Original standard number GB 4494-84 HG/T 2875-1997 Test method for characteristic value of crosslink density of microporous materials for rubber and plastic shoes HG/T2875-1997 Standard download decompression password: www.bzxz.net

HG/T2875—1997
This standard is a revision of the original GB/T 4494—84.
This standard adds the content of definitions and referenced standards, and requires that the environmental adjustment and size measurement of the test specimens shall be carried out in accordance with the relevant standards.
The main revisions of this standard to the original GB/T 4494—84 are as follows. 1 In the section “Result Expression*” in GB/T 4494—84, it is stipulated that the characteristic value of crosslinking density V is calculated as follows: (1)
The formula (1) was incorrectly printed when it was published. The correct calculation formula should be: L
2 The meaning of the characteristic value of crosslinking density V in the calculation formula is explained as “the weight fraction of the polymer in the formula” according to GB/T4494--84. In actual applications, the vulcanization (crosslinking) medium used for rubber and rubber-plastic combination is not the same. Generally, rubber is cross-linked with mercapto yellow, while rubber and plastic are cross-linked with peroxide. When rubber and plastic are used to produce microporous materials, the rubber component is added to modify the plastic, and this part of the rubber does not participate in the cross-linking reaction in the peroxide cross-linking system. In the calculation formula of the characteristic value of the cross-linking density derived from the Flory-Rehncr equation, the α value should be the weight fraction of the polymer participating in the cross-linking reaction. Therefore, the general calculation value should be different according to the type of cross-linking system, and the α value cannot be calculated as the sum of the weight fractions of all polymers. Therefore, the α value in formula (2) refers to the weight fraction of the polymer participating in the cross-linking reaction. From the date of implementation of this standard, the original GB/T4494-84 will be abolished. This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of Shanghai Rubber Shoes Research Institute. This standard was drafted by Shanghai Rubber Shoes Research Institute. The main drafters of this standard are Lv Zhiqiang, Shi Qiong and Xu Chun. ICS 61.060wwW.bzxz.Net
Registration No. 447---1997
Chemical Industry Standard of the People's Republic of China
Cellular material for rubber-plastic shoes-Determinationof intrinsic value of crosslink densify1Scope
This standard specifies the method for determining the characteristic value of crosslink density of rubber-plastic combined microporous materials. 2Referenced standards
HG/T28751997
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were all valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest version of the following standards: GB2941-91 Standard temperature, humidity and time for environmental conditioning and testing of rubber specimens. (cqvISO471:1983, ISO1826:1981)
GB/T572393 Determination of dimensions of test specimens and products for vulcanized rubber or thermoplastic rubber testing (cqVISO4648:1991)
CB9865-88 Preparation of vulcanized rubber samples and test specimens (ncqIS04661/1:1986)HG/T2198-91 General requirements for physical test methods for vulcanized rubber 3 Terms and definitions
Crosslink density: the number of moles of crosslinking bonds per unit volume of polymer, characteristic value of crosslink density: when a crosslinked polymer is immersed in a solvent, its volume changes due to swelling and gradually reaches equilibrium. The change in the volume of the polymer before and after swelling, that is, the volume fraction of the polymer in the swollen sample, can be used as a characterization of its crosslink density. This is called the characteristic value of cross-linking density.
4 Source
When the cross-linked network polymer is soaked in the solvent, the solvent molecules can penetrate into its network structure. As the solvent molecules continue to penetrate, the polymer swells. During the swelling process of the polymer, its network structure also produces stress that tends to shrink and prevents the solvent molecules from entering: when the solvent penetration force is equal to the internal shrinkage stress generated by the polymer due to swelling, the swelling reaches a balanced state. Experiments show that the cross-linking density is linearly related to the degree of swelling in the selected solvent. Since the volume ratio of the polymer before and after the sample swells is equal to the ratio of the corresponding millivolts output by the instrument's photocell, the characteristic value of the material's cross-linking density can be calculated by measuring the volt value of the instrument's photocell output current before and after the sample swells.
5 Test instruments and equipment
5.1 Cross-linking density tester
The cross-linking density tester is mainly composed of a sample dissolution pool and temperature control indicator, photoelectric signal generation and heating, control and automatic recording units. Approved by the Ministry of Chemical Industry of the People's Republic of China on April 21, 1997 and implemented on October 1, 1997
HG/T 2875 — 1997
, through photoelectric conversion, the corresponding voltmeter before and after the sample is swollen is determined. The domestic 819 crosslink density tester meets the requirements of this standard. 5.2 The circular cutting force
circular knife for making the sample is divided into large and small types, with inner diameters of @15.0mm and 10.0.0mm respectively. 6 Solvent
6.1 The swelling solvent used in this test is AR 6.2 The amount of solvent in the sample swelling pool during the test is 2/3 of the pool volume. 6.3 After three samples are made, the solvent in the sample swelling pool is replaced with fresh solvent. 7 Samples
7.1 Sample preparation
7.1.1 Remove the skin of the sample with a slicer and slice it into 1.0mm±0.1mm thick flat slices. 7.1.2 Select the foaming part and cut it to make the sample. 7.1.3 The cutter should be sharp, lubricate the blade with soapy water, and be careful to contact the sample. The sample should be placed on a suitable support material. The cutting force should be as small as possible to avoid the formation of concave shapes on the surface during cutting. 7.2 Specimen size
7.2.1 Large specimen diameter a15.0 mm±0.1 mm, thickness 1.0 mm±0.1 mm.7.2.2 Small specimen diameter @10.0 mm±0.1 mm, thickness 1.0 mm±0.1 mm7.3 Number of specimens
Three large specimens (or three small specimens) should be taken from the same material for separate tests. 8 Test
8.1 Test conditions
The test temperature is specified as (30±1)℃. The sample must be pre-conditioned at the test temperature for 3 minutes before testing. 8.2 Preparation before testing
8.2.1 Turn on the power supply and press the "Power" key. The power indicator light will immediately display 8.2.2 Open the darkroom door, observe and adjust the position of the parallel aperture to coincide with the center of the swelling cell. 8.2.3 Press the "Heat" and "Calibrate" keys at the same time, adjust the "Calibrate Full" knob, calibrate the "Temperature Indicator" to full scale, and then press the "Measure" key.
8.2.4 Inject the solvent into the swelling cell and control the temperature to (30±1) after preheating for 20 minutes. The test can only be started after the swelling pool reaches a constant temperature.
8.3 Test steps
8.3.1 Adjust the balance regulator (coarse and fine adjustment) and select the initial position of the recording pen. Usually, the "coarse adjustment" is set to 10 and the attenuation ratio is set to 1.
8.3.2. Press a stainless steel weight that does not exceed the diameter of the sample on one side of the test piece, quickly and carefully move it to the center of the swelling pool and close the darkroom door.
8.3.3 Record the initial millivolt and equilibrium millivolt of the swelling sample. Result Expression
9.1 The characteristic value of crosslink density V, can be calculated as follows: HG / T 2875 -- 1997
Where: V,--corresponding millivolt value before sample swelling, mV; V--corresponding millivolt value when sample swelling reaches equilibrium, V; a--weight percentage of the polymer participating in the crosslinking reaction in the formula, 9.2 The result is expressed as the arithmetic mean of the three measured V, values. 10 Test Report
The test report shall include the following contents:
Name and code of the sample;
weight percentage of the polymer participating in the crosslinking reaction in the sample; solvent name and grade;
test temperature and humidity;
number and number of samples;
arithmetic mean of the characteristic value of crosslink density; test date;
test personnel and reviewer.
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