Chemical fiber anti-droplet detection method

Abstract

The invention discloses a chemical fiber anti-droplet detection method, which comprises the following steps: igniting a fiber, recording the generation time of a first droplet, the number of droplets and the total mass of the droplets, testing the change rate of fiber heating bending strength and the change rate of sound wave transmission speed, and carrying out scoring and grading by combining data obtained by testing. Through combination of ignition performance external analysis and heating performance internal analysis, fibers can be comprehensively analyzed under the ignition condition and the heating condition, the molten drop ignition and heating structure change direction is comprehensively evaluated, and the defect that performance evaluation is inconsistent due to test condition difference in a chemical fiber molten drop resistance detection method is overcome; according to the method, indexes such as first droplet generation time, droplet number, total droplet mass, bending strength change rate, sound wave transmission speed change rate and the like are subjected to score assignment and comprehensive evaluation, so that the anti-droplet performance of chemical fibers can be reflected more comprehensively and objectively, and misjudgment on the anti-droplet performance of the fibers due to one-sidedness of a certain index is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of material analysis by means of the chemical or physical properties of materials, in particular to a thermal method for testing and analysis, and particularly to a method for detecting the melt dripping resistance of chemical fibers. Background Art

[0002] Chemical fibers are fibers made by chemically processing natural or synthetic polymer materials and are an important category of materials in the textile industry. The preparation process of chemical fibers is that monomer molecules form long-chain polymers through polycondensation or addition polymerization, and the molten or dissolved polymer is extruded through a spinneret hole and cooled and stretched to form fibers.

[0003] When chemical fibers are heated, the thermal motion of the polymer chains inside them intensifies. If the temperature exceeds the melting point but is lower than the decomposition temperature, the fibers will first soften into a liquid state and then form melt droplets due to the action of gravity or surface tension, rather than directly carbonizing or gasifying.

[0004] The melt droplets carry high temperature and drip onto the lower combustibles, forming new ignition points. The ignition probability of the melt droplets is 40% higher than that of direct flame contact, and the melt droplets adhering to the skin cause deep burns, which cause great harm to the human body in a fire. It is of great significance to detect the melt dripping resistance performance of chemical fibers.

[0005] In the prior art, the detection of melt dripping resistance is to directly ignite the chemical fibers and observe the melt droplet phenomenon. However, due to the differences in the regulations of ignition time, flame height, and sample clamping method for different testing methods, the comparability of the results is low.

[0006] Therefore, it is necessary to improve the method for detecting the melt dripping resistance of chemical fibers 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 the melt dripping resistance of chemical fibers, aiming to solve the defect of inconsistent performance evaluation caused by differences in testing conditions in the method for detecting the melt dripping resistance of chemical fibers in the prior art.

[0008] To achieve the above object, the technical solution adopted by the present invention is: a method for detecting the melt dripping resistance of chemical fibers, comprising the following steps: S1: Set the ignition temperature according to the density of the chemical fiber to ignite the chemical fiber, and record the generation time of the first melt droplet, the number of melt droplets, and the total mass of the melt droplets respectively; S2: Obtain the heating temperature according to the ignition temperature in S1; S3: Heat the chemical fiber according to the heating temperature in S2, and measure the flexural strength and acoustic wave transmission speed of the chemical fiber before and after heating respectively to obtain the flexural strength change rate and the acoustic wave transmission speed change rate; S4: Grade and classify the chemical fiber according to the first-drop molten droplet generation time, the number of molten droplets, and the total mass of the molten droplets in S1, as well as the bending strength change rate and the acoustic wave transmission speed change rate in S2.

[0009] In a preferred embodiment of the present invention, the ignition temperature in S1 is positively correlated with the density of the chemical fiber.

[0010] In a preferred embodiment of the present invention, the ignition temperature T i has the following relationship with the density ρ of the chemical fiber: , where T d is the melting point of the chemical fiber.

[0011] 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.

[0012] In a preferred embodiment of the present invention, in step S2, obtaining the heating temperature includes: when the density ρ of the chemical fiber is less than 1.2, the heating temperature Th is: , where T i is the ignition temperature.

[0013] In a preferred embodiment of the present invention, in step S2, obtaining the heating temperature includes: when the density ρ of the chemical fiber is greater than or equal to 1.2, the heating temperature T h is: , where T i is the ignition temperature.

[0014] In a preferred embodiment of the present invention, the bending strength determination in S3 is based on a three-point bending test and is tested according to 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 σ 0 , and the bending strength after heating is σ 1 , and the calculation formula for the bending strength change rate Δσ is .

[0015] In a preferred embodiment of the present invention, the acoustic wave transmission speed v in S3 is measured according to the calculation formula, where L 0 is the initial spacing, L 1 is the modified spacing, the value of the modified spacing is greater than the value of the initial spacing, Δt is the acoustic wave transmission time at the initial spacing, Δt’ is the acoustic wave transmission time at the modified spacing, and the acoustic wave transmission speed before heating is v0 After heating, the acoustic wave transmission speed is V 1 The calculation formula for the change rate Δv of the acoustic wave transmission speed is The modified spacing L before and after heating 1 is consistent.

[0016] In a preferred embodiment of the present invention, the grading in S4 includes grade A, grade B, grade C, and grade D, and the corresponding numerical ranges are [90, 100], [80, 90), [60, 80), (0, 60). The scoring weights for the first-drop droplet generation time, the number of droplets, the total mass of droplets, the change rate of bending strength, and the change rate of the acoustic wave transmission speed are 0.15, 0.2, 0.15, 0.2, and 0.3 respectively.

[0017] In a preferred embodiment of the present invention, the score S for the first-drop droplet generation time T is , where t is the first-drop droplet generation time, the score SN for the number of droplets is , where N is the number of droplets, the score Sm for the total mass of droplets is , where m is the total mass of droplets, the score Sσ for the change rate of bending strength is , and the score Sv for the change rate of the acoustic wave transmission speed is .

[0018] The present invention solves the defects existing in the background technology and has the following beneficial effects: (1) The present invention provides a method for detecting the anti-droplet property of chemical fibers. By igniting the fiber, recording the first-drop droplet generation time, the number of droplets, and the total mass of droplets, and testing the change rate of the heating bending strength and the change rate of the acoustic wave transmission speed of the fiber, and combining the test data for grading. Through the combination of the external analysis of the ignition performance and the internal analysis of the heating performance, compared with the existing chemical fiber anti-droplet detection methods, it can comprehensively analyze the fiber under the ignition condition and the heating condition, comprehensively evaluate the direction of the ignition droplet and the change of the heating structure, and solve the defect of inconsistent performance evaluation caused by the difference in test conditions in the existing chemical fiber anti-droplet detection methods.

[0019] (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 correlating the heating temperature with the density, the temperature gradient can be adjusted according to the thermal characteristics of fibers with different densities. Compared with the existing technology, it can simulate the differentiated thermal environment that the fiber may experience in actual applications, so that the thermal response of the fiber can be triggered more precisely during the detection process, and thus its anti-droplet performance can be observed and evaluated more accurately.

[0020] (3) In the present invention, the flexural strength is measured based on the three-point bending test and tested according to the calculation formula of to accurately measure the flexural strength of the chemical fiber before and after heating. Compared with the prior art, the change in the mechanical properties of the fiber before and after heating can be accurately obtained, and the degree of change in the mechanical properties of the fiber due to heating can be intuitively reflected in a quantitative form, providing a specific numerical index for evaluating the anti-dripping performance and reflecting the anti-dripping performance of the fiber.

[0021] (4) In the present invention, by calculating the acoustic wave transmission speed and its change rate, and relying on the characteristic that the propagation speed of acoustic waves in a medium is closely related to the elastic modulus of the medium, the anti-dripping performance of the fiber is evaluated. Compared with the prior art, the change in the internal structure of the chemical fiber during heating will affect its elastic modulus and crystallinity, and thus affect the acoustic wave transmission speed, enabling the quantification of the microscopic structural changes of the chemical fiber before and after heating and highlighting the anti-dripping performance of the fiber.

[0022] (5) In the present invention, by assigning scores to and comprehensively evaluating multiple indicators such as the generation time of the first dripping droplet, the number of dripping droplets, the total mass of dripping droplets, the change rate of flexural strength, and the change rate of acoustic wave transmission speed, compared with the prior art, the anti-dripping performance of the chemical fiber can be reflected more comprehensively and objectively. Single indicators often have limitations, and combining multiple indicators can avoid misjudging the anti-dripping performance of the fiber due to the one-sidedness of a certain indicator. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings; Figure 1 It is a flowchart of the method steps of the preferred embodiment of the present invention. Detailed Embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0026] As shown Figure 1 in the figure, a method for detecting the anti - dripping property of chemical fibers includes the following steps: S1: Set the ignition temperature according to the density of the chemical fiber to ignite the chemical fiber, and record the generation time of the first dripping droplet, the number of dripping droplets, and the total mass of the dripping droplets respectively; S2: Obtain the heating temperature according to the ignition temperature in S1; S3: Heat the chemical fiber according to the heating temperature in S2, and measure the flexural strength and the acoustic wave transmission speed of the chemical fiber before and after heating respectively to obtain the flexural strength change rate and the acoustic wave transmission speed change rate; Specifically, when heating, another chemical fiber of the same material is taken for heating, and the chemical fiber during heating is the same as the chemical fiber in the ignition step in S1 in terms of density, fineness, and length.

[0027] S4: Grade the chemical fiber according to the generation time of the first dripping droplet, the number of dripping droplets, and the total mass of the dripping droplets in S1, and the flexural strength change rate and the acoustic wave transmission speed change rate in S2.

[0028] A method for detecting the anti - dripping property of chemical fibers ignites the fiber to record the generation time of the first dripping droplet, the number of dripping droplets, and the total mass of the dripping droplets, and tests the flexural strength change rate and the acoustic wave transmission speed change rate of the fiber during heating. By combining the obtained data for grading, through the combination of external analysis of ignition performance and internal analysis of heating performance, it is possible to comprehensively analyze the fiber under ignition and heating conditions, comprehensively evaluate the direction of ignition dripping and heating structure changes, and solve the defect of inconsistent performance evaluation caused by differences in test conditions in the existing methods for detecting the anti - dripping property of chemical fibers.

[0029] The ignition temperature in S1 is positively correlated with the density of the chemical fiber. The ignition temperature T i has the following relationship with the density ρ of the chemical fiber: , where T d is the melting point of the chemical fiber.

[0030] Setting a relatively low ignition temperature at low density can avoid premature ignition of the fiber in normal use or in a low - energy environment, thereby reducing the possibility of accidental fires. As the density increases, the setting formula of the ignition temperature changes accordingly, which can ensure appropriate ignition conditions are set at different densities, prevent ignition at an unexpected low temperature, and improve safety. Since the ignition temperature is associated with parameters such as the melting point, this setting relationship can ensure that the fiber is likely to be ignited only when it reaches near its melting point, enabling the fiber to maintain good thermal stability in a normal temperature environment and reducing the risks of thermal runaway and spontaneous combustion caused by factors such as temperature fluctuations.

[0031] 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. Since the heating temperature is lower than the melting point, it can ensure that the fiber does not melt during the test, which enables the subsequent bending strength and acoustic wave transmission speed tests to truly reflect the performance changes of the material in the heated but non-molten state. Specifically, heating the chemical fiber according to the heating temperature means heating the fiber in a uniform temperature environment at the heating temperature for 5 minutes.

[0032] High-density fibers usually have a higher molecular chain packing density, stronger intermolecular forces, a faster heat conduction rate, but a lower coefficient of thermal expansion; low-density fibers are the opposite. Associating the heating temperature with the density can adjust the temperature gradient according to the thermal characteristics of fibers with different densities, simulating the differential thermal environments they may experience in actual applications.

[0033] In step S2, obtaining the heating temperature includes: when the density ρ of the chemical fiber is less than 1.2, the heating temperature Th is: , where T i is the ignition temperature. When the density ρ of the chemical fiber is greater than or equal to 1.2, the heating temperature T h is: , where T i is the ignition temperature.

[0034] For low-density fibers, such a temperature setting can provide sufficient energy for the fiber to undergo necessary physical or chemical changes during the test, such as the appropriate movement of molecular chains, etc., without overheating. For chemical fibers with a density less than 1.2, their heating temperature settings are different from those of fibers with a larger density. This distinction takes into account the differences in structure and performance of fibers with different densities, because different densities may mean differences in the microscopic structures such as molecular arrangement and crystallinity inside the fiber, which in turn affect its thermal response and physical and chemical changes during heating.

[0035] For high-density fibers, the influence of density increase on heat absorption and transfer is considered. A larger density may require a higher temperature to achieve uniform heating and corresponding physical and chemical changes, but it is reasonably restricted by this formula to avoid quality problems such as fiber degradation and embrittlement caused by too high a temperature.

[0036] Considering key factors such as fiber density and melting point to set the heating temperature enables the thermal response of the fiber to be triggered more precisely during the detection process, so as to more accurately observe and evaluate its anti-dripping performance. For example, testing low-density fibers at a relatively low and reasonable temperature can avoid masking their true anti-dripping ability due to premature or excessive melting of the fiber caused by too high a temperature; testing high-density fibers under appropriate conditions can also accurately reflect their performance under corresponding thermal conditions.

[0037] Heating the fiber at a temperature close to the melting point for testing can more accurately evaluate its anti-drip performance near the critical melting state, and can reflect the performance of the fiber under high-temperature conditions that it may actually encounter.

[0038] The flexural strength in S3 is determined according to the three-point bending test and tested according to the calculation formula, where F is the maximum load, L is the span, the span is the distance from the load point to the clamping point, b is the fiber width, d is the fiber diameter, and the flexural strength before heating is σ 0 , and the flexural strength after heating is σ 1 , and the calculation formula for the change rate of flexural strength Δσ is .

[0039] The flexural strength of chemical fibers before and after heating can be measured more precisely, and the changes in the mechanical properties of the fibers before and after heating can be accurately obtained, so as to reflect its anti-drip performance indirectly. It can visually reflect the degree of change in the mechanical properties of the fiber due to heating in a quantitative form, providing a specific numerical index for evaluating the anti-drip performance.

[0040] Based on a standardized test method such as the three-point bending test, the entire detection process has normativity and repeatability. Different laboratories or researchers can obtain relatively consistent and comparable results when testing according to this setting, which is conducive to the unified evaluation and comparative analysis of the anti-drip performance of chemical fibers.

[0041] By measuring the flexural strength and its change rate before and after heating, the anti-drip performance of the fiber can be inferred from the perspective of the change in mechanical properties. If the decrease in flexural strength after heating is small, it may mean that the structure of the fiber remains relatively stable when heated, the dripping phenomenon is not obvious, and the anti-drip performance is better; otherwise, the anti-drip performance is poor.

[0042] The calculation formula involves multiple parameters related to the geometric size and stress of the fiber, comprehensively considering the influence of factors such as the shape characteristics of the fiber itself and its performance under the stress state on its mechanical properties. This comprehensive consideration of multiple parameters can more comprehensively reflect the complex stress and heating conditions that the fiber may encounter in actual use, thus more accurately evaluating its anti-drip performance.

[0043] The acoustic wave transmission velocity v in S3 is measured according to the calculation formula, where L 0 is the initial spacing, L 1 is the modified spacing, the value of the modified spacing is greater than the value of the initial spacing, Δt is the acoustic wave transmission time at the initial spacing, Δt’ is the acoustic wave transmission time at the modified spacing, the acoustic wave transmission velocity before heating is v 0 , and the acoustic wave transmission velocity after heating is V 1, the calculation formula for the rate of change Δv of the acoustic wave transmission speed is , the modified spacing L before and after heating 1 Consistent.

[0044] By calculating the acoustic wave transmission speed and its rate of change, the microscopic structural changes of chemical fibers before and after heating can be quantified. Since the propagation speed of acoustic waves in a medium is closely related to physical properties such as the elastic modulus of the medium, and the internal structure change of chemical fibers during heating will affect their elastic modulus, etc., and then affect the acoustic wave transmission speed. This quantification helps to more accurately evaluate the physical changes related to the melt dripping resistance performance of chemical fibers, making the detection process have clear quantifiable indicators, reducing the errors caused by subjective judgment, and improving the accuracy of detection.

[0045] The rate of change of the acoustic wave transmission speed can reflect the movement of molecular chain segments, the change of crystallinity, and the defect conditions such as possible pores inside the chemical fiber during heating. Fibers with good melt dripping resistance have relatively stable internal structures during heating, and their rate of change of acoustic wave transmission speed is relatively small; on the contrary, fibers with poor melt dripping resistance have large internal structure changes during heating, and the rate of change of acoustic wave transmission speed is large. Therefore, this parameter can effectively reflect the internal structure changes related to the melt dripping resistance performance of chemical fibers.

[0046] Due to the clear calculation formula and the regulations on relevant physical quantities, when different laboratories or different operators conduct detections, as long as they operate according to the same standard procedures, relatively consistent results can be obtained, ensuring the repeatability and stability of the detection.

[0047] The measurement of the acoustic wave transmission speed and its rate of change is relatively less affected by some conventional factors in the external environment. Compared with some other detection methods that are more easily affected by the environment, this detection setting based on the acoustic wave characteristics has higher reliability.

[0048] The acoustic wave detection technology is relatively mature. Using the corresponding acoustic wave detection instrument, data such as the acoustic wave transmission time can be quickly obtained, and then parameters such as the acoustic wave transmission speed and its rate of change can be quickly calculated, improving the detection efficiency. Compared with some methods that require complex chemical treatments or long-term mechanical tests, this detection setting based on acoustic waves has certain advantages in terms of time cost.

[0049] The grading in S4 includes grade A, grade B, grade C, and grade D, and the corresponding numerical ranges are [90, 100], [80, 90), [60, 80), (0, 60). The weights of the scores for the first-drop melt dripping generation time, the number of melt drips, the total mass of melt drips, the rate of change of bending strength, and the rate of change of acoustic wave transmission speed are 0.15, 0.2, 0.15, 0.2, and 0.3 respectively.

[0050] By assigning scores and comprehensively evaluating various indicators such as the generation time of the first molten droplet, the number of molten droplets, the total mass of molten droplets, the change rate of bending strength, and the change rate of sound wave transmission speed, the anti-melting droplet performance of chemical fibers can be more comprehensively and objectively reflected. Single indicators often have limitations, and combining multiple indicators can avoid misjudging the anti-melting droplet performance of fibers due to the one-sidedness of a certain indicator.

[0051] The score S for the generation time of the first molten droplet T is , where t is the generation time of the first molten droplet. The longer the generation time of the first molten droplet, the less likely it is for the chemical fiber to quickly generate molten droplets under conditions such as heating, indicating relatively good stability and stronger anti-melting droplet performance. This can quantify the degree of this anti-melting droplet ability and facilitate comparison between different fibers.

[0052] The score S for the number of molten droplets N is , where N is the number of molten droplets. The fewer the number of molten droplets, the higher the score, indicating that the fiber produces fewer molten droplets during the melting process, reflecting relatively good anti-melting droplet performance from the quantity dimension. Combining with the score for the generation time of the first molten droplet can more comprehensively evaluate the anti-melting droplet performance of chemical fibers. This can avoid situations where some fibers have a long generation time of the first molten droplet but a large number of subsequent molten droplets, or fibers have a short generation time of the first molten droplet but a limited total number of molten droplets. The scores from these two dimensions can more accurately evaluate.

[0053] The score S for the total mass of molten droplets m is , where m is the total mass of molten droplets, indicating that the smaller the total mass of molten droplets, the higher the score, meaning that the fiber has less total material loss during the melting process, that is, the generated molten droplet scale is small. A smaller total mass of molten droplets often means that the fiber material can still maintain relatively high integrity after experiencing conditions that may cause melting, and the decline in its physical and mechanical properties is relatively small, thus ensuring its reliability in subsequent use.

[0054] The score S for the change rate of bending strength σ is , the smaller the change rate of bending strength, the lower the score, indicating that the change in the mechanical properties (bending strength) of the fiber after experiencing the melting-related process is small. The score Sv for the change rate of sound wave transmission speed is . Combining the score for the change rate of sound wave transmission speed with other indicators such as the change rate of bending strength can more comprehensively judge the comprehensive change in the physical properties of chemical fibers before and after the melting process. Different indicators reflect the properties of the fiber from different angles. The change rate of sound wave transmission speed focuses on the microscopic structure level, while the change rate of bending strength focuses on the mechanical property level. The two complement each other and can more accurately evaluate the anti-melting droplet performance of the fiber.

[0055] Example 1

[0056] This Example 1 provides a method for detecting the melt dripping resistance of chemical fibers. The steps of the detection method are as follows: S1: Set the ignition temperature according to the density of the chemical fiber and ignite the chemical fiber. The relationship between the ignition temperature T i and the density ρ of the chemical fiber is: , where T d is the melting point of the chemical fiber. Record the generation time of the first melt droplet, the number of melt droplets, and the total mass of the melt droplets respectively; S2: Obtain the heating temperature according to the ignition temperature in S1. When the density ρ of the chemical fiber is less than 1.2, the heating temperature Th is: , where T d is the melting point of the chemical fiber. When the density ρ of the chemical fiber is greater than or equal to 1.2, the heating temperature Th is: , where T d is the melting point of the chemical fiber.

[0057] S3: Heat the chemical fiber according to the heating temperature in S2, and measure the flexural strength and acoustic wave transmission velocity of the chemical fiber before and after heating to obtain the flexural strength change rate and the acoustic wave transmission velocity change rate. The flexural strength is measured based on the three-point bending test and tested according to 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 flexural strength before heating is σ 0 , the flexural strength after heating is σ 1 , and the calculation formula for the flexural strength change rate Δσ is . The acoustic wave transmission velocity v is measured according to the calculation formula, where L 0 is the initial spacing, L 1 is the modified spacing, the value of the modified spacing is greater than the value of the initial spacing, Δt is the acoustic wave transmission time at the initial spacing, Δt’ is the acoustic wave transmission time at the modified spacing, the acoustic wave transmission velocity before heating is v 0 , the acoustic wave transmission velocity after heating is V 1 , and the calculation formula for the acoustic wave transmission velocity change rate Δv is . The modified spacing L 1 before and after heating is the same. Specifically, when heating, another chemical fiber of the same material is taken for heating, and the chemical fiber during heating is the same as the chemical fiber in the ignition step in S1 in terms of density, fineness, and length.

[0058] S4: Score and classify the chemical fiber according to the generation time of the first molten droplet, the number of molten droplets, and the total mass of the molten droplets in S1, as well as the change rate of bending strength and the change rate of acoustic wave transmission speed in S2. The score and classification include Grade A, Grade B, Grade C, and Grade D, corresponding to the numerical ranges of [90, 100], [80, 90), [60, 80), and (0, 60). The weights of the scores for the generation time of the first molten droplet, the number of molten droplets, the total mass of the molten droplets, the change rate of bending strength, and the change rate of acoustic wave transmission speed are 0.15, 0.2, 0.15, 0.2, and 0.3 respectively. The score S for the generation time of the first molten droplet T is , where t is the generation time of the first molten droplet, and the score SN for the number of molten droplets is , where N is the number of molten droplets, and the score Sm for the total mass of the molten droplets is , where m is the total mass of the molten droplets, and the score Sσ for the change rate of bending strength is , and the score Sv for the change rate of acoustic wave transmission speed is .

[0059] Comparative Example 1 This comparative example provides a method for detecting the anti-melting droplet performance of chemical fibers. The specific detection method is to ignite the fiber and record the time from ignition to the appearance of molten droplets. When the molten droplet time exceeds 10 s, the anti-melting droplet performance is qualified; otherwise, it is unqualified.

[0060] Comparative Example 2 This comparative example provides a method for detecting the anti-melting droplet performance of chemical fibers. The specific detection method is to ignite the fiber and record the number of molten droplets falling within one minute from the start of ignition. When the number of molten droplets does not exceed 10 drops, the anti-melting droplet performance is qualified; otherwise, it is unqualified.

[0061] Comparative Example 3 This comparative example provides a method for detecting the anti-melting droplet performance of chemical fibers. The specific detection method is to ignite the fiber and record the total mass of the molten droplets falling within one minute from the start of ignition. When the total mass of the molten droplets falling is less than 5 g, the anti-melting droplet performance is qualified; otherwise, it is unqualified.

[0062] Respectively take conventional polyester, polyester containing 8% by mass of aluminum hydroxide, and aramid, and use the methods of Example 1 and Comparative Examples 1 to 3 to detect the anti-melting droplet performance of chemical fibers. Among them, the fineness and length of conventional polyester, polyester containing 8% by mass of aluminum hydroxide, and aramid are the same. The score value of Example 1 is rounded, and the detection data are shown in Table 1.

[0063] Table 1 Detection data of anti-melting droplet performance in Example 1 and Comparative Examples 1 to 3

[0064] As can be seen from Table 1, for conventional polyester, Comparative Example 1 was judged to be qualified, Comparative Example 2 was judged to be unqualified, Comparative Example 3 was judged to be unqualified, and Example 1 was judged to be Grade D. Due to factors such as more subsequent molten droplets of the fiber, it can be seen that the anti-melting-drop performance of conventional polyester is poor; for polyester containing 8% by mass of aluminum hydroxide, Comparative Example 1 was judged to be unqualified, Comparative Example 2 was judged to be qualified, Comparative Example 3 was judged to be qualified, and Example 1 was judged to be Grade C. Since the first-drop molten-drop time of the fiber is relatively fast, but the number of generated molten droplets is small and the mass of the molten droplets is small, it is concluded that the anti-melting-drop performance of the modified polyester is average; for aramid, Comparative Example 1 was judged to be qualified, Comparative Example 2 was judged to be qualified, Comparative Example 3 was judged to be qualified, and Example 1 was judged to be Grade A. The first-drop molten-drop time of the fiber is slow and the number of subsequent generated molten droplets is small. Therefore, the anti-melting-drop performance of aramid is good.

[0065] Comparative Examples 1 to 3 can only judge whether the anti-melting-drop performance of the fiber is qualified, and the anti-melting-drop performance of the fibers among multiple comparative examples cannot be unified, making it difficult to evaluate the anti-melting-drop performance of the fiber. Example 1 can quantify the anti-melting-drop performance of the fiber and accurately evaluate the anti-melting-drop performance of the fiber in numerical form. Thus, it can be seen that this example has superiority.

[0066] Based on the ideal embodiments of the present invention as an inspiration, through the above description, relevant personnel can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and the technical scope 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: setting the ignition temperature according to the density of the chemical fiber to ignite the chemical fiber, and recording the time of the first droplet generation, the number of droplets and the total mass of the droplets respectively; S2: Obtaining a heating temperature according to the ignition temperature of S1; S3: heating the chemical fiber according to the heating temperature in S2, and measuring the bending strength and the acoustic wave transmission velocity of the chemical fiber before and after heating, respectively, to obtain the bending strength change rate and the acoustic wave transmission velocity change rate; S4: Score and grade the chemical fiber according to the time of generation of the first droplet, the number of droplets and the total mass of droplets in S1, and the bending strength change rate and the sound wave transmission speed change rate in S2.

2. A chemical fiber anti-drip detection method according to claim 1, characterized in that: The ignition temperature in S1 is positively correlated with the chemical fiber density.

3. A chemical fiber anti-drip detection method according to claim 2, characterized in that: The ignition temperature T i The relationship with the chemical fiber density ρ is: , where T d It is the melting point of chemical fiber.

4. A chemical fiber anti-drip detection method according to claim 1, characterized in that: 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.

5. A chemical fiber anti-drip detection method according to claim 4, characterized in that: In the step S2, the obtaining of 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.

6. A chemical fiber anti-drip detection method according to claim 4, characterized in that: 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.

7. 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 according to The test is performed according to 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 of the bending strength change rate Δσ is: .

8. A chemical fiber anti-drip detection method 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, wherein 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.

9. A chemical fiber anti-drip detection method according to claim 1, characterized in that: 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 speed change rate are 0.15, 0.2, 0.15, 0.2 and 0.3 respectively.

10. A chemical fiber anti-drip detection method according to claim 9, characterized in that: The time for the first droplet to be generated is assigned to S T for , where t is the time when the first drop of molten drop is generated, and the SN assigned to the number of molten droplets 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 fraction Sσ of the bending strength change rate is , the score Sv of the change rate of the acoustic wave transmission speed is .

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