures are followed, relatively consistent results can be obtained, ensuring the repeatability and stability of the test.

[0058] The measurement of sound wave transmission speed and its rate of change is relatively unaffected by some common factors in the external environment. Compared with some other detection methods that are more susceptible to environmental interference, this detection setting based on sound wave characteristics is more reliable.

[0059] Acoustic wave testing technology is relatively mature. Using appropriate acoustic wave testing instruments, data such as acoustic wave transmission time can be quickly acquired, allowing for rapid calculation of parameters such as acoustic wave transmission velocity and its rate of change, improving testing efficiency. Compared to methods requiring complex chemical treatments or lengthy mechanical testing, this acoustic wave-based testing setup offers significant time and cost advantages.

[0060] The scoring levels in S4 include A, B, C and D, and the corresponding numerical ranges are [90,100], [80,90), [60,80), (0,60), and the weights of the first droplet generation time, the number of droplets, the total mass of droplets, the bending strength change rate and the acoustic wave transmission velocity change rate are 0.15, 0.2, 0.15, 0.2 and 0.3 respectively.

[0061] By assigning scores and comprehensively evaluating multiple indicators, including the time to first droplet generation, number of droplets, total droplet mass, rate of change in bending strength, and rate of change in acoustic wave transmission velocity, the anti-drip performance of chemical fibers can be more comprehensively and objectively reflected. A single indicator often has limitations, and combining multiple indicators can avoid misjudging the fiber's anti-drip performance due to the one-sidedness of any one indicator.

[0062] The time of first droplet generation S T for , where t is the time it takes for the first drop of molten drop to be generated. The longer the time it takes for the first drop of molten drop to be generated, the less likely the chemical fiber is to quickly generate molten droplets under conditions such as heat, and its stability is relatively good, and its anti-melt droplet performance is also stronger. The degree of this anti-melt droplet ability can be quantified, which is convenient for comparison between different fibers.

[0063] Score of droplet number N for , where N is the number of droplets. Fewer droplets yield a higher score, indicating a low number of droplets produced during the droplet formation process, reflecting its superior droplet resistance from a quantitative perspective. Combined with the scoring of the time to first droplet generation, this allows for a more comprehensive assessment of a chemical fiber's droplet resistance. This approach avoids situations where some fibers have a long first droplet generation time but a high number of subsequent droplets, or fibers have a short first droplet generation time but a limited number of droplets overall. Scoring these two dimensions provides a more accurate evaluation.

[0064] S is the fraction of the total mass of the droplet m for , where m is the total mass of the molten droplet, indicating that the smaller the total mass of the molten droplet, the higher the score, which means that the total material loss of the fiber in the molten droplet process is less, that is, the scale of the generated molten droplets is small. A smaller total mass of the molten droplet often means that the fiber material can still maintain a relatively high integrity after experiencing conditions that may cause molten droplets, and the decline in its physical and mechanical properties is relatively small, thereby ensuring its reliability in subsequent use.

[0065] Score of bending strength change rate σ for The smaller the bending strength change rate, the lower the score, indicating that the mechanical properties (bending strength) of the fiber have changed little after the droplet-related process. The score Sv for the change rate of the acoustic wave transmission velocity is Combining the sonic velocity change rate with other indicators, such as the flexural strength change rate, provides a more comprehensive assessment of the overall changes in the physical properties of chemical fibers before and after the droplet process. Different indicators reflect fiber performance from different perspectives: the sonic velocity change rate focuses on the microstructure, while the flexural strength change rate focuses on mechanical properties. The two complement each other and provide a more accurate assessment of a fiber's anti-droplet performance.

[0066] Example 1

[0067] This embodiment provides a method for detecting the anti-drip resistance of chemical fibers. The detection method comprises the following steps:

[0068] S1: Set the ignition temperature according to the density of the chemical fiber to ignite the chemical fiber. The ignition temperature T i The relationship with chemical fiber density ρ is:

[0069] , where T d The melting point of chemical fiber is recorded, and the time of first droplet generation, number of droplets and total mass of droplets are recorded respectively;

[0070] S2: Obtain the heating temperature based on the ignition temperature of S1. When the chemical fiber density ρ is less than 1.2, the heating temperature Th is: , where T d is the melting point of chemical fiber. When the density of chemical fiber ρ is greater than or equal to 1.2, the heating temperature Th is: , where T d It is the melting point of chemical fiber.

[0071] S3: Heat the chemical fiber according to the heating temperature in S2, and measure the bending strength and acoustic wave transmission speed of the chemical fiber before and after heating, and obtain the bending strength change rate and acoustic wave transmission speed change rate. The bending strength is measured according to the three-point bending test and the The test was performed using the calculation formula, where F is the maximum load, L is the span, the span is the distance between the load point and the clamping point, b is the fiber width, d is the fiber diameter, the bending strength before heating is σ0, the bending strength after heating is σ1, and the calculation formula for the bending strength change rate Δσ is: , the speed of sound wave transmission v is The calculation formula is used for determination, where L0 is the initial spacing, L1 is the modified spacing, the value of the modified spacing is greater than the value of the initial spacing, Δt is the sound wave transmission time at the initial spacing, Δt' is the sound wave transmission time at the modified spacing, the sound wave transmission speed before heating is v0, the sound wave transmission speed after heating is V1, and the calculation formula of the sound wave transmission speed change rate Δv is The modified spacing L1 before and after heating is consistent. Specifically, another chemical fiber of the same material is heated. The chemical fiber during heating is consistent with the chemical fiber ignited in step S1 in density, fineness and length.

[0072] S4: The chemical fiber is scored and graded according to the time of first droplet generation, the number of droplets and the total mass of droplets in S1, and the bending strength change rate and the acoustic wave transmission velocity change rate in S2. The scoring grades include A, B, C and D, and the corresponding value ranges are [90,100], [80,90), [60,80), (0,60). The weights of the first droplet generation time score, the number of droplets score, the total mass of droplets score, the bending strength change rate score and the acoustic wave transmission velocity change rate score are 0.15, 0.2, 0.15, 0.2 and 0.3 respectively. The weight of the first droplet generation time score S T for , where t is the time when the first droplet is generated, and the number of droplets assigned SN is , where N is the number of droplets and Sm is the total mass of the droplets. , where m is the total mass of the droplet, and the bending strength change rate Sσ is , the value of the rate of change of the acoustic wave transmission velocity Sv is .

[0073] Comparative Example 1

[0074] This comparative example provides a method for detecting the anti-melting dripping performance of chemical fibers. The specific detection method is to ignite the fiber and record the time from ignition to dripping. When the dripping time exceeds 10s, the anti-melting dripping performance is qualified, otherwise it is unqualified.

[0075] Comparative Example 2

[0076] This comparative example provides a method for detecting the anti-melt dripping of chemical fibers. The specific detection method is to ignite the fiber and record the number of melt drops falling within one minute from the start of ignition. When the number of melt drops does not exceed 10, the anti-melt dripping performance is qualified, otherwise it is unqualified.

[0077] Comparative Example 3

[0078] This comparative example provides a method for detecting the anti-melt dripping of chemical fibers. The specific detection method is to ignite the fiber and record the total mass of the melt dripping within one minute from the start of ignition. When the total mass of the melt dripping is less than 5g, the anti-melt dripping performance is qualified, otherwise it is unqualified.

[0079] Conventional polyester, polyester containing 8% by mass of aluminum hydroxide, and aramid were respectively used to test the anti-melt droplet performance of chemical fibers using the methods of Example 1 and Comparative Examples 1 to 3. Among them, the fineness and length of conventional polyester, polyester containing 8% by mass of aluminum hydroxide, and aramid were consistent. The score values of Example 1 were rounded, and the test data are shown in Table 1.

[0080] Table 1 Anti-melting droplet performance test data of Example 1 and Comparative Examples 1 to 3

[0081]

[0082] It can be seen from Table 1 that for conventional polyester, Comparative Example 1 is qualified, Comparative Example 2 is unqualified, Comparative Example 3 is unqualified, and Example 1 is judged as Class D. It can be seen that the conventional polyester has poor anti-melting droplet performance due to factors such as the large number of subsequent melt droplets in the fiber; for polyester containing 8% by mass of aluminum hydroxide, Comparative Example 1 is unqualified, Comparative Example 2 is qualified, Comparative Example 3 is qualified, and Example 1 is judged as Class C. The first drop melting time of the fiber is fast, but the number of melt droplets produced is small, and the melt drop mass is small, which shows that the modified polyester has general anti-melting droplet performance; for aramid, Comparative Example 1 is qualified, Comparative Example 2 is qualified, Comparative Example 3 is qualified, and Example 1 is judged as Class A. The first drop melting time of the fiber is slow and the number of subsequent melt droplets produced is small, so the aramid has good anti-melting droplet performance.

[0083] Comparative Examples 1 to 3 can only determine whether the fiber anti-melt drip performance is qualified, and the fiber anti-melt drip performance among multiple comparative examples cannot be unified, making it difficult to evaluate the fiber anti-melt drip performance. Example 1 can quantify the fiber anti-melt drip performance and accurately evaluate the fiber anti-melt drip performance in a numerical way. It can be seen that this example is superior.

[0084] The above description is based on the ideal embodiment of the present invention. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the content of the specification and must be determined according to the scope of the claims.

Claims

1. A method for detecting anti-drip of chemical fiber, characterized in that: The following steps are involved: S1: Set the ignition temperature according to the density of the chemical fiber to ignite the chemical fiber. The ignition temperature T i The relationship with chemical fiber density ρ is: , where T d The melting point of chemical fiber is recorded, and the time of first droplet generation, number of droplets and total mass of droplets are recorded respectively; S2: Obtaining a heating temperature according to the ignition temperature of S1, wherein obtaining the heating temperature includes: when the chemical fiber density ρ is less than 1.2, the heating temperature Th is: , where T i is the ignition temperature; when the chemical fiber density ρ is greater than or equal to 1.2, the heating temperature T h for: , where T i is the ignition temperature; S3: heating the chemical fiber according to the heating temperature in S2, and measuring the bending strength and acoustic wave transmission velocity of the chemical fiber before and after heating, respectively, to obtain a bending strength change rate and an acoustic wave transmission velocity change rate; S4: scoring and grading the chemical fiber according to the first droplet generation time, the number of droplets and the total mass of droplets in S1, and the bending strength change rate and the acoustic wave transmission speed change rate in S2; The scoring grading includes A, B, C and D, and the corresponding numerical ranges are [90, 100], [80, 90), [60, 80), (0, 60), and the weights of the first droplet generation time, the number of droplets, the total mass of droplets, the bending strength change rate and the acoustic wave transmission velocity change rate are 0.15, 0.2, 0.15, 0.2 and 0.3 respectively; The time for the first droplet to be generated is assigned S T for , where t is the time when the first droplet is generated, and the number of droplets assigned SN is , where N is the number of droplets, and the fraction Sm of the total mass of the droplets is , where m is the total mass of the droplet, and the bending strength change rate Sσ is The score Sv of the acoustic wave transmission velocity change rate is .

2. A chemical fiber anti-drip detection method according to claim 1, characterized in that: The bending strength in S3 is determined by a three-point bending test and according to The test was performed using the calculation formula, where F is the maximum load, L is the span, the span is the distance between the load point and the clamping point, b is the fiber width, d is the fiber diameter, the bending strength before heating is σ0, the bending strength after heating is σ1, and the calculation formula for the bending strength change rate Δσ is: .

3. A method for detecting anti-drip properties of chemical fibers according to claim 1, characterized in that: The sound wave transmission speed v in S3 is calculated according to The calculation formula is used for determination, where L0 is the initial spacing, L1 is the modified spacing, the value of the modified spacing is greater than the value of the initial spacing, Δt is the sound wave transmission time at the initial spacing, Δt' is the sound wave transmission time at the modified spacing, the sound wave transmission speed before heating is v0, the sound wave transmission speed after heating is V1, and the calculation formula of the sound wave transmission speed change rate Δv is: , the modified spacing L1 is consistent before and after heating.

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