ASTM D1925 PDF

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ASTM D [ Withdrawn ]. Standard Test Method for Yellowness Index of Plastics. standard by ASTM International, 01/22/ View all. wnessIndex was developed for the definition of the Yellowness of homogeneous, non-fluorescent, almost. Yellowness – ASTM D A measure of the yellowing of a plastic, such as might occur after long-term exposure to light. The deviation in chroma from.

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Whiteness and Yellowness Indices in a SpectroEye Yellowness Yellowness is defined as a measure of the degree to which the color of a surface is shifted from preferred white or colorless towards yellow. Yellowness, as defined by ASTM Ehas been applied successfully to a variety of white or near-white materials, including paints, plastics, and textiles. Its derivation assumed that, because of the limitation of the concept asrm yellow or blue colors, it was necessary to take account of variations in the amber or red colorimeter readings.

Yellowness according to ASTM E D was developed specifically for determining the yellowness of homogeneous, non-fluorescent, nearly colorless, transparent, nearly white translucent, or opaque plastics, as viewed under daylight lighting conditions. It can also be applied to materials other than plastic fitting this description. The indices can be calculated, rounded, and adjusted in the last retained aetm digit to minimize the residual error in the white point values. Whiteness Whiteness atsm defined as a measure of how closely a surface matches the properties of a perfect reflecting diffuser, i.

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Whiteness and Yellowness Indices in a SpectroEye

For the purposes of this standard, the color of such a surface is known as asstm white. This method is based on the use of colorimeter readings B and G. The idea was that chromaticity factor G-B required three times the weighting of the lightness factor G of the lightness. However, the equation is commonly used with other illuminants and xstm functions, therefore the value shown will depend on the primary illuminant and the observer function you have chosen.

ASTM D Standard Testing Instruments

Stensby — based on Hunter Lab color coordinates. Values greater than indicate a bluish white, while values less then indicate a yellowish white. It entails a filter with a maximum transmission curve of nm wavelength lambda and a specific half peak width. Standard ISO specifies a half peak width of 44 nm.

The ISO brightness value indicates xstm blue reflection of the paper. In the case of non lightened samples, standard illuminant C, i. Standard illuminant D65 must be used for measurement of optically lightened papers. The optical lightener is effective only xstm to the UV radiation.

The effect occurs 1d925 approximately nm; maximum radiation is at approximately nm. It should be clear that the distribution of relative spectral radiation of the light on the sample during measurement plays an important role.

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The greater the illumination intensity zstm the UV-range, the more the greater the detection of the optical lightener. However, this also intensifies ISO brightness. Comparable values between two instruments can be obtained only when both are measured with the same light.

Yellow Index YI caculation standard E D_图文_百度文库

CIE Whiteness — Some disadvantages of the previously-mentioned indices is that a whiteness that is calculated with this formula does not differ if the measured sample has a color drift or is just less white.

However, the equation is commonly used with other illuminants; therefore the value shown will depend on the primary illuminant you have chosen. What is mainly annoying with the one-dimensional white evaluation is, that in the same measurement value there is a quality valuation How white is the sample? The color deviation number Tw shows additionally, if there is a red hue negative value of Tw or a green hue positive value of Tw.

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