This standard specifies the method for determining the color of natural raw rubber according to the standard color scale. This standard is applicable to the determination of the color of natural raw rubber. GB/T 14796-1993 Determination of the color index of natural raw rubber GB/T14796-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Natural raw rubber
Color index test method
Raw natural rubber--Colour index test This standard is equivalent to the international standard ISO4660-1991 "Natural raw rubber 1 Subject content and scope of application
This standard specifies the method for determining the color of natural raw rubber according to the standard color scale. This standard is applicable to the determination of the color of natural raw rubber. 2 Reference standards
GB8083 Natural raw rubber standard rubber sampling
GB8084 Preparation of natural raw rubber samples)
Color index determination".
(GB3510 Plasticity determination of raw rubber and unvulcanized compound rubber-Rapid plasticometer method GB/T 14796---93
Note: 1) The national standard GB8084 is different from the international standard ISO1796 "Raw rubber: Sampling method for sample preparation". However, there is no difference in the color index determination value between the two sampling methods.
3 Principle
The raw rubber is molded into a disc-shaped test piece according to the specified thickness, and then the test piece is compared with a standard color glass piece, and the colors of the two are as similar as possible. When comparing colors, it is carried out under diffuse sunlight and set against a matte white background. The standard glass piece is divided into a color index scale based on the chromaticity of the color (amber). The higher the index value, the darker the color. 4 Equipment
4.1 Laboratory open rubber mixer: in accordance with GB8084 regulations. 4.2 Mold: Made of stainless steel or aluminum, with a thickness of 1.6±0.05mm, with a mold cavity of about 14mm in diameter, and two mold cover plates of the same material as the mold, with a thickness of 1~2mm. The specifications of the mold are shown in Figure 1. 4.3 Flat vulcanizer: The pressure applied to the plate surface is not less than 3.5MPa, and the temperature of the hot plate is maintained at 150±3C. The specifications of the hot plate are preferably 200 mm×200 mm.
4.4 Test piece cutter: see GB3510.
4.5 Colorless transparent polyester or cellulose film, thickness about 0.025mm. 4.6 Colorimeter, as shown in Figure 2.
4.7 Standard color glass: should meet the requirements of the standard glass calibration table (see Table 1). When the color index scale is 1 to 5, it is divided into half scales, and when it is 5 to 16, it is divided into 1 scale. These standard glass plates are also called Lavibond colorimetric disks, 4/19A is 1~~5 scale, and 4/19B is 5~16 scale. Approved by the State Bureau of Technical Supervision on December 25, 1993, 131
, implemented on August 1, 1994
Color index
GB/T 14796-93
When using standard light source B (IE\'s chromaticity coordinate system Y
Note: 1) CIE is the abbreviation of the International Commission on Illumination (Commission Internationale de I'Eclairage). Standard light source B is equivalent to the yellower tone of daylight (color temperature 4870K)
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GB/T 14796-93
Φ152±0.5
Figure 1 Mould
5 Operation steps
5.1 Sample preparation
GB/T14796-93
105 ± 0.www.bzxz.net
T-0±8
Figure 2 Colorimeter for matching Lavibond colorimetric disc
Mix the raw rubber evenly according to the requirements of national standard GB8084. The rubber mixer must be cleaned before use. 5.2 Preparation of test pieces
Take 30 test pieces from the uniformly mixed small sample and pass the test pieces between the rollers of the rubber mixer three times at room temperature. Fold the film in half during the second and third passes and adjust the roller distance so that the thickness of the final extruded film is about 1.7 mm. The film should be uniform in texture and free of voids. Fold the film in half immediately and press it together gently by hand to avoid bubbles. Cut two round test pieces (about 13 mm in diameter) from the folded film (3.2 mm to 3.6 mm thick) with a cutter (4.4) and press them together gently. Place the test piece in the mold cavity (4.2), cover the upper and lower parts with polyester or cellulose films (4.5), cover the mold cover plate, and press at 150 ± 3°C for 5 ± 1.2 min. The pressure should not be less than 3.5 MPa. Leave the test piece together with the transparent film in the mold for testing. The thickness of the test piece after molding, excluding the film covering it, should be 1.6 ± 0.1 mm, and there should be no external contamination. 5.3 Color comparison
The comparison between the test piece and the standard color glass piece (4.7) should be carried out under diffuse sunlight and against a matte white background. The visual direction should be facing the main surface of the test piece. The color index of the test piece should be determined according to the color of the standard glass piece that is closest to the color of the test piece. When comparing colors, first place a matte white paper on the bottom plate of the colorimeter (cut a round hole according to the flange), then install the Lavibond colorimetric disk and the mold containing the test piece (together with the covering transparent film) on the flange, cover the colorimeter cover, and compare the colors. 6 Test results
If the color index of the rubber sample is within the range of 1 to 5, the nearest half-scale value shall be taken; if it is within the range of 5 to 16, the nearest full-scale value shall be taken. In individual cases, when the rubber is dark yellow, green or gray and color comparison cannot be made, the test report shall state that the color index cannot be determined.
Additional instructions:
This standard is proposed by the Ministry of Agriculture of the People's Republic of China. This standard was drafted by the South China Tropical Crops Product Processing Design Institute. The main drafters of this standard are Liang Senyuan and Zhou Daolong. 138
Xia Run Zao Luo District
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