The effects of the inclusion of 1,2,4-triazole derivatives into the main chains of the polyurethane urea exposed to UV radiation

Linear polyurethane urea containing 1,2,4-triazole segments was obtained by polyaddition of the 3,5-diamino-1,2,4-triazole (DATA) to urethane prepolymer. Also, three crosslinked polymers with different crosslinkers (2,4,6-triaminopyrimidine (TAP), glycerin (Gly), castor oil (CO)) were synthesized. Thermogravimetric analysis, of the obtained polymers, indicated good thermal stability up to 310°C. The polyurethane urea chemical structure was confirmed by FTIR analysis. The glass transition temperatures (Tg) of these polymers, measured by differential scanning calorimetry (DSC), were found in the range of −52°C to −56°C. These values were not significantly influenced by the structure of the hard domain and the intermolecular interactions. The tensile testing showed that the inclusion of 1,2,4-triazole in polyurethane structure substantially improves the tensile strength up to 58 MPa. The obtained polyurethane urea presents surface slight hydrophobic and low interfacial tension. The positive effect of the 1,2,4-triazole segment from the polymer main chain in the UV aging process of these polymer materials has been studied. After exposure to UV radiation, few changes were observed in the molecular structure, in the surface morphology and the mechanical properties.

Effect of Thermal Aging on the Physico-Chemical and Optical Properties of Poly(ester urethane) Elastomers Designed for Passive Damping (Pads) of the Railway

The aim of this study consists of monitoring the effect of thermal aging on the physico-chemical and optical properties of poly(ester urethane) elastomers designed as damping materials for railways. The materials were obtained by polyaddition in two stages in melt, resulting in regular structures. The structural modifications during the thermal aging of the samples were monitored using FTIR, color changes, TGA in non-isothermal and isothermal conditions, DSC and physico-mechanical measurements. The structural regularity of the rigid and flexible segments maintained the good mechanical properties of the structures up to 200 h of thermal aging at the elevated temperatures of 40 °C, 70 °C, 100 °C and 130 °C. It was observed that at 40 °C and low exposure times, changes occur mainly to the carbonyl groups of the soft segments. At higher temperatures and longer exposure times urethane groups were affected. Extended thermal aging led to significant changes in thermo-mechanical and optical properties.

Synthesis and properties of shape memory polyurethanes generated from schiff-base chain extender containing benzoyl and pyridyl rings

In this study, 4,4′-diphenylmethane diisocyanate and polytetramethylene glycol were used to prepare a prepolymer; N,N′-bis(4-hydroxybenzylidene)-2,6-diaminopyridine (BHBP) was used as a chain extender; and these elements were combined to prepare a novel polyurethane, BHBP/PU. Gel permeation chromatography revealed that the molecular weight of the BHBP/PU samples increased as the BHBP content was increased. Fourier transform infrared spectroscopy demonstrated that high BHBP content facilitated strong hydrogen bonding in the samples. Differential thermogravimetry indicated that the initial decomposition temperature of BHBP/PU-3 was approximately 10 °C higher than that of BHBP/PU-1. Differential scanning calorimetry and dynamic mechanical analysis revealed that increasing the BHBP content substantially increased both the glass transition and dynamic glass transition temperatures of the BHBP/PU samples. The tensile strengths of BHBP/PU-1, BHBP/PU-2, and BHBP/PU-3 were 7.7, 10.9, and 21.6 MPa, respectively, with corresponding Young’s moduli of 0.7, 1.9, and 3.3 MPa. These results demonstrated that both the tensile strength and Young’s modulus of the BHBP/PU samples increased as the BHBP content was increased. Moreover, the BHBP/PU samples exhibited excellent shape recovery of >90%.