OptLab-SPX    Determination of Haze

The haze of a transparent sample, e.g. a transparent plastics pane, describes the amount of light scattering, when the light passes the sample. It is defined as the percentage of transmitted light, which in passing through the specimen deviates from the incident beam by forward scattering. Thus haze results help to quantify surface or internal specimen defects that might disturb clear vision.

The procedure for measuring haze is described in the norm ASTM D 1003. The norm describes the measurement of 4 spectra: two spectra without sample and two spectra with the sample. One measurement is performed as the baseline correction run. For each measured spectrum, the Luminous Transmittance is calculated. The Luminous Transmittance values are combined to generate the % Haze value of the sample. The evaluations are given below.

For measurement, a recording spectrophotometer equipped with an integrating sphere is applied. The sphere and the beam geometry must fulfill certain conditions. The main measurement is the measurement of the diffuse transmittance of the sample. This is done by placing the sample before the integrating sphere and leaving the reflectance port open. Additional measurements are done to determine the diffuse transmittance spectrum of the sphere itself and to determine the total transmittance (directed and diffuse) of the sample. All measurements are referenced against the total transmittance data of the integrating sphere (without sample). On a modern spectrophotometer this is handled by the obligatory background correction run internally and must not be considered with the calculations.

OptLab3_e

OptLab-SPX guides the user through the required measurements and automatically generates the single Haze value of the sample as an important quality criterion for transparent polymer materials.