Extruded product color was determined with a Konica Minolta
ChromaMeterCR-400 set
to C illuminant/2 observer.
A CIE-Lab color scale was used to measure
the degree of lightness (L*), redness (þa*) or greenness (a*),
and yellowness (þb*) or blueness (b*) of the films. Extruded
products color was measured on the surface of this standard plate
and total color difference (DE*) was calculated as follow: