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

Fabrication of Polyurethane Elastomer/Hindered Phenol Composites with Tunable Damping Property

Vibration and noise-reduction materials are indispensable in various fields. Polyurethane (PU)-based damping materials can dissipate the external mechanical and acoustic energy through molecular chain movements to mitigate the adverse effects of vibrations and noise. In this study, PU-based damping composites were obtained by compositing PU rubber prepared using 3-methyltetrahydrofuran/tetrahydrofuran copolyether glycol, 4,4'-diphenylmethane diisocyanate, and trimethylolpropane monoallyl ether as raw materials with hindered phenol, viz., and 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)proponyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecane (AO-80). Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and tensile tests were conducted to evaluate the properties of the resulting composites. The glass transition temperature of the composite increased from -40 to -23 °C, and the tan δ_Max of the PU rubber increased by 81%, from 0.86 to 1.56 when 30 phr of AO-80 was added. This study provides a new platform for the design and preparation of damping materials for industrial applications and daily life.

Assessment of the Anti-Thrombogenic Activity of Polyurethane Starch Composites

The increasing morbidity and mortality of patients due to post-surgery complications of coronary artery bypass grafts (CABPG) are related to blood–material interactions. Thus, the characterization of the thrombogenicity of the biomaterial for cardiovascular devices is of particular interest. This research evaluated the anti-thrombogenic activity of polyurethanes–starch composites. We previously synthesized polyurethane matrices that were obtained from polycaprolactone diol (PCL), polyethylene glycol (PEG), pentaerythritol (PE), and isophorone diisocyanate (IPDI). In addition, potato starch (AL-N) and zwitterionic starch (AL-Z) were added as fillers. The anti-thrombogenic property was characterized by the clot formation time, platelet adhesion, protein absorption, TAT complex levels, and hemolysis. Additionally, we evaluated the cell viability of the endothelial and smooth muscle cells. Statically significant differences among the polyurethane matrices (P1, P2, and P3) were found for protein absorption and the blood clotting time without fillers. The polyurethanes composites with AL-Z presented an improvement in the anti-thrombogenic property. On the other hand, the composites with AL-Z reduced the viability of the endothelial cells and did not significantly affect the AoSCM (except for P1, which increased). These results classify these biomaterials as inert; therefore, they can be used for cardiovascular applications.

Influence of Starch on the Structure–Properties Relationship in Polyethylene Glycol/Polycaprolactone Diol Polyurethanes

Improvements in the antithrombogenicity activity of biomaterials for cardiovascular applications are necessary to meet the demand for vascular grafts in the world. Zwitterionic compounds tend to be used due to their anti-fouling properties, which reduce platelet adhesions and protein absorptions. Therefore, in this research, potato starch (AL-N) and zwitterionic starch (AL-Z) (obtained by Williamson etherification) were included as fillers in polyurethane (PU) matrices from polycaprolactone diol (PCL), polyethylene glycol (PEG), pentaerythritol (PE) and isophorone diisocyanate (IPDI) in order to study their effect in terms of their physicochemical, mechanical and thermal properties. We conducted our evaluation using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), contact angle analysis, swelling behavior, thermogravimetric analysis (TGA), tensile/strain analysis, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDS), dynamic mechanic analysis (DMA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The results showed that AL-N and AL-Z modified these properties, where AL-N improved tensile strength, and AL-Z increased the hydrophilicity of polyurethanes matrices; additionally, AL-N had interactions with the soft segments, and AL-Z had interactions with the hard segments. Finally, both fillers reduced the degree of crystallinity and did not affect the thermal stability of polyurethanes.

Reactivity of multi-arm polyols towards isocyanates

In this research, the kinetics of the reaction of various polymer polyol crosslinking agents with phenyl isocyanate is reported.

Mechanical Assessment and Hyperelastic Modeling of Polyurethanes for the Early Stages of Vascular Graft Design

The material design of vascular grafts is required for their application in the health sector. The use of polyurethanes (PUs) in vascular grafts intended for application in the body appears to be adequate due to the fact that native tissues have similar properties as PUs. However, the influence of chemical structure on the biomechanics of PUs remains poorly described. The use of constitutive models, together with numerical studies, is a powerful tool for evaluating the mechanical behavior of materials under specific physiological conditions. Therefore, the aim of this study was to assess the mechanical properties of different PU mixtures formed by polycaprolactone diol, polyethylene glycol, and pentaerythritol using uniaxial tensile, strain sweep, and multistep creep-recovery tests. Evaluations of the properties were also recorded after samples had been soaked in phosphate-buffer saline (PBS) to simulate physiological conditions. A hyperelastic model based on the Mooney–Rivlin strain density function was employed to model the performance of PUs under physiological pressure and geometry conditions. The results show that the inclusion of polyethylene glycol enhanced viscous flow, while polycaprolactone diol increased the elastic behavior. Furthermore, tensile tests revealed that hydration had an important effect on the softening phenomenon. Additionally, after the hydration of PUs, the ultimate strength was similar to those reported for other vascular conduits. Lastly, hyperelastic models revealed that the compliance of the PUs showed a cyclic behavior within the tested time and pressure conditions and is affected by the material composition. However, the compliance was not affected by the geometry of the materials. These tests demonstrate that the materials whose compositions are 5–90–5 and 46.3–46.3–7.5 could be employed in the designs of vascular grafts for medical applications since they present the largest value of compliance, ultimate strength, and elongation at break in the range of reported blood vessels, thus indicating their suitability. Moreover, the polyurethanes were revealed to undergo softening after hydration, which could reduce the risk of vascular trauma.

A Fluorescent Polyurethane with Covalently Cross-Linked Rhodamine Derivatives

Rhodamine derivatives (RDs) with three reactive hydrogens were synthesized and well characterized by Fourier transform infra-red spectroscopy (FTIR), 1H nuclear magnetic resonance (1H NMR) and electrospray ionization mass spectra (ESI mass). Then, the obtained RD was covalently cross-linked into polyurethane (PU) matrix through chemical linkages to fabricate a network structure, and the fluorescent properties, mechanical properties, thermal stability, and emulsion particle size were systematically investigated. Results demonstrate that PU-RD maintains initial fluorescent properties and emits desirable yellow fluorescence under ultraviolet irradiation. Moreover, compared with linear PU without fluorescers, PU-RD shows clearly improved mechanical properties and thermal stability, on account of the formed network structures.