A Chain-Intrinsic Fluorescence Study of Orientation-Strain Behavior in Uniaxially Drawn Poly(ethylene terephthalate) Film

Abstract

The chain-intrinsic fluorescence technique was used to investigate the development of orientation in the noncrystalline phase of PET film during drawing at 90 "C. It was confirmed that orientation develops faster at higher strain rate. In the low draw ratio (precrystallization) regime, the orientation-strain data at high strain rate can be fitted to the affine network model, but at low strain rate, where relaxation effects are substantial, this model is not applicable. We found considerable deviation from the linear stress-optical law: it appears that a stress threshold must be reached before significant orientation takes place and that the threshold value increases with strain rate. Crystallization onset seems to increase the rate of development of orientation at the lower strain rate, probably by providing additional junction points. At both high and low strain rates, however, there eventually occurs an abrupt decrease in the rate of development of orientation (and crystallinity) which coincides with a sharp increase in stress. By comparing our data to some results in the literature on uncrystallizable PEMT, we infer that the slowing of orientation development arises from chain slippage and that the increase in stress largely results from the reinforcing effect of crystallites and an increase in polymer viscosity arising from the interconnection of crystallites.

Interfacial adhesion of nanoparticles in polymer blends by intrinsic fluorescence spectra

“…Actually, the intrinsic fluorescence of polymers (e.g. polystyrene) has also been shown to be highly sensitive to issues ranging from local polymer conformational populations in solution and phase behavior in solvents and polymer blends to local microenvironments in bulk homopolymers [26][27][28][29][30]. Thus, intrinsic fluorescence was employed to investigate the phase separation behavior of polymer blends in our work.…”

Modeling morphology evolution and mechanical behavior during thermo-mechanical processing of semi-crystalline polymers

“…Salem (1992a, b) demonstrated from experimental work that the relaxation effect is dominant, and the onset of SIC is delayed at lower strain rates. Higher strain rates reduce the degree of chain relaxation at a given strain level, resulting in more preferred orientation and increased likelihood for crystal nuclei to form (Le Bourvellec et al, 1986;Salem, 1992aSalem, , b, 1998Clauss and Salem, 1995), even at lower strains.…”

Intrinsic fluorescence studies of compatibility in thermoplastic phenol formaldehyde resin / poly(ε-caprolactone) blends

“…In addition, in most of the fluorimetric studies of polymer, the fluorescent probe was covalently attached to one of the polymers, which in fact changed the microenvironment of macromolecules and made the macromolecules more hydrophobic, thus enhancing their complexation ability. It is worth noting that the intrinsic fluorescence of polymers has also shown to be highly sensitive to issues ranging from local polymer conformational populations in solution and phase behavior in solvents and polymer blends to local microenvironments in bulk homopolymers [20][21][22][23]. Due to its intrinsic sensitivity, this fluorescence method also proved to be powerful in the study of small-scale phase separation and low-concentration miscibility [24].…”