This standard specifies the method for determining the plasticity retention rate (PRI) of natural rubber. PRI is a measure of the thermal oxidation resistance of natural rubber. A high value indicates good thermal oxidation resistance. GB/T 3517-2002 Determination of the plasticity retention rate (PRI) of natural rubber GB/T3517-2002 Standard download decompression password: www.bzxz.net

ICS83.040.10
National Standard of the People's Republic of China
GB/T3517—2002
Replaces GB/T3517—1992
Natural raw rubber
Determination of plasticity retention index (PRI)
Rubber, raw natural-Determination of plasticity retention index (PRD) (ISO29301995.MOD)
Issued on February 19, 2002
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
Implementation on May 1, 2002
GB/T3517—2002
This standard corresponds to ISO2930:1995 "Determination of plasticity retention index of natural raw rubber" (English version of 1995). The consistency of this standard with ISO2930:1995 is modified adoption, and the main differences are as follows: Article 4.5 "After the tray, dish and sample are placed in the aging box, within 2 minutes, the temperature in the aging box should be raised to within 1°C of the control temperature" is revised to "After the sample is placed in the aging box, within 6 minutes, the aging temperature should be raised to 140°C ± 0.5°C"; Article 4.6 is cancelled;
A recommended product "TST" cigarette paper related to padding paper in Article 4.7 is cancelled. This standard replaces GB/T3517-1992 "Determination of Plastic Retention Rate of Natural Raw Rubber". The main differences between this standard and GB/T3517-1992 are as follows: GB/T2941-1991 "Standard temperature, humidity and time for environmental conditioning and testing of rubber samples" has been cancelled in the normative reference documents, and GB/T15340-1994 "Natural and synthetic raw rubber sampling and sample preparation methods" has been added; - Sample preparation, the mass of the rubber sample taken from the homogenized rubber sheet is changed from 30g to 20g ± 2g, the number of rollers is changed from 3 times to 2 times;
The sample thickness is changed from 3.2mm~3.6mm to 3.4mm±0.4mm; the roller temperature is changed from the original room temperature to 27℃±3℃. This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard is under the jurisdiction of the Natural Rubber Sub-Technical Committee of the National Rubber and Rubber Standardization Technical Committee. The drafting unit of this standard: South China Tropical Agricultural Products Processing Design Institute. The main drafters of this standard: Yu Heping and Huang Maofang. The previous versions of the standards replaced by this standard are: GB3517-1983, GB/T3517-1992. Determination of the plasticity retention rate (PRI) of natural raw rubber GB/T3517-2002
Warning: Personnel using this standard should be familiar with the operating procedures of regular laboratories. This standard does not intend to involve all safety issues that may arise from the use of this standard. Users are responsible for establishing appropriate safety and health systems and ensuring compliance with relevant regulations. 1 Scope
This standard specifies the method for determining the plasticity retention rate (PRI) of natural raw rubber. PRI is a measure of the thermal oxidation resistance of natural raw rubber. A high value indicates good thermal oxidation resistance. 2 Normative references
The clauses in the following documents become clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not suitable for this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version applies to this standard. GB/T3510 --1992 Determination of plasticity of raw rubber and mixed rubber Rapid plasticity meter method (eqVISO2007:1991) GB/T6038 Rubber test rubber ingredients, mixing and vulcanization equipment and operating procedures (neqISO/DIS2393:1989) 1) GB/T15340 Natural and synthetic raw rubber sampling and sample preparation methods (idtISO1795:1992) 3 Principle
Use a parallel plate plasticity meter with a 10 mm diameter indenter According to the operating procedures specified in Chapter 5 of GB/T3510-1992, the rapid plasticity values ​​PRI of the unaged specimen and the specimen after heating and aging for 30 minutes in an aging box at 140°C are measured. The PRI is the ratio of the rapid plasticity value (P3) of the specimen after heating and aging to the rapid plasticity value (P) of the unaged specimen multiplied by 100. 4 Instruments
4.1 Parallel plate plasticity gauge. It shall comply with the provisions of 2.1 of GB/T3510-1992 and have a pressure head with a diameter of 10mm. 4.2 Punch cutter. It shall comply with the provisions of 2.2 of GB/T3510-1992 and can press the sample for test to a thickness of about 3mm and punch out a disc with a diameter of about 13mm to prepare the sample. 4.3 Thickness gauge. It has a dial with a graduation unit of 0.01mm, equipped with a flat contact with a diameter of about 10mm, and an operating pressure of 20kPa±3kPa. wwW.bzxz.Net
4.4 The open rubber mixing machine in the laboratory shall comply with the provisions of GB/T6038, but shall have the following characteristics: Roller diameter
150mm250mm
Rear (fast) roller linear speed14.6m/min±0.5m/minRoller speed ratio1:1.4
Roller temperature27℃±3℃
Roller length between baffles265mm±15mm4.5, Aging box, at 140℃, shall meet the following requirements: The temperature near the sample is controlled within ±0.2℃ within a 30min cycle (some aging boxes may not have such precise temperature deviation, and a temperature deviation of ±0.5℃ may be required. Relaxation of the temperature deviation may damage the precision of the test. If an aging box with a temperature deviation of ±0.5℃ is used, it should be stated in the test report); after the sample is placed in the aging box, the aging temperature should rise to 140℃±0.5℃ within 6min; 1 The latest version of this international standard is IS02393:1994. GB/T3517-2002
Replace the air 10 times per hour.
4.6 Thin paper should comply with the provisions of 5.1 of GB/T3510-1992. 5 Operating procedures
5.1 Preparation of samples
Hybridize the raw rubber according to the provisions of GB/T15340. Take 20g ± 2g from the homogenized film and pass it through the rubber mixer roll twice (overlap the film each time), and adjust the roller distance so that the final thickness of the film is about 1.7mm (in order to obtain a smooth film from the aged rubber, it is necessary to pass the roll three times. If this is the case, it should be stated in the test report). The temperature of the rubber mixer roll should be maintained at 27℃ ± 3℃ when the film passes through the roll. Immediately fold the film with uniform texture and no holes in half, and carefully press the two halves together tightly by hand to avoid the formation of bubbles. Use a punch (4.2) to cut a sample from the folded film, and use a thickness gauge (4.3) to measure the thickness between them. Take 6 samples with a thickness of 3.4mm ± 0.4mm and randomly divide them into 2 groups, one group for determining the rapid plasticity value before aging, and the other group for aging test to determine the rapid plasticity value after aging.
Because the thickness of the sample has an impact on PRI, it should be determined carefully as above. The roller spacing varies with different rubbers and rubber mixers. Prepare a new folded film
5.2 Aging
Prepare the sample as specified. The required roller spacing should be based on preliminary tests. If six specimens of the above-specified thickness cannot be obtained, the temperature of the aging box (4.5) should be set at least before the aging begins to ensure temperature stability. In order to ensure that all specimens are aged at the calibrated temperature, the aging is stable and the temperature uniformity of the aging box (4.5) is destroyed. The aging box cannot be overloaded, as this will make it difficult to restore the temperature of the aging box. Place a new set of specimens to be prepared for aging testing on a preheated tray. Place the tray (4.6) in the calibrated temperature area of ​​the aging box, close the aging box door, and start timing. It should be checked whether the plate and tray containing the sample are quickly placed in the temperature zone calibrated in GB/T3510. After checking whether the aging box can quickly recover and maintain its calibrated temperature, remove the tray from the aging box, remove the plate from the tray and let them cool to the standard test room temperature. According to the operating procedures specified in Chapter 5, the rapid plasticity value of the sample is determined using a parallel plate plastometer (4.1). The rapid plasticity value of the unaged sample is measured first, and then the rapid plasticity value of the aged sample is measured. These measurements should usually be completed within at least 0.5h and no more than 2h of aging, but the sample must be allowed to cool to room temperature. The unaged sample uses the same type of pad paper. The rapid plasticity value reading should be accurate to 0.5 units (1 unit phase and plasticity value measurement point of the aged sample
is equivalent to 10um)
6 Representation of results
Use the middle value of the rapid plasticity values ​​of 3 unaged samples and 3 aged samples to calculate the plasticity retention rate (PRI) according to formula (1). PRI
Where:
Plasticity retention rate:
P. —- Rapid plasticity value of unaged sample; P30
Rapid plasticity value of sample after aging.
7 Repeatability of results
The coefficient of variation (CV) depends on the accuracy of the aging temperature. Take the middle value of the plasticity value according to the PRI value calculated in Chapter 6. When the aging temperature is 140℃±0.2℃, the CV is 3%, and when the aging temperature is 140℃±1℃, the CV is 6%. For a single rapid plasticity determination, 2
both CV values ​​are consistent with a precision of 3%. 8 Test report
The test report shall include the following:
a) the number of this standard;
b) all details required to identify the sample;
c) the intermediate value of the rapid plasticity value of each sample unaged and aged specimens:
d) the PRI of each sample;
e) the model of the aging box used:
f) the allowable deviation of the temperature of the aging box used;
g) the test date:
h) the tester;
GB/T3517—2002
i) any operation not included in this standard or normative reference documents, and any operation considered to be optional. GB/T3517-2002
People's Republic of China
National Standard
Determination of plasticity retention rate (PRI) of natural raw rubber GB/T3517-2002
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