Quantitative determination of color of crystalline poly(ethylene furandicarboxylate) with integral of absorbance in the visible region

Poly(ethylene furandicarboxylate) (PEF) is prone to discolor and its color is an important quality index. However, in the case of crystalline PEF, its chromatic values (CVs) measured by colorimeter are underestimated significantly due to whitening caused by crystallization and thus does not reflect its true/intrinsic color correctly. In this study, the CIELAB CVs ( L *, a * and b *) and UV–vis spectra of 35 amorphous PEF samples were measured. A new comprehensive CV (Δ E 6 ) is defined from CIELAB CVs and used to characterize the color of PEF. A quaternary power function model between Δ E 6 and integrals of absorbance of PEF solution in yellow, red, blue and green visible sub-regions is established. Δ E 6 agrees well with those calculated from absorbance integrals. As the absorbance measurement is convenient and not affected by crystallization, this model can be used to measure real/intrinsic color of crystalline PEF as well as amorphous one.