Newly UV-Curable Polyurethane Coatings Prepared by Multifunctional Thiol- and Ene-Terminated Polyurethane Aqueous Dispersions: Photopolymerization Properties

A novel approach toward the preparation of newly UV-curable polyurethane coatings composed of multifunctional thiol- and ene-terminated polyurethane aqueous dispersions is presented. By a synergistic combination of polyurethane dispersions synthesis and thiol-ene chemistry, strategies for the preparation of newly UV-curable polyurethane coatings are developed. Photo-DSC, real-time FTIR, DMA and tensile tests measurements are used to investigate the photopolymerization and mechanical behaviors of newly UV-curable polyurethane coatings. The newly polyurethane coatings have 1.5 times higher polymerization rate and final 99% functional groups conversion in air conditions compared to current urethane-acrylate based UV-curable polyurethane dispersions coatings. UV-cured polyurethane films prepared by this method are also found to exhibit increase in Young\u27s modulus and tensile strength at break by 25% and 10%, respectively. These experiment facts suggest that the incorporation of thiol-ene chemistry to the polyurethane dispersion coatings increase their polymerization rate, producing a high degree of cross-linking. This confirms the preparation of the targeted novel UV-curable polyurethane coatings and reveals the dramatic effect that changes in incorporation of thiol-ene chemistry can have on the photopolymerization behaviors of UV-curable polyurethane dispersions coatings systems. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved

Newly UV-Curable Polyurethane Coatings Prepared by Multifunctional Thiol- and Ene-Terminated Polyurethane Aqueous Dispersions Mixtures: Preparation and Characterization

A series of newly developed UV-curable polyurethane coatings were prepared by blending multifunctional thiol- and ene-terminated polyurethane aqueous dispersions. The composition, structure, solution stability and mechanical properties of the title coatings were characterized in detail by FT-IR, photo-DSC and DMA measurements. It was found that the resulting polyurethane coatings showed good solution stability and high photopolymerization activity even after a long time (i.e. 1 month). The incorporation of a waterborne polyurethane chain into the both multifunctional thiols and ene monomers promoted their solution stability and avoided any reaction between thiols and ene groups as a result of their high reacting activity in non-aqueous systems. UV-cured films prepared by this method were found to exhibit excellent physical properties with improvements over what can be attained directly with current UV-curable urethane-acrylate based systems. This method allows for the preparation of high performance UV-curable polyurethane aqueous coatings based on thiol-ene chemistry systems. (C) 2008 Elsevier Ltd. All rights reserved

Exosomal CircHIPK3 Released from Hypoxia-Induced Cardiomyocytes Regulates Cardiac Angiogenesis after Myocardial Infarction

Exosomes play critical roles in mediating cell-to-cell communication by delivering noncoding RNAs (including miRNAs, lncRNAs, and circRNAs). Our previous study found that cardiomyocytes (CMs) subjected to hypoxia released circHIPK3-rich exosomes to regulate oxidative stress damage in cardiac endothelial cells. However, the role of exosomes in regulating angiogenesis after myocardial infarction (MI) remains unknown. The aim of this study was to establish the effects of exosomes derived from hypoxia-induced CMs on the migration and angiogenic tube formation of cardiac endothelial cells. Here, we reported that hypoxic exosomes (HPC-exos) can effectively reduce the infarct area and promote angiogenesis in the border surrounding the infarcted area. HPC-exos can also promote cardiac endothelial cell migration, proliferation, and tube formation in vitro. However, these effects were weakened after silencing circHIPK3 in hypoxia-induced CMs. We further verified that silencing and overexpressing circHIPK3 changed cardiac endothelial cell proliferation, migration, and tube formation in vitro by regulating the miR-29a expression. In addition, exosomal circHIPK3 derived from hypoxia-induced CMs first led to increased VEGFA expression by inhibiting miR-29a activity and then promoted accelerated cell cycle progression and proliferation in cardiac endothelial cells. Overexpression of miR-29a mimicked the effect of silencing circHIPK3 on cardiac endothelial cell activity in vitro. Thus, our study provides a novel mechanism by which exosomal circRNAs are involved in the communication between CMs and cardiac endothelial cells

Microstructure and mechanical properties of laser welded hot-press-formed steel with varying thicknesses of Al–Si coatings cleaned by nanosecond pulsed laser

The Al–Si coatings are commonly used for hot-press-forming (HPF) steel to prevent oxidation in the automobile industry. However, due to the presence of Al–Si coating, undesirable intermetallic compounds are easily formed in the welds of HPF steel. In this work, an environment-friendly and effective nanosecond pulsed laser cleaning process was used to remove the Al–Si coating, and HPF steel with varying thicknesses of coatings was prepared for laser welding. The microstructure and mechanical properties of laser welded HPF steel with different thicknesses of coatings were further investigated. The results showed that there was a threshold of power to remove the Al–Si coatings in the laser cleaning process. The reduced thickness of coatings not only could improve the stability of the welding process due to the diminishing of metal vapor generated by coating ablation, but also decrease the content of the Fe–Al phase in the welded joint, which is detrimental to weld performance. The tensile strength and cupping test pass rate of weld joints gradually increased with the decreasing thickness of coatings to 5 μm. After that, the Al–Si coating almost had no effect on the mechanical properties of the laser weld joints. The laser weld joint with 5 μm-thick of Al–Si coating showed, a tensile strength of 1435.05 MPa, a microhardness of 488.38 HV and a pass rate of 100% for the cupping test