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GB/T 1232 consists of four parts under the general title Rubber, unvulcanized - Determinations using a shearing-disc viscometer:
——Part 1: Determination of Mooney viscosity;
——Part 2: Determination of pre-vulcanization characteristics;
——Part 3: Determination of the Delta Mooney value for non-pigmented, oil-extended emulsion-polymerized SBR
——Part 4: Determination of the Mooney stress-relaxation rate
This is Part 1 of GB/T 1232.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 1232.1-2000 Rubber, unvulcanized - Determinations using a shearing-disc viscometer - Part 1: Determination of Mooney viscosity and the following main technical changes have been made with respect to GB/T 1232.1-2000:
——In the Clause of “Normative References”, ISO 6508-1 Metallic materials - Rockwell hardness test - Part 1: Test method and ISO 18899:2013 Rubber - Guide to the calibration of test equipment (see Clause 2) are added;
——The diameter requirements for flexible wire used for instrument calibration are deleted (see 4.7.3 of Edition 2000);
——The thickness of heat-stable film is changed from “0.03mm” to “0.02 mm~0.03 mm” (see the note of 7.1, the note of 7.2 of Edition 2000);
——The requirement “The measured value is accurate to 0.5 Mooney viscosity, and the test results are rounded off to an integer.” is deleted (see 8.2 of Edition 2000);
——The content “The Mooney viscosity of the sample is expressed as the arithmetic mean of at least two test results. The difference between two test results shall not be greater than 2 Mooney viscosity.” is deleted (see 8.3 of Edition 2000);
——Contents of the test report are updated and improved (see Clause 10, Clause 10 of Edition 2000);
——Annex A (Informative) "Precision statement" is added (see Annex A);
——Annex B (Informative) "Heat-stable film for Mooney viscosity measurements" is added (see Annex B);
——Annex C (Normative) "Calibration schedule" is added (see Annex C);
This part, by means of translation, is identical to ISO 289-1:2014 Rubber, unvulcanized - Determinations using a shearing-disc viscometer - Part 1: Determination of Mooney viscosity.
The Chinese documents identical to the normative international documents given in this part are as follows:
——GB/T 230.1-2009 Metallic Rockwell hardness test - Part 1: Test Method (Scales A, B, C, D, E, F, G, H, K, N, T) (ISO 6508-1:2005, MOD)
——GB/T 2941-2006 Rubber - General procedures for preparing and conditioning test pieces for physical test methods (ISO 23529:2004, IDT)
——GB/T 6038-2006 Rubber test mixes - Preparation, mixing and vulcanization - Equipment and procedures (ISO 2393:1994, MOD)
——GB/T 14838-2009 Rubber and rubber products - Determination of precision for test method standards (ISO/TR 9272:2005, IDT)
——GB/T 15340-2008 Rubber，raw natural and raw synthetic - Sampling and further preparative procedures (ISO 1795:2000, IDT)
——GB/T 25269-2010 Rubber - Guide to the calibration of test equipment (ISO 18899:2004, IDT)
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).
The previous editions of this part are as follows:
——GB/T 1232-1992 and GB/T 1232.1-2000.
Rubber, unvulcanized - Determinations using a shearing-disc viscometer - Part 1: Determination of Mooney viscosity
Warning: It has been assumed in the drafting of this part that the execution of its provisions is entrusted to appropriately qualified and experienced people. This part does not address all of the 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.
1 Scope
This part of GB/T 1232 specifies the method for determining the Mooney viscosity of raw rubber or rubber compounds by a shearing-disc viscometer.
This part is applicable to the determination of Mooney viscosity of raw rubber or rubber compounds.
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 (including any amendments) applies.
ISO 1795 Rubber, raw natural and raw synthetic - Sampling and further preparative procedures
ISO 2393 Rubber test mixes - Preparation，mixing and vulcanization - Equipment and procedures
ISO 6508-1 Metallic materials - Rockwell hardness test - Part 1:Test method
ISO/TR 9272 Rubber and rubber products - Determination of precision for test method standards
ISO 18899:2013 Rubber - Guide to the calibration of test equipment
ISO 23529 Rubber - General procedures for preparing and conditioning test pieces for physical test methods
3 Principle
The torque, which has to be applied under specified conditions in order to rotate the rotor in a cylindrical cavity filled with rubber, is measured. The resistance offered by the rubber to this rotation is expressed in arbitrary units as the Mooney viscosity of the test piece.
4 Instruments
4.1 General
Typical shearing-disc viscometer (see Figure 1), consisting of:
a) two dies to form a cylindrical cavity;
b) a rotor;
c) a device for maintaining the cavity at a constant temperature;
d) a device for maintaining the closure pressure of a specified cavity;
e) a device for rotating the rotor at constant angular velocity;
f) a device for indicating the torque of the rotor.
The rotor and die cavity have the dimensions shown in Table 1.
Table 1 Dimensions of essential parts of the apparatus
Part Dimension/mm
Rotor diameter 38.10±0.03
Rotor thickness 5.54±0.03
Die cavity diameter 50.9±0.1
Die cavity depth 10.59±0.03
Note: Normally, a rotor with these dimensions is called a large rotor.
It is permissible to use a smaller rotor if rubber with high viscosity is tested. This small rotor shall have the same dimensions as the large rotor except that the diameter shall be 30.48mm±0.03mm. Results obtained with the small rotor are not identical with those obtained using the large rotor.
The instruments shall be calibrated according to those specified in Annex C.
4.2 Die cavity
The two dies forming the cavity shall be formed from non-deforming unplated hardened steel of minimum Rockwell hardness 60HRC (see ISO 6508-1). The dimensions of the cavity are given in Figure 1 and the height shall be measured from the top surfaces. For good heat transfer, each die shall preferably be made from only one piece of steel. The upper and lower surfaces of die shall have radial V-grooves to prevent slippage. The grooves shall be spaced radially at 20° intervals and shall extend from an outer circle of diameter 47mm to an inner circle of diameter 7mm for the upper die and to within 1.5mm of the hole in the lower die; each groove shall form a 90° angle in the die surface with the bisector of the angle perpendicular to the die surface and shall be 1.0mm±0.1mm wide at the surface (see Figure 2).
4.3 Rotor
The rotor shall be fabricated from non-deforming unplated hardened steel of minimum Rockwell hardness 60 HRC. The rotor surfaces shall have rectangular-section grooves 0.80mm±0.02mm wide, of uniform depth 0.30mm±0.05mm, and spaced 1.60mm±0.04mm apart (distance between central axes). The rotor surfaces of the rotor shall have two sets of such grooves at right angles to each other (see Figure 3). The edge of the rotor shall have vertical grooves of the same dimensions. The large rotor shall have 75 vertical grooves and the small rotor shall have 60. The rotor is fastened at right angles to a shaft having a diameter of 10mm±1mm and a length such that, in the closed die cavity, the clearance above the rotor does not differ from that below by more than 0.25mm. The rotor shaft shall bear on the spindle which turns the rotor shaft, not on the inner wall of the die cavity. The clearance at the point where the rotor shaft enters the cavity shall be small enough to prevent the rubber from leaving the cavity. A grommet, O-ring, or other sealing device can be used as a seal at this point.
The eccentricity or runout of the rotor while turning shall not exceed 0.1mm.
The angular velocity of the rotor shall be 0.209rad/s±0.002rad/s (2.00r/min±0.02r/min).
4.4 Heating device
The upper and lower dies are equipped with a heating device capable of maintaining the temperature of the die cavity and that of the dies to within ±0.5℃ of the test temperature. After insertion of the test piece into the die cavity, the devices shall be capable of returning the temperature of the die cavity to within ±0.5℃ of the test temperature within 4min.
Note: Older machines might not comply with these requirements and might give less reproducible results.
Foreword i
1 Scope
2 Normative references
3 Principle
4 Instruments
5 Preparation of test piece
6 Temperature and duration of test
7 Test procedures
8 Expression of results
9 Precision
10 Test report
Annex A (informative) Precision statement
Annex B (Informative) Heat-stable film for Mooney viscosity measurements
Annex C (Normative) Calibration schedule
