Synthesis and properties of waterborne UV‐curable polydimethylsiloxane‐based polyurethane oligomers: UV‐cured film with excellent water resistance and thermostability

Abstract

This paper designed and synthesized a series of waterborne UV-curable polydimethylsiloxane‐based polyurethane oligomers which contain polydimethylsiloxane segment in the end of the main chain, a plurality of double bonds in the side chain and two kinds of hydrophilic groups including nonionic polyethylene glycol with low molecular weight and ionic quaternary ammonium salt groups. The unique structure endowed not only the oligomer with an excellent water solubility, but also the UV-cured film with hydrophobicity, thermostability and mechanical properties. The prepared oligomers could form a stable white emulsion and had excellent photopolymerization capability, and their conversions of double bonds were all over 92%. The UV-cured film containing long chain polydimethylsiloxane exhibited better hydrophobicity, heat resistance and tensile strength. The polydimethylsiloxane segment located in the end of the oligomer molecular chain was more conducive to its enrichment in the surface of the cured films and improving of the hydrophobicity of the cured films. The water absorption, surface water contact angle and the initial decomposition temperature (T_5%) of the obtained UV-cured films were 2.7%, 91 and 301?°C, respectively.     

Using a β-Cyclodextrin-functional Fe3O4 as a Reinforcement of PLA: Synthesis,Thermal, and Combustion Properties

In this work, Fe₃O₄ nanoparticles were chemically grafted with β-cyclodextrin (β-CD@Fe₃O₄). Fe₃O₄ nanoparticles were modified using N,N-dimethylformamide as a solvent, β-cyclodextrin as a modifier, and 3-glycidoxypropyltrimethoxysilane as a coupling agent at room temperature. The obtained modified Fe₃O₄ were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis techniques. β-CD@Fe₃O₄ was incorporated into a poly(lactic acid) matrix to prepare new green nanocomposites with modified properties. β-CD@Fe₃O₄ showed good dispersion in the poly(lactic acid) matrix and thermal and combustion properties of the nanocomposites were improved.     

In Situ Synthesis of Silver Nanoparticles in Novel L-Phenylalanine Based Poly(Amide-Benzimidazole-imide) Matrix Through Metal Complexation Method Using N,N′-Dimethylformamide as a Reaction Medium and Reducing Agent

Silver nanoparticles were obtained in novel optically active poly(amide-benzimidazole-imide) (PABI) matrix through an in situ procedure. Chiral PABI was prepared by polycondensation of amino acid based diacid and benzimidazole containing diamine in the presence of molten tetrabutylammonium bromide. Synthesized PABI was characterized by several techniques, including Fourier transform infrared spectra, ¹H-NMR, elemental analysis, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy (FE-SEM). Then, PABI/Ag nanocomposite was fabricated based on metal complexation route for preparing silver nanoparticles in the PABI matrix and was characterized by various techniques. Microscopic images revealed good dispersion of Ag nanoparticles in the polymer matrix.     

Fischer�CTropsch Synthesis: Influence of CO Conversion on Selectivities, H2/CO Usage Ratios, and Catalyst Stability for a Ru Promoted Co/Al2O3 Catalyst Using a Slurry Phase Reactor

The effect of CO conversion on hydrocarbon selectivities (i.e., CH₄, C₅₊, olefin and paraffin), H₂/CO usage ratios, CO₂ selectivity, and catalyst stability over a wide range of CO conversion (12?C94%) on 0.27%Ru?C25%Co/Al₂O₃ catalyst was studied under the conditions of 220 °C, 1.5 MPa, H₂/CO feed ratio of 2.1 and gas space velocities of 0.3?C15 NL/g-cat/h in a 1-L continuously stirred tank reactor (CSTR). Catalyst samples were withdrawn from the CSTR at different CO conversion levels, and Co phases (Co, CoO) in the slurry samples were characterized by XANES, and in the case of the fresh catalysts, EXAFS as well. Ru was responsible for increasing the extent of Co reduction, thus boosting the active site density. At 1%Ru loading, EXAFS indicates that coordination of Ru at the atomic level was virtually solely with Co. It was found that the selectivities to CH₄, C₅₊, and CO₂ on the Co catalyst are functions of CO conversion. At high CO conversions, i.e. above 80%, CH₄ selectivity experienced a change in the trend, and began to increase, and CO₂ selectivity experienced a rapid increase. H₂/CO usage ratio and olefin content were found to decrease with increasing CO conversion in the range of 12?C94%. The observed results are consistent with water reoxidation of Co during FTS at high conversion. XANES spectroscopy of used catalyst samples displayed spectra consistent with the presence of more CoO at higher CO conversion levels.