Tuning thermal, morphological, and physicochemical properties of Thermoplastic Polyurethanes (TPUs) by the 1,4-butanediol (BDO)/dipropylene glycol (DPG) ratio

Thermoplastic polyurethanes (TPUs) are versatile polymers presenting a broad range of properties as a result of their countless combination of raw materials—in essence, isocyanates, polyols, and chain extenders. This study highlights the effect of two different chain extenders and their combination on the structure–property relationships of TPUs synthesized by reactive extrusion. The TPUs were obtained from 4,4-diphenylmethane diisocyanate (MDI), polyester diols, and the chain extenders 1,4-butanediol (BDO) and dipropylene glycol (DPG). The BDO/DPG ratios studied were 100/0, 75/25, 50/50, 25/75, and 0/100 wt.%. The TPUs were characterized by size exclusion chromatography (SEC), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), UV–vis spectroscopy, and physical-mechanical properties. The results indicate that DPG promotes compatibility between rigid (HS) and flexible (SS) segments of TPUs. Consequently, increasing DPG content (>75 wt.%) reduced the organization of the rigid segments and the degree of phase separation, increasing the polydispersity of the interdomain distance and the transparency in the UV–visible spectrum of the TPUs. Furthermore, increasing DPG content also reduced the amount of hydrogen bonds present in the rigid phase, reducing or extinguishing its glass transition temperature (TgHS) and melting temperature (Tm), and increasing the glass transition temperature of the flexible phase (TgSS). Therefore, increasing DPG content leads to a deterioration in mechanical properties and hydrolysis resistance

Recycling Tetrafluoroethylene–Perfluoroalkyl Vinylether Copolymer (PFA) Using Extrusion Process

Abstract Tetrafluoroethylene–perfluoroalkyl vinylether copolymer (PFA) has a broad application ranging from biomedical and aerospace to corroding environments in the chemical industry. Despite a low share in end‐of‐life products, PFA processing can produce up to 30% of waste. Thus, understanding how recycled fluorinated polymers affect product performance is crucial to ensure primary recycling, besides economic and environmental reasons. In this paper, the utilization feasibility of PFA waste materials is investigated, i.e., recycled PFA (PFAr) in closed‐loop recycling. The effect of PFAr loading (5–100 wt.%) on the thermal, mechanical, rheological, and color properties and chemical resistance are studied. Thermal properties and chemical resistance showed no significant changes in all ranges of PFAr content tested. The addition of higher loads of PFAr (≥50 wt.%) leads to a reduction in mechanical properties, particularly stress‐strength analysis and elongation at break. However, elastic modulus and hardness have improved concurrently with an increase in the degree of crystallinity. The decrease in complex viscosity and yellowing of the samples occurred probably induced by a polymer chain degradation. Despite that, the addition of up to 10 wt.% of PFAr proved to be an effective alternative to reusing PFA residues based on mechanical recycling