Method for testing dynamic thermal stress of pre-oriented yarn

Abstract

The invention belongs to the technical field of fiber performance testing, and relates to a pre-oriented yarn dynamic thermal stress testing method, a dynamic thermal stress tester is adopted for testing, the dynamic thermal stress tester comprises a fixing frame, a tow drafting device and a heating box, the fixing frame is of a hollow cube structure, one face of the hollow cube is an instrument control panel, and the other face of the hollow cube is an instrument control panel; the tow drafting device comprises a pre-tension device, a fixed roller, a drafting roller, a motor, a measuring wheel, a force measuring sensor, a negative pressure tow suction device and a heating box, the fixed roller, the drafting roller, the measuring wheel and the negative pressure tow suction device are installed on an instrument control panel of the dynamic thermal stress tester, and the heating box is arranged between the drafting roller and the measuring wheel. And the fixed roller and the drawing roller are arranged in parallel and are vertical to the instrument control panel. According to the testing method, the heating temperature of the pre-oriented yarn can be controlled within the range of + / -1 DEG C; after the aluminum alloy drawing roller is subjected to anodic oxidation treatment, the surface hardness and friction force are obviously improved, and dynamic thermal stress test data are more accurate and stable.

Description

Technical Field

[0001] The invention belongs to the technical field of fiber performance testing and relates to a method for testing dynamic thermal stress of pre-oriented yarns. Background Art

[0002] When testing the dynamic thermal stress of pre-oriented yarns, the pre-oriented yarn fibers are stretched while being heated in the heat box, and the state change of the macromolecular chain during stretching is closely related to the temperature environment. When the temperature of the macromolecular chain of thermoplastic materials such as polyester, polypropylene and nylon is higher than its glass transition temperature (Tg), the macromolecular chain segments begin to move, and the macromolecular chain straightens from the curled state, so the control of the temperature of the yarn bundle is crucial for testing. The traditional heat box adopts direct electric heating conduction. For example, patent CN216955428U discloses a heating mechanism and a chemical fiber filament thermal stress detection mechanism, and provides a multi-segment cavity segmented heating frame design, which is divided into 5 sections. The purpose of segmented heating is to ensure uniform temperature of the heating box. Assuming that the length of the heating box is 800mm, there is a distance of about 150mm between each section, and the temperature uniformity cannot be guaranteed; in addition, the patent designs multiple temperature sensors, which makes the heating box complicated to manufacture and high in cost, and the measurement errors of multiple sensors will lead to differences in the actual control temperature at each end, and more control elements will also lead to an increase in the failure rate.

[0003] In addition, when conducting thermal stress testing in the prior art, the filament bundle needs to be heated up first, then stretched, and the stress changes during the stretching process are tested. The main stretching component is the stretching roller, which is usually made of aluminum alloy. The traditional surface is oxidized to whiten or blacken. After long-term use, the following problems exist: ① The hardness is not enough, and silk marks will appear on the surface; ② The surface of the silk marks is very smooth, and the friction is insufficient, so the wire will slip during rotation; ③ Silk scraps will be adsorbed on the roller after long-term operation, and need to be cleaned frequently.

[0004] Therefore, it is of great significance to study a dynamic thermal stress testing method for pre-oriented yarns to solve the problems existing in the prior art. Summary of the invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for testing the dynamic thermal stress of pre-oriented yarns.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for testing dynamic thermal stress of pre-oriented yarns is applicable to thermoplastic chemical fibers such as polyester, polypropylene and nylon. The test is performed using a dynamic thermal stress tester, which comprises a fixed frame, a yarn drawing device and a heating box. The fixed frame is a hollow cube structure, and one face of the hollow cube is an instrument control panel. The yarn drawing device comprises a pre-tension device, a fixed roller, a drawing roller, a motor, a measuring wheel, a force sensor and a negative pressure wire suction device. The pre-tension device is installed on a face of the fixed frame adjacent to the instrument control panel, and the heating box, the fixed roller, the drawing roller, the measuring wheel and the negative pressure wire suction device are installed on the dynamic thermal stress tester. On the instrument control panel of the tester, the negative pressure wire suction device is installed in the direction of wire drawing. The position does not require to be very precise, and it is sufficient to ensure that the wire bundle is sucked normally. The heating box is arranged between the drafting roller and the measuring wheel. The fixed roller and the drafting roller are arranged parallel to each other and perpendicular to the instrument control panel. The drafting roller is composed of a front drafting roller and a rear drafting roller connected coaxially. The circumference of the front drafting roller is smaller than that of the rear drafting roller. The motor is installed in the fixed frame. The output shaft of the motor passes through the instrument control panel and is connected to the front drafting roller. The force sensor is arranged inside the fixed frame. The measuring wheel is connected to the force sensor through a connecting rod. The connecting rod passes through the instrument control panel to the fixed frame.

[0008] The pre-oriented filaments are introduced through the pre-tension device, passed through the front drafting roller and the fixed roller, and then vertically passed through the heating box, and introduced upward from the measuring wheel arranged under the heating box to the rear drafting roller and the fixed roller, and then enter the negative pressure wire suction device; then the motor is started, the front drafting roller and the rear drafting roller rotate coaxially, the pre-oriented filaments passing through the heating box are drafted, and the force sensor connected to the measuring wheel measures the thermal stress value;

[0009] The dynamic thermal stress tester of the present invention can reduce one running guide motor by combining the guide roller and the drafting roller in the prior art, thus achieving energy saving effect, and less interference factors of the drafting ratio in the test process; the present invention shares a coaxial motor, and the drafting ratio is only related to the distance and size between the drafting roller and the fixed roller. However, when two motors are used for control, the fluctuation of the motor speed will cause the actual drafting ratio to change, which is more difficult to detect and calibrate. The change of the drafting ratio will significantly affect the dynamic thermal stress value of the real-time test, resulting in a larger thermal stress CV value of the test result;

[0010] The front drafting roller and the rear drafting roller are aluminum alloy drafting rollers, and the surface of the aluminum alloy drafting roller is first pre-treated and then anodized;

[0011] Pretreatment refers to degreasing, alkaline etching, neutralization and polishing in sequence; degreasing is to remove surface grease with alkaline or neutral cleaning agent; alkaline etching is to etch the surface with sodium hydroxide solution to remove oxide layer and impurities; neutralization is to neutralize residual alkali solution with nitric acid or sulfuric acid; polishing can be electrolytic polishing or chemical polishing to improve surface finish;

[0012] Anodizing treatment refers to immersing the aluminum alloy drafting roller into an electrolyte of sulfuric acid, oxalic acid or mixed acid, applying a DC power supply, so that an oxide film is formed on the surface of the aluminum alloy. The mixed acid is a mixture of sulfuric acid and oxalic acid. The temperature of anodizing treatment is 0~5℃, the current density is 1~3A / dm², the voltage is 12~20 V (adjusted according to the type of electrolyte), the time is 20~60 minutes, and the thickness of the formed film is 75μm as tested by the eddy current thickness gauge method in ISO 2360.

[0013] After anodizing treatment, the aluminum alloy drafting roller significantly improves the surface hardness and friction, which prevents the wire bundle from slipping and increases the service life. The dynamic thermal stress test data can be guaranteed to be accurate and stable.

[0014] As the preferred technical solution:

[0015] A method for testing dynamic thermal stress of pre-oriented yarn as described above, the heating box includes a stainless steel hollow tube, a circular ring-shaped closed jacket and a gas-phase heat medium evaporator; the middle of the stainless steel hollow tube is used for the pre-oriented yarn filament to pass through, the upper end of the stainless steel hollow tube is the silk road inlet, and the lower end is the silk road outlet; the circular ring-shaped closed jacket is arranged outside the stainless steel hollow tube, and two temperature sensors are arranged on the circular ring-shaped closed jacket, and the two temperature sensors are arranged on the circular ring-shaped closed jacket at positions close to the silk road inlet and close to the silk road outlet in height respectively; the gas-phase heat medium evaporator is arranged at a position lower than the height of the silk road outlet, the gas-phase heat medium evaporator is heated by an electric heating element, the gas-phase heat medium evaporator is filled with low-temperature gas-phase heat transfer oil with a boiling point of 100~120℃, and the gas-phase heat medium evaporator is connected to the middle and bottom of the circular ring-shaped closed jacket at the same time through two different pipelines; in order to realize the gas phase circulation in the system, prevent a small amount of residual air from accumulating at the top to cause the temperature difference of the upper heating sleeve, and reduce the pipeline layout at the same time, an exhaust port is arranged on the top of the circular ring-shaped closed jacket and is connected to the upper part of the gas-phase heat medium evaporator. In the absence of heating, the heat transfer oil forms condensate, and the condensate at the bottom of the annular closed jacket flows back to the gas phase heat medium evaporator through the pipeline; when the heating box is working, the gas phase heat transfer oil boils and produces steam, which fills the entire heating box, making the temperature of the upper and lower sections of the heating uniform.

[0016] In the above-mentioned method for testing dynamic thermal stress of pre-oriented yarns, the pre-tension device is an electronic tensioner.

[0017] In the above-mentioned pre-oriented yarn dynamic thermal stress test method, the circumference ratio of the front drafting roller and the rear drafting roller is 1:1.25~1:1.6, and the draft ratio selection varies according to different fibers: generally 1.65 times for polyester, 1.70 times for polypropylene, and 1.25 times for nylon.

[0018] In the above-mentioned method for testing the dynamic thermal stress of pre-oriented yarns, the pre-oriented yarn filaments are wound around the front drafting roller and the fixed roller for 9 to 12 turns, and around the rear drafting roller and the fixed roller for 9 to 12 turns.

[0019] In the above-mentioned pre-oriented wire dynamic thermal stress test method, the electrolyte concentration is 12~15wt%, the thickness of the oxide film generated on the surface of the aluminum alloy drawing roller after anodizing treatment is 75μm, the surface hardness of the aluminum alloy drawing roller is HV 400~600, and the friction coefficient is 0.6~0.8.

[0020] In the above-mentioned method for testing the dynamic thermal stress of a pre-oriented yarn, the linear density of the pre-oriented yarn is 50-500 dtex, and the heating time of the pre-oriented yarn in the heating box is more than 0.5 s.

[0021] Considering the applicable range of fiber linear density test of 50~500dtex, the test is carried out at a test speed of 100m / min. The fiber bundle in the hot box is subjected to radiation heat transfer, and its heat transfer rate is determined by the Stefan-Boltzmann law, so the temperature rise time is calculated:

[0022] ;

[0023] Where: m: mass of substance (kg);

[0024] c: specific heat capacity (J / kg·K);

[0025] σ: Stefan-Boltzmann constant, 5.67×10 −8 W / m 2 K 4 ;

[0026] : emissivity (between 0 and 1);

[0027] A: radiant surface area (m²);

[0028] Tsource: radiation source temperature (constant, K);

[0029] T final : End point temperature of fiber heating;

[0030] T initial : Starting point temperature of fiber heating;

[0031] T: Real-time temperature of the fiber.

[0032] Combined with the simulation software ANSYS, it is calculated that the heating time of the coarse denier pre-oriented yarn in the heat box is at least 0.5s, and the corresponding requirement is that the length of the heating box needs to reach more than 800mm. Combined with the appropriate heating temperature for different varieties, the fiber can reach a certain molecular chain relaxation state, so as to simulate the normal operation of the drafting process in the next step, and at the same time effectively reduce the difference in test results between instruments from different manufacturers.

[0033] In the above-mentioned method for testing dynamic thermal stress of pre-oriented yarns, the heating temperature fluctuation range of the pre-oriented yarns in the heating box is ±1°C.

[0034] Beneficial effects:

[0035] (1) A method for testing the dynamic thermal stress of a pre-oriented yarn of the present invention, wherein the pre-oriented yarn passes through the center of a heating box. While ensuring straightness, the heating temperature can be controlled within a range of ±1°C and the pre-oriented yarn does not contact a heating tube, thereby avoiding yarn abrasion and static electricity generation.

[0036] (2) In a method for testing dynamic thermal stress of pre-oriented yarns of the present invention, the heat pipe used in the heating box is heated by a uniform gas phase heat medium, which reduces the temperature difference between the segments and improves the temperature control stability; the guide roller and the drawing roller are combined to reduce one running guide motor, which has an energy-saving effect, and there are fewer interference factors in the drawing ratio during the test process.

[0037] (3) A method for testing the dynamic thermal stress of pre-oriented yarns according to the present invention achieves the following effects after the front and rear drawing rollers are anodized: ① The surface hardness is high, and the microhardness tester reaches HV 400-600, the wear resistance is improved, and no silk marks will appear during long-term operation; ② Long-term use does not affect the surface friction, ensuring that the fiber does not slip or get damaged during drawing; ③ Good corrosion resistance, and is not affected by the temperature, humidity, dust, etc. of the external environment; ④ The surface static electricity is effectively eliminated, and waste yarn will not stick. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a side view of the dynamic thermal stress instrument;

[0039] Figure 2 This is a schematic diagram of the interior of the heating box;

[0040] Figure 3 It is a schematic diagram of the structure of the connection between the measuring wheel and the force sensor;

[0041] Among them, 1-fixed frame, 2-pretension device, 3-fixed roller, 4-1-front stretching roller, 4-2-rear stretching roller, 5-motor, 6-heating box, 7-measuring wheel, 8-negative pressure wire suction device, 9-stainless steel hollow tube, 10-circular closed jacket, 11-pipeline, 12-temperature sensor, 13-gas phase heat medium evaporator, 14-electric heating components, 15-connecting rod, 16-force sensor. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0043] Example 1

[0044] A method for testing dynamic thermal stress of pre-oriented yarns, the specific process is as follows:

[0045] The dynamic thermal stress tester is used for testing, such as Figure 1 As shown, the dynamic thermal stress tester includes a fixed frame 1, a tow drawing device and a heating box 6, the fixed frame 1 is a hollow cube structure, and one surface of the hollow cube is an instrument control panel;

[0046] The yarn drawing device includes a pre-tension device 2, a fixed roller 3, a drawing roller, a motor 5, a measuring wheel 7, a force sensor 16 and a negative pressure yarn suction device 8;

[0047] The pre-tension device 2 is an electronic tensioner; the pre-tension device 2 is installed on a surface of the fixing frame 1 adjacent to the instrument control panel;

[0048] The heating box 6, the fixed roller 3, the drafting roller, the measuring wheel 7 and the negative pressure wire suction device 8 are installed on the instrument control panel of the dynamic thermal stress tester; Figure 2As shown, the heating box 6 includes a stainless steel hollow tube 9, a circular closed jacket 10 and a gas phase heat medium evaporator 13; the inner diameter of the stainless steel hollow tube 9 is 8 mm, and the inner diameter of the circular closed jacket 10 is 20 mm; the upper end of the stainless steel hollow tube 9 is a silk road inlet, and the lower end is a silk road outlet; the circular closed jacket 10 is arranged outside the stainless steel hollow tube 9, and two temperature sensors 12 are arranged on the circular closed jacket 10, and the two temperature sensors 12 are arranged on the circular closed jacket 10 at the height, respectively. The position is close to the Silk Road inlet and the Silk Road outlet; the gas phase heat medium evaporator 13 is set at a position lower than the Silk Road outlet, the gas phase heat medium evaporator 13 is heated by an electric heating element 14, the gas phase heat medium evaporator 13 is filled with low-temperature gas phase heat transfer oil with a boiling point of 100°C, and the gas phase heat medium evaporator 13 is connected to the middle and bottom of the annular closed jacket 10 through two different pipelines 11; the top of the annular closed jacket 10 is provided with an exhaust port and is connected to the upper part of the gas phase heat medium evaporator 13;

[0049] The heating box 6 is arranged between the drafting roller and the measuring wheel 7. The fixed roller 3 and the drafting roller are arranged parallel to each other and perpendicular to the instrument control panel. The drafting roller is composed of a front drafting roller 4-1 and a rear drafting roller 4-2 which are coaxially connected. The front drafting roller 4-1 and the rear drafting roller 4-2 are aluminum alloy drafting rollers. The ratio of the circumference of the front drafting roller 4-1 to the circumference of the rear drafting roller 4-2 is 1:1.25. The surface hardness of the aluminum alloy drafting roller is HV 400 and the friction coefficient is 0.6. The motor 5 is installed in the fixed frame 1, and the output shaft of the motor 5 passes through the instrument control panel and is connected to the front drafting roller 4-1.

[0050] like Figure 3 As shown, the force sensor 16 is arranged inside the fixing frame 1, and the measuring wheel 7 is connected to the force sensor 16 via a connecting rod 15;

[0051] The surface of the aluminum alloy drafting roller is first pretreated and then anodized;

[0052] Pretreatment refers to degreasing with calcium bicarbonate aqueous solution (the mass ratio of calcium bicarbonate to water is 1:300), alkaline etching with 0.1wt% sodium hydroxide solution, neutralization with 30wt% nitric acid and electrolytic polishing in sequence;

[0053] Anodizing treatment refers to immersing the aluminum alloy in a sulfuric acid electrolyte with a concentration of 12wt% and applying a DC power supply to form an oxide film with a thickness of 75μm on the surface of the aluminum alloy; the anodizing temperature is 0℃, the current density is 1A / dm², the voltage is 12V, and the time is 20 minutes;

[0054] The pre-oriented filaments with a specification of 50dtex / 36f are introduced through the pre-tension device 2, and after being wound 9 times by the front stretching roller 4-1 and the fixed roller 3, they are vertically passed through the heating box 6 with a length of 800mm and heated for 0.5s, and are introduced upward from the measuring wheel 7 arranged under the heating box 6 to the rear stretching roller 4-2 and the fixed roller 3 for 9 turns, and then enter the negative pressure wire suction device 8; then the motor 5 is started, the front stretching roller 4-1 and the rear stretching roller 4-2 rotate coaxially, and the pre-oriented filaments passing through the heating box 6 are stretched, and the force sensor 16 connected to the measuring wheel 7 measures the thermal stress value, which is 33.3cN, and the thermal stress CV value is 1.13%.

[0055] The heating temperature fluctuation range of the pre-oriented yarn in the heating box is ±0.6°C.

[0056] Comparative Example 1

[0057] A method for testing dynamic thermal stress of pre-oriented yarns is basically the same as that of Example 1, except that the aluminum alloy drafting roller is not anodized.

[0058] The thermal stress values ​​and thermal stress CV values ​​of the pre-oriented yarn after 5 tests are shown in Table 1:

[0059] Table 1

[0060]

[0061] By comparing Comparative Example 1 and Example 1, it can be found that the same sample was tested 5 times, and the thermal stress value fluctuation of Example 1 was significantly smaller, and the thermal stress CV value was also smaller each time, which better reflects the actual intrinsic quality of the sample. This is because after the drafting roller of Example 1 was improved, the sample and the drafting roller fit more closely and no slippage would occur.

[0062] Example 2

[0063] A method for testing dynamic thermal stress of pre-oriented yarns, the specific process is as follows:

[0064] The test is performed using a dynamic thermal stress tester, which includes a fixed frame, a tow drawing device and a heating box. The fixed frame is a hollow cube structure, and one surface of the hollow cube is an instrument control panel.

[0065] The yarn tow drawing device includes a pre-tension device, a fixed roller, a drawing roller, a motor, a measuring wheel, a force sensor and a negative pressure yarn suction device;

[0066] The pre-tension device is an electronic tensioner; the pre-tension device is installed on a surface of the fixed frame adjacent to the instrument control panel;

[0067] The heating box, fixed roller, drawing roller, measuring wheel and negative pressure wire suction device are installed on the instrument control panel of the dynamic thermal stress tester; the heating box includes a stainless steel hollow tube, an annular closed jacket and a gas-phase heat medium evaporator; the inner diameter of the stainless steel hollow tube is 8mm, and the inner diameter of the annular closed jacket is 24mm; the upper end of the stainless steel hollow tube is the silk road inlet, and the lower end is the silk road outlet; the annular closed jacket is arranged outside the stainless steel hollow tube, and two temperature sensors are arranged on the annular closed jacket, and the two temperature sensors are arranged on the annular closed jacket at positions close to the silk road inlet and close to the silk road outlet in height respectively; the gas-phase heat medium evaporator is arranged at a position lower than the height of the silk road outlet, and the gas-phase heat medium evaporator is heated by electric heating components, and the gas-phase heat medium evaporator is filled with low-temperature gas-phase heat transfer oil with a boiling point of 105°C, and the gas-phase heat medium evaporator is simultaneously connected to the middle and bottom of the annular closed jacket through two different pipelines; an exhaust port is arranged on the top of the annular closed jacket and is connected to the upper part of the gas-phase heat medium evaporator;

[0068] The heating box is arranged between the drafting roller and the measuring wheel. The fixed roller and the drafting roller are arranged parallel to each other and perpendicular to the instrument control panel. The drafting roller is composed of a front drafting roller and a rear drafting roller which are coaxially connected. The front drafting roller and the rear drafting roller are aluminum alloy drafting rollers. The circumference ratio of the front drafting roller and the rear drafting roller is 1:1.3. The surface hardness of the aluminum alloy drafting roller is HV 500 and the friction coefficient is 0.65. The motor is installed in the fixed frame, and the output shaft of the motor passes through the instrument control panel and is connected to the front drafting roller.

[0069] The force sensor is arranged inside the fixed frame, and the measuring wheel is connected to the force sensor through a connecting rod;

[0070] The surface of the aluminum alloy drafting roller is first pretreated and then anodized;

[0071] The pretreatment refers to degreasing with a sodium carbonate aqueous solution of 0.3wt%, alkaline etching with a sodium hydroxide solution of 0.1wt%, neutralization with 25wt% sulfuric acid and chemical polishing in sequence;

[0072] Anodizing treatment refers to immersing the aluminum alloy in an oxalic acid electrolyte with a concentration of 13wt% and applying a DC power supply to form an oxide film with a thickness of 75μm on the surface of the aluminum alloy; the anodizing temperature is 1°C, the current density is 1.5A / dm², the voltage is 15V, and the time is 30 minutes;

[0073] The pre-oriented filaments with a specification of 165dtexdtex / 48f were introduced through the pre-tension device, and after being wound around the front stretching roller and the fixed roller for 10 turns, they were vertically passed through a heating box with a length of 801mm and heated for 0.6s. They were introduced upward from the measuring wheel arranged under the heating box to the rear stretching roller and the fixed roller for 10 turns, and then entered the negative pressure wire suction device; then the motor was started, the front stretching roller and the rear stretching roller rotated coaxially, and the pre-oriented filaments passing through the heating box were stretched, and the force sensor connected to the measuring wheel measured the thermal stress value, which was 65.8cN, and the thermal stress CV value was 1.85%.

[0074] The heating temperature fluctuation range of the pre-oriented yarn in the heating box is ±0.8°C.

[0075] Comparative Example 2

[0076] A method for testing dynamic thermal stress of pre-oriented yarns is basically the same as that of Example 2, except that the aluminum alloy drafting roller is not anodized.

[0077] The thermal stress values ​​and thermal stress CV values ​​of the pre-oriented yarn after 5 tests are shown in Table 2:

[0078] Table 2

[0079]

[0080] By comparing Comparative Example 2 and Example 2, it can be found that when the same sample is tested 5 times, the fluctuation of the thermal stress value of Example 2 is significantly smaller, and the CV value of the thermal stress each time is also smaller, which better reflects the intrinsic quality of the sample. This is because after the drafting roller of Example 2 is improved, the sample and the drafting roller fit more closely and no slippage occurs.

[0081] Example 3

[0082] A method for testing dynamic thermal stress of pre-oriented yarns, the specific process is as follows:

[0083] The test is performed using a dynamic thermal stress tester, which includes a fixed frame, a tow drawing device and a heating box. The fixed frame is a hollow cube structure, and one surface of the hollow cube is an instrument control panel.

[0084] The yarn tow drawing device includes a pre-tension device, a fixed roller, a drawing roller, a motor, a measuring wheel, a force sensor and a negative pressure yarn suction device;

[0085] The pre-tension device is an electronic tensioner; the pre-tension device is installed on a surface of the fixed frame adjacent to the instrument control panel;

[0086] The heating box, fixed roller, drawing roller, measuring wheel and negative pressure wire suction device are installed on the instrument control panel of the dynamic thermal stress tester; the heating box includes a stainless steel hollow tube, an annular closed jacket and a gas-phase heat medium evaporator; the inner diameter of the stainless steel hollow tube is 8mm, and the inner diameter of the annular closed jacket is 27mm; the upper end of the stainless steel hollow tube is the silk road inlet, and the lower end is the silk road outlet; the annular closed jacket is arranged outside the stainless steel hollow tube, and two temperature sensors are arranged on the annular closed jacket, and the two temperature sensors are arranged on the annular closed jacket at positions close to the silk road inlet and close to the silk road outlet in height respectively; the gas-phase heat medium evaporator is arranged at a position lower than the height of the silk road outlet, and the gas-phase heat medium evaporator is heated by electric heating components, and the gas-phase heat medium evaporator is filled with low-temperature gas-phase heat transfer oil with a boiling point of 110°C, and the gas-phase heat medium evaporator is simultaneously connected to the middle and bottom of the annular closed jacket through two different pipelines; an exhaust port is arranged on the top of the annular closed jacket and is connected to the upper part of the gas-phase heat medium evaporator;

[0087] The heating box is arranged between the drafting roller and the measuring wheel. The fixed roller and the drafting roller are arranged parallel to each other and perpendicular to the instrument control panel. The drafting roller is composed of a front drafting roller and a rear drafting roller which are coaxially connected. The front drafting roller and the rear drafting roller are aluminum alloy drafting rollers. The circumference ratio of the front drafting roller and the rear drafting roller is 1:1.4. The surface hardness of the aluminum alloy drafting roller is HV 550 and the friction coefficient is 0.75. The motor is installed in the fixed frame, and the output shaft of the motor passes through the instrument control panel and is connected to the front drafting roller.

[0088] The force sensor is arranged inside the fixed frame, and the measuring wheel is connected to the force sensor through a connecting rod;

[0089] The surface of the aluminum alloy drafting roller is first pretreated and then anodized;

[0090] Pretreatment refers to degreasing with detergent (Libai antibacterial lime detergent produced by Guangzhou Libai Company, pH value 6~7, item number: 6920174745436), alkaline etching with 0.1wt% sodium hydroxide solution, neutralization with 33% nitric acid and electrolytic polishing in sequence;

[0091] Anodizing treatment refers to immersing the aluminum alloy in a mixed acid electrolyte with a concentration of 14wt%, applying a DC power supply, so that an oxide film with a thickness of 75μm is formed on the surface of the aluminum alloy. The mixed acid is a mixture of sulfuric acid and oxalic acid with a volume ratio of 15:4; the anodizing temperature is 2℃, the current density is 2A / dm², the voltage is 18V, and the time is 50 minutes;

[0092] The pre-oriented filaments with a specification of 330dtex / 96f were introduced through the pre-tension device, and after being wound around the front stretching roller and the fixed roller for 12 turns, they were vertically passed through a heating box with a length of 801mm and heated for 0.8s. They were introduced upward from the measuring wheel arranged under the heating box to the rear stretching roller and the fixed roller for 12 turns, and then entered the negative pressure wire suction device; then the motor was started, the front stretching roller and the rear stretching roller rotated coaxially, and the pre-oriented filaments passing through the heating box were stretched, and the force sensor connected to the measuring wheel measured the thermal stress value, which was 137.5cN, and the thermal stress CV value was 2.03%.

[0093] The heating temperature fluctuation range of the pre-oriented yarn in the heating box is ±0.7°C.

[0094] Comparative Example 3

[0095] A method for testing dynamic thermal stress of pre-oriented yarns is basically the same as that of Example 3, except that the aluminum alloy drafting roller is not anodized.

[0096] The thermal stress values ​​and thermal stress CV values ​​of the pre-oriented yarn after 5 tests are shown in Table 3:

[0097] Table 3

[0098]

[0099] By comparing Comparative Example 3 and Example 3, it can be found that the same sample was tested 5 times, and the thermal stress value fluctuation of Example 3 was significantly smaller, and the thermal stress CV value each time was also small, which better reflects the intrinsic quality of the sample. This is because after the drafting roller of Example 3 was improved, the sample and the drafting roller fit more closely and no slippage would occur.

[0100] Example 4

[0101] A method for testing dynamic thermal stress of pre-oriented yarns, the specific process is as follows:

[0102] The test is performed using a dynamic thermal stress tester, which includes a fixed frame, a tow drawing device and a heating box. The fixed frame is a hollow cube structure, and one surface of the hollow cube is an instrument control panel.

[0103] The yarn tow drawing device includes a pre-tension device, a fixed roller, a drawing roller, a motor, a measuring wheel, a force sensor and a negative pressure yarn suction device;

[0104] The pre-tension device is an electronic tensioner; the pre-tension device is installed on a surface of the fixed frame adjacent to the instrument control panel;

[0105] The heating box, fixed roller, drawing roller, measuring wheel and negative pressure wire suction device are installed on the instrument control panel of the dynamic thermal stress tester; the heating box includes a stainless steel hollow tube, an annular closed jacket and a gas-phase heat medium evaporator; the inner diameter of the stainless steel hollow tube is 8mm, and the inner diameter of the annular closed jacket is 30mm; the upper end of the stainless steel hollow tube is the silk road inlet, and the lower end is the silk road outlet; the annular closed jacket is arranged outside the stainless steel hollow tube, and two temperature sensors are arranged on the annular closed jacket, and the two temperature sensors are arranged on the annular closed jacket at positions close to the silk road inlet and close to the silk road outlet in height respectively; the gas-phase heat medium evaporator is arranged at a position lower than the height of the silk road outlet, and the gas-phase heat medium evaporator is heated by electric heating components, and the gas-phase heat medium evaporator is filled with low-temperature gas-phase heat transfer oil with a boiling point of 120°C, and the gas-phase heat medium evaporator is simultaneously connected to the middle and bottom of the annular closed jacket through two different pipelines; an exhaust port is arranged on the top of the annular closed jacket and is connected to the upper part of the gas-phase heat medium evaporator;

[0106] The heating box is arranged between the drafting roller and the measuring wheel. The fixed roller and the drafting roller are arranged parallel to each other and perpendicular to the instrument control panel. The drafting roller is composed of a front drafting roller and a rear drafting roller which are coaxially connected. The front drafting roller and the rear drafting roller are aluminum alloy drafting rollers. The circumference ratio of the front drafting roller and the rear drafting roller is 1:1.6. The surface hardness of the aluminum alloy drafting roller is HV 600 and the friction coefficient is 0.8. The motor is installed in the fixed frame, and the output shaft of the motor passes through the instrument control panel and is connected to the front drafting roller.

[0107] The force sensor is arranged inside the fixed frame, and the measuring wheel is connected to the force sensor through a connecting rod;

[0108] The surface of the aluminum alloy drafting roller is first pretreated and then anodized;

[0109] Pretreatment refers to degreasing with washing powder (Libai Bright White Washing Powder produced by Guangzhou Libai Company, pH value 6~7, item number: 196675865), alkaline etching with 0.1wt% sodium hydroxide solution, neutralization with 35wt% nitric acid and electrolytic polishing in sequence;

[0110] Anodizing treatment refers to immersing the aluminum alloy in an oxalic acid electrolyte with a concentration of 15wt%, applying a DC power supply, so that an oxide film with a thickness of 75μm is formed on the surface of the aluminum alloy; the anodizing temperature is 5℃, the current density is 3A / dm², the voltage is 20V, and the time is 60 minutes;

[0111] The pre-oriented filaments with a specification of 500dtex / 144f were introduced through the pre-tension device, and after being wound around the front drawing roller and the fixed roller for 10 turns, they were vertically passed through a heating box with a length of 802mm and heated for 1s, and were introduced upward from the measuring wheel arranged under the heating box to the rear drawing roller and the fixed roller for 10 turns, and then entered the negative pressure wire suction device; then the motor was started, the front drawing roller and the rear drawing roller rotated coaxially, and the pre-oriented filaments passing through the heating box were stretched, and the force sensor at the rear end of the measuring wheel measured the thermal stress value, which was 186.7cN, and the thermal stress CV value was 1.89%.

[0112] For the heating box of the present invention, the temperature measurement is performed once a week and recorded as shown in Table 4:

[0113] Table 4

[0114]

[0115] It can be seen from the above table that the heating box data is accurate, the upper and lower uniformity is good, and the heating temperature fluctuation range of the pre-oriented yarn in the heating box is ±0.5℃.

[0116] Comparative Example 4

[0117] A method for testing dynamic thermal stress of pre-oriented yarns is basically the same as that of Example 4, except that the aluminum alloy drafting roller is not anodized.

[0118] The thermal stress values ​​and thermal stress CV values ​​of the pre-oriented yarn after 5 tests are shown in Table 5:

[0119] Table 5

[0120]

[0121] By comparing Comparative Example 4 and Example 4, it can be found that the same sample was tested 5 times, and the fluctuation of the thermal stress value of Example 4 was significantly smaller, and the CV value each time was also smaller, which better reflects the intrinsic quality of the sample. This is because after the drafting roller of Example 4 was improved, the sample and the drafting roller fit more closely and no slippage would occur.

[0122] After the drafting rollers of Examples 1 to 4 were treated with anodization, the surface was smooth and brownish gray. After long-term use (one-year observation period) in an environment with temperature and humidity changes (temperature 5°C to 30°C, humidity 40%RH to 80%RH), the surface did not change. After the drafting rollers of Comparative Examples 1 to 4 were treated with oxidation whitening, the surface was smooth and grayish white. After long-term use (one-year observation period) in an environment with temperature and humidity changes (temperature 5°C to 30°C, humidity 40%RH to 80%RH), the surface became lighter white, black and brown spots of varying sizes appeared, and severe parts had gravure marks.

Claims

1. A method for testing dynamic thermal stress of pre-oriented yarns, characterized in that: The test is performed using a dynamic thermal stress tester, which comprises a fixed frame (1), a yarn drawing device and a heating box (6); the fixed frame (1) is a hollow cube structure, and one surface of the hollow cube is an instrument control panel; the yarn drawing device comprises a pre-tension device (2), a fixed roller (3), a drawing roller, a motor (5), a measuring wheel (7), a force sensor (16) and a negative pressure wire suction device (8), the pre-tension device (2) being mounted on a surface of the fixed frame (1) adjacent to the instrument control panel, and the heating box (6), the fixed roller (3), the drawing roller, the measuring wheel (7) and the negative pressure wire suction device (8) being mounted on the dynamic thermal stress tester. On the instrument control panel of the stress tester, a heating box (6) is arranged between a drafting roller and a measuring wheel (7), a fixed roller (3) and the drafting roller are arranged parallel to each other and perpendicular to the instrument control panel, the drafting roller is composed of a front drafting roller (4-1) and a rear drafting roller (4-2) which are coaxially connected, the circumference of the front drafting roller (4-1) is smaller than that of the rear drafting roller (4-2), a motor (5) is installed in a fixed frame (1), an output shaft of the motor (5) passes through the instrument control panel and is connected to the front drafting roller (4-1), a force sensor (16) is arranged inside the fixed frame (1), and the measuring wheel (7) is connected to the force sensor (16) through a connecting rod (15); The pre-oriented filaments are introduced through the pre-tension device (2), passed through the front drafting roller (4-1) and the fixed roller (3), and then vertically passed through the heating box (6), and introduced upward from the measuring wheel (7) arranged below the heating box (6) to the rear drafting roller (4-2) and the fixed roller (3), and then enter the negative pressure wire suction device (8); then the motor (5) is started, the front drafting roller (4-1) and the rear drafting roller (4-2) rotate coaxially, the pre-oriented filaments passing through the heating box (6) are stretched, and the force sensor (16) connected to the measuring wheel (7) measures the thermal stress value; The front drafting roller (4-1) and the rear drafting roller (4-2) are aluminum alloy drafting rollers, and the surfaces of the aluminum alloy drafting rollers are first pre-treated and then anodized; Pretreatment refers to degreasing, alkali etching, neutralization and polishing in sequence; Anodizing treatment refers to immersing the aluminum alloy in an electrolyte of sulfuric acid, oxalic acid or a mixed acid and applying a direct current power supply to form an oxide film on the surface of the aluminum alloy. The mixed acid is a mixture of sulfuric acid and oxalic acid.

2. A method for testing dynamic thermal stress of pre-oriented yarn according to claim 1, characterized in that: The heating box (6) comprises a stainless steel hollow tube (9), a circular closed jacket (10) and a gas phase heat medium evaporator (13); the upper end of the stainless steel hollow tube (9) is a silk road inlet, and the lower end is a silk road outlet; the circular closed jacket (10) is arranged outside the stainless steel hollow tube (9), and two temperature sensors (12) are arranged on the circular closed jacket (10), and the two temperature sensors (12) are arranged on the circular closed jacket (10) at positions close to the silk road inlet and close to the silk road outlet in terms of height, respectively; The gas phase heat medium evaporator (13) is arranged at a position lower than the height of the silk road outlet. The gas phase heat medium evaporator (13) is heated by an electric heating element (14). The gas phase heat medium evaporator (13) is filled with low-temperature gas phase heat transfer oil with a boiling point of 100 to 120° C. The gas phase heat medium evaporator (13) is simultaneously connected to the middle and bottom of the annular closed jacket (10) through two different pipelines (11); an exhaust port is arranged at the top of the annular closed jacket (10) and is connected to the upper part of the gas phase heat medium evaporator (13).

3. A method for testing dynamic thermal stress of pre-oriented yarn according to claim 1, characterized in that: The pre-tension device (2) is an electronic tensioner.

4. A method for testing dynamic thermal stress of pre-oriented yarn according to claim 1, characterized in that: The ratio of the circumference of the front drafting roller (4-1) and the rear drafting roller (4-2) is 1:1.25~1:1.

6.

5. A method for testing dynamic thermal stress of pre-oriented yarn according to claim 4, characterized in that: The pre-oriented filaments are wound around the front drafting roller (4-1) and the fixed roller (3) for 9 to 12 turns, and around the rear drafting roller (4-2) and the fixed roller (3) for 9 to 12 turns.

6. A method for testing dynamic thermal stress of pre-oriented yarn according to claim 1, characterized in that: The electrolyte concentration is 12~15wt%, the thickness of the oxide film generated on the surface of the aluminum alloy drafting roller after anodizing treatment is 75μm, the surface hardness of the aluminum alloy drafting roller is HV 400~600, and the friction coefficient is 0.6~0.

8.

7. A method for testing dynamic thermal stress of pre-oriented yarns according to claim 2, characterized in that: The linear density of the pre-oriented yarn is 50-500 dtex, and the heating time of the pre-oriented yarn in the heating box is more than 0.5 s.

8. A method for testing dynamic thermal stress of pre-oriented yarns according to claim 7, characterized in that: The heating temperature fluctuation range of the pre-oriented yarn in the heating box is ±1°C.

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