GB/T 4498-1997 Determination of ash content in rubber

This standard specifies two methods for determining the ash content of raw rubber, rubber mixes and vulcanized rubber. Except for the restrictions stated in 1.2 and 1.3, these methods are applicable to raw rubber, rubber mixes or vulcanized rubber of categories M, N, O, R and U in GB/T 5576. This standard does not include the interpretation of ash produced by inorganic compounding ingredients in rubber mixes or vulcanized rubber. This is the responsibility of the analyst, who must understand the behavior of various rubber compounding ingredients at high temperatures. Method A is not applicable to the determination of ash content of various rubber mixes and vulcanized rubber containing chlorine, bromine or iodine. Method B is applicable to the determination of rubber mixes or vulcanized rubber containing chlorine, bromine or iodine, but not to unmixed rubber. Lithium and fluorine-containing compounds may react with quartz crucibles to form volatile compounds, resulting in low ash determination results. Platinum crucibles should be used for ashing fluorinated rubber and lithium polymerized rubber. In all cases, the two ashing methods cannot give the same results, so the ashing method used must be stated in the test report. GB/T 4498-1997 Determination of ash content of rubber GB/T4498-1997 Standard download decompression password: www.bzxz.net

GB/T 4498---1997
This standard is equivalent to the international standard ISO247:1990 "Rubber - Determination of ash content". Due to historical reasons, my country has formulated three national standards, GB4498-84 "Determination of ash content of vulcanized rubber", GB6736--86 "Determination of ash content of synthetic raw rubber" and GB8085-87 "Determination of ash content of natural raw rubber" based on the international standard ISO247. In accordance with the spirit of the national standard cleanup and rectification and the resolutions of the 1993 and 1994 annual meetings of the National Technical Committee for Standardization of Rubber and Rubber Products, in order to meet the needs of international integration, this standard was formulated by combining the above three standards on the basis of the work of the Synthetic Rubber Subcommittee, the Natural Rubber Subcommittee and the General Chemical Test Method Subcommittee of the National Technical Committee for Standardization of Rubber and Rubber Products.
The main difference between this standard and IS0247:1990 is the addition of a chapter on precision. This standard replaces GB4498-84, GB6736-86 and GB8085-87 from the date of entry into force. This standard is proposed and managed by the National Technical Committee for Standardization of Rubber and Rubber Products. The drafting units of this standard are: Chemical Research Institute of Lanzhou Chemical Industry Corporation, South China Tropical Agricultural Products Processing Design Institute, and Beijing Rubber Industry Research and Design Institute of the Ministry of Chemical Industry.
The main drafters of this standard are: Zeng Anqun, Deng Yaojun, Deng Pingyang, Wu Peizhi, Zhang Xiuting, and Liu Huichun. This standard was first published in June 1984. bzxz.net
GB/T4498---1997
ISO Foreword
ISO (International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of formulating international standards is usually carried out by ISO technical committees. Any member interested in the subject of an established technical committee has the right to participate in the technical committee. All governmental and non-governmental international organizations that have relations with ISO may also participate in this work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committee are circulated to the member bodies for voting. Publication as an International Standard requires a vote by at least 75 % of the member bodies casting a vote.
International Standard ISO 247 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products. This third edition cancels and replaces the second edition (ISO 247:1978), which contained three determination methods instead of two. 637
1 Scope
National Standard of the People's Republic of China
Rubber-Determination of ash
GB/T 4498—1997
eqy Iso 247:1990
Replaces GB 4498--84
GB6736-86
GB8085--87
1.1 This standard specifies two methods for the determination of ash content in raw rubber, rubber mixes and vulcanized rubber. Except for the restrictions stated in 1.2 and 1.3, these methods are applicable to raw rubber, rubber mixes or vulcanized rubber of categories M, N, O, R and U in GB/T5576. This standard does not include the interpretation of ash resulting from inorganic compounding agents in rubber mixes or vulcanized rubber. It is the responsibility of the analyst to understand the behavior of various rubber compounding ingredients at elevated temperatures. 1.2 Method A is not suitable for determining the ash content of various rubber mixes and vulcanized rubbers containing nitrogen, bromine, or iodine. 1.3 Method B is suitable for determining the ash content of rubber mixes or vulcanized rubbers containing chlorine, bromine, or iodine, but not for unmixed rubber. 1.4 Lithium and fluorine compounds may react with quartz crucibles to form volatile compounds, causing the ash content to be lower. Platinum crucibles should be used to ash fluorinated rubbers and lithium polymer rubbers. 1.5 In all cases, the two ashing methods do not give identical results, so the ashing method used must be stated in the test report.
2 Referenced Standards
The following standards contain provisions that, through reference in this standard, constitute provisions of this standard. At the time of publication of this standard, the versions shown are valid. All standards are subject to revision, and parties using this standard should investigate the possibility of using the most recent versions of the following standards. GB/T5576—1997 Rubber and latex nomenclature (idtISO1629:1996) GB/T6737—1997 Determination of volatile content of raw rubber (eqvISO248:1991) GB/T15340—93 Sampling and preparation of natural and synthetic raw rubber (idtISO1795:1992) 3 Principle
3.1 Method A
Put the weighed sample into a crucible and heat it on a thermostatic electric furnace (or Bunsen burner). After the volatile decomposition products have escaped, transfer it to a muffle furnace and continue heating until the carbon-containing substances are completely burned out and the mass is constant. 3.2 Method B
Put the weighed sample into a crucible and heat it on a thermostatic electric furnace (or Bunsen burner) in the presence of sulfuric acid, then place it in a muffle furnace and burn it until the carbon-containing substances are completely burned out and the mass is constant. 4 Reagents
Sulfuric acid (only for method B), analytical grade, p=1.84 g/cm2. 5 Instruments
Common laboratory instruments and:
Approved by the State Administration of Technical Supervision on October 14, 1997 638
Implemented on April 1, 1998
GB/T 4498--1997
5.1 Crucible: A porcelain, quartz or platinum crucible with a volume of about 50 cm3. For synthetic raw rubber, a crucible with a volume of at least 25 cm3 per gram of sample can be used.
5.2 Asbestos board: 100 mm square, about 5 mm thick, with a circular hole in the center for (5.1). Make about 2/3 of the crucible exposed under the board.
5.3 Bunsen burner or thermostatic electric furnace 1.
5.4 Muffle furnace: equipped with flue and able to control the airflow into the furnace (can be adjusted by the size of the furnace door opening). Equipped with temperature control device to keep the furnace temperature at 550℃±25℃ or 950℃±25℃. 6 Sample preparation
6.1 Natural raw rubber samples should be cut from the homogenized rubber sample prepared according to GB/T15340. Synthetic raw rubber samples should be cut from the dry rubber after the volatile matter is measured according to GB/T6737.
6.2 Mixed rubber samples should be crushed by hand. 6.3 Vulcanized rubber samples should be pressed into thin sheets or crushed on an open mill, or they can be crushed by hand. 6.4 Care should be taken to ensure that the mixed rubber and vulcanized rubber samples are truly representative. 7 Operating Procedures
7.1 Method A
Place a clean and appropriately sized empty crucible (5.1) in a muffle furnace (5.4) at 550°C ± 25°C for about 30 min, then cool to room temperature in a desiccator and weigh to the nearest 0.1 mg. Weigh about 5 g of raw rubber sample or 1 g to 5 g of mixed rubber or vulcanized rubber sample according to the estimated ash content to the nearest 0.1 mg. Place the weighed sample in the crucible in the hole of the asbestos board (5.2). In a properly ventilated fume hood, heat the crucible slowly with a Bunsen burner (or electric furnace) (5.3) to avoid ignition of the sample. If material is lost due to splashing or spilling, it is necessary to resample and repeat the above steps. When the rubber is decomposed and carbonized, gradually increase the temperature until the volatile decomposition products are basically driven out, leaving only dry carbonized residues. Move the crucible containing the residue into a muffle furnace at a temperature of 550℃±25℃ (see the note below), slightly open the furnace door and let in enough air to oxidize the carbon.
Continue heating until the carbon is completely reduced to clean ash. Take out the crucible containing ash from the furnace, put it in a desiccator to cool to room temperature, and weigh it to an accuracy of 0.1 mg. Put this crucible containing ash into a muffle furnace at 550℃±25℃ (or 950℃±25℃-see note) and heat it for about 30 minutes, take it out and put it in a desiccator to cool to room temperature, and weigh it again to an accuracy of 0.1 mg. For raw rubber, the difference between the two masses should not be less than 1 mg, and for compound rubber and vulcanized rubber, it should not be greater than 1% of the ash content. If this requirement cannot be met, repeat the heating, cooling and weighing operations until the difference between the two consecutive weighing results meets the above requirements. Note: For compound rubber and vulcanized rubber, the temperature used can be 950℃±25℃. 7.2. Method B
Place a clean and properly sized empty crucible (5.1) in a muffle furnace (5.4) at 950°C ± 25°C for about 30 minutes, then place it in a desiccator and cool it to room temperature. Take it out and weigh it to an accuracy of 0.1 mg. Weigh 1g to 5g of the mixed rubber or vulcanized rubber sample to an accuracy of 0.1 mg. Place the weighed sample in a crucible, then pour about 3.5cm of concentrated sulfuric acid (Chapter 4) on the sample to completely wet the rubber. Place the crucible containing the sample on an asbestos board (5.2) in the hole. Heat slowly with a Bunsen burner or electric furnace in a properly ventilated fume hood. If the mixture expands severely at the beginning of the reaction, remove the heat source to avoid possible loss of material. When the reaction becomes slower, increase the temperature until the excess sulfuric acid evaporates, leaving a dry carbonized residue. Move the crucible containing the residue into a muffle furnace at a temperature of 950℃±25℃ and heat for about 1 hour until the carbon is completely oxidized to clean ash. Remove the crucible containing ash from the muffle furnace and place it in a desiccator to cool to room temperature, weigh it to the nearest 0.1 mg. Then place the crucible containing ash in a muffle furnace at 950℃±25℃, heat it for about 30 minutes, remove it from the desiccator and cool it to room temperature, and weigh it to the nearest 0.1 mg. Instructions for use:
17IS) 247:1990 does not specify a temperature-controlled electric furnace. 639
GB/T 449B—1997
If the difference between the two weighings is greater than 1% of the ash content, repeat the heating, cooling and weighing steps until the difference between the two consecutive weighings is less than 1% of the ash content.
8 Result display
Use formula (1) to calculate the mass percentage of ash: mz-mr
-sample mass, g;
where: mo
ml————-empty crucible mass, g;
the sum of the crucible and the ash mass, nominal.
The result should be expressed to two decimal places.
9 Tolerance 13
9.1 For natural rubber, the difference between the two determination results shall not exceed 0.02%. 9.2 For synthetic raw rubber
, when the ash content is less than 0.07%, the difference between the two test results shall not exceed 0.02%; when the ash content is between 0.08% and 0.24%, the difference between the two test results shall not exceed 0.03%; when the ash content is between 0.25% and 1.00%, the difference between the two test results shall not exceed 0.08%. 9.3 For vulcanized rubber
, when the ash content is between 1% and 5%, the difference between the two test results shall not exceed 0.20%; when the ash content is between 5% and 10%, the difference between the two test results shall not exceed 0.30%; when the ash content is between 10% and 50%, the difference between the two test results shall not exceed 0.40%. 10 Test report
The test report shall include the following:
The number of this standard;
Detailed description of the sample;
The method used - method A or method B,
The temperature used, and the reason for choosing 950℃ for method A; d)
Ash content of the tested product, expressed as mass percentage; f) Test date.
Instructions for use:
1] There is no such chapter in ISO 247.
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