A kind of carbon black water absorption performance in-situ karl fischer titration testing device and method

Abstract

The application relates to the technical field of material performance testing, in particular to a carbon black water absorption performance in-situ Karl Fischer titration testing device and method. The testing device comprises an environment cabin, a multi-station turntable, an in-situ titration sealing cover, a liquid supply system and a main control system. A temperature and humidity adjusting module and a circulating fan are arranged in the environment cabin, which are used for providing a controllable temperature and humidity closed testing environment; the multi-station turntable is rotatably arranged in the environment cabin, and a plurality of testing points for loading crucibles are arranged on the multi-station turntable; the in-situ titration sealing cover is installed above the multi-station turntable in a lifting mode; the liquid supply system is communicated with ethanol injection needle tubes and Karl Fischer titration agent injection needle tubes on the in-situ titration sealing cover; and the main control system is used for controlling the cooperation of the components. According to the application, the whole process from moisture absorption to titration of the sample is arranged in the same environment cabin, so that the sample does not need to be transferred and exposed to the external environment, and the problems of water evaporation and secondary moisture absorption caused by sample transfer are fundamentally eliminated.

Description

Technical Field

[0001] This application relates to the field of material performance testing technology, and in particular to an in-situ Karl Fischer titration test device and method for carbon black water absorption performance. Background Technology

[0002] Carbon black, as an important reinforcing agent and conductive filler in rubber, plastics, cable materials, and new energy batteries, readily absorbs moisture from the environment due to its polar surface groups. In applications such as new energy batteries, high-end cable insulation materials, and ultra-high voltage shielding materials, the moisture content of carbon black must be strictly controlled at the ppm (parts per million) level. Even trace amounts of moisture can severely affect the electrochemical performance, electrical performance, extrusion stability, and service life of the final product.

[0003] Currently, the industry standard method for testing the water absorption of carbon black is to place the sample in a constant temperature and humidity chamber, manually take samples at regular intervals, and then transfer them to a Karl Fischer moisture analyzer or use an oven weighing method for testing. However, the aforementioned traditional methods have several prominent drawbacks: First, during the process of removing the sample from the humidity chamber and transferring it to the moisture analyzer, it is inevitably exposed to the laboratory environment (typically with a humidity of 30%-60%), leading to the loss of trace amounts of moisture or secondary moisture absorption, resulting in test results that deviate significantly from the true value, with errors exceeding 20%; second, manual sampling, weighing, titration, and other steps are highly dependent on the operator's skill level, resulting in poor repeatability and difficulty in meeting the accuracy requirements at the ppm level; third, traditional methods have low throughput and poor efficiency, and require repeated sampling at different time points, making it impossible to achieve parallel comparisons under multiple conditions and at multiple time points; furthermore, the oven weighing method is not sensitive to ppm-level moisture, and carbon black may undergo thermal decomposition or oxidation at high temperatures, affecting the accuracy of the results; finally, repeated opening and sampling will disrupt the microenvironmental balance within the temperature and humidity chamber, leading to distortion of subsequent moisture absorption conditions, and the data cannot truly reflect the in-situ moisture absorption process.

[0004] Therefore, there is an urgent need for a highly accurate, efficient moisture content testing device and method that can truly reflect the moisture absorption process, so as to achieve accurate evaluation of the water absorption performance of powder materials such as carbon black. Summary of the Invention

[0005] This application provides an in-situ Karl Fischer titration test device and method for the water absorption properties of carbon black, which solves the problems in the prior art such as large moisture loss error caused by sampling and transfer, poor repeatability of manual operation, low test throughput and large environmental disturbance.

[0006] This application provides an in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black, comprising: The environmental chamber is equipped with a temperature and humidity control module and a circulating fan to provide a closed testing environment with controllable temperature and humidity. A multi-station turntable is rotatably mounted inside the environmental chamber, with multiple test points on its upper ring for carrying crucibles containing carbon black samples. The multi-station turntable is a servo motor-driven, indexed, rotating disc turntable used to transport the specified crucibles one by one to a fixed working position. The in-situ titration sealing cap is mounted on the multi-station turntable in a height-adjustable manner, corresponding to the multiple test points. Each in-situ titration sealing cap corresponds to one of the crucibles. The in-situ titration sealing cap integrates an elastically retractable platinum electrode probe, an ethanol injection needle, and a Karl Fischer titrant injection needle. The liquid supply system is connected to the ethanol injection needle and Karl Fischer titrant injection needle on each of the in-situ titration sealing caps, and is used to quantitatively inject anhydrous ethanol and Karl Fischer titrant into each crucible. The main control system is electrically connected to the above-mentioned components and is used to control the coordinated operation of the components. It also determines the titration endpoint based on the electrical signal collected by the platinum electrode probe to calculate the moisture content of the sample in each crucible.

[0007] Preferably, the crucible is a square quartz crucible with two platinum contacts embedded at its mouth edge, and the two platinum contacts are respectively connected to two platinum electrodes fixed on the inner wall of the crucible. The test point is a square positioning base that matches the shape of the crucible, and the crucible is set in the positioning base with a clearance fit. A magnetically coupled stirrer is also provided below the positioning base for non-contact driving of the magnetic rotor inside the crucible.

[0008] Preferably, the magnetically coupled stirrer includes a first drive motor fixedly disposed below the multi-station turntable and a permanent magnet mounted on the shaft end of the first drive motor, for driving the magnetic rotor inside the crucible to rotate under the control of the main control system, so as to uniformly disperse carbon black in anhydrous ethanol.

[0009] Preferably, the in-situ titration sealing cap is further provided with a lifting drive assembly. Each lifting drive assembly includes a second drive motor and a lifting adjustment screw driven by the second drive motor. Each lifting drive assembly is independently controlled by the main control system, so that different crucibles can be assigned different moisture absorption test time points to achieve parallel testing at multiple time points.

[0010] Preferably, the in-situ titration sealing cap is further provided with a sealing ring and a pressure sensor; The platinum electrode probe consists of two platinum-iridium alloy probes corresponding to the platinum contact. The two platinum-iridium alloy probes are installed in the in-situ titration sealing cover by built-in micro springs and can extend and retract independently. The lower ends of the two platinum-iridium alloy probes extend to 1.5-2.5 mm below the lower edge of the sealing ring. During the descent of the in-situ titration sealing cap, the main control system can monitor in real time the resistance between the platinum electrode probe and the corresponding platinum contact on the crucible, as well as the real-time sealing pressure at the pressure sensor. When the resistance drops to a preset resistance threshold, it is determined that the electrical contact is good. When the main control system detects that the in-situ titration sealing cap has descended to a preset sealing pressure, it is determined that the sealing is complete.

[0011] Preferably, it also includes an automatic weighing system, which comprises an electronic balance located outside the environmental chamber and a gripping robotic arm for transferring the crucible between the environmental chamber and the electronic balance, wherein: The gripping robotic arm is a multi-joint or Cartesian coordinate robotic arm, with a parallel pneumatic gripper at its end. A sliding sealing door that can be automatically opened and closed by the adjusting screw of the sealing door is provided between the environmental chamber and the electronic balance. The electronic balance is isolated from the environmental chamber by the sliding sealing door with a silicone rubber sealing ring. The gripping robotic arm is suspended above the multi-station turntable near the sliding sealing door via a fixed rod installed at the center of the multi-station turntable, and is used to grip the crucible on the test station. The gripping robotic arm can transfer the crucible from the multi-station turntable through the sliding sealing door to the electronic balance for weighing.

[0012] The liquid supply system includes an external anhydrous ethanol storage tank, a titrant storage tank, a multi-channel injection pump for providing injection power, and corrosion-resistant liquid supply pipelines for connecting the various storage tanks. The environmental chamber is also equipped with an anti-corrosion filter at the exhaust port, and the liquid supply system is also covered with a heating belt on the outside of the liquid supply pipeline inside the environmental chamber.

[0013] This application also provides a test method based on the in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black as described in any of the above claims, including: Step S1, Initial Weighing: The gripping robotic arm sequentially grips the empty crucibles at each test station, passes them through the sliding sealing door, and sends them to the electronic balance for weighing to record the empty weight. After all the empty crucibles have been weighed, carbon black samples are added to the crucibles, and the total weight of the crucibles and carbon black samples is weighed again by the gripping robotic arm in conjunction with the electronic balance. The net weight of the added carbon black sample is then calculated. If the net weight at a certain point exceeds the set weight ±0.2g range, an alarm is triggered to prompt the sample to be added again. Step S2, Drying treatment: After the net weight of the samples at all test stations has been confirmed, each crucible containing the carbon black samples is heated and dried in the environmental chamber. Step S3, constant temperature and humidity absorption: After drying, adjust the temperature and humidity in the environmental chamber to the target humidity absorption conditions and start timing. During this period, control the in-situ titration sealing caps of each test station to keep them raised so that the samples can absorb moisture in an open environment with constant temperature and humidity. Step S4, in-situ titration: When the moisture absorption time reaches the preset test time point, control the in-situ titration sealing cover of the corresponding test station to drop down to seal the crucible at that station. Then, ethanol is injected through the liquid supply system to disperse the sample. Subsequently, the magnetic coupling stirrer is started to stir for a predetermined stirring time to make the carbon black uniformly dispersed in anhydrous ethanol. Then, Karl Fischer titrant is injected for titration, and the titration endpoint is monitored in real time through a platinum electrode during the titration process. Step S5, Data Calculation: After titration, the moisture content of the carbon black sample is calculated based on the net weight of the sample recorded in the previous steps and the amount of titrant consumed during the titration process.

[0014] Preferably, in step S3, the multiple test stations in the environmental chamber are assigned to different moisture absorption time gradients; The main control system automatically executes step S4 for each test station in chronological order. During this process, test stations that have not reached the preset test time remain open and absorb moisture, while the in-situ titration sealing caps of test stations that have completed titration remain in a lowered and sealed state.

[0015] Preferably, in step S4, the specific process of the in-situ titration is as follows: The in-situ titration sealing cap is controlled to descend while the platinum electrode resistance is monitored in real time. The descent stops when the resistance drops below a preset resistance threshold and the pressure sensor reaches a preset pressure value. Subsequently, anhydrous ethanol was injected into the crucible through the liquid supply system, and the magnetically coupled stirrer was started to stir for a predetermined stirring time to ensure that the carbon black was evenly dispersed in the anhydrous ethanol before stirring was stopped. After stirring is stopped, the Karl Fischer titrant is injected at a preset titration rate under the control of the main control system, and the voltage signal at the platinum electrode probe is continuously monitored. When the voltage signal jumps from the initial value to the preset endpoint threshold, it is determined that the titration endpoint has been reached, the injection is stopped, and the volume of titrant consumed is recorded.

[0016] Preferably, in step S5, the formula for calculating the moisture content is: ω = V × Titer / Wsample × 10 6 Where ω is the moisture content to be calculated, V is the volume of titrant consumed, Titer is the titer of the titrant, and Wsample is the net weight of the sample.

[0017] The beneficial effects of this application are as follows: The in-situ Karl Fischer titration test apparatus and method for carbon black water absorption properties disclosed in this application place the sample in the same environmental chamber throughout the entire process from moisture absorption to titration. This eliminates the need for sample transfer and exposure to the external environment, fundamentally preventing moisture loss or secondary moisture absorption caused by sample transfer. The test results can more accurately reflect the in-situ water absorption state of the carbon black sample under the target temperature and humidity. By setting multiple independent test points and using an in-situ titration sealing cap that can be independently controlled by the main control system, different moisture absorption times can be allocated to different points in a single experiment. This allows for the acquisition of a relatively complete moisture absorption kinetic curve in a single experiment, effectively improving the testing efficiency.

[0018] Furthermore, by having the entire process automatically controlled by the main control system, the degree of human intervention is reduced, data fluctuations caused by differences in the proficiency of different operators are minimized, and the repeatability and consistency of test results are improved.

[0019] In particular, this application uses in-situ Karl Fischer titration to directly determine the moisture content in the crucible, accurately determining the endpoint through the abrupt change in platinum electrode potential, and directly measuring the absolute moisture content of the carbon black sample. This avoids the problems of insensitivity to trace moisture and sample deterioration caused by high temperature in the oven weighing method, thus meeting the requirements for high-precision testing at the ppm level.

[0020] Furthermore, the main control system controls the independent lifting and lowering of each test point. Only the in-situ titration sealing cap at the point that reaches the preset test time point is lowered for titration, while the other points remain open and continue to absorb moisture. This simulates the moisture absorption process at different durations, avoiding the disturbance to the temperature and humidity inside the chamber caused by repeated opening and sampling in traditional methods, and making the test data closer to the actual application scenario. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall structure of the in-situ Karl Fischer titration test device for the water absorption properties of carbon black provided in the embodiments of this application. Figure 2 for Figure 1 A schematic diagram of the specific structure of the in-situ titration sealing cap in the apparatus shown; Figure 3 for Figure 1 A schematic diagram of the crucible in the apparatus shown. Figure 4 A flowchart of the in-situ Karl Fischer titration test method for the water absorption properties of carbon black provided in the embodiments of this application.

[0023] Figure label: 1. Exhaust port; 2. Environmental chamber; 3. Lifting connecting frame; 4. Lifting adjusting screw; 5. In-situ titration sealing cap; 6. Liquid supply system; 7. Fixing rod; 8. Crucible; 9. Multi-station turntable; 10. Gripping mounting frame; 11. Magnetic coupling stirrer; 12. Station switching motor; 13. Drive shaft; 14. Weighing isolation chamber; 15. Electronic balance; 16. Sliding sealing door; 17. Parallel pneumatic gripper; 18. Vertical adjusting arm; 19. Horizontal adjusting arm; 20. Sealing door adjusting screw; 21. Circulating fan; 22. Ethanol injection syringe; 23. Miniature spring; 24. Sealing ring; 25. Platinum electrode probe; 26. Karl Fischer titrant injection syringe; 27. Platinum contact; 28. Platinum electrode. Detailed Implementation

[0024] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The following is combined Figure 1-4 This application describes the in-situ Karl Fischer titration test apparatus and method for carbon black water absorption performance provided in the embodiments of this application.

[0026] Reference Figures 1 to 3As shown in the embodiment of this application, an in-situ Karl Fischer titration test device for the water absorption performance of carbon black is provided. It is mainly used to conduct high-throughput in-situ moisture titration tests on powders such as carbon black in a closed environment with controllable temperature and humidity. The device mainly includes an environmental chamber 2, a multi-station turntable 9, an in-situ titration sealing cover 5, a liquid supply system 6, an automatic weighing system, and a main control system.

[0027] The environmental chamber 2 is a rectangular stainless steel sealed cavity, equipped with a temperature and humidity control module and a circulating fan 21. The temperature and humidity control module can be an infrared heating tube and an ultrasonic humidifier to provide a precise and controllable temperature and humidity sealed testing environment. A multi-station turntable 9 is rotatably mounted inside the environmental chamber 2, with multiple test points on its upper ring for holding crucibles 8 containing carbon black samples. The multi-station turntable 9 is a disc-type turntable driven by a servo motor for indexing rotation, used to transport designated crucibles 8 one by one to a fixed working position.

[0028] Specifically, in this embodiment, the environmental chamber 2 is a rectangular sealed cavity made of 304 stainless steel, with external dimensions of 800mm wide, 800mm deep, and 600mm high, and its inner walls are polished. For ease of sample loading and unloading by operators, a main door made of transparent polycarbonate is installed on the front of the chamber, and the edges of the main door are equipped with silicone rubber sealing strips for sealing. In addition, an exhaust port 1 is located on the top of the chamber, and to prevent harmful gases generated during testing from escaping or corroding the exhaust channels, an anti-corrosion filter made of ceramic material is specially installed at the exhaust port 1. The interior of the chamber is equipped with a temperature and humidity control module and a circulating fan 21 to create a stable testing microenvironment.

[0029] The temperature and humidity control module includes a heating module, a humidification module, and temperature and humidity sensors for monitoring temperature and humidity. The heating module uses three 200W infrared heating tubes installed on the rear wall of the chamber, with a maximum heating temperature of 150℃ and a temperature control accuracy of ±0.5℃. The humidification module uses an ultrasonic humidifier with a spray rate of 300mL / h, introducing moisture into the chamber through pipes, with a humidity control range of 10% to 95% RH and an accuracy of ±2% RH. Simultaneously, a 50 CFM axial flow circulating fan 21 is installed on the top of the chamber to ensure uniform temperature and humidity distribution within the chamber.

[0030] Within this enclosed environment, the multi-station turntable 9, serving as the core load-bearing and conveying component, adopts a disc-shaped structure made of aluminum alloy, with a diameter of 600mm and a thickness of 15mm, and is horizontally installed inside the environmental chamber 2. Thirty test points are evenly arranged around the circumference of the multi-station turntable 9. The center of the turntable is connected to the station switching motor 12, installed at the bottom of the chamber, via a drive shaft 13. This station switching motor 12 is a servo motor with a power of 200W and a repeatability accuracy ≤0.1°, capable of driving the turntable to perform precise indexing rotation, thereby conveying each test point to a fixed working position, which is either the gripping position of the robotic arm or the corresponding position of the in-situ titration sealing cover 5.

[0031] Furthermore, such as Figure 3 As shown, in this embodiment, the crucible 8 is a square quartz crucible with two platinum contacts 27 embedded at its rim. These two contacts 27 are connected to two platinum electrodes 28 fixed to the inner wall of the crucible 8. The test point is a square positioning base that matches the crucible's shape. This square positioning base is a square groove fixedly mounted or embedded in the surface of the multi-station turntable 9. It has a side length of 40mm, a groove depth of 4mm, and rounded corners of 2.5mm. The bottom of the groove is flat and made of non-magnetic and corrosion-resistant PEEK or 304 stainless steel. The crucible 8 is a square with a side length of 40mm, a height of 50mm, a wall thickness of 2mm, a flat bottom, and rounded corners. The crucible 8 is securely placed in the groove of the positioning base with a clearance fit. To enable in-situ electrical signal conduction, a platinum contact 27, 20 mm long and 2 mm wide, and 0.2 mm above the surface, is embedded on each of the two long sides of the mouth edge of the crucible 8. These two platinum contacts 27 are electrically connected to two platinum electrodes 28 with a diameter of 0.5 mm that extend into the bottom of the crucible through platinum sintering.

[0032] To ensure sufficient dispersion of carbon black powder during titration, a magnetically coupled stirrer 11 is installed below each test point. This stirrer 11 includes a first drive motor with a rotation speed adjustable from 0 to 2000 rpm, and a 25mm diameter neodymium magnet disk with four pairs of magnetic poles mounted on the shaft of the first drive motor. The first drive motor is a brushless motor fixed to a mounting bracket below the multi-station turntable 9, with a 5mm gap between the motor and the turntable for non-contact operation. Under the control of the main control system, the first drive motor can be energized to generate a rotating magnetic field, driving the magnetic rotor inside the crucible 8 to rotate, thus uniformly dispersing the carbon black sample in anhydrous ethanol. In non-operating states, the first drive motor must be completely de-energized to avoid interference with other workstations.

[0033] Specifically, in this embodiment, to correspond to the aforementioned 30 test points, 30 in-situ titration sealing caps 5 are also provided, each operating independently. For example... Figure 2 As shown, each in-situ titration sealing cap 5 is composed of a sealing cap body, a lifting drive assembly, a platinum electrode probe 25, a miniature spring 23, an ethanol injection needle 22, and a Karl Fischer titrant injection needle 26.

[0034] In this embodiment, the sealing cap is a square PEEK cover plate with a side length of 40mm and a wall thickness of 5mm. A sealing ring 24 is installed around its lower surface to ensure sealing during titration. This sealing ring 24 is made of fluororubber. The lifting drive assembly includes a second drive motor and a lifting adjustment screw 4 with a lead of 2mm driven by the motor. The second drive motor is a stepper motor and is equipped with a linear guide rail for guiding the sealing cap. The lifting stroke of the lifting drive assembly should be no less than 30mm to ensure proper sealing. This assembly is mounted on a ring-shaped bracket fixed above the multi-station turntable 9 via a lifting connecting frame 3. The lifting and lowering movements of each in-situ titration sealing cap are independently controlled by the main control system to meet the needs of titration at different points and times.

[0035] Specifically, in terms of electrical signal detection, the platinum electrode probes 25 are two independently configured platinum-iridium alloy probes with a diameter of 1.5 mm. The protruding length of their lower ends must extend 1.5 mm to 2.5 mm beyond the lower edge of the sealing ring 24; in this embodiment, 2.0 mm is preferred. The positions of the two platinum electrode probes precisely correspond to the positions of the two platinum contacts 27 located on the crucible 8. Each platinum electrode probe 25 can be independently telescopically mounted within the sealing cover body via a built-in miniature spring 23 with a spring force of 40 g and a stroke of 2 mm. This ensures reliable contact while avoiding instantaneous rigid impact caused by descent. A 0.1 mm silver-plated copper wire is also welded to the tail of the platinum electrode probe 25 for connection to the detection circuit after being led out from the top of the cover. In addition, in this embodiment, both the ethanol injection needle 22 and the Karl Fischer titrant injection needle 26 are stainless steel needles with an outer diameter of 0.7 mm and an inner diameter of 0.4 mm. Their upper ends extend above the sealing cap and are connected to the corresponding liquid interfaces located on the walls of the environmental chamber through corresponding liquid supply lines to connect to the liquid supply system 6.

[0036] In some specific embodiments, the liquid supply system 6 for providing liquid to the aforementioned syringes mainly includes an external ethanol storage tank, a titrant storage tank, a multi-channel syringe pump, and corrosion-resistant supply tubing. The ethanol storage tank is a 500mL glass bottle with a silicone stopper, connected to the common inlet of a 30-channel switching valve; the titrant storage tank is a 500mL amber glass bottle, connected to another common inlet of the switching valve to protect the reagent from light. The multi-channel syringe pump is a precision syringe pump equipped with a 250μL glass syringe, which can accurately dispense liquid to the syringes on each sealed cap through the switching valve. The supply tubing is made of corrosion-resistant PTFE material. To prevent liquid crystallization or bubble formation within the tubing, the tubing inside the chamber is specially covered with a heating band to maintain it at the required constant temperature.

[0037] In some specific embodiments, the automatic weighing system includes an electronic balance 15, a gripping robotic arm, and a sliding sealing door 16. The electronic balance 15 is a high-precision electronic balance with a weighing range of 120g and an accuracy of 0.01mg. It is housed in an independent weighing isolation chamber 14 (300mm × 300mm × 200mm) located on one side of the outer casing to minimize vibration interference. The sliding sealing door 16 is vertically positioned between the environmental chamber 2 and the electronic balance 15. It is a 150mm × 150mm 304 stainless steel vertical sliding door with a silicone rubber sealing ring embedded in the door frame. It can be automatically opened and closed by a sealing door drive motor and a sealing door adjusting screw 20.

[0038] In this embodiment, the gripping robotic arm is a three-axis Cartesian coordinate robotic arm, which includes a horizontal adjustment arm 19 for adjusting the horizontal length of the arm, a vertical adjustment arm 18 for adjusting the vertical height of the arm, and a parallel pneumatic gripper 17 made of PEEK material with adjustable clamping force installed at the end of the vertical adjustment arm 18. The gripping robotic arm is suspended above the test point on the side of the multi-station turntable 9 near the sliding sealing door 16 via a gripping mounting frame 10 installed at the center of the turntable 9. During operation, the gripping robotic arm grips the crucible 8 located at the test point and delivers it through the sliding sealing door 16 to the electronic balance 15 located in the weighing isolation chamber 14 for weighing. After weighing, the weighing data is automatically transmitted to the main control system.

[0039] In some specific embodiments, the main control system coordinates the aforementioned components, primarily including a PLC, a touchscreen, motor drivers, and a data acquisition card. The PLC has an analog input module for acquiring data from temperature and humidity sensors, pressure sensors, and a balance. The touchscreen is used for external interaction, facilitating parameter settings and real-time monitoring by operators. The motor drivers are further divided into servo drivers for driving the station switching motor, stepper drivers for driving the second drive motor and the sealing door drive motor, and a DC brushless driver for driving the first drive motor. At the data acquisition level, the platinum electrode signal, after being conditioned by an operational amplifier, is input to the PLC's 0-10V analog input terminal, where the system software determines the titration endpoint (voltage jump ≥150mV). Through the coordinated operation of the aforementioned hardware and software, the main control system can achieve comprehensive closed-loop management of the timing control, action scheduling, and data processing of the entire testing device. More specifically, during the descent of the in-situ titration sealing cap 5, the main control system can monitor the resistance between the platinum electrode probe 25 and the corresponding platinum contact 27 on the crucible 8 in real time. When the resistance drops to a preset resistance threshold (e.g., ≤50mΩ), it is determined that the electrical contact is good. Subsequently, when the in-situ titration sealing cap 5 continues to descend to a preset sealing pressure (e.g., 8N), it is determined that the sealing is complete.

[0040] In some specific embodiments, such as Figure 4 As shown, the present invention also provides a test method based on the above-mentioned in-situ Karl Fischer titration test device for the water absorption properties of carbon black, comprising the following specific steps: Step S10, Preparation: Cleaning 30 quartz crucibles 8: The crucibles 8 were ultrasonically cleaned with deionized water and anhydrous ethanol for 10 minutes in sequence, and then the cleaned crucibles 8 were placed in an oven at 120℃ to dry for 2 hours. After drying, place the crucible 8 into the square positioning base corresponding to each test point on the multi-station turntable 9, press it lightly so that its bottom surface fits into the positioning base, and then place a magnetic rotor into each crucible 8.

[0041] Step S1, Initial weighing: Close the main hatch on the environmental chamber 2, start the system, and select the "initial weighing" mode on the touch screen; At this time, the system will automatically perform empty weighing: control the multi-station turntable 9 to rotate, send the empty crucibles 8 at each test point to the gripping position of the gripping robot arm in sequence, and then control the gripping robot arm to grip the empty crucibles 8 at each test station in sequence for weighing, so as to record the empty weight W1. For example, the multi-station turntable 9 is rotated to send the initial point 1 to the gripping position of the gripping robot arm. After the gripping robot arm grips the empty crucible 8 at that point, the sliding sealing door 16 is opened. After the electronic balance 15 returns to zero, the gripping robot arm places the currently gripped crucible 8 on the weighing pan of the electronic balance 15. The sliding sealing door 16 is then closed. After stabilizing for 3 seconds, the empty weight W1 of the currently weighed crucible is recorded. After recording, the sliding sealing door 16 is opened, and the robot arm removes the crucible 8 and puts it back in its original position. The multi-station turntable 9 is then rotated to the next position, and the above process is repeated until the empty weights of 30 points are recorded, until the turntable returns to the original point, which is the gripping position aligned with the initial point 1.

[0042] After the empty weight of crucible 8 at each test point has been tested, open the main hatch and add about 2,000g of carbon black sample to each crucible 8 using a micro-spoon. Record the actual sample addition position and the corresponding relationship between the sample and the sample, then close the main hatch. Then, the weighing mode is restarted. By selecting the "sample weighing" mode on the touch screen, the system will repeat the above weighing process and record the total weight W2 of the carbon black sample plus crucible 8 at each test point. Then, the software will automatically calculate the net weight W_sample = W2-W1 of the carbon black sample added at each point.

[0043] Furthermore, to more accurately control the testing range, a precise alarm program can be added. For example, if the net weight of the sample at a certain point exceeds the range of 1.800g to 2.200g, the system will issue an alarm prompting the operator to add the sample again to maintain the net weight range of the test sample within a relatively close quantitative range.

[0044] Step S2, drying process: After the net weight of the samples at all test stations is confirmed, the main door is closed, and the crucible 8 containing the samples is heated and dried in the sealed environmental chamber 2. The preferred drying temperature is 100-120℃, the drying time is 2-4 hours, and after drying, the temperature needs to be lowered to below 30℃ before proceeding with subsequent steps to completely remove the original moisture from the samples.

[0045] Specifically, set the drying temperature to 110℃ and the drying time to 3 hours on the touchscreen. The system will start the heating module and the circulating fan 21, and simultaneously open the exhaust port 1 to start exhaust. If the humidity inside the chamber is >5% RH, dehumidification will be started to keep the chamber dry. After 3 hours, the system will automatically stop heating and wait for the temperature inside the chamber to drop below 30℃ before proceeding to the next step.

[0046] Step S3, constant temperature moisture absorption: After drying, adjust the temperature and humidity in environmental chamber 2 to the target moisture absorption conditions (e.g., 20℃, 80% RH) and start timing. During this period, keep the in-situ titration sealing caps 5 of each test station in the raised state, allowing the samples to absorb moisture under constant temperature and humidity in an open environment. At the same time, assign multiple test points in the sealed environmental chamber to different moisture absorption time gradients, such as 0h, 24h, 48h, 72h, etc. The main control system automatically executes the next step for each gradient point in time sequence. Points that have not reached their test time remain in an open moisture absorption state, while the sealing caps of points that have completed titration remain in a lowered sealed state.

[0047] Specifically, the target moisture absorption temperature and humidity are set to 20℃ and 80% RH on the touchscreen. The main control system will automatically adjust the humidifier and heating element to regulate the temperature and humidity inside the chamber, while simultaneously starting the circulating fan 21 to ensure uniform temperature and humidity distribution within the chamber. Once the measured temperature and humidity reach the target values ​​and stabilize, timing begins, and this moment is recorded as the moisture absorption start point. During this period, all in-situ titration sealing caps 5 remain raised, allowing the samples in each crucible 8 to absorb moisture under constant temperature and humidity in an open environment until the moisture absorption time at the test point reaches the preset test time.

[0048] For example, in this embodiment, the 30 test points are sequentially assigned to 5 different moisture absorption time gradients, with 6 parallel samples set for each gradient, used for testing 6 different carbon black samples. The specific arrangement is as follows: Points 1 to 6: 0h testing (sample order: A, B, C, D, E, F); Test at points 7 to 12:24h (sample order: A, B, C, D, E, F); Testing was conducted at points 13 to 18:48 (sample order: A, B, C, D, E, F). Testing at points 19 to 24:72h (sample order: A, B, C, D, E, F); Points 25 to 30: 96h testing (sample order: A, B, C, D, E, F); The main control system can automatically seal the test points that have reached each time gradient and perform in-situ titration steps in the above time sequence; test points that have not reached the preset test time will remain open and absorb moisture. When the titration of a point has been completed but other points have not been fully titrated, its sealing cover will remain in the lowered position to keep the crucible that has completed in-situ titration sealed, so as to ensure that the moisture data of the tested sample is not affected by subsequent environmental changes.

[0049] Step S4, in-situ titration: When the moisture absorption time at a certain test station reaches the preset test time point, the in-situ titration sealing cap 5 at that station is lowered to seal the crucible 8 and the carbon black sample inside. The specific process is as follows: the in-situ titration sealing cap 5 is lowered while the resistance between the platinum electrode probe 25 and the platinum contact 27 is monitored in real time. When the resistance drops below the preset resistance threshold of 50mΩ and the pressure sensor reaches the preset pressure value of 8N, the lowering stops. Subsequently, anhydrous ethanol is injected into the corresponding crucible 8 through the corresponding liquid supply pipeline, and the magnetically coupled stirrer 11 is started to stir for a predetermined stirring time, such as 30s, so that the carbon black is uniformly dispersed in the anhydrous ethanol and then the stirring stops. After the stirring stops, the main control system controls the Karl Fischer titrant to be injected at a preset titration rate of 0.5μL / s and continuously monitors the voltage signal at the platinum electrode probe 25. When the voltage signal jumps from an initial value of about 50mV to a preset endpoint threshold, such as greater than or equal to 150mV, the titration endpoint is determined to have been reached, the injection stops, and the volume V of titrant consumed is recorded.

[0050] Taking a 24-hour time gradient (points 7 to 12) as an example, when the moisture absorption time reaches 24 hours, the system controls the in-situ titration sealing cap 5 of that group of points to descend and automatically completes the titration according to the following sub-steps: During the descent of the sealing cap, the main control system monitors the resistance between the platinum electrode probe 25 and the platinum contact 27 on the crucible 8 in real time. When the resistance drops from infinity (∞) to no more than 50mΩ, it is determined that the electrode contact is good, and the sealing cap continues to descend until the pressure sensor feedback force reaches 8N and stops descending. At this time, it can be determined that the sealing ring 24 is tightly fitted with the mouth of the crucible 8 to form a closed titration chamber. Then, anhydrous ethanol reagent is drawn up by the precision injection pump in the liquid supply system, and 2.0 mL of anhydrous ethanol is injected into the crucible 8 through the ethanol injection syringe 22; the bottom magnetic coupling stirrer 11 is started and stirred at 800 rpm for 30 s to make the carbon black sample evenly dispersed in anhydrous ethanol, and then the stirring is stopped. Karl Fischer titrant is drawn up by a precision injection pump and injected into crucible 8 at a rate of 0.5 μL / s through Karl Fischer titrant injection syringe 26. At the same time, the main control system continuously monitors the voltage signal at platinum electrode probe 25. When the voltage jumps from the initial value (about 50 mV) to ≥150 mV, the titration endpoint is determined to have been reached, the injection is stopped, and the volume of titrant consumed V is recorded. After titration is complete, keep the sealing cap in the lowered position to keep the titrated sample sealed. Repeat the above titration process until all titrations at points 7 to 12 are completed.

[0051] When 48h is reached, the system repeats the above process to titrate points 13 to 18, and so on for 72h, 96h, and so on.

[0052] Step S5, Data Calculation After titration, the main control system calculates the moisture content of the carbon black sample based on the net weight W_sample recorded in the preceding steps and the titrant consumption V during the titration process. The specific calculation formula is as follows: ω = V × Titer / Wsample × 10 6 Wherein, ω is the moisture content to be calculated, in ppm; V is the volume of titrant consumed, in mL; Titer is the titer of the titrant, in mg H2O / mL, which is pre-calibrated, and in this example, it is 2.0 mg H2O / mL; Wsample is the net weight of the sample, in g.

[0053] After the experiment, the system reduces the humidity inside the chamber to a safe range and uniformly lifts all in-situ titration sealing caps 5, generating an Excel report containing sample information at each point, test time, moisture ppm value, and average value of parallel samples. Then, the operator can open the chamber door and take out the crucible 8 for cleaning.

[0054] Specifically, after the experiment, once the humidity inside the chamber drops below 30%, all in-situ titration sealing caps 5 are lifted, the main chamber door is opened, the crucibles 8 are taken out, the samples are poured out, and the crucibles 8 are cleaned according to the aforementioned cleaning steps for future use.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

[0056] The in-situ Karl Fischer titration test apparatus for carbon black water absorption performance of this application effectively eliminates the interference of environmental moisture through fully enclosed in-situ titration, achieves high-throughput parallel testing through multi-station independent control, and ensures ppm-level testing accuracy through Karl Fischer titration. It can be widely used in the evaluation of water absorption performance of powder materials such as carbon black, white carbon black, and nano calcium carbonate, providing a more reliable testing method for accurate characterization of material properties and product quality control.

[0057] Specifically, the in-situ Karl Fischer titration test apparatus for carbon black water absorption performance provided in this application embodiment can be used to perform the above-mentioned test methods to achieve the desired technical effect, which will not be elaborated further here.

[0058] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0059] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0060] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0061] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0062] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black, characterized in that, include: The environmental chamber is equipped with a temperature and humidity control module and a circulating fan to provide a closed testing environment with controllable temperature and humidity. A multi-station turntable is rotatably mounted inside the environmental chamber, and its upper ring is equipped with multiple test points for supporting crucibles; The in-situ titration sealing cap is mounted on the multi-station turntable in a height-adjustable manner, corresponding to the multiple test points. The in-situ titration sealing cap integrates an elastically retractable platinum electrode probe, an ethanol injection needle, and a Karl Fischer titrant injection needle. The liquid supply system is connected to the ethanol injection needle and Karl Fischer titrant injection needle on each of the in-situ titration sealing caps; The main control system is electrically connected to the above-mentioned components and is used to control the coordinated operation of the components and to determine the titration endpoint based on the electrical signals collected by the platinum electrode probe.

2. The in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black according to claim 1, characterized in that, The crucible is a square quartz crucible with two platinum contacts embedded at its mouth edge, and the two platinum contacts are respectively connected to two platinum electrodes disposed on the inner wall of the crucible. The test point is a square positioning base that matches the shape of the crucible, and the crucible is set in the positioning base with a clearance fit. A magnetically coupled stirrer is also provided below the positioning base for non-contact driving of the magnetic rotor inside the crucible.

3. The in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black according to claim 2, characterized in that, The magnetically coupled stirrer includes a first drive motor fixedly disposed below the multi-station turntable and a permanent magnet mounted on the shaft end of the first drive motor, used to drive the magnetic rotor inside the crucible to rotate under the control of the main control system, so as to uniformly disperse carbon black in anhydrous ethanol.

4. The in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black according to claim 3, characterized in that, The in-situ titration sealing cap is also provided with a lifting drive assembly. Each lifting drive assembly includes a second drive motor and a lifting adjustment screw driven by the second drive motor. Each lifting drive assembly is independently controlled by the main control system.

5. The in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black according to claim 4, characterized in that, The in-situ titration sealing cap is also equipped with a sealing ring and a pressure sensor; The platinum electrode probe consists of two platinum-iridium alloy probes corresponding to the platinum contact. The two platinum-iridium alloy probes can be independently telescopically installed in the in-situ titration sealing cover by a built-in micro spring, and the lower ends of the two platinum-iridium alloy probes extend to 1.5mm to 2.5mm below the lower edge of the sealing ring. During the descent of the in-situ titration sealing cap, the main control system can monitor the resistance between the platinum electrode probe and the corresponding platinum contact in real time. When the resistance drops to a preset resistance threshold, it is determined that the electrical contact is good.

6. The in-situ Karl Fischer titration test apparatus for the water absorption properties of carbon black according to claim 5, characterized in that, It also includes an automatic weighing system, which comprises an electronic balance located outside the environmental chamber and a gripping robotic arm for transferring the crucible, wherein: The gripping robotic arm is a multi-joint or Cartesian coordinate robotic arm, with a parallel pneumatic gripper at its end. The environmental chamber and the electronic balance are connected by an automatically opening and closing sliding sealing door, and the electronic balance is separated from the environmental chamber by the sliding sealing door. The gripping robotic arm is suspended above the multi-station turntable near the sliding sealing door via a fixed rod installed at the center of the multi-station turntable. The gripping robotic arm can transfer the crucible from the multi-station turntable through the sliding sealing door to the electronic balance for weighing.

7. A test method for in-situ Karl Fischer titration of carbon black water absorption properties based on the apparatus described in any one of claims 1-6, characterized in that, include: Step S1, Initial Weighing: Control the gripping robotic arm to sequentially grip the empty crucibles at each test station and send them to the electronic balance for weighing to record the empty weight; after all empty crucibles have been weighed, add carbon black sample into the crucibles, and weigh the total weight of the crucibles and carbon black sample again using the gripping robotic arm in conjunction with the electronic balance, and then calculate the net weight of the added carbon black sample. If the net weight of the sample measured at a certain point exceeds the set weight range of ±0.2g, an alarm prompts to add the sample again; Step S2, Drying treatment: After the net weight of the samples at all test stations has been confirmed, each crucible containing the carbon black samples is heated and dried in the environmental chamber. Step S3, constant temperature and humidity absorption: After drying, adjust the temperature and humidity in the environmental chamber to the target humidity absorption conditions and start timing to allow the sample to absorb moisture in an open environment under constant temperature and humidity. Step S4, in-situ titration: When the moisture absorption time reaches the preset test time point, control the in-situ titration sealing cover of the corresponding test station to drop down to seal the crucible at the station. Then, inject anhydrous ethanol reagent and Karl Fischer titrant into the corresponding crucible through the liquid supply system for titration. During the titration process, monitor the titration endpoint in real time through a platinum electrode. Step S5, Data Calculation: After titration, the moisture content of the carbon black sample is calculated based on the net weight of the sample recorded in the previous steps and the amount of titrant consumed during the titration process.

8. The test method according to claim 7, characterized in that, In step S3, the multiple test stations in the environmental chamber are assigned to different moisture absorption time gradients; The main control system automatically executes step S4 for each test station in chronological order. During this process, test stations that have not reached the preset test time remain open and absorb moisture, while the in-situ titration sealing caps of test stations that have completed titration remain in a lowered and sealed state.

9. The test method according to claim 7, characterized in that, In step S4, the specific process of the in-situ titration is as follows: The in-situ titration sealing cap is controlled to descend while the platinum electrode resistance is monitored in real time. The descent stops when the resistance drops below a preset resistance threshold and the pressure sensor reaches a preset pressure value. Subsequently, anhydrous ethanol was injected into the crucible through the liquid supply system, and the magnetically coupled stirrer was started to stir for a predetermined stirring time to ensure that the carbon black was evenly dispersed in the anhydrous ethanol before stirring was stopped. After stirring is stopped, the Karl Fischer titrant is injected at a preset titration rate under the control of the main control system, and the voltage signal at the platinum electrode probe is continuously monitored. When the voltage signal jumps from the initial value to the preset endpoint threshold, it is determined that the titration endpoint has been reached, the injection is stopped, and the volume of titrant consumed is recorded.

10. The test method according to claim 9, characterized in that, In step S5, the formula for calculating the moisture content is: ω=V×Titer / Wsample×10 6 Where ω is the moisture content to be calculated, V is the volume of titrant consumed, Titer is the titer of the titrant, and Wsample is the net weight of the sample.

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