Method and device for testing high-temperature volume resistance and resistivity of plastic

Abstract

The invention belongs to the field of plastic electrical performance measurement, and discloses a plastic high-temperature volume resistance and resistivity testing method and device.The testing method comprises the steps that a plastic sample filled in an insulating plate is heated to the set temperature through an upper metal heating plate and a lower metal heating plate, meanwhile, direct-current voltage is conducted, and the current value is tested; the volume resistance and the volume resistivity are obtained through voltage, current and sample size calculation, and the method can be used for testing the volume resistance and the resistivity of the plastic at any temperature ranging from room temperature to 500 DEG C. The device can conveniently and quickly test volume resistance and resistivity at different temperatures, different pressures and different voltages, and has the characteristics of adjustable pressurization pressure, adjustable test voltage, adjustable heat preservation time, convenience in operation, safety, reliability and good repeatability.

Description

Technical Field

[0001] The invention belongs to the field of plastic electrical property measurement, and in particular relates to a method and a device for testing high-temperature volume resistance and resistivity of plastic. Background Art

[0002] During the application of plastic materials, it is necessary to understand their resistance and resistivity under high temperature conditions to avoid failure due to current breakdown. Some plastics, such as polyester films, require surface treatment or attachment using voltage during the processing process to facilitate smooth processing, and their resistance and resistivity also need to be tested. Resistance and resistivity at room temperature are easy to test, but resistance and resistivity at high temperatures, especially under molten conditions, are difficult to test, and there is no commercial testing instrument yet. This is mainly because plastic materials are easy to flow, oxidize, deteriorate, and decompose in a molten state, so special treatment and protection of samples are required.

[0003] Patent publication CN 107907746 B discloses a method for testing the molten resistivity of polymers. This method manually stacks two heating electrodes on a test sample to test the resistance value. The test pressure and test voltage cannot be adjusted, and a multimeter is used to directly measure the resistance. This method is not applicable to polymer materials with a resistance higher than 200MΩ, and the test conditions are limited. The sample placement hole provided in this patent is square, and after the polymer melt is melted, it is easy to produce voids, causing errors in the test data.

[0004] In addition, CN109374975A ​​discloses a device and method for measuring the resistivity of a polymer film under high field strength. The method uses a high-precision DC voltage source to provide voltage to the polymer film through a protective resistor, and then uses an electrometer to test the loop current. The thickness and electrode area of ​​the polymer film are measured, the current flowing through the polymer film is collected, and the product of the voltage and the film electrode area is divided by the product of the current and the film thickness to obtain the resistivity of the polymer film. However, this test method can only test the resistivity of film materials in a solid state below the melting point, and cannot test the resistivity of polymer materials in a molten state, and the use conditions are limited. Summary of the invention

[0005] Aiming at the problems of limited test conditions and easy error in test data in the existing plastic resistivity test method, the present invention proposes a method and device for testing the high-temperature volume resistance and resistivity of plastic.

[0006] The present invention is mainly used for testing the volume resistance and resistivity of plastics under high temperature conditions, especially under melting conditions. The technical principle is to heat the plastic sample filled in the insulating plate to a set temperature through an upper heating plate and a lower heating plate, and at the same time pass a DC voltage to test the current value. The volume resistance and resistivity are calculated by the voltage, current and sample size. The present invention can be used to test the volume resistance and resistivity of plastics at any temperature from room temperature to 500°C.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention is to provide a method for testing the high temperature volume resistance and resistivity of plastics, comprising the steps of:

[0009] (1) The upper heating plate and the lower heating plate are heated to the set temperature respectively, and the upper heating plate is in the raised position;

[0010] (2) Place an insulating plate with a thickness of T on the upper surface of the lower heating plate, and then fill the circular hole with an area of ​​S on the insulating plate with an accurately weighed plastic sample to ensure that the filling amount can fill the circular hole after melting;

[0011] (3) Move the upper heating plate downward to above the insulating plate through the lifting mechanism, and keep it warm and under pressure;

[0012] (4) Apply a DC voltage to the upper heating plate and the lower heating plate. After a certain period of time, read the reading I of the ammeter;

[0013] (5) The volume resistivity is obtained by the formula: R = U / I; and the volume resistivity is obtained by the formula: ρ = R × S / T.

[0014] Where S is the area of ​​the circular hole (cm 2 ), T is the thickness of the insulating plate (cm), U is the voltage (v), I is the current (A), R is the volume resistance (Ω), and ρ is the volume resistivity (Ω×cm).

[0015] Preferably, in step (1), the upper heating plate and the lower heating plate are square plates of the same size, and are made of one or more of aluminum, copper or stainless steel.

[0016] More preferably, in step (1), the surface area of ​​the upper heating plate and the lower heating plate is 100×100 mm to 150×150 mm, and the thickness is 20 to 50 mm.

[0017] Preferably, in step (1), the power supply of the heating wires in the upper heating plate and the lower heating plate is AC 220ACV, with a power of 500-1000W.

[0018] Preferably, in step (2), the insulating board is made of one or more of a ceramic board, a mica board, and a fluoroplastic board.

[0019] Preferably, in step (2), the size of the insulating plate is similar to that of the upper heating plate and the lower heating plate, and its thickness is 2 to 3 mm, and the diameter of the middle circular hole is 20 to 30 mm.

[0020] Preferably, in step (3), the heating temperature of the upper heating plate and the lower heating plate is 5 to 30°C above the melting point of the plastic sample, the insulation time is 2 to 5 minutes, and the applied pressure is 2 to 6 kg / cm 2 .

[0021] Preferably, in step (4), the DC voltage is adjustable within a range of 5 to 120 DCV, and the ammeter used is a high-precision ammeter with a measurement resolution of not less than 0.01 uA.

[0022] The second aspect of the present invention is to provide a testing device for high temperature volume resistance and resistivity of plastics used in the above method, comprising a support seat, a lifting mechanism, an upper heating plate, a lower heating plate and an insulating plate, wherein:

[0023] The support seat is in a C-shaped structure, the upper end of which is connected to the upper heating plate through the lifting mechanism, and the lower end of which is installed with the lower heating plate corresponding to the upper heating plate;

[0024] The insulating plate is arranged on the top of the lower heating plate, and a circular through hole for filling the plastic sample to be tested is opened in the middle thereof.

[0025] Preferably, the upper heating plate and the lower heating plate are insulated and heat-insulated from other metal parts connected thereto, and are respectively connected in series via high-temperature wires, a DC power supply and an ammeter.

[0026] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0027] The testing method and device provided by the present invention can conveniently and quickly test the volume resistance and resistivity at different temperatures, different pressures, and different voltages, and has the characteristics of adjustable pressurization pressure, adjustable test voltage, adjustable insulation time, convenient operation, safety, reliability, and good repeatability. It provides a convenient testing means for quality control and scientific research, and can be used for product testing as well as for scientific research. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of a testing device for high-temperature volume resistance and resistivity of plastics according to the present invention;

[0029] Figure 2The figure is a schematic diagram of the top view of the structure of an insulating plate in a device for testing high-temperature volume resistance and resistivity of plastics according to the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail and specifically by specific examples below to provide a better understanding of the present invention, but the following examples do not limit the scope of the present invention.

[0031] Example 1

[0032] A method for testing high-temperature volume resistance and resistivity of plastics is provided, comprising the steps of:

[0033] (1) The upper heating plate and the lower heating plate are heated to the set temperature respectively, and the upper heating plate is in the raised position;

[0034] (2) Place an insulating plate with a thickness of T on the upper surface of the lower heating plate, and then fill the circular hole with an area of ​​S on the insulating plate with an accurately weighed plastic sample to ensure that the filling amount can fill the circular hole after melting;

[0035] (3) Move the upper heating plate downward to above the insulating plate through the lifting mechanism, and keep it warm and under pressure;

[0036] (4) Apply a DC voltage to the upper heating plate and the lower heating plate. After a certain period of time, read the reading I of the ammeter;

[0037] (5) The volume resistance and volume resistivity are obtained by the formulas R = U / I and ρ = R×S / T.

[0038] In step (1), the upper heating plate and the lower heating plate are square plates of the same size, and are made of one or more of aluminum, copper or stainless steel, preferably aluminum or copper. The lower heating plate is fixed on a metal base, and the upper heating plate is fixed on a telescopic cylinder, and the upper heating plate is moved up and down by telescoping.

[0039] In step (1), the upper heating plate and the lower heating plate are square plates of the same size, with a surface area of ​​100×100mm to 150×150mm and a thickness of 20 to 50mm; preferably, the thickness is 20 to 30mm.

[0040] In step (1), the upper heating plate and the lower heating plate are respectively provided with a heating wire and a temperature sensor, and the power supply of the heating wire is AC 220ACV, and the power is 500-1000W.

[0041] In step (2), the insulating board is required to be heat-resistant and insulating, and is made of one or more of a ceramic board, a mica board, and a fluoroplastic board, preferably a fluoroplastic board.

[0042] In step (2), the size of the insulating plate is similar to that of the upper heating plate and the lower heating plate, and its thickness is 2 to 3 mm. The diameter of the middle circular hole is 20 to 30 mm. The middle circular hole is used to place the plastic particles or plastic film to be tested.

[0043] In step (3), the heating temperature of the upper heating plate and the lower heating plate is 5 to 30°C above the melting point of the plastic sample, the insulation time is 2 to 5 minutes, and the applied pressure is 2 to 6 kg / cm 2 , the volume resistance and resistivity of plastics can be tested at any temperature from room temperature to 500℃.

[0044] In step (4), a DC voltage is applied to the upper heating plate and the lower heating plate, and the DC voltage is adjustable within a range of 5 to 120 DCV. It should be noted that the upper heating plate and the lower heating plate are insulated and heat-insulated from other metal parts connected thereto, and are connected in series with an external DC power supply and an ammeter through a high-temperature wire to provide a DC voltage and facilitate current measurement.

[0045] In addition, it is also worth noting that for plastic materials that are extremely easy to absorb water and decompose, such as polyester materials and nylon materials, the samples need to be dried in an oven at 100°C for 60 minutes before testing. For materials such as polypropylene and polyethylene, they can be tested directly.

[0046] Example 2

[0047] like Figure 1 As shown, a testing device for high-temperature volume resistance and resistivity of plastics used in the above-mentioned method is provided, and the testing device mainly includes a support base 1, a lifting mechanism 2, an upper heating plate 3, a lower heating plate 4, an insulating plate 5, a DC power supply 6 and an ammeter 7.

[0048] Specifically, the support base 1 has a C-shaped structure, and is connected to the upper heating plate 3 at its upper end through the lifting mechanism 2. The upper heating plate 3 can move up and down driven by the lifting mechanism 2; the lower heating plate 4 corresponding to the upper heating plate 3 is installed at the lower end of the support base 1; the insulating plate 5 is arranged on the top of the lower heating plate 4, and a circular through hole 51 is opened in the middle thereof for filling the plastic sample to be tested.

[0049] According to the needs, the lifting mechanism 2 can adopt hydraulic lifting, pneumatic lifting or electric lifting, such as using lifting cylinders, hydraulic lifters, electric screws or electric screw lifting modules, etc. It is preferred to use hydraulic lifting and electric screws, which have the advantages of compact and reasonable layout, large transmission ratio, stable operation, better pressure regulation accuracy and high-speed operation, which greatly improves the working efficiency and operation stability.

[0050] The upper heating plate 3 and the lower heating plate 4 are both heating plates and test electrode plates. The upper heating plate 3 and the lower heating plate 4 are both installed with electric heating wires, high-temperature wires of temperature measuring sensors, and a DC power supply 6 and an ammeter 7 connected in series. The upper heating plate 3 and the lower heating plate 4 are insulated and heat-insulated from the surrounding metal connectors.

[0051] The insulating plate 5 is placed between the upper heating plate 3 and the lower heating plate 4, and its size and shape are similar to those of the upper heating plate 3 and the lower heating plate 4. The thickness of the insulating plate 5 is between 2 and 3 mm, and a circular hole is opened in the center of the insulating plate, and the diameter of the hole is 20 to 30 mm.

[0052] In order to realize the automation and intelligence of the test device, the test device also includes a PLC controller or other control unit, such as a computer. The DC power supply 6 and the ammeter 7 are electrically connected to the PLC controller or the computer, so that the DC voltage and current data can be transmitted to the computer through the transmitter card for data collection, and the test DC voltage, cylinder pressure, and holding time are adjustable.

[0053] When the test device is used for testing, an accurately weighed plastic sample is filled into the circular hole of the insulating block, and the amount of the sample can be calculated according to the volume of the circular hole. The insulating plate is placed on the upper surface of the lower heating plate.

[0054] Before placing the sample, the upper heating plate 3 and the lower heating plate 4 are heated to the required temperature in advance, and the upper heating plate 3 is kept in the raised position. After the sample is placed, the upper heating plate 3 is moved down by the lifting mechanism 2 and pressed on the upper surface of the insulating plate 5.

[0055] Then set the required pressure, holding time and test voltage, and read the test current of ammeter 7 in time. If necessary, the test current can be input into the computer through the transmission acquisition card, and the current curve can be automatically recorded and the volume resistance and resistivity can be calculated.

[0056] After the test time reaches the set value, the lifting mechanism 2 automatically rises and the measurement ends.

[0057] The present invention is further described below in conjunction with specific application implementation methods. These embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0058] Application Example 1

[0059] The upper and lower heating plates are made of copper, with dimensions of 100mm×100mm×20mm. The insulating plate is made of ceramic, with a thickness of 2mm and a center hole diameter of 20mm. The test DC voltage is 48DCV and the cylinder pressure is 2kg / cm 2 .

[0060] The test sample is 12um biaxially oriented polyester film (BOPET). After heating the upper and lower heating plates to 285℃, the film is cut into discs with a diameter of 20mm using a circular die cutter. A balance with an accuracy of 0.001g is used to weigh about 1g of the cut film discs. The insulating plate is placed on top of the lower heating plate. At this time, the upper heating plate is in a raised position. The plastic film discs are stacked in the circular holes of the insulating plate, and the upper heating plate is pressed down on the insulating plate by the lifting mechanism. The timing time is 5 minutes. During this time, the reading of the ammeter is recorded.

[0061] During the test, the maximum current was used as the calculation basis. At the end of the test, the maximum current recorded was 4.2×10 -6 (A).

[0062] Substituting the above data into the formula R = U / I and ρ = R×S / T, the volume resistance and volume resistivity are as follows:

[0063] R = 48 / (4.2×10 -6 )=1.142×10 7 (Ω).

[0064] ρ=1.142×10 7 ×(3.14×(2 / 2) 2 ) / 0.2=1.79×10 8 (Ω×cm).

[0065] Application Example 2

[0066] The upper and lower heating plates are made of aluminum, with dimensions of 150mm×150mm×20mm. The insulating plate is made of Teflon, with a thickness of 3mm and a center hole diameter of 25mm. The test DC voltage is 80DCV and the cylinder pressure is 4kg / cm 2 .

[0067] The test sample is film-grade polyester chips FG620, which are dried in an electric drying oven at 100°C for 60 minutes in advance, and then weighed about 2g of the dried chips on a balance with an accuracy of 0.001g.

[0068] After heating the upper and lower heating plates to 270°C, place the insulating plate on top of the lower heating plate, with the upper heating plate in a raised position. Place the weighed polyester chips in the circular hole of the insulating plate, and press the upper heating plate down on the insulating plate through the lifting mechanism for 3 minutes.

[0069] The maximum current recorded at the end of the timing is 3.74×10 -5 (A).

[0070] Substituting the above data into the formula R = U / I and ρ = R×S / T, the volume resistance and volume resistivity are as follows:

[0071] R = 80 / (3.74×10 -5 )=2.14×10 6 (Ω).

[0072] ρ=2.14×10 6 ×(3.14×(2.5 / 2) 2 ) / 0.3=3.5×10 7 (Ω×cm).

[0073] Application Example 3

[0074] The upper and lower heating plates are made of stainless steel, with dimensions of 100mm×100mm×20mm. The insulating plate is made of Teflon, with a thickness of 2mm and a center hole diameter of 20mm. The test DC voltage is 12DCV and the cylinder pressure is 4kg / cm 2 .

[0075] The test sample is dried polybutylene terephthalate (PBT) particles. After the upper and lower heating plates are heated to 265°C, the upper heating plate is in a raised position. The weighed PBT slices are placed in the circular holes of the insulating plate, and the upper heating plate is pressed down on the insulating plate by the lifting mechanism. The timing time is 3 minutes.

[0076] The maximum current recorded at the end of the timing is 9.79×10 -7 (A).

[0077] Substituting the above data into the formula R = U / I and ρ = R×S / T, the volume resistance and volume resistivity are as follows:

[0078] R = 12 / (9.79×10 -7 )=1.23×10 7 (Ω).

[0079] ρ=1.23×10 7 ×(3.14×(2 / 2) 2 ) / 0.2=1.93×10 8 (Ω×cm).

[0080] Application Example 4

[0081] The upper and lower heating plates are made of aluminum alloy, with dimensions of 100mm×100mm×20mm. The insulating plate is made of Teflon, with a thickness of 2mm and a center hole diameter of 20mm. The test DC voltage is 120DCV and the cylinder pressure is 3.5kg / cm2 .

[0082] The test sample is the dried super-glossy polyester chips FG600. After the upper and lower heating plates are heated to 285°C, the upper heating plate is in the raised position. The weighed polyester chips are placed in the round hole of the insulating plate, and the upper heating plate is pressed down on the insulating plate by the lifting mechanism. The timing time is 5 minutes.

[0083] The maximum current recorded at the end of the timing was 2.03×10 -6 (A).

[0084] Substituting the above data into the formula R = U / I and ρ = R×S / T, the volume resistance and volume resistivity are as follows:

[0085] R = 120 / (2.03×10 -6 )=5.91×10 7 (Ω).

[0086] ρ=5.91×10 7 ×(3.14×(2 / 2) 2 ) / 0.2=9.28×10 8 (Ω×cm).

[0087] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention should be included in the scope of the present invention.

Claims

1. A method for testing the high-temperature volume resistance and resistivity of plastics, characterized in that: Including steps: (1) The upper heating plate and the lower heating plate are heated to the set temperature respectively, and the upper heating plate is in the raised position; (2) Place an insulating plate with a thickness of T on the upper surface of the lower heating plate, and then fill the circular hole with an area of ​​S on the insulating plate with an accurately weighed plastic sample, ensuring that the filling amount can fill the circular hole after melting; (3) Move the upper heating plate downward to above the insulating plate through the lifting mechanism, and keep it warm and under pressure; (4) Apply a DC voltage to the upper and lower heating plates. After a certain period of time, read the ammeter reading I; (5) The volume resistivity is obtained by the formula: R = U / I; and the volume resistivity is obtained by the formula ρ = R × S / T; Among them, S is the area of ​​the circular hole (cm 2 ), T is the thickness of the insulating plate (cm), U is the voltage (v), I is the current (A), R is the volume resistance (Ω), and ρ is the volume resistivity (Ω×cm).

2. The method for testing the high-temperature volume resistance and resistivity of plastics according to claim 1, characterized in that: In step (1), the upper heating plate and the lower heating plate are square plates of the same size, and are made of one or more of aluminum, copper or stainless steel.

3. The method for testing the high-temperature volume resistance and resistivity of plastics according to claim 2, characterized in that: In step (1), the surface area of ​​the upper heating plate and the lower heating plate are both 100×100mm to 150×150mm, and the thickness is 20 to 50mm.

4. The method for testing the high-temperature volume resistance and resistivity of plastics according to claim 1, characterized in that: In step (1), the power supply of the heating wires in the upper heating plate and the lower heating plate is AC 220ACV, with a power of 500 to 1000W.

5. The method for testing the high-temperature volume resistance and resistivity of plastics according to claim 1, characterized in that: In step (2), the insulating plate is made of one or more of a ceramic plate, a mica plate, and a fluoroplastic plate.

6. The method for testing the high-temperature volume resistance and resistivity of plastics according to claim 1, characterized in that: In step (2), the size of the insulating plate is similar to that of the upper heating plate and the lower heating plate, and its thickness is 2 to 3 mm, and the diameter of the central circular hole is 20 to 30 mm.

7. The method for testing high-temperature volume resistance and resistivity of plastics according to claim 1, characterized in that: In step (3), the heating temperature of the upper heating plate and the lower heating plate is 5 to 30°C above the melting point of the plastic sample, the holding time is 2 to 5 minutes, and the applied pressure is 2 to 6 kg / cm 2 .

8. The method for testing high-temperature volume resistance and resistivity of plastics according to claim 1, characterized in that: In step (4), the DC voltage is adjustable within a range of 5 to 120 DCV, and the ammeter used is a high-precision ammeter with a resolution of not less than 0.01 uA.

9. A device for testing the high-temperature volume resistance and resistivity of plastics used in the method according to any one of claims 1 to 8, characterized in that: It includes a support base, a lifting mechanism, an upper heating plate, a lower heating plate and an insulating plate, wherein: The support base is in a C-shaped structure, the upper end of which is connected to the upper heating plate through the lifting mechanism, and the lower end of which is installed with the lower heating plate corresponding to the upper heating plate; The insulating plate is arranged on the top of the lower heating plate, and a circular through hole for filling the plastic sample to be tested is opened in the middle thereof.

10. The method for testing the high-temperature volume resistance and resistivity of plastics according to claim 9, characterized in that: The upper heating plate and the lower heating plate are insulated and heat-insulated from other metal parts connected thereto, and are respectively connected in series via high-temperature wires, a DC power supply and an ammeter.

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