CN-121687663-B - Polymer positive temperature coefficient device based on strong water absorbent protection and preparation method thereof

Abstract

The invention discloses a polymer positive temperature coefficient device based on strong water absorbent protection and a preparation method thereof, belonging to the field of fuses, wherein calcium chloride powder and tungsten carbide powder are mixed and subjected to vacuum grinding to obtain modified tungsten carbide powder; PPTC is prepared by blending modified tungsten carbide and polyvinylidene fluoride (PVDF), and the PPTC resistance is detected. The calcium ions in the calcium chloride have strong coordination capability, can form coordination bonds with hydroxyl oxygen atoms on the surface of the tungsten carbide, and reduce the water absorption capability of the tungsten carbide. Calcium chloride forms different forms of hydrates through chemical reaction with water molecules, so that the moisture is firmly fixed. The PPTC device has the advantages of strong water absorption, providing a dry environment, inhibiting tungsten carbide oxidation, and remarkably improving the resistance stability and the service life of the PPTC device in the use environment.

Inventors

• CHEN JINGJIE
• LI ZENING
• ZHU ZHEYAN
• WANG RUN

Assignees

• 西南石油大学

Dates

Publication Date

20260508

Application Date

20260210

Claims (8)

1. 1. A method for preparing a polymer positive temperature coefficient device based on strong water absorbent protection, which is characterized by comprising the following steps: mechanically mixing anhydrous calcium chloride powder and tungsten carbide powder to form mixed powder; carrying out vacuum ball milling on the mixed powder to obtain modified tungsten carbide powder; And blending the modified tungsten carbide powder with PVDF to obtain the polymer positive temperature coefficient device.
2. 2. The method of manufacturing a positive temperature coefficient device according to claim 1, wherein the mechanical mixing is performed in a stirrer for 0.2 to 1.0 hour at a stirring speed of 50 to 120 r/min.
3. 3. The method for manufacturing a positive temperature coefficient device according to claim 1, wherein the vacuum ball milling is performed in a vacuum ball mill, the stirring time is 0.5-2.0 hours, the milling speed is 80-150r/min, the vacuum degree is lower than 50Pa, and the temperature is controlled to be lower than 80 ℃.
4. 4. The method of manufacturing a polymeric positive temperature coefficient device according to claim 1, wherein a mass ratio of the anhydrous calcium chloride powder to the tungsten carbide powder is (0.10-0.65): 100.
5. 5. The method for manufacturing a positive temperature coefficient polymer device according to claim 1, wherein the tungsten carbide powder is micron-sized tungsten carbide powder produced by a mechanical alloying method, a direct reduction carbonization method or a sol-gel method, and the particle size of the tungsten carbide powder is 1um to 10um.
6. 6. The method of manufacturing a polymeric positive temperature coefficient device according to claim 1, wherein the particle size of the anhydrous calcium chloride powder is less than 0.5 μm.
7. 7. The method of manufacturing a polymeric positive temperature coefficient device according to claim 1, wherein the mass ratio of PVDF to modified tungsten carbide powder is 1:7-13.
8. 8. A polymeric positive temperature coefficient device based on strong water absorbent protection, characterized in that it is prepared by the preparation method according to any one of claims 1 to 7.

Description

Polymer positive temperature coefficient device based on strong water absorbent protection and preparation method thereof Technical Field The invention belongs to the field of fuses, relates to a self-recovery fuse preparation technology, and in particular relates to a polymer positive temperature coefficient device based on strong water absorbent protection and a preparation method thereof. Background The core of the polymer positive temperature coefficient device (PPTC) is a PTC effect of a composite material formed by conductive filler and a polymer matrix, the device is in a low resistance state in a normal state, and when overcurrent occurs, the device generates heat to cause the polymer to expand, a conductive path is broken, and the resistance rises sharply, so that the circuit is cut off. And after the fault is removed, cooling and resetting. Tungsten carbide is an ideal PPTC conductive filler due to good conductivity, hardness and thermal expansion coefficient matched with a polymer, however, micron-sized tungsten carbide powder has large specific surface area, is easy to oxidize in a high-temperature and high-humidity environment, and generates insulating tungsten oxide on the surface, so that the initial resistance of the PPTC device is increased, the resistivity recovery rate is reduced, even the PPTC device fails after multiple cycles, and the instability severely restricts the application of the PPTC device in the field of high-reliability requirements. At present, the method for improving the stability of the PPTC is mainly focused on tungsten carbide coating and surface treatment, but the technology is often complicated, an organic solvent is also used, and the environmental protection performance is poor, so that the development of a technology capable of fundamentally inhibiting the oxidation of the conductive filler is a key for improving the long-term stability of the PPTC device. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a polymer positive temperature coefficient device based on strong water absorbent protection and a preparation method thereof, so as to solve the problem of insufficient long-term stability of a PPTC device in the prior art. In order to solve the technical problems, the invention adopts the following technical scheme: In one aspect, the invention provides a method for preparing a positive temperature coefficient device based on strong water absorbent protection, comprising the following steps: step 1, mechanically mixing anhydrous calcium chloride powder and tungsten carbide powder to form mixed powder; Step 2, carrying out vacuum ball milling on the mixed powder to obtain modified tungsten carbide powder; and 3, blending the modified tungsten carbide powder and PVDF (polyvinylidene fluoride) powder to obtain the polymer positive temperature coefficient device PPTC. Preferably, in the step 1, the mechanical mixing is performed in a common stirrer, the stirring time is 0.2-1.0 hours, and the grinding rotation speed is 50-120 r/min; Preferably, in the step 1, the mass ratio of the anhydrous calcium chloride powder to the tungsten carbide powder is (0.10-0.65) 100, the content of the anhydrous calcium chloride powder is too small, the modification effect is poor, the content of the anhydrous calcium chloride powder is too large to influence the initial resistance of the PPTC, and the mass ratio is a common proportion range capable of meeting the use requirement; preferably, in the step 1, the tungsten carbide powder is micron-sized tungsten carbide powder produced by a mechanical alloying method, a direct reduction carbonization method or a sol-gel method, and the particle size of the tungsten carbide powder is 1um-10um; Preferably, in the step 1, the particle size of the anhydrous calcium chloride powder is less than 0.5 μm; Preferably, in the step 2, the time of the vacuum ball milling treatment is 0.5-2 hours, the reaction is insufficient due to the too short vacuum ball milling time, the long-term stability of the device obtained later is affected, the unnecessary energy waste is caused due to the too long vacuum ball milling time, and the stability of the subsequent device is also affected due to the excessive ball milling; Preferably, in the step 2, the rotation speed of the vacuum ball milling treatment is 80-150r/min; preferably, in the step 2, the temperature of the vacuum ball milling treatment is lower than 80 ℃; Preferably, in the step 2, the vacuum degree of the vacuum ball milling treatment is lower than 50.0Pa; Preferably, in the step 3, the mass ratio of PVDF to modified tungsten carbide powder is 1:7-13. Too little tungsten carbide powder content can cause too high resistance, poor service performance and influence the mechanical properties of the composite material. On the other hand, the invention provides a polymer positive temperature coefficient device based on strong water absorbent protection, whic