Equilibrium disperse dye sorption by drawn polypropylene films

Abstract

AbstractIsotactic polypropylene (PP) films drawn at various temperatures ranging from 100 to 155°C have been dyed at 80°C with p‐aminoazobenzene (PAAB) or C.I. Disperse Yellow 7 (Y‐7). The equilibrium dye sorption (M0) of PAAB obtained for these films decreased with an increase in draw ratio (λ) of the films. The M0 values of Y‐7, however, increased with increasing in λ similarly the crystallinities of these films increased slightly with draw ratios. By use of fine structural data of these films, the change in M0 of Y‐7 for drawn PP films were analyzed in terms of a mosaic‐block structural model. The increase in M0 with increasing in λ was thus ascribed to enhanced sorption by the amorphous side region between crystalline cores located parallelly in the direction to the molecular axis. The side regions of the drawn systems become rich in interfibrillar tie chains in a higher range of λ. The side region seem to have a strong affinity particularly to a long rodlike dye molecule such as Y‐7; this feature is probably associated with the amount of the amorphous chains having extended chain conformation, the fraction of which increases during drawing.