CN111965090B - A measuring device and characterization method for swelling properties of polymers for lithium batteries - Google Patents

Abstract

The invention provides a measuring device for the swelling characteristics of high polymers used in lithium batteries, including a swelling chamber for placing high polymers and solvents, a steel mesh is movable in the swelling chamber, and a guide rod is fixed on the top of the steel mesh. The liquid inlet of the swelling chamber is plugged with a rubber plug, and there is an opening for the guide rod to pass through on the rubber plug. A laser rangefinder is arranged above the swelling chamber, and a laser for the laser rangefinder is also opened on the rubber plug. The passing through holes also provide a method for characterizing the swelling properties of the high polymer, including the following steps: calculating the mass of the high polymer to be added and characterization of the swelling properties of the high polymer. Through the constant monitoring of the volume, the data acquisition and processing system converts the volume into a swelling characteristic value, and forms a characteristic curve of time and swelling characteristic value, indicating that the small solvent molecule enters the macromolecular polymer particle, causing the particle to expand and the molecular chain to open. , The process of stretching to reach a thermodynamically stable binary homogeneous system.

Description

A measuring device and characterization method for swelling properties of polymers for lithium batteries

technical field

The invention belongs to the technical field of lithium batteries, and in particular relates to a measuring device and a characterization method for swelling properties of polymers used in lithium batteries.

Background technique

With the widespread application of lithium batteries and nickel batteries in the field of new energy, major battery manufacturers compete fiercely in terms of new technology, high quality, low cost, and rapid manufacturing, especially in the rapid evaluation of physical properties in the initial stage of new material development and after mass production. A lot of research has been done on the formulation of reasonable and effective production process parameters.

High molecular polymers such as CMC, PVDF, HPMC, PTFE, and xanthan gum are commonly used binders for lithium batteries and nickel batteries. characteristics play a key role. When in use, fully dissolve the high polymer powder in a solvent to make a glue. The glue is mixed with active material, conductive agent and other powders to form a slurry and added to the battery. The swelling and dissolving characteristics of polymers in solvents are the main factors affecting the production process of glue.

The formation of a homogeneous phase of a polymer in a solvent is divided into two processes: swelling and dissolution. The swelling is a process in which small solvent molecules enter the pores of polymer particles, polymer particles expand, and macromolecular chains stretch and open. Dissolution is a process in which the opened macromolecules and small solvent molecules form a binary homogeneous phase. In the development process of new materials, the mastery of swelling characteristics is necessary for development and application, and plays a vital role in the good application of new materials in the manufacturing process.

At present, the evaluation of the swelling and dissolution characteristics of polymers for lithium-ion batteries is relatively simple in the industry. There is no unified method and standard, and it is impossible to give quantitative values, and it is impossible to provide quantitative values for the swelling process of polymer materials.

Contents of the invention

In view of this, the present invention aims to propose a measuring device and characterization method for the swelling characteristics of polymers used in lithium batteries, so that the volume can be converted into a swelling characteristic value by the data acquisition and processing system through constant monitoring of the volume, forming time, The characteristic curve of the swelling characteristic value represents the process of small solvent molecules entering the polymer macromolecular particles to expand the particles, open the molecular chains, and stretch to achieve a thermodynamically stable binary homogeneous system.

In order to achieve the above object, the technical solution created by the present invention is achieved in this way:

A measuring device for the swelling properties of high polymers used in lithium batteries, including a swelling chamber for placing high polymers and solvents, a steel mesh is movable in the swelling chamber, and a guide rod is fixed on the top of the steel mesh. The liquid port is plugged with a rubber plug, and the rubber plug has an opening for the guide rod to pass through. A laser rangefinder is arranged above the swelling chamber, and a hole for the laser rangefinder’s laser to pass through is also opened on the rubber plug. hole.

Further, it also includes a fixing frame, and the top of the fixing frame is downwardly opened with a groove for placing the swelling chamber.

Further, the top of the ejector rod is suspended from the top of the rubber plug.

Further, a data collection and processing system is also included, and the laser distance meter is connected to the data collection and processing system through electrical signals.

A method for characterizing the swelling properties of polymers, comprising the steps of:

(1) Calculate the mass of polymer to be added:

(A) Measure the solvent used to dissolve the high polymer, and leave it to defoam under negative pressure;

Further, the negative pressure condition is vacuum degree≤-90KPa.

(B) measure the distance from the laser range finder to the bottom of the swelling chamber with a laser range finder, denoted as H ₀ ;

Further, the operation step of constant temperature is carried out in a constant temperature bath.

Further, the temperature fluctuation of the constant temperature tank is ±0.05°C, the digital display resolution is 0.01°C, the temperature control range is 0°C-90°C, the volume is preferably 10L, and the heating medium is preferably water.

(D) after the constant temperature is completed, the distance between the top of the liquid surface of the solvent and the laser range finder in the laser range finder measurement step (3) is denoted as H ₁ ;

(E) Calculate the total volume V ₀ of the solvent in the swelling chamber according to the following formula:

V ₀ =(H ₁ -H ₀ )×(Φ/2) ² ×3.14, where Φ is the inner diameter of the swelling chamber;

(F) Calculate the mass W ₀ of the high polymer that needs to be added into the swelling chamber according to the following formula;

W ₀ =V ₀ /(1-α)×α, where α is the mass percentage of the polymer in the swollen solution;

When calculating, the density of common solvents is calculated according to 1g/cm ³ .

(2) Characterization of polymer swelling properties:

(A) Weigh a high polymer with a mass of W ₁ , wherein W ₁ =W ₀ ±0.0005g, and put the weighed high polymer into the swelling chamber;

Further, when organic solvents are used as polymer solvents, for example, when NMP and cyclohexane are used to dissolve PVDF, the rubber plug is mainly corrosion-resistant, and the material of the rubber plug is preferably EPDM; pure water is used as the polymer solvent For example, when measuring the swelling properties of CMC with pure water, ordinary rubber plugs are sufficient.

(C) The laser range finder measures the swelling time T in real time and the distance H ₂ from the top of the liquid surface in step (B) in step (2) to the laser range finder, and calculates the volume of the solution in the swelling process according to the following formula: V ₂ ＝(H ₂ -H ₀ )×(Φ/2) ² ×3.14;

(D) When the swelling characteristic value η does not change or changes very little with the swelling time T, stop the measurement, wherein the swelling characteristic value η=V ₂ /W ₁ ; draw the relationship curve between the swelling time T and the swelling characteristic value η to characterize the polymer The curve of the material swelling property.

Further, the units of H ₂ , H ₁ , H ₀ , and Φ are mm, the units of V ₂ and V ₁ are mL, the units of W ₁ and W ₀ are g, and the η The unit is mL/g.

Further, the constant temperature of step (C) in step (1) is preferably 20-25°C.

Further, the inner diameter of the swelling chamber is 5mm≤inner diameter≤15mm, the precision of the inner diameter of the swelling chamber is not less than ±0.01mm, the cylindricity of the swelling chamber is not higher than 3um, and the surface roughness of the swelling chamber is not lower than 0.8, The height value of the swelling chamber is 100mm≤height≤300mm.

Further, the diameter of the guide rod is ≤0.5mm, and the steel mesh has holes with a diameter of ≤20um.

Further, the material of the steel mesh is preferably sus304.

Further, a balance is used to weigh the mass of the polymer, and the precision of the balance is 0.0001 g.

Further, the measurement accuracy of the laser range finder is 0.01 mm, and the range is selected according to the height of the swelling chamber. The preferred brand of the laser range finder is KEYENCE.

Further, the data collection and processing system can automatically read and record the data output by the laser rangefinder, the data collection time, frequency, and interval can be set through the system window, and the collection frequency is ≥1/5s; and it has the ability to form a monitoring curve from time to time The function is convenient for operators to view; it has the function of exporting original data.

Compared with the prior art, the invention creates the measurement device and characterization method of the swelling properties of the polymer for lithium batteries and has the following advantages:

(1) The measurement device and characterization method for the swelling characteristics of polymers for lithium batteries according to the present invention, through the constant monitoring of the volume, the data acquisition and processing system converts the volume into swelling characteristic values, forming the characteristics of time and swelling characteristic values The curve represents the process of small solvent molecules entering the polymer macromolecular particles, making the particles swell, molecular chains open, and stretched to reach a thermodynamically stable binary homogeneous system.

(2) The measurement device and characterization method for the swelling characteristics of polymers for lithium batteries described in the present invention can quickly grasp the swelling characteristics of materials through the swelling quantification curve, which is helpful for the rapid application of new materials to the formulation of process parameters in the manufacturing process , When developing new materials, by comparing the quantitative characteristic curves of new materials and existing models, we can quickly grasp the swelling and dissolution characteristics of polymers of new materials, which will help to quickly formulate reasonable production process parameters.

(3) The measuring device and characterization method for the swelling characteristics of high polymers for lithium batteries according to the present invention, through the characteristic curves of time and swelling characterization values, quantify the swelling process of high polymers, and provide a method for measuring the swelling characteristics of high polymers The device quantifies the swelling process through the volume change in the swelling process and gives a quantitative curve.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

Fig. 1 is the schematic diagram of the measurement device described in the creation embodiment of the present invention;

Fig. 2 is a partial enlarged view of A in the accompanying drawing 1 of the invention specification;

Fig. 3 is a schematic diagram of the SEM morphology of the sample A described in the inventive embodiment of the present invention;

Fig. 4 is the SEM schematic diagram of the sample B described in the inventive embodiment of the present invention;

Fig. 5 is a schematic diagram of the swelling curve of PVDF described in the inventive embodiment of the present invention.

Explanation of reference signs:

1-polymer powder layer; 2-swelling chamber; 3-constant temperature tank; 4-steel mesh; 5-guide rod; 6-rubber plug; 7-fixing frame; system.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", The orientations or positional relationships indicated by "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention Creation and simplification of description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as limiting the invention. In addition, the terms "first", "second", etc. are used for descriptive purposes only, and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, a feature defined as "first", "second", etc. may expressly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be interpreted in a broad sense, for example, it can be a fixed connection or a flexible connection. Detachable connection, or integral connection; it can be mechanical connection or electrical connection; it can be direct connection or indirect connection through an intermediary, and it can be the internal communication of two components. Unless otherwise clearly specified and limited, the term "fixed connection" may refer to commonly used fixed connection methods such as plugging, welding, threaded connection, and bolted connection. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention based on specific situations.

The invention will be described in detail below with reference to the accompanying drawings and examples.

A measuring device for the swelling properties of polymers used in lithium batteries, including a swelling chamber 2 for placing polymers and solvents, a steel mesh 4 is movable in the swelling chamber 2, and a guide rod is fixed on the top of the steel mesh 4 5. The liquid inlet of the swelling chamber 2 is plugged with a rubber plug 6, and the rubber plug 6 has an opening for the guide rod 5 to pass through. Have the through hole that the laser of laser rangefinder 8 passes through.

It also includes a fixing frame 7, and the top of the fixing frame 7 is downwardly opened with a groove for placing the swelling chamber 2.

During the experiment, pay attention to maintaining the level of the fixing frame 7 and the swelling chamber 2.

The top of the push rod is suspended on the top of the rubber plug 6 .

A data collection and processing system 9 is also included, and the laser rangefinder 8 is connected to the data collection and processing system 9 through electrical signals.

A method for characterizing the swelling properties of polymers, comprising the steps of:

(1) Calculate the mass of polymer to be added:

(A) Measure the solvent used to dissolve the high polymer, and leave it to defoam under negative pressure;

The negative pressure condition is vacuum degree≤-90KPa.

(B) measure the distance from the laser range finder 8 to the bottom of the swelling chamber 2 with the laser range finder 8, denoted as H0;

When the size of the swelling chamber 2 and the position of the laser rangefinder 8 are changed, the H0 value needs to be collected again.

Put the solvent that has been defoamed in step (1) into the swelling chamber 2, and keep the temperature constant for a certain period of time;

The operation step of constant temperature is carried out in the constant temperature tank 3 .

The temperature fluctuation of the constant temperature tank 3 is ±0.05°C, the digital display resolution is 0.01°C, the temperature control range is 0°C-90°C, the volume is preferably 10L, and the heating medium is preferably water.

(D) After the constant temperature is completed, the distance between the top of the liquid level of the solvent and the laser range finder 8 in the laser range finder 8 measurement step (3) is denoted as H ₁ ;

(E) Calculate the total volume V ₀ of the solvent in the swelling chamber 2 according to the following formula:

V ₀ =(H ₁ -H ₀ )×(Φ/2) ² ×3.14, where Φ is the inner diameter of the swelling chamber 2;

(F) Calculate the mass W ₀ of the high polymer that needs to be added to the swelling chamber 2 according to the following formula;

W ₀ =V ₀ /(1-α)×α, where α is the mass percentage of the polymer in the swollen solution;

(2) Characterization of polymer swelling properties:

(A) Weigh a high polymer with a mass of W ₁ , wherein W ₁ =W ₀ ±0.0005g, and put the weighed high polymer into the swelling chamber 2;

After drying, the polymer needs to be weighed at room temperature and humidity ≤ 10%. Before adding to the swelling chamber 2, it is not allowed to be exposed to a high-humidity environment, so as to avoid the influence of the polymer on the solvent due to water absorption. The stretching and opening of the chain.

Use the steel mesh 4 to press-soak the polymer powder into the solvent, hang the guide rod 5 on the top of the steel mesh 4 at the opening of the rubber plug 6, and then plug the rubber plug 6 into the liquid inlet of the swelling chamber 2;

On the premise that the hole diameter of the rubber plug 6 meets the operation requirements, the smaller the hole diameter, the better, so as to reduce the error caused by NMP volatilization during the swelling process.

When an organic solvent is used as a polymer solvent, such as NMP or cyclohexane to dissolve PVDF, the rubber plug 6 is mainly corrosion-resistant, and the material of the rubber plug 6 is preferably EPDM; when pure water is used as a polymer solvent , for example, when measuring the swelling properties of CMC with pure water, the rubber plug 6 made of ordinary rubber is sufficient.

(C) laser rangefinder 8 real-time measurement swelling time T and the distance H2 of the top of the liquid surface in (B) step in step (2) from laser rangefinder 8, and calculate the volume of solution in the swelling process according to the following formula: V ₂ =(H ₂ -H ₀ )×(Φ/2) ² ×3.14;

(D) When the swelling characteristic value η does not change or changes very little with the swelling time T, stop the measurement, wherein the swelling characteristic value η=V ₂ /W ₁ ; draw the relationship curve between the swelling time T and the swelling characteristic value η to characterize the polymer The curve of the material swelling property.

The units of H ₂ , H ₁ , H ₀ and Φ are mm, the units of V ₂ and V1 are mL, the units of W ₁ and W ₀ are g, and the unit of η is mL /g.

The constant temperature of step (C) in step (1) is preferably 20-25°C.

The inner diameter of the swelling chamber 2 is 5mm≤inner diameter≤15mm, the accuracy of the swelling chamber 2 is not less than ±0.01mm, the cylindricity of the swelling chamber 2 is not higher than 3um, and the surface roughness of the swelling chamber 2 is not lower than 0.8, The height value of the swelling chamber 2 is 100mm≤height≤300mm.

The smaller the inner diameter of the swelling chamber 2 and the higher the liquid level will make the measurement more accurate, but the inner diameter of the swelling chamber 2 cannot be too small, otherwise the inner diameter is too small to make the rubber plug 6 smaller, and the opening aperture on the rubber plug 6 will also be smaller. If it is too small, the laser alignment of the laser range finder 8 is not accurate enough, which affects the accuracy of the measurement data. If the inner diameter is too small, a meniscus may be formed on the top of the liquid surface, resulting in inaccurate measurement.

During the swelling process, as the polymer continues to swell in the solvent, the total volume of the solution will gradually decrease.

The swelling chamber 2 is a tool for precise volume measurement. It should be kept properly and avoid bumping. When cleaning, it should be washed with high-pressure water and dried with compressed air to avoid scratches caused by hard objects such as steel wool.

The diameter of the guide rod 5 is ≤0.5mm, and the steel mesh 4 is provided with a mesh with a diameter of ≤20um.

The material of the steel mesh 4 is preferably sus304.

Use a balance to weigh the mass of the polymer with an accuracy of 0.0001 g.

Put the weighed PVDF into the swelling chamber 2 slowly, and pay attention to avoid the powder sticking to the inner wall of the swelling chamber 2 during the process.

The measurement accuracy of the laser rangefinder 8 is 0.01mm, and the range is selected according to the height of the swelling chamber 2. The preferred brand of the laser rangefinder 8 is KEYENCE.

The data collection and processing system 9 can automatically read and record the data output by the laser range finder 8, the data collection time, frequency, and interval can be set through the system window, and the collection frequency is ≥1/5s; and it has the function of forming a monitoring curve from time to time, It is convenient for operators to check; it has the function of exporting original data.

The amount of solvent added needs to be slightly higher than the amount of solvent required for the swelling and dissolving of the polymer, so as to reduce the influence of the swelling speed of the polymer due to too little amount of solvent.

Example

Preparation:

One beaker (200ml), one pipette (10ml), one ear washing ball, the vacuum chamber is connected to the vacuum pump; the fixing frame is leveled; the diameter of the swelling chamber is 10mm, and the height is 200mm; two PVDF samples, the physical parameters are as follows in Table 1:

Table 1 List of parameters of two PVDF samples

Specific operation process:

Measurement of sample A:

(1) Polymer NMP defoaming: take about 100ml NMP in a beaker, place it in a negative pressure chamber to defoam, the vacuum degree is ≤ -90KPa, and the defoaming time is 30min;

(2) NMP pipetting: Use a pipette to take 10ml of NMP solution into the swelling chamber 2, open the constant temperature tank 3, set the constant temperature to 20°C, and keep the temperature constant for 1 hour. Turn on the laser range finder 8, turn on the data acquisition and processing system 9, measure and calculate the volume V ₀ of NMP in the swelling chamber 2 = 10.0602ml;

(3) PVDF weighing: PVDF powder is dried for 12 hours at 80°C and vacuum degree ≤ -90KPa; according to V ₀ =10.0602ml, the mass percentage of PVDF with a mass percentage of 6% is calculated according to the following formula: W ₀ =V ₀ /(1-6%)×6%=10.0602/(1-6%)×6%=0.6421g;

Weigh W ₁ =0.6425g, and input the actual value of W ₁ into the data acquisition and processing system 9 .

(4) Slowly send the weighed PVDF powder into the swelling chamber 2, use steel mesh 4 to slowly press-immerse the powder floating on the liquid surface under the liquid surface, and visually inspect the powder to press-immerse in the middle of the NMP solvent liquid surface Preferably, the rubber plug 6 is pressed against the liquid inlet of the swelling chamber 2;

(5) The data acquisition and processing system 9 measures and calculates V ₁ , and converts V ₁ into a swelling characteristic value η;

(6) execution mode is set on the data acquisition and processing system 9:

The first step: the data collection interval is 10s, and the execution time is 12 hours;

The second step: the data collection interval is 60s, and the execution time is 12 hours;

The third step: the data collection interval is 120s, the execution time is 24 hours, and the end;

Measurement of sample B:

(7) Repeat above step (1) to step (6), test sample B;

(8) Export data and organize;

(9) Data analysis:

The above two samples are two products of different models from the same manufacturer. From the comparison of the characteristic curves, it can be concluded that:

It takes about 30 hours for sample A to reach binary homogeneous phase, and about 46 hours for sample B, so the swelling property of sample A is better than that of sample B;

In the early stage of swelling, the ability of NMP solvent to enter the powder particles of sample A is better than that of sample B;

In the later stage of swelling, the stretching and opening of the polymer of sample B is not as good as that of sample A;

Assuming that sample A is the currently used product, according to the glue production parameters of sample A, it can be speculated that sample B needs to improve the stirring time, temperature, rotation speed, etc. of sample A slightly on the basis of sample A to achieve high-quality glue.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the Within the scope of protection of the present invention.

Claims (5)

1. A method for characterizing swelling properties of a polymer by a measuring device for swelling properties of a polymer for a lithium battery, characterized by: the device for measuring the swelling characteristics of the high polymer for the lithium battery comprises a swelling chamber (2) for placing the high polymer and a solvent, wherein a steel mesh (4) is movably placed in the swelling chamber (2), a guide rod (5) is fixed at the top of the steel mesh (4), a rubber plug (6) is plugged at a liquid inlet of the swelling chamber (2), an opening for allowing the guide rod (5) to pass through is formed in the rubber plug (6), a laser range finder (8) is arranged above the swelling chamber (2), and a through hole for allowing laser of the laser range finder (8) to pass through is formed in the rubber plug (6);

a method for characterizing swelling properties of a polymer using the device described above, comprising the steps of:

(1) Calculating the mass of the polymer to be added:

(A) Measuring a solvent for dissolving the high polymer, and standing under the negative pressure condition to remove bubbles;

(B) The distance from the laser distance meter (8) to the bottom of the swelling chamber (2) is measured by the laser distance meter (8), and is marked as H ₀ ；

(C) Putting the solvent after the bubble removal in the step (A) in the step (1) into a swelling chamber (2), and keeping the temperature for a certain time;

(D) After the constant temperature is finished, the distance from the top of the liquid level of the solvent in the step (C) to the laser distance meter (8) in the step (1) is measured by the laser distance meter (8), and is recorded as H ₁ ；

(E) The total volume V of the solvent in the swelling chamber (2) was calculated according to the following formula ₀ ：

V ₀ ＝(H ₁ -H ₀ )×(Φ/2) ² X 3.14, wherein Φ is the inner diameter of the swelling chamber (2);

(F) The mass W of the polymer to be added into the swelling chamber (2) is calculated according to the following formula ₀ ；

W ₀ ＝V ₀ /(1- α) ×α, where α is the mass percent of polymer in the post-swelling solution;

(2) Characterization of the swelling Properties of the Polymer:

(A) The weighing mass is W ₁ Wherein W is ₁ ＝W ₀ 0.0005g, placing the weighed polymer into a swelling chamber (2);

(B) Pressing and immersing high polymer powder into a solvent by using a steel mesh (4), hanging a guide rod (5) at the top of the steel mesh (4) at an opening of a rubber plug (6), and then plugging the rubber plug (6) at a liquid inlet of a swelling chamber (2);

(C) The laser distance meter (8) measures the swelling time T in real time and the distance H from the top of the liquid level to the laser distance meter (8) in the step (B) in the step (2) ₂ And the volume of the solution during swelling was calculated according to the following formula: v (V) ₂ ＝(H ₂ -H ₀ )×(Φ/2) ² ×3.14；

(D) Stopping the measurement when the swelling behaviour value η does not change or changes very little with the swelling time T, wherein the swelling behaviour value η = V ₂ /W ₁ The method comprises the steps of carrying out a first treatment on the surface of the And drawing a relation curve of the swelling time T and the swelling characterization value eta to obtain a curve for characterizing the swelling characteristic of the polymer.

2. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the measuring device also comprises a fixing frame (7), and a groove for placing the swelling chamber (2) is formed in the top of the fixing frame (7) downwards.

3. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the constant temperature of the step (C) in the step (1) is 20-25 ℃.

4. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the inner diameter value of the swelling chamber (2) is less than or equal to 5mm and less than or equal to 15mm, the inner diameter precision of the swelling chamber (2) is not lower than +/-0.01 mm, the cylindricity of the swelling chamber (2) is not higher than 3um, the surface roughness of the swelling chamber (2) is not lower than 0.8, and the height value of the swelling chamber (2) is less than or equal to 100mm and less than or equal to 300mm.

5. The method for characterizing swelling properties of a polymer according to claim 1, wherein: the diameter of the guide rod (5) is less than or equal to 0.5mm, and the steel mesh (4) is provided with meshes with the aperture of less than or equal to 20 mu m.