Recycling opaque Polyethylene terephthalate (PET), which contains 1 to 10 wt % TiO2 submicron particles, has become of interest in the past few years. However, the bottle-to-fiber recyclability of opaque PET has not been assessed yet. In this work, opaque PET packaging has been characterized, and high-speed melt-spun filaments with different amounts of opaque PET (30–50–100%) blended with standard transparent recycled PET (rPET) have been produced in a pilot system. The opaque PET filaments produced have also been compared to a transparent rPET blend with masterbatch PET/TiO2 at different amounts of filler (1–3–6 wt %), produced with the same parameters. The structure-properties relationship of rPET melt-spun fibers has been investigated with crystallinity measurements, amorphous and crystalline phases orientation, and tenacity. It has been observed that the degree of crystallinity, the crystalline and amorphous phases orientation and the tenacity decreases with opaque PET addition and, to a lesser extent, with TiO2 addition. It has been suggested that TiO2 particles are not entirely responsible for the decrease in mechanical properties of opaque PET filaments since opaque rPET filaments have inferior properties to r-PET/TiO2 filaments at the same filler content.

Polyimides are commonly synthesized in a 2-step solution polymerization process. Such process requires long reaction times as well as specific care due to the use of potentially harmful solvents. In the present study, the total reaction time for producing polyimides has been lowered to less than 10 min by using a solvent-free continuous reactive extrusion process. The proof of concept was determined with the system based on 3,3',4,4'benzophenone-tetracarboxylic dianhydride (BTDA) and an aliphatic diamine, Jeffamine D-230 within a micro-extruder. Conversion degrees to polyimide, determined with 13 C NMR and DSC analysis, are over 90 mol% after 5 min of extrusion at 180 °C, 200 °C and 225 °C respectively. These syntheses were then transferred to a twin-screw extruder to form linear aliphatic-aromatic polyimides with two types of dianhydride: BTDA and pyromellitic dianhydride (PMDA). Comparison with a conventional solution polymerization process showed no significant differences in the polymers characteristics. The polyimides produced with this method presented glass transition temperatures ranging from 5 to 90 °C. The number average molar masses measured were between 11000 and 15000 g.mol -1 .

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This work aims to evaluate the spinnability of recycled poly­(ethylene terephthalate) (rPET) modified by chain extenders. Pyromellitic anhydride (PMDA), JONCRYL ADR 4400, 2,2′-bis­(2-oxazoline) (BOZ), and 1,3-phenylene-bis-oxazoline (PBO) were used from 0.1 to 1 wt% on transparent postconsumer PET bottle flakes and opaque rPET flakes containing TiO2 particles. The created molecular architectures were characterized in the first section. Second, their spinnability was assessed via a pilot high-speed spinning process. The corresponding shear rheology, intrinsic viscosity, and elongational rheology were reported. It was observed that PMDA and JONCRYL induce a more drastic increase in melt strength and melt elasticity than BOZ and PBO due to chain branching. In a second step, melt-spun filaments were produced with a low content of chain extenders on standard rPET and opaque rPET matrices. Finally, their degree of crystallinity, molecular orientation, and mechanical properties were determined. PMDA and JONCRYL strongly decrease the spinnability and, consequently, the properties of filaments. However, BOZ improves the opaque rPET filaments’ tenacity while decreasing their degree of crystallinity.

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