Improving Poly(ethylene terephthalate) Through Self‐nucleation

Abstract

As‐received poly(ethylene terephthalate) (asr‐PET) may be reorganized by precipitation from trifluoroacetic acid upon gradual addition to a large excess of rapidly stirred acetone (p‐PET). Unlike asr‐PET, p‐PET repeatedly crystallizes rapidly from the melt, and can be used in small quantities (a few %) as an effective self‐nucleating agent to control and improve the bulk semi‐crystalline morphology and properties of asr‐PET. Nuc‐PET film has significantly increased hardness and Young's modulus and is much less permeable to CO2, while its un‐drawn fibers exhibit higher tenacities and moduli. Because nuc‐PET contains no incompatible additives, it may be readily recycled.

Enhancing the melt crystallization of polymers, especially slow crystallizing polymers like PLLA and PET

“…Though not shown here, reducing the amount of p‐PET added to asr‐PET to 2 wt% yielded a nuc‐PET showing DSC behavior similar to that seen in Figure for asr‐PET nucleated with 5 wt% p‐PET . Glass‐transitions observed in both the cooling and subsequent heating scans of the asr‐PET nucleated with 2 wt% p‐PET was the only difference.…”

“…Our initial motivation was the improvement in the properties of PET by processing with cyclodextrins (CDs) . During several control experiments performed during the formation of c‐PET, we noticed that PET rapidly precipitated (p‐PET) from a trifluoroacetic acid (TFA)/chloroform solution upon slow addition to rapidly stirred acetone, evidenced behavior closely similar to that of c‐PET obtained from its γ‐CD‐IC . Because p‐PET is also repeatedly and rapidly crystallize from its melt, it could also be used to nucleate the melt‐crystallization of asr‐PET.…”

“…First cooling (−50°C/min) and second heating (20°C/min) DSC scans for asr‐, precipitated (p) or coalesced (c), and self‐nucleated (nuc) PET (95% asr‐PET/5% p‐PET), with publisher permission …”

“…It is important to mention that the DSC scans of p‐ and nuc‐PET remained unchanged by repeated cycling between their melts and semi‐crystalline solids . Because they are able to develop their full semi‐crystalline morphologies upon cooling from their melts, p‐ and nuc‐PETs should retain their as‐ processed mechanical properties at temperatures approaching their melt, without the need for extended annealing above T g .…”

Self‐nucleation–induced nonisothermal crystallization of nylon 6 from the melt

“…Self‐nucleation has much influence on polymer morphology, crystal form, and polymer properties because there is a wide temperature range where un‐molten crystallites and molten polymer co‐exist . Over the past decades, self‐nucleation has been extensively used to affect crystallization behavior of polymers, polymer blends, and block copolymers …”