EFFECT OF DYES ON THE TENSILE PROPERTIES OF COLORED POLY(ETHYLENE-TEREPHTHALATE) FILM

The effect of dye/substrate interaction on the tensile properties of c olored poly(ethylene terephthalate) (PET) film has been examined. The PET is colored with anthracene (AC) and its hydroxyl derivatives (grou p I dyes) as well as with anthraquinone (AQ) and its hydroxyl derivati ves (group II dyes), The offset yield stress of PET colored with anthr arobin (group I B) and with 2,6-dihydroxyanthraquinone (group II H)inc reases respectively by 16 and 12 MPa more than the control. After anne aling, 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 (grou p II E) has a plasticizing effect. Dye H has a slower stress-relaxatio n rate than the control, whereas dye E has a faster rate. As the dye c oncentration in the films increases, the melting points (T-m) of melt- quenched dye/PET mixed systems are depressed. The interaction paramete r between dye and substrate X(1) is obtained using Flory's equation, w hich shows T-m depression of the systems. The values, of X(1) for AC a nd AQ are approximately zero, but other dyes have positive values. The se results suggest that most of dye molecules aggregate in PET because the affinity of dyes for the substrate is inadequate. However, the va lues depend somewhat on the strength of the dye/substrate interaction.