CN114397181A - Method for testing looseness of internal reinforced fibers of chlor-alkali ion membrane - Google Patents
Method for testing looseness of internal reinforced fibers of chlor-alkali ion membrane Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 25
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- 238000006073 displacement reaction Methods 0.000 claims abstract description 34
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- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 28
- 230000007062 hydrolysis Effects 0.000 claims abstract description 27
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- 238000005070 sampling Methods 0.000 claims description 5
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 4
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 4
- 229910052801 chlorine Inorganic materials 0.000 claims description 4
- 239000000460 chlorine Substances 0.000 claims description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Chemical compound [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 4
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- 239000007832 Na2SO4 Substances 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 2
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- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 2
- 150000003467 sulfuric acid derivatives Chemical class 0.000 claims description 2
- 238000010998 test method Methods 0.000 claims 7
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- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical class C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 4
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- 238000009864 tensile test Methods 0.000 description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G01N2203/0017—Tensile
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Abstract
The invention discloses a method for testing the relaxation degree of internal reinforcing fibers of a chlor-alkali ion membrane, which comprises the following steps: (1) measuring the hydrolytic swelling ratio of the chlor-alkali ionic membrane precursor containing no reinforcing fibers, the swelling ratio (TD or MD) being 100% × (post membrane hydrolysis size-pre membrane hydrolysis size)/pre membrane hydrolysis size; (2) calculating the ultimate displacement of a chlor-alkali ionic membrane precursor sample to be detected containing the reinforced fibers, and obtaining the stretching force at the ultimate displacement through a stretching curve, wherein the ultimate displacement is the effective length multiplied by the swelling ratio of the stretched sample; (3) and (3) calculating the fiber relaxation degree in the chlor-alkali ionic membrane precursor containing the reinforced fibers to be detected sample, wherein the fiber relaxation degree is (1/stretching force at the limit displacement) multiplied by 100%. The method solves the problem that the looseness of the fiber after being compounded into the film cannot be directly measured, can adjust parameters such as equipment tension and the like in time, achieves the purpose of reducing the generation probability of pockmarks, and provides guidance for the subsequent production of the chlor-alkali ionic film.
Description
Technical Field
The invention relates to a method for testing the looseness of internal reinforcing fibers of a chlor-alkali ion membrane, which realizes the data analysis of the looseness of the internal reinforcing fibers of the chlor-alkali ion membrane through simple instruments and operations, fills the technical blank of the actual looseness determination after the fibers are compounded into the membrane material, provides powerful support for further analyzing the internal structure and swelling state of the membrane and predicting the appearance condition of the membrane after hydrolysis, and belongs to the technical field of chlor-alkali ion exchange membranes.
Technical Field
In the production and processing process of the chlor-alkali ionic membrane, size swelling phenomenon occurs to a chlor-alkali membrane precursor due to hydrolysis reaction, criss-cross reinforced fibers exist in the membrane, and the membrane swelling can be actually divided into two steps: firstly, swelling a membrane matrix, and straightening reinforced fibers with certain looseness; and secondly, after the reinforced fibers are straightened, the membrane continuously swells. Because the reinforcing fibers have limited looseness and are relatively stable in size and are not easy to swell, the membrane matrix is bound by the surrounding reinforcing fibers when the second-step swelling occurs, and the part without the reinforcing fibers swells and protrudes along the Z direction (the direction perpendicular to the membrane matrix) to form 'pock marks' (as shown in figure 1). The membrane surface may be in contact with and rubbed by the electrode mesh, which may cause mechanical damage and may also affect the appearance.
From the above, the degree of relaxation of the reinforcing fibers inside the film is an important factor in whether or not the film appears to have pock marks and whether or not the pock marks are serious. When the looseness of the reinforcing fibers in the film is higher, the film is generally less prone to pocking, or the pocking is shallower, and when the looseness of the reinforcing fibers in the film is lower and the fibers are tighter, the film is more prone to pocking and the pocking is deeper.
However, the existing method only indirectly estimates the tightness degree of the reinforcing fibers inside the membrane by using the running tension of equipment in the production process, and cannot intuitively and accurately represent the real state of the fibers. The sag of the reinforcing fiber in the film cannot be accurately measured before the film is hydrolyzed, so that whether the film generates pockmarks after hydrolysis under the existing production parameters cannot be predicted, the parameters such as the tension of production equipment cannot be adjusted before hydrolysis, and the probability of generation of the pockmarks in the later period is increased. Therefore, it is very important to examine the degree of relaxation of the reinforcing fibers inside the film in order to reduce the probability of generation of pockmarks.
Disclosure of Invention
The invention aims to provide a method for testing the relaxation degree of a reinforcing fiber in a chlor-alkali ion membrane, which can realize the detection and analysis of the actual relaxation condition of the reinforcing fiber in the membrane material and the prediction of the apparent condition (mainly pockmarks) of the hydrolyzed membrane and solve the problem that the relaxation degree of the fiber cannot be directly measured after the fiber is compounded into the membrane. After the method is used for measuring the fiber relaxation degree, parameters such as equipment tension and the like can be adjusted in time, the aim of reducing the generation probability of pockmarks is fulfilled, and guidance is provided for the subsequent production of the chlor-alkali ionic membrane.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for testing the relaxation degree of internal reinforced fibers of a chlor-alkali ionic membrane is characterized by comprising the following steps:
(1) measuring the hydrolytic swelling ratio of the chlor-alkali ionic membrane precursor containing no reinforcing fibers, the swelling ratio (TD or MD) being 100% × (post membrane hydrolysis size-pre membrane hydrolysis size)/pre membrane hydrolysis size;
(2) calculating the ultimate displacement of a sample to be tested of the chlor-alkali ionic membrane precursor containing the reinforced fibers, obtaining the stretching force at the ultimate displacement through a stretching curve,
ultimate displacement ═ tensile sample effective length × swell ratio;
(3) calculating the fiber relaxation degree of a chlorine-alkali ion membrane precursor containing reinforcing fibers in a sample to be detected,
fiber relaxation (1/tensile force at ultimate displacement) × 100%.
The chlorine-alkali ion membrane precursor is an unhydrolyzed perfluorosulfonic acid resin film, a perfluorocarboxylic acid resin film or a composite film of perfluorosulfonic acid resin and perfluorocarboxylic acid resin. The precursor includes a fluororesin film containing reinforcing fibers or containing no reinforcing fibers. The testing method is suitable for testing the relaxation degree of the reinforcing fibers in the perfluorosulfonic acid resin layer in the preparation process of the chlor-alkali ionic membrane, particularly after the reinforcing fibers are added. The preparation process of the chlor-alkali ionic membrane is a conventional means in the field, and for better understanding of the method of the present invention, reference may be made to the preparation process of chlor-alkali ionic membrane in chinese patent document CN102978654A (CN 201210545793.6).
The hydrolysis process of the chlorine-alkali ion film precursor is a conventional method, and reference can be made to the hydrolysis process of the reinforced ion film in chinese patent document CN102978654A (CN 201210545793.6).
The effective length of the stretched sample, i.e. the part actually elongated during stretching, such as a standard dumbbell-type sample, is not calculated because the two ends of the sample are fixedly clamped and the sample is not elongated by force during stretching.
In the step (2), the abscissa of the tensile curve is tensile force (N), and the ordinate is tensile displacement (mm).
In the step (2), the ultimate displacement refers to the tensile displacement of the film sample corresponding to the size of the chlor-alkali ion film precursor when the chlor-alkali ion film precursor swells to the maximum extent in the hydrolysis process. It is believed that under ideal conditions, the tensile force of the reinforcing fibers at ultimate displacement is most reflective of their relaxation within the film.
Preferably, in the step (1), the TD-direction swelling ratio is a swelling ratio of the film perpendicular to the machine production direction, and the MD-direction swelling ratio is a swelling ratio parallel to the machine production direction.
Preferably, the size of the sample to be tested of the chlor-alkali ionic membrane precursor containing the reinforcing fibers in the step (2) is a strip with the length of 100-300 mm and the width of 10-50 mm, or a dumbbell-shaped standard style. Preferably, the dumbbell-shaped standard style is cut according to the dumbbell-shaped standard style in GB/T1040.2-2006 test for tensile property of plastics. Further preferably, the number of the strip-shaped or dumbbell-shaped standard forms in the step (2) is 1 or more, preferably 2 to 20.
Preferably, the sampling method of the sample to be tested of the chlor-alkali ionic film precursor containing reinforcing fibers in the step (2) is as follows: selecting the length of the chlorine alkali ion film precursor film roll to be 100-1000 mm in the MD direction, selecting a complete horizontal width or a certain width in the TD direction of the chlorine alkali ion film precursor film roll, and then further cutting to obtain a sample to be detected. Preferably, the length is 150-500 mm, and more preferably, the length is 250-300 mm; preferably, the width is 100 to 2000mm, and more preferably, the width is 200 to 500 mm.
Further preferably, the sample of the chlor-alkali ionic film precursor containing reinforcing fibers in step (2) is pretreated before being subjected to further cutting treatment. The pre-treatment further ensures that all samples to be tested are in the same initial state. The pretreatment is to make the sample reach an equilibrium state, i.e. the sample absorbs water or absorbs equilibrium liquid to reach a saturated state, which can be determined according to the fact that the size and the mass of the sample do not change with time.
The pretreatment method comprises the following steps: soaking a chlor-alkali ionic membrane precursor (hereinafter referred to as a membrane) sample containing the reinforced fibers in pure water or a balanced solution at room temperature for balanced treatment, taking out after balancing, and wiping the sample, or blowing the sample for drying by using room temperature air. More preferably, the equilibrium solution is a neutral solution, and comprises one or more of water solutions of alcohol, aldehyde, ketone, chloride or sulfate with the mass concentration of 0.1-50.0%. Still more preferably, the chloride salt is one of LiCl, NaCl, or KCl; the sulfate salt comprises Li2SO4、Na2SO4Or K2SO4One kind of (1).
Preferably, the tensile curve of step (2) is determined by measuring the tensile curve of a film sample using a universal tester.
And (4) completing data conversion of the tensile force and the fiber relaxation of the sample at the limit displacement, and mapping and analyzing the slope condition of the tensile curve of different samples. The slope represents the unit displacement stress of the film in the stretching process, and the smaller the fiber looseness in the film is, the larger the slope is.
The invention also provides a method for preventing pocking marks from being generated on the chlor-alkali ionic membrane, which is characterized in that the looseness of fibers in the membrane is controlled to be more than 7%.
During the actual production of the film, the fiber relaxation can be improved by reducing the running tension of the equipment.
The principle of the invention is that in the production and processing process of the chlor-alkali ionic membrane, the lower the looseness and the tighter the tension of the composite reinforcement fibers in TD and MD directions in the precursor membrane, the smaller the swelling degree of the membrane in the first step in the hydrolysis process, and the larger the self-swelling degree of the membrane in the Z direction in the second step, the easier the generation of pockmarks, i.e. in an ideal state, the key of whether the pockmarks are generated on the appearance of the membrane in the hydrolysis process is that whether the binding force of the reinforcement fibers is too large when the membrane matrix (perfluorinated ion exchange resin base membrane) is swelled to the limit. In the stretching process of the film sample, the degree of tightness of the reinforcing fibers inside the film can be indirectly reflected by the magnitude of stretching force when the film is stretched to the limit displacement corresponding to the swelling rate of the matrix. When a reinforcing fiber having a low degree of relaxation, i.e., a high degree of tension, is reflected in a tensile curve, the larger the slope of the curve, the larger the tensile force at the limit displacement.
The invention has the beneficial effects that:
compared with the traditional way of generally estimating the relaxation degree of the reinforcing fibers in the film by only utilizing the running tension of equipment in the production process, the invention has the advantages that: (1) the relaxation of the fibers in the film can be more clearly characterized; (2) the obtained relative data is closer to the relative relaxation degree of the reinforced fibers in the film; (3) the method has the advantages of simple used apparatus, low cost, simple operation and less related personnel, and can complete the test only by one person. (4) The method solves the problem that the looseness of the fiber composite film after the fiber composite film is arranged inside the film can not be directly measured. After the method is used for measuring the fiber relaxation degree, parameters such as equipment tension and the like can be adjusted in time, the aim of reducing the generation probability of pockmarks is fulfilled, guidance is provided for the subsequent production of the chlor-alkali ionic membrane, and the accuracy rate of the method can reach more than 80%.
Drawings
FIG. 1 is a schematic diagram of the swelling process of chlor-alkali ionic membrane and producing pockmarks (the straight line in the figure is a schematic diagram of the reinforcing fibers inside the membrane, and the arrow is the swelling direction);
FIG. 2 is the TD-direction and MD-direction stretch curves of chlor-alkali ionic membrane A of example 1;
FIG. 3 is the TD-directional and MD-directional stretch curves of chlor-alkali ionic membrane B of example 2;
FIG. 4 is a picture of the appearance of chlor-alkali ionic membrane A of example 1 after hydrolysis;
FIG. 5 is a picture of the appearance of chlor-alkali ionic membrane B of example 2 after hydrolysis;
fig. 6 is TD-direction and MD-direction tensile curves of the chlor-alkali ionic membrane C of example 3.
Detailed Description
The present invention will be further described by the following examples, however, the scope of the present invention is not limited to the following examples. It will be understood by those skilled in the art that various changes and modifications may be made to the invention without departing from the spirit and scope of the invention.
The perfluorinated ion exchange membranes used in the embodiment of the invention are all chlor-alkali ion exchange membranes DF2807 produced by the Shandong east Yue Fluorosilicone technology group and related products thereof. However, the applicable objects of the treatment method provided by the present invention are not limited to the film.
Example 1
A method for testing the looseness of internal reinforcing fibers of a chlor-alkali ionic membrane comprises the following steps:
(1) determining the swelling ratio of a certain batch of the chlor-alkali ionic membrane A with the model DF2807 in the preparation process, wherein the matrix swelling ratio in the hydrolysis process is determined by sampling a 10 x 10cm fibrous membrane hydrolysis precursor without adding a precursor of a reinforcing fiber (perfluorinated ion exchange resin base membrane), and the swelling ratio is TD: 11.03%, MD: 9.87 percent.
(2) A film sample with the length of 150mm and the width of the middle area of 200mm is taken from a film roll of the chlor-alkali ionic film A precursor (reinforced ionic film) containing the reinforced fibers, soaked in pure water for 16h, dried, and cut along the TD and MD directions by a dumbbell type standard model die in GB/T1040.2-2006 "Plastic tensile Property", and 5 sample strips are cut along each direction.
By the formula: the ultimate displacement (tensile sample effective length (115mm) × swelling ratio) was calculated to give the ultimate displacement TD of the corresponding standard dumbbell-type tensile sample: 5.5mm, MD: 4.9 mm.
Fixing the cut sample strip on a universal testing machine for tensile testing, wherein the testing software is Material Test V4.3, and the testing conditions are as follows: the distance between the clamps is 115 mm; pressure sensor 200N, tensile rate 25 mm/min. The tensile curve obtained after stretching until the sample strip breaks is shown in FIG. 2:
from the stretching curves, it was found that the stretching force of the film sample at the ultimate displacement in the TD direction (5.5mm) was 12.78. + -. 0.49N and that the stretching force at the ultimate displacement in the MD direction (4.9mm) was 9.34. + -. 0.35N.
(3) The film sample had a fiber sag of 7.82% in the TD direction and a fiber sag of 10.71% in the MD direction calculated according to the formula (1/tensile force at ultimate displacement) × 100%. From this, it is found that the MD direction reinforcing fibers are looser than the TD direction in the film sample.
Example 2
A method for testing the looseness of internal reinforcing fibers of a chlor-alkali ionic membrane comprises the following steps:
(1) determining the swelling ratio of a certain batch of the DF2807 chlor-alkali ionic membrane B in the preparation process, which is not added with a precursor of a reinforcing fiber (perfluorinated ion exchange resin base membrane), in the hydrolysis process, sampling a 10 x 10cm non-fibrous membrane hydrolysis precursor, wherein the swelling ratio is TD: 10.82%, MD: 8.56 percent.
(2) A film sample with the length of 300mm and the width of the middle area of 400mm is taken from a film roll of the chlor-alkali ionic film B precursor (reinforced ionic film) containing the reinforced fibers, soaked in pure water for 16h, dried, and cut along the TD and MD directions by a dumbbell type standard model die in GB/T1040.2-2006 "Plastic tensile Property", and 5 sample strips are cut along each direction.
By the formula: the ultimate displacement (tensile sample effective length (115mm) × swelling ratio) was calculated to give the ultimate displacement TD of the corresponding standard dumbbell-type tensile sample: 5.4mm, MD: 4.7 mm.
Fixing the cut sample strip on a universal testing machine for tensile testing, wherein the testing software is Material Test V4.3, and the testing conditions are as follows: the distance between the clamps is 115 mm; pressure sensor 200N, tensile rate 25 mm/min. The tensile curve obtained after stretching to break the sample strip is shown in FIG. 3:
from the stretching curve, it was found that the stretching force of the film sample at the ultimate displacement in the TD direction (5.4mm) was 21.22. + -. 0.96N and the stretching force at the ultimate displacement in the MD direction (4.7mm) was 26.47. + -. 1.43N.
(3) The film sample was calculated to have a TD direction fiber sag of 4.71% and an MD direction fiber sag of 3.78%. From this, it is found that the TD direction reinforcing fibers are looser than the MD direction reinforcing fibers in the film sample.
Comparing example 1 and example 2, it can also be seen that the looseness of the reinforcing fibers inside the chlor-alkali ionic film a is greater than that of the chlor-alkali ionic film B, i.e. the fibers inside the film a are more loose, since the sample treatment methods are the same. In response to production practices, film B appeared pockmarked after hydrolysis (fig. 5), while film a appeared pockmarkless (fig. 4).
Example 3
A method for testing the looseness of internal reinforcing fibers of a chlor-alkali ionic membrane comprises the following steps:
(1) determining the swelling ratio of a certain batch of the DF2807 chlor-alkali ionic membrane C in the preparation process, which is not added with a precursor of a reinforcing fiber (perfluorinated ion exchange resin base membrane), of a matrix in the hydrolysis process, sampling a 10 x 10cm non-fibrous membrane hydrolysis precursor, wherein the swelling ratio is TD: 12.52%, MD: 10.98 percent.
(2) A film sample with the length of 250mm and the width of the middle area of 300mm is taken from a film roll of the chlor-alkali ionic film C precursor (reinforced ionic film) containing the reinforced fibers, the film sample is soaked in pure water for 16h and dried,
the samples were cut into long strips with a length of 250mm and a width of 10mm in the TD and MD directions, respectively, and 5 sample strips were cut in each direction.
By the formula: the ultimate displacement (tensile sample effective length (200mm) × swell ratio) was calculated as follows: TD: 6.3mm, MD: 4.7 mm.
Fixing the cut sample strip on a universal testing machine for tensile testing, wherein the testing software is Material Test V4.3, and the testing conditions are as follows: the distance between the clamps is 200 mm; pressure sensor 200N, tensile rate 25 mm/min. The tensile curve obtained after stretching until the sample strip breaks is shown in FIG. 6:
from the stretching curve, it was found that the stretching force at the ultimate displacement in the TD direction (6.3mm) of the film sample was 22.82. + -. 0.81N, and the stretching force at the ultimate displacement in the MD direction (4.7mm) was 26.75. + -. 1.03N.
(3) The film sample was calculated to have a TD direction fiber sag of 4.38% and an MD direction fiber sag of 3.74%. From this, it is found that the TD direction reinforcing fibers are looser than the MD direction reinforcing fibers in the film sample. Corresponding to the actual production situation, pockmarks appear on the membrane C after hydrolysis.
The reason why the fiber sag of the chlor-alkali ionic membrane A, B, C described in examples 1 to 3 is different is due to the instability of the equipment tension during the production process. The method can accurately test the fiber relaxation degree and adjust the parameters such as tension in the subsequent batch production process, thereby solving the problems of unstable relaxation degree and easy generation of pockmarks.
Claims (10)
1. A method for testing the relaxation degree of internal reinforced fibers of a chlor-alkali ionic membrane is characterized by comprising the following steps:
(1) the hydrolytic swelling ratio of the chlor-alkali ionic film precursor containing no reinforcing fibers was measured,
swelling ratio (TD or MD) 100% × (size after membrane hydrolysis-size before membrane hydrolysis)/size before membrane hydrolysis;
(2) calculating the ultimate displacement of a sample to be tested of the chlor-alkali ionic membrane precursor containing the reinforced fibers, obtaining the stretching force at the ultimate displacement through a stretching curve,
ultimate displacement ═ tensile sample effective length × swell ratio;
(3) calculating the fiber relaxation degree of a chlorine-alkali ion membrane precursor containing reinforcing fibers in a sample to be detected,
fiber relaxation (1/tensile force at ultimate displacement) × 100%.
2. The test method according to claim 1, wherein the TD-direction swelling ratio in step (1) is a swelling ratio of the film perpendicular to the machine production direction, and the MD-direction swelling ratio is a swelling ratio parallel to the machine production direction.
3. The test method according to claim 1, wherein in the step (2), the effective length of the stretched sample is a portion which is actually elongated when stretched; the ultimate displacement refers to the tensile displacement of the membrane sample corresponding to the size of the chlor-alkali ion membrane precursor when the chlor-alkali ion membrane precursor swells to the maximum extent in the hydrolysis process.
4. The test method according to claim 1, wherein the tensile curve in the step (2) is a tensile curve measured by a universal tester for a film sample.
5. The test method according to claim 1, wherein the size of the chlor-alkali ionic film precursor containing reinforcing fibers to be tested in step (2) is a strip with a length of 100 to 300mm and a width of 10 to 50mm, or a standard dumbbell-shaped sample.
6. The test method according to claim 5, wherein the dumbbell standard form is cut according to the standard form of GB/T1040.2-2006 "determination of tensile Properties of plastics". Preferably, the number of the strip-shaped or dumbbell-shaped standard forms in the step (2) is 1 or more, preferably 2 to 20.
7. The testing method according to claim 5, wherein the sample to be tested of the reinforcement fiber-containing chlor-alkali ionic film precursor in the step (2) is sampled by: selecting the length of the chlorine alkali ion film precursor film roll to be 100-1000 mm in the MD direction, selecting a complete horizontal width or a certain width in the TD direction of the chlorine alkali ion film precursor film roll, and then further cutting to obtain a sample to be detected.
Preferably, the sampling length is 150-500 mm, and the width is 100-2000 mm; further preferably, the length is 250-300 mm; the width is 200 to 500 mm.
8. The test method according to claim 7, wherein the sample of the chlor-alkali ion membrane precursor containing reinforcing fibers in step (2) is pre-treated before being subjected to a further slitting treatment by: soaking a chlor-alkali ionic membrane precursor sample containing the reinforcing fibers in pure water or a balance solution at room temperature for balance treatment, taking out after balance, and wiping the sample, or blowing the sample dry by using air at room temperature.
9. The test method according to claim 8, wherein the equilibrium solution is a neutral solution comprising one or more of alcohol, aldehyde, ketone, chloride salt or sulfate in an aqueous solution with a mass concentration of 0.1-50.0%. Preferably, the chloride salt is one of LiCl, NaCl or KCl; the sulfate salt comprises Li2SO4、Na2SO4Or K2SO4One kind of (1).
10. A method for preventing pockmarks from being generated by a chlor-alkali ionic membrane is characterized in that the looseness of fibers in the membrane is controlled to be more than 7%.
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