Effect of polypropylene morphology on thermal cis-trans isomerization and photofading of some azo dyes: A kinetic study

✍ Scribed by Pier Luigi Beltrame; Ernestina Dubini Paglia; Bruno Marcandalli; Alberto Seves

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 493 KB
• Volume: 38
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1989.070380413

✦ Synopsis

Five polypropylene films were prepared having different crystallinity and morphology, the latter having been modified by stretching. They were colored with azo dyes XC6H4N=N&H4N(C,H5), (where X=H, OCH,, CN, and NO,). The kinetics of the thermal cis-trans isomerization of these dyes has been studied in the range 21-4loC, much above the glass transition temperature of the polymer. The isomerization process was found to be strictly first-order; the kinetic parameter values have been correlated with the free volume extent in the amorphous regions of the matrix. Lightfastness of the dyes in the polymer matrices has been also investigated: It appeared to be more important for the unoriented samples with respect to the stretched ones and substantially independent on the crystallinity degree.