Tunable ionization degree in cationic polyurethanes and effects on phase separation

Ecofriendly Dyeing Strategy Based on Dyeing Kinetics and Thermodynamic Analysis for Melt-Spun Polyurethane Fibers

Melt-spun polyurethane fibers (MSPUFs) have garnered popularity owing to efficient production methods and exceptional stability. However, the development of the MSPUF has been restricted by challenges such as poor dyeability as well as energy and cost concerns associated with the dyeing process. Herein, we devised a highly efficient dyeing technique that operates at a lower temperature and a shorter duration. In comparison to conventional dyeing methods, our novel approach reduces the temperature from 98 to 75 °C, while reducing the amount of dye utilized by 25% and the dyeing time by 50%. In this method, the modifier increases both the positive charge and the amorphous zone of the fiber, while rational dyeing conditions are designed based on thermodynamic and kinetic analyses. This strategy enabled a 76.3% increase in E% and a 45.9% increase in K/S values at reduced temperatures and a shorter time while simultaneously improving the dye-fiber bonding fastness. This research methodology not only enhances the dyeing performance of MSPUF but also reduces energy consumption and dyeing costs, presenting an ecofriendly and economically novel approach for the development of dyeable MSPUF.

Influence of the Molecular Weight of the Polycarbonate Polyol on the Intrinsic Self-Healing at 20 °C of Polyurethanes

Different polyurethanes (PUs) were synthesized with polycarbonate polyols of molecular weights of 500, 1000, and 2000 Da. Their self-healing abilities at 20 °C were tested, and their structural, thermal, and mechanical properties were analyzed. The PUs made with polycarbonates of molecular weights 500 (YC500) and 1000 Da (YC1000) exhibited self-healing at 20 °C, and the self-healing time of YC1000 was the shortest. The absence of crystallinity and the low degree of micro-phase separation favored self-healing at 20 °C in YC500. However, the presence of tack and the existence of allophanate species and urethane-carbonate and urea-carbonate hydrogen bonds disfavored self-healing. Consequently, the self-healing time at 20 °C of YC500 was longer than expected. On the other hand, YC1000 exhibited an "equilibrium" between urethane-carbonate and urea-carbonate hydrogen bonds and carbonate-carbonate interactions among the soft segments, so a particular structural order was produced that was associated with its fastest self-healing at 20 °C. The PU made with the polycarbonate of molecular weight 2000 Da did not exhibit self-healing at 20 °C because of its significant micro-phase separation, the presence of semi-crystalline soft domains, and the lower density of hydrogen bonds.

Influence of Polyol/Crosslinker Blend Composition on Phase Separation and Thermo-Mechanical Properties of Polyurethane Thin Films

Polyurethanes (PUs) from Polyethylene glycol (PEG) and polycaprolactone diol (PCL) and a crosslinker, Pentaerythritol (PE), were synthetized with isophorone diisocyanate (IPDI). In this study, we investigated the effect of polyol and crosslinker composition on phase separation and thermo-mechanical properties. The properties were studied through dynamic mechanical analysis, X-ray scattering, atomic force microscopy (AFM), and thermogravimetric analysis (TGA). The results showed changes in PUs properties, microphase structure, and separation due to the composition of polyol/crosslinker blend. So, the largest concentration of PE produced multimodal loss factor patterns, indicating segment segregation while PUs with a PEG/PCL = 1 displayed a monomodal loss factor pattern, indicating a homogeneously distributed microphase separation. Additionally, the increase of the PEG concentration enhanced the damping capacity. On the other hand, agglomeration and thread-like structures of hard segments (HS) were observed through AFM. Finally, the thermal behavior of PUs was affected by chemical composition. Lower concentration of PE reduced the crosslinking; hence, the temperature with the maximum degradation rate.