Abstract The dichroism of polypropylene film dyed with C. I. Disperse Yellow 7 was investigated at various temperatures up to 160°C. The dichroic value D drops as the temperature is raised. So long as the amorphous structure does not change irreversibly, D changes reversibly with temperature. The experimental results agree qualitatively with those obtained on poly(ethylene terephthalate) in our previous paper, although the effect of temperature on the extent of the reversible change in D is larger in PP than in PET. The plot of D versus temperature exhibits breaks at 40°–50°C ( T 0 ), 70°–80°C ( T 1 ), and 115°–120°C ( T 3 ). These temperatures agree with the transition points of polypropylene in the literature. From the change in the intrinsic dichroism D 0 with temperature, it is concluded that the decrease in D at high temperatures is due to the drop of D 0 caused by the disorientation of dye molecules in the amorphous region, while the amorphous polymer chain is not disoriented. Such a conclusion is supported by the fact that Δ n of a heat‐set specimen is kept constant during heating, in contrast to D .
The dielectric constant ( ε '), dielectric loss factor ( ε ''), and dielectric loss tangent ( tan δ) of polychlorotrifluoroethylene were calculated using the relaxation parameters derived from the thermal sampling TSDC analysis. Numerical results of dielectric data were represented by three-dimensional (3-D) and/or two-dimensional (2-D) spectra and were compared with the available experimental data. The progression of ε '' in a simulated 3-D spectrum revealed that the incorporation of two γ relaxation modes ( γ a and γ c ) occurred near 1 Hz resulting in the formation of a single peak.
Polyamide 11 (PA11) and epoxy group modified polyethylene (EGMA) were melt-blended in a segment mixer at 230 degrees C. The reactive nature of the blend is reflected in the mixing torque behavior of the blend at different compositions. The dynamic mechanical analysis reveals shifted glass transition temperatures for both PAl 1 and EGMA, indicating the improved miscibility by the reactive blending. Transmission electron microscopy (TEM) shows that EGMA is precisely dispersed in PAl 1 matrix with the domain size of several hundred nanometers for the reactive blends. The mechanical properties were also measured for the obtained material and it exhibits greatly improved impact strength as compared with the neat PA11. In addition, the toughening mechanism for the blend system was also studied.
Melt-extruded sheets of blends of recycled poly(ethylene terephthalate) (R-PET) with poly(ε-caprolactone) (PCL) were exposed to plasmas of different reactivity; non-oxidative Ar and N 2 , and oxidative O 2 . Mass loss by etching and morphology changes to the surfaces were investigated with regard to the discharge power effects as well as the plasma gas source reactivity. The sheets of PCL and PCL-rich blends were more susceptible to the oxidative plasmas, although still resistant to non-oxidative plasmas. Generation of microstructures was observed on wavy or granular forms of morphology of the original sheets after the plasma treatments, according to the SPM observations.
The visible dichroism (D) of poly (ethylene terephthalate) film dyed with C. I. Disperse Yellow 7 or C. I. Disperse Red 17 was measured at 20_??_180°C. and the temperature effect on D was investigated. For this purpose a spectrophotometer equipped with a specially designed heating cell was used. Dyed PET films were prepared in two ways: (A) Undrawn film was dyed (70°C., 20 hr.) and then drawn (68°C.), and (B) Undrawn film was drawn (57 or 68°C.), heat-treated (190°C.) and then dyed (130°C., 90 min.).The results are following:(1) The measurements of D at elevated temperatures could be carried out as accurately as in the usual measurement at room temperatures.(2) D decreases linearly as the temperature is elevated. In the case of films which have never been heat-treated above 120°C., two inflection points appear on heating in the relation D vs temperature at 80°C. and 120°C., and the change of D with temperature is irreversible, whereas in the case of films previously subjected to heat-treatment above 120°C., D changes reversibly when the temperature of the film remains below the temperature of treatment and the inflection point at 80°C. can hardly be observable.From this phenomenon it is concluded that D of the heat-treated or thermally contracted PET, measured even at room temperature, indicates correctly the degree of amorphous orientation of polymer changed through the treatment and the intrinsic dichroism of the dyed polymer remains constant. As to the 120°C. inflection point, it is attributed to another transition point of the amorphous region remaining in PET after the cold crystallization.
Abstract Visible dichroism can be utilized as a measure of the degree of orientation of an amorphous region in a polymer. But the relations between dichroism and states of dyes in polymer must be elucidated before dichroism can be used more widely as a reliable means for study of amorphous orientation. To calculate the orientation factor for visible dichroism, it is necessary to decide the dichroism of an ideally oriented polymer chain. For this purpose, a single crystal of Congo Red was prepared and the dichroic spectrum of the crystal was measured. It was found that the dichroism of the Congo Red molecule itself is unity in a suitable wavelength region. As a result, a simple means for the treatment of dichroic spectra was given. The angle between the polymer chain axis and the principal axis of the absorbed dye molecule was discussed.
