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Spectrophotometer for YI Measurement of Transparent Plastic Sheet

Plastic Industry | 2017-07-29 18:05:23

The yellowness index(YI) is used to characterize the degree of yellowing of a white sample, which may be transparent or opaque. The yellowness index and the degree of yellowing observed under daylight can be matched, so the quality of the plastic and the degree of aging can be well evaluated. The yellowness index is calculated as follows: YI = 100 (1.28X-1.06Z) / Y. Where X, Y and Z are the tristimulus values representing the color of the material measured by a spectrometer, colorimeter or spectrophotometer in standard C light source. CS-580, CS-600, CS-610, CS-650, CS-660 spectrophotometer made by CHNSpec Technology are able to test the yellowness index(YI).

color management system


Today we will introduce how to measure it.

Instrument: CS-600 Portable Spectrophotometer Made by CHNSpec Technology

Measurement Condition: Standard C Light Source, color temperature 6774K, A light source (color temperature of 2856K inflatable spiral tungsten lamp, the light color yellow) plus cover C-D-G liquid filter composition, the light color is equivalent to the cloud of sky light.

Observer Angle: 2°

Measurement Range: YI for transparent, translucence and white opaque plastic sheets. It is suitable for plastic sheets, plastic pieces, plastic film, plastic pellets and powder plastic. It is not suitable for measuring the plastic containing fluorescent substances.


Measurement Step

Step 1. Prepare the instrument and samples. From left to right, sample 1,sample 2 and sample 3.

Sample 1 is new sample. Sample 2 is aged for 12 hours, Sample 3 is aged for 24 hours.

color management system


Step 2. Calibrate the instrument : Put the instrument on calibration tile. 

sphere spectrophotometer


Step 3. After calibration, press “up” or “down” to choose “measure setting” and then press “enter” to enter into measure setting page. Choose “YI”, “C light source” and “observer angle 2°”.

sphere spectrophotometer


Step 4. After we finish the measurement setting, we could start to test. When we measure the YI of plastic sheet, we need hold the sample in the air for measurement to make sure no object is under it. Then press “print” to view the measurement area. At last, press “test”, after hearing the sound of “beep”, we could see the testing result.

color spectrophotometer delta E


Step 5. Measure other 2 samples as same procedure, we will get all sample YI values.

color spectrophotometer delta E

After we finish measurement, △YI represents the yellowness index difference value. According to the testing result, we could know that longer aging time of the sample, the greater of the yellow index. Instrument methods for measurement of YI provide more objective data than the subjective viewing of YI by a small number of individuals. Our instrument could meet the manufacturer’s requirement for the plastic sheet quality control without any problem.


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