Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
GB/T 24131 consists of the following two parts under the general title Rubber, raw - Determination of volatile matter content:
——Part 1: Hot-mill method and oven method;
——Part 2: Thermogravimetric methods using an automatic analyser with an infrared drying unit.
This is Part 1 of GB/T 24131.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 24131-2009 Rubber, raw - Determination of volatile matter content. In addition to a number of editorial changes, the following technical changes have been made with respect to GB/T 24131-2009:
——“Terms and definitions” is added (see Clause 3);
——the technical contents of hot-mill method, procedure A are modified to be consistent with those in ISO 248-1: 2011 (see 5.3.1 and 5.4.1; 4.2.1 and 4.3.1 of Edition 2009);
——the hot-mill method, procedure B is modified to be classified into hot-mill method, procedure B1 and hot-mill method, procedure B2, among which, hot-mill method, procedure B1 is hot-mill method, procedure B in GB/T 24131-2009, and hot-mill method, procedure B2 is hot-mill method, procedure A in GB/T 24131-2009 (see 5.3.2; 4.2.2 of Edition 2009);
——the reserved decimal places of test results are added (see 5.4.1, 5.4.2, 6.4.1.1, 6.4.1.2 and 6.4.2);
——"Allow to cool to room temperature before the final weighing" is added (see 6.3.1.1.1);
——the requirements for oven method, procedure B are modified:
a) the requirement of passing the test sample twice through the mill is added (see 6.3.2.1);
b) the requirements for weighing dish are modified to be consistent with those specified in oven method, procedure A (see 6.3.2.2; 5.2.2.2 of Edition 2009);
c) the drying time is modified to 2h (see 6.3.2.2; 5.2.2.2 of Edition 2009).
——the requirements for precision are modified;
a) Annex A of Edition 2009 is adjusted to Annex C of this standard.
b) the requirements for precision of hot-mill method, procedure A are added (see Annex C);
c) the guidance for application of tolerance and precision is deleted (see 6.2 of Edition 2009);
——Annexes A and B are added.
This part has been redrafted and modified in relation to ISO 248-1:2011 Rubber, raw - Determination of volatile-matter content Part 1: Hot-mill method and oven method.
Technical deviations between this part and ISO 248-1:2011 are as follows:
——adjustments on technical differences are made for the normative references of this part in order to adapt to the technical conditions of China, as follows:
ISO 1629 is replaced by GB/T 5576, which is identical to the international standard;
ISO 2393 is replaced by GB/T 6038, which is modified in relation to the international standard;
ISO 1795 is replaced by GB/T 15340, which is identical to the international standard.
——in hot-mill method, procedure A, the clearance of the mill rolls is modified from 0.25±0.05mm to 0.30±0.05mm (see 5.3.1.2 and 5.3.2.1.2; 5.3.1.2 of ISO 248-1:2011);
——the requirements for hot-mill method, procedure B are modified:
a) hot-mill method, procedure B is classified into hot-mill method, procedure B1 and hot-mill method, procedure B2, among which, hot-mill method, procedure B1 is hot-mill method, procedure B in ISO 248-1:2011, and hot-mill method, procedure B2 is an added procedure (see 5.3.2.1 and 5.3.2.2; 5.3.2 of ISO 248-1:2011);
b) the clearance of the mill rolls is modified from 0.25±0.05mm to 0.30±0.05mm (see 5.3.2.1.2 and 5.3.2.2.2; 5.3.2.2 of ISO 248-1:2011).
——the reserved decimal places of test results are added (see 5.4.1, 5.4.2, 6.4.1.1, 6.4.1.2 and 6.4.2);
——"Allow to cool to room temperature before the final weighing" is added (see 6.3.1.1.1);
——the requirements for oven method, procedure B are modified:
a) the requirement of passing the test sample twice through the mill is added (see 6.3.2.1);
b) the clearance of the mill rolls is modified from 0.25±0.05mm to 0.30±0.05mm (see 6.3.2.1; 6.3.2.1 of ISO 248-1:2011);
c) the requirements for weighing dish are modified to be consistent with those specified in oven method, procedure A (see 6.3.2.2; 6.3.2.2 of ISO 248-1:2011);
d) the drying time is modified to 2h (see 6.3.2.1 and 6.3.2.2; 6.3.2.1 and 6.3.2.2 of ISO 248-1:2011).
Editorial changes have been made in this part as follows:
——the requirements for precision of hot-mill method, procedure A are added (see Annex C).
This part was proposed by China Petroleum and Chemical Industry Association.
This part is under the jurisdiction of National Technical Committee on Rubber & Products of Standardization Administration of China (SAC/TC 35).
Drafting organizations of this part: Petrochemical Research Institute of PetroChina Company Limited, Rubber Branch, Chambroad Petrochemicals Co., Ltd., Agricultural Products Processing Research Institute of Chinese Academy of Tropical Agricultural Sciences, CNPC Daqing Petrochemical Complex and Shenyang Rubber Research and Design Institute Co., Ltd.
Chief drafters of this part: Zhai Yueqin, Liu Baicen, Lu Guang, Yan Guangyao, Zhao Chuanhua, Wu Yi, Kong Bo, Bai Yingjun, Zhao Huihui, Li Xiaoyin, Chen Genping, Sun Lijun and Shen Hailong.
The previous edition of this part is as follows:
——GB/T 24131-2009.
Rubber, raw - Determination of volatile matter content - Part 1: Hot-mill method and oven method
WARNING — Persons using this part should be familiar with normal laboratory practice. This part does not address all potential safety problems. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
IMPORTANT — Certain procedures specified in this part might involve the use or generation of substances, or the generation of waste, that could constitute a local environmental hazard. Reference should be made to appropriate documentation on safe handling and disposal after use.
1 Scope
1.1 This part of GB/T 24131 specifies two methods for the determination of volatile matter content in raw rubbers by using a hot mill or an oven.
1.2 The methods are applicable to the determination of the volatile matter content in the “R” group of rubbers listed in GB/T 5576. These are rubbers having an unsaturated carbon chain, for example natural rubber and synthetic rubbers derived at least partly from diolefins. The methods may also be applicable to other raw rubbers, but in these cases, it is necessary to demonstrate that the change in mass is due solely to loss of actual volatile matter and not to rubber degradation.
1.3 The hot-mill method is not applicable to natural rubber, to synthetic rubbers which are too difficult to handle on a hot mill or to synthetic rubbers in powder or chip form.
1.4 The test methods do not necessarily give identical results. Therefore, in cases of dispute, the oven method, procedure A, is the reference method.
Note: The applicability of each test method to various types of rubber is summarized in Annex A.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 5576 Rubber and latices - Nomenclature (GB/T 5576-1997, ISO 1629:1995, IDT)
GB/T 6038 Rubber test mixes - Preparation, mixing and vulcanization - Equipment and procedures (GB/T 6038-2006, ISO 2393:1994, MOD)
GB/T 15340 Rubber, raw natural and raw synthetic - Sampling and further preparative procedures (GB/T 15340-2008, ISO 1795:2002, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 15340 as well as the following apply.
3.1
test portion
rubber taken from the test sample or laboratory sample for the purpose of a single specific test, for example, rubber weighed out for a single determination of volatile matter content
4 Principle
4.1 Hot-mill method
A test portion is sheeted out on a heated mill until all volatile matter is driven off. The loss in mass during milling is calculated and expressed as the volatile matter content. If the test portion is homogenized in accordance with Annex B before drying, the loss in mass during the homogenization is included in the calculation.
4.2 Oven method
A test portion is dried in an oven to constant mass. The loss in mass is calculated and expressed as the volatile matter content. If the test portion is homogenized in accordance with Annex B before drying, the loss in mass during the homogenization is included in the calculation.
5 Hot-mill method
5.1 General
5.1.1 Two procedures are specified, as follows:
Hot-mill method, procedure A: A test sample is homogenized using a laboratory mill, and a test portion from the homogenized test sample is dried to constant mass using a hot mill.
Hot-mill method, procedure B: A test portion is dried to constant mass using a hot mill.
Note: Procedure B is a simplified one which does not include a homogenization process.
5.1.2 When the sample is flaky or becomes sticky on the hot mill, making weighing difficult or impossible, the oven method shall be used.
5.1.3 The number of test portions shall be agreed between the interested parties.
5.2 Apparatus
5.2.1 Mill, complying with the requirements of GB/T 6038.
5.2.2 Balance, capable of weighing to the nearest 0.000 1g.
5.3 Procedure
5.3.1 Hot-mill method, procedure A
5.3.1.1 Take a test sample of about 250g from the laboratory sample in accordance with GB/T 15340 and homogenize it in accordance with Annex B. Weigh to the nearest 0.1g before and after homogenization (masses m1 and m2, respectively). Cut test portions needed for other chemical and physical tests from the homogenized test sample, if necessary.
5.3.1.2 Adjust the clearance of the mill rolls to 0.30±0.05mm, using lead strips as specified in GB/T 6038. Maintain the surface temperature of the rolls at 105±5℃.
5.3.1.3 Pass a weighed test portion (mass m3), preferably of 100g or more, taken from the homogenized test sample repeatedly through the mill for 4min. Do not allow the test portion to band and take care to prevent any loss of material. Weigh the test portion to the nearest 0.1g. Pass the test portion through the mill for an additional 2min and reweigh to the nearest 0.1g. If the masses at the end of the 4min and 6min periods differ by less than 0.1g, calculate the volatile matter content. Otherwise, continue passing the test portion through the mill for 2min periods until the mass does not decrease by more than 0.1g between successive weighings (final mass m4). Before each weighing, allow the test portion to cool to room temperature in a desiccator.
5.3.2 Hot-mill method, procedure B
5.3.2.1 Hot-mill method, procedure B1
5.3.2.1.1 Take a test portion of about 250g from the laboratory sample and weigh to the nearest 0.1g (mass m5).
5.3.2.1.2 Adjust the clearance of the mill rolls to 0.30±0.05mm, using lead strips as specified in GB/T 6038. Maintain the surface temperature of the rolls at 105±5℃. Pass the test portion through the mill not less than twice, then reweigh to the nearest 0.1g, followed by passing through the mill not less than twice again and reweighing.
5.3.2.1.3 If the difference in mass of the test portion before and after it is passed through the rolls is less than 0.1g, the test portion is considered to be well dried. If it is not well dried, continue passing the test portion twice through the rolls until the mass difference is less than 0.1g (final mass m6).
5.3.2.2 Hot-mill method, procedure B2
5.3.2.2.1 Take a test portion of about 250g from the laboratory sample and weigh to the nearest 0.1g (mass m5).
5.3.2.2.2 Adjust the clearance of the mill rolls to 0.30±0.05mm, using lead strips as specified in GB/T 6038. Maintain the surface temperature of the rolls at 105±5℃. Pass the test portion repeatedly through the mill for 4min, then reweigh to the nearest 0.1g, followed by passing through the mill for an additional 2min and reweighing to the nearest 0.1g.
5.3.2.2.3 If the masses at the end of the 4min and 6min periods differ by less than 0.1g, calculate the volatile matter content. Otherwise, continue passing the test portion through the mill for 2min periods until the mass does not decrease by more than 0.1g between successive weighings (final mass m6).
Note: Cooling in a desiccator before weighing is desirable.
5.4 Expression of results
5.4.1 Hot-mill method, procedure A
The volatile matter content ω1 is given, as a percent mass fraction (%), by Equation (1):
(1)
where,
m2——the mass of the test sample after homogenization, g;
m4——the mass of the test portion after milling, g;
m1——the mass of the test sample before homogenization, g;
m3——the mass of the test portion before milling, g.
The calculation result is rounded off to two decimal places.
5.4.2 Hot-mill method, procedure B
The volatile matter content ω2 is given, as a percent mass fraction (%), by Equation (2):
(2)
where,
m5——the mass of the test portion before milling, g;
m6——the mass of the test portion after milling, g.
The calculation result is rounded off to two decimal places.
6 Oven method
6.1 General
6.1.1 Two procedures are specified, as follows:
Oven method, procedure A: A test sample is homogenized using a laboratory mill, and a test portion taken from the homogenized test sample is dried in an oven to constant mass. If the sample is in powder form or impossible to weigh before and after homogenization, a test portion shall simply be dried, without carrying out the homogenization process.
Oven method, procedure B: A test sample is sheeted out using a laboratory mill, and a test portion taken from the sheeted test sample is dried in an oven for 1h. If the sample is in powder form or is difficult to pass through the mill, the test portion shall simply be dried, without carrying out the sheeting process. This procedure is only applicable to synthetic rubbers since natural rubber requires homogenization.
6.1.2 The number of test portions shall be agreed between the interested parties.
6.2 Apparatus
6.2.1 Oven: ventilated, preferably of the air-circulation type, capable of being maintained at 105±5℃.
Foreword i 1 Scope 2 Normative references 3 Terms and definitions 4 Principle 5 Hot-mill method 6 Oven method 7 Precision 8 Test report Annex A (Informative) Selection of appropriate test method Annex B (Normative) Homogenization Annex C (Informative) Precision Bibliography
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
GB/T 24131 consists of the following two parts under the general title Rubber, raw - Determination of volatile matter content:
——Part 1: Hot-mill method and oven method;
——Part 2: Thermogravimetric methods using an automatic analyser with an infrared drying unit.
This is Part 1 of GB/T 24131.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 24131-2009 Rubber, raw - Determination of volatile matter content. In addition to a number of editorial changes, the following technical changes have been made with respect to GB/T 24131-2009:
——“Terms and definitions” is added (see Clause 3);
——the technical contents of hot-mill method, procedure A are modified to be consistent with those in ISO 248-1: 2011 (see 5.3.1 and 5.4.1; 4.2.1 and 4.3.1 of Edition 2009);
——the hot-mill method, procedure B is modified to be classified into hot-mill method, procedure B1 and hot-mill method, procedure B2, among which, hot-mill method, procedure B1 is hot-mill method, procedure B in GB/T 24131-2009, and hot-mill method, procedure B2 is hot-mill method, procedure A in GB/T 24131-2009 (see 5.3.2; 4.2.2 of Edition 2009);
——the reserved decimal places of test results are added (see 5.4.1, 5.4.2, 6.4.1.1, 6.4.1.2 and 6.4.2);
——"Allow to cool to room temperature before the final weighing" is added (see 6.3.1.1.1);
——the requirements for oven method, procedure B are modified:
a) the requirement of passing the test sample twice through the mill is added (see 6.3.2.1);
b) the requirements for weighing dish are modified to be consistent with those specified in oven method, procedure A (see 6.3.2.2; 5.2.2.2 of Edition 2009);
c) the drying time is modified to 2h (see 6.3.2.2; 5.2.2.2 of Edition 2009).
——the requirements for precision are modified;
a) Annex A of Edition 2009 is adjusted to Annex C of this standard.
b) the requirements for precision of hot-mill method, procedure A are added (see Annex C);
c) the guidance for application of tolerance and precision is deleted (see 6.2 of Edition 2009);
——Annexes A and B are added.
This part has been redrafted and modified in relation to ISO 248-1:2011 Rubber, raw - Determination of volatile-matter content Part 1: Hot-mill method and oven method.
Technical deviations between this part and ISO 248-1:2011 are as follows:
——adjustments on technical differences are made for the normative references of this part in order to adapt to the technical conditions of China, as follows:
ISO 1629 is replaced by GB/T 5576, which is identical to the international standard;
ISO 2393 is replaced by GB/T 6038, which is modified in relation to the international standard;
ISO 1795 is replaced by GB/T 15340, which is identical to the international standard.
——in hot-mill method, procedure A, the clearance of the mill rolls is modified from 0.25±0.05mm to 0.30±0.05mm (see 5.3.1.2 and 5.3.2.1.2; 5.3.1.2 of ISO 248-1:2011);
——the requirements for hot-mill method, procedure B are modified:
a) hot-mill method, procedure B is classified into hot-mill method, procedure B1 and hot-mill method, procedure B2, among which, hot-mill method, procedure B1 is hot-mill method, procedure B in ISO 248-1:2011, and hot-mill method, procedure B2 is an added procedure (see 5.3.2.1 and 5.3.2.2; 5.3.2 of ISO 248-1:2011);
b) the clearance of the mill rolls is modified from 0.25±0.05mm to 0.30±0.05mm (see 5.3.2.1.2 and 5.3.2.2.2; 5.3.2.2 of ISO 248-1:2011).
——the reserved decimal places of test results are added (see 5.4.1, 5.4.2, 6.4.1.1, 6.4.1.2 and 6.4.2);
——"Allow to cool to room temperature before the final weighing" is added (see 6.3.1.1.1);
——the requirements for oven method, procedure B are modified:
a) the requirement of passing the test sample twice through the mill is added (see 6.3.2.1);
b) the clearance of the mill rolls is modified from 0.25±0.05mm to 0.30±0.05mm (see 6.3.2.1; 6.3.2.1 of ISO 248-1:2011);
c) the requirements for weighing dish are modified to be consistent with those specified in oven method, procedure A (see 6.3.2.2; 6.3.2.2 of ISO 248-1:2011);
d) the drying time is modified to 2h (see 6.3.2.1 and 6.3.2.2; 6.3.2.1 and 6.3.2.2 of ISO 248-1:2011).
Editorial changes have been made in this part as follows:
——the requirements for precision of hot-mill method, procedure A are added (see Annex C).
This part was proposed by China Petroleum and Chemical Industry Association.
This part is under the jurisdiction of National Technical Committee on Rubber & Products of Standardization Administration of China (SAC/TC 35).
Drafting organizations of this part: Petrochemical Research Institute of PetroChina Company Limited, Rubber Branch, Chambroad Petrochemicals Co., Ltd., Agricultural Products Processing Research Institute of Chinese Academy of Tropical Agricultural Sciences, CNPC Daqing Petrochemical Complex and Shenyang Rubber Research and Design Institute Co., Ltd.
Chief drafters of this part: Zhai Yueqin, Liu Baicen, Lu Guang, Yan Guangyao, Zhao Chuanhua, Wu Yi, Kong Bo, Bai Yingjun, Zhao Huihui, Li Xiaoyin, Chen Genping, Sun Lijun and Shen Hailong.
The previous edition of this part is as follows:
——GB/T 24131-2009.
Rubber, raw - Determination of volatile matter content - Part 1: Hot-mill method and oven method
WARNING — Persons using this part should be familiar with normal laboratory practice. This part does not address all potential safety problems. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
IMPORTANT — Certain procedures specified in this part might involve the use or generation of substances, or the generation of waste, that could constitute a local environmental hazard. Reference should be made to appropriate documentation on safe handling and disposal after use.
1 Scope
1.1 This part of GB/T 24131 specifies two methods for the determination of volatile matter content in raw rubbers by using a hot mill or an oven.
1.2 The methods are applicable to the determination of the volatile matter content in the “R” group of rubbers listed in GB/T 5576. These are rubbers having an unsaturated carbon chain, for example natural rubber and synthetic rubbers derived at least partly from diolefins. The methods may also be applicable to other raw rubbers, but in these cases, it is necessary to demonstrate that the change in mass is due solely to loss of actual volatile matter and not to rubber degradation.
1.3 The hot-mill method is not applicable to natural rubber, to synthetic rubbers which are too difficult to handle on a hot mill or to synthetic rubbers in powder or chip form.
1.4 The test methods do not necessarily give identical results. Therefore, in cases of dispute, the oven method, procedure A, is the reference method.
Note: The applicability of each test method to various types of rubber is summarized in Annex A.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 5576 Rubber and latices - Nomenclature (GB/T 5576-1997, ISO 1629:1995, IDT)
GB/T 6038 Rubber test mixes - Preparation, mixing and vulcanization - Equipment and procedures (GB/T 6038-2006, ISO 2393:1994, MOD)
GB/T 15340 Rubber, raw natural and raw synthetic - Sampling and further preparative procedures (GB/T 15340-2008, ISO 1795:2002, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 15340 as well as the following apply.
3.1
test portion
rubber taken from the test sample or laboratory sample for the purpose of a single specific test, for example, rubber weighed out for a single determination of volatile matter content
4 Principle
4.1 Hot-mill method
A test portion is sheeted out on a heated mill until all volatile matter is driven off. The loss in mass during milling is calculated and expressed as the volatile matter content. If the test portion is homogenized in accordance with Annex B before drying, the loss in mass during the homogenization is included in the calculation.
4.2 Oven method
A test portion is dried in an oven to constant mass. The loss in mass is calculated and expressed as the volatile matter content. If the test portion is homogenized in accordance with Annex B before drying, the loss in mass during the homogenization is included in the calculation.
5 Hot-mill method
5.1 General
5.1.1 Two procedures are specified, as follows:
Hot-mill method, procedure A: A test sample is homogenized using a laboratory mill, and a test portion from the homogenized test sample is dried to constant mass using a hot mill.
Hot-mill method, procedure B: A test portion is dried to constant mass using a hot mill.
Note: Procedure B is a simplified one which does not include a homogenization process.
5.1.2 When the sample is flaky or becomes sticky on the hot mill, making weighing difficult or impossible, the oven method shall be used.
5.1.3 The number of test portions shall be agreed between the interested parties.
5.2 Apparatus
5.2.1 Mill, complying with the requirements of GB/T 6038.
5.2.2 Balance, capable of weighing to the nearest 0.000 1g.
5.3 Procedure
5.3.1 Hot-mill method, procedure A
5.3.1.1 Take a test sample of about 250g from the laboratory sample in accordance with GB/T 15340 and homogenize it in accordance with Annex B. Weigh to the nearest 0.1g before and after homogenization (masses m1 and m2, respectively). Cut test portions needed for other chemical and physical tests from the homogenized test sample, if necessary.
5.3.1.2 Adjust the clearance of the mill rolls to 0.30±0.05mm, using lead strips as specified in GB/T 6038. Maintain the surface temperature of the rolls at 105±5℃.
5.3.1.3 Pass a weighed test portion (mass m3), preferably of 100g or more, taken from the homogenized test sample repeatedly through the mill for 4min. Do not allow the test portion to band and take care to prevent any loss of material. Weigh the test portion to the nearest 0.1g. Pass the test portion through the mill for an additional 2min and reweigh to the nearest 0.1g. If the masses at the end of the 4min and 6min periods differ by less than 0.1g, calculate the volatile matter content. Otherwise, continue passing the test portion through the mill for 2min periods until the mass does not decrease by more than 0.1g between successive weighings (final mass m4). Before each weighing, allow the test portion to cool to room temperature in a desiccator.
5.3.2 Hot-mill method, procedure B
5.3.2.1 Hot-mill method, procedure B1
5.3.2.1.1 Take a test portion of about 250g from the laboratory sample and weigh to the nearest 0.1g (mass m5).
5.3.2.1.2 Adjust the clearance of the mill rolls to 0.30±0.05mm, using lead strips as specified in GB/T 6038. Maintain the surface temperature of the rolls at 105±5℃. Pass the test portion through the mill not less than twice, then reweigh to the nearest 0.1g, followed by passing through the mill not less than twice again and reweighing.
5.3.2.1.3 If the difference in mass of the test portion before and after it is passed through the rolls is less than 0.1g, the test portion is considered to be well dried. If it is not well dried, continue passing the test portion twice through the rolls until the mass difference is less than 0.1g (final mass m6).
5.3.2.2 Hot-mill method, procedure B2
5.3.2.2.1 Take a test portion of about 250g from the laboratory sample and weigh to the nearest 0.1g (mass m5).
5.3.2.2.2 Adjust the clearance of the mill rolls to 0.30±0.05mm, using lead strips as specified in GB/T 6038. Maintain the surface temperature of the rolls at 105±5℃. Pass the test portion repeatedly through the mill for 4min, then reweigh to the nearest 0.1g, followed by passing through the mill for an additional 2min and reweighing to the nearest 0.1g.
5.3.2.2.3 If the masses at the end of the 4min and 6min periods differ by less than 0.1g, calculate the volatile matter content. Otherwise, continue passing the test portion through the mill for 2min periods until the mass does not decrease by more than 0.1g between successive weighings (final mass m6).
Note: Cooling in a desiccator before weighing is desirable.
5.4 Expression of results
5.4.1 Hot-mill method, procedure A
The volatile matter content ω1 is given, as a percent mass fraction (%), by Equation (1):
(1)
where,
m2——the mass of the test sample after homogenization, g;
m4——the mass of the test portion after milling, g;
m1——the mass of the test sample before homogenization, g;
m3——the mass of the test portion before milling, g.
The calculation result is rounded off to two decimal places.
5.4.2 Hot-mill method, procedure B
The volatile matter content ω2 is given, as a percent mass fraction (%), by Equation (2):
(2)
where,
m5——the mass of the test portion before milling, g;
m6——the mass of the test portion after milling, g.
The calculation result is rounded off to two decimal places.
6 Oven method
6.1 General
6.1.1 Two procedures are specified, as follows:
Oven method, procedure A: A test sample is homogenized using a laboratory mill, and a test portion taken from the homogenized test sample is dried in an oven to constant mass. If the sample is in powder form or impossible to weigh before and after homogenization, a test portion shall simply be dried, without carrying out the homogenization process.
Oven method, procedure B: A test sample is sheeted out using a laboratory mill, and a test portion taken from the sheeted test sample is dried in an oven for 1h. If the sample is in powder form or is difficult to pass through the mill, the test portion shall simply be dried, without carrying out the sheeting process. This procedure is only applicable to synthetic rubbers since natural rubber requires homogenization.
6.1.2 The number of test portions shall be agreed between the interested parties.
6.2 Apparatus
6.2.1 Oven: ventilated, preferably of the air-circulation type, capable of being maintained at 105±5℃.
Contents of GB/T 24131.1-2018
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Hot-mill method
6 Oven method
7 Precision
8 Test report
Annex A (Informative) Selection of appropriate test method
Annex B (Normative) Homogenization
Annex C (Informative) Precision
Bibliography
