Effect of Dyes on the Tensile Properties of Colored Poly(ethylene Terephthalate) Film

The effect of dye / substrate interaction on the tensile properties of colored poly(ethylene terephthalate) (PET) film has been examined. The PET is colored with anthracene (AC) and its hydroxyl derivatives ( group I dyes) as well as with anthra quinone (AQ) and its hydroxyl derivatives ( group II dyes). The offset yield stress of PET colored with anthrarobin (group IB) and with 2,6-dihydroxyanthraquinone (group II H) increases respectively by 16 and 12 MPa more than the control. After annealing, the values increase further by 7 and 5 MPa, respectively. This reinforcing effect is thought to arise from the formation of hydrogen bondings between dye and substrate, while 1-hydroxyanthraquinone (group II E) has a plasticizing effect. Dye H has a slower stress-relaxation rate than the control, whereas dye E has a faster rate. As the dye concentration in the films increases, the melting points ( T m ) of melt-quenched dye/PET mixed systems are depressed. The interaction parameter between dye and substrate X 1 is obtained using Flory's equation, which shows T m depression of the systems. The values of X 1 for AC and AQ are approximately zero, but other dyes have positive values. These results suggest that most of dye molecules aggregate in PET because the affinity of dyes for the substrate is inadequate. However, the values depend somewhat on the strength of the dye/substrate interaction.