Zhaofeng Wu

The effects of polydimethylsiloxane on transparent and hydrophobic waterborne polyurethane coatings containing polydimethylsiloxane.

The effects of polydimethylsiloxane (PDMS) on phase separation, optical transmittance and surface properties including surface composition, morphology and wettability of waterborne polyurethane (WPU) containing PDMS were investigated. After the introduction of PDMS into the WPU backbone by polymerization, the large difference in the solubility parameter of the non-polar PDMS segment and the high-polar urethane segments promoted PDMS enrichment at the air-polymer interface and enhanced phase separation, resulting in rough structures. Accordingly, the combination of PDMS enrichment and the rough structures contributed to the high or superhydrophobic surfaces and the highest contact angle with water achieved was 156.5°. The optical transmittance of the highly hydrophobic coatings reached about 78-87% throughout most of the visible light region. Importantly, the highly hydrophobic and transparent properties will greatly broaden the applications of WPU, showing potential for the environmental protection and industrial applications.

Aluminum-doped zinc oxide nanoparticles with tunable near-infrared absorption/reflectance by a simple solvothermal process

Transparent conductive oxides have attracted wide attention over the past decade due to their great potential applications. In this manuscript, we report the preparation of aluminum-doped zinc oxide (AZO) nanoparticles (NPs) through the solvothermal method. The effective incorporation of Al as a dopant is demonstrated by tracking free carrier absorption in the infrared region and energy-dispersive X-ray spectroscopy (EDX). The obtained AZO NPs present tunable absorption and reflectance in the near infrared (NIR) range at different doping levels. Moreover, the optimal precursor ratio of Al to (Al + Zn) is 4 mol% to achieve the largest NIR reflectance and absorbance of AZO NPs.

Preparation and Flame Retardancy of Polyurethane/POSS Nanocomposites

Polyurethane/polyhedral oligomeric sisesquioxane (PU/POSS) nanocomposites were synthesized via polymerization utilizing the compatibility between POSS nanoparticles and 4,4′‐diphenyl methylene diisocyanate. Scanning electron microscope images and Fourier transform infrared spectra revealed that POSS nanoparticles were dispersed in PU matrix. Thermal gravimetric analysis was employed to investigate the thermal decomposition behavior of PU/POSS nanocomposites at elevated temperatures. Then fire performance was evaluated by limiting oxygen index, underwriters laboratories 94 testing and char residue morphology. These results showed that the addition of POSS promoted the formation of char residues which were covered on the surface of polymer composites, leading to the improvement of thermal stability and flame retardancy.

Preparation and characterization of EPDM ultrafine fibers by electrospinning

Ethylene-propylene-diene monomer (EPDM) ultrafine fibers have been prepared by electrospinning method, with an average diameter of micron grade and fibrous structural morphology. The effects of experimental parameters, including the solution concentration, applied voltage, collection distance, and flow rate, were investigated carefully. It shows that the morphology and fiber diameter of electrospun EPDM fibers are greatly influenced by the process parameters. Fourier transform infrared, X-ray diffraction, and differential scanning calorimetry apparatuses were used to analyze the structural and thermal properties of the electrospun fiber mat, with EPDM cast film as a comparison. The results reveal that the electrospun fiber mat has a lower degree of crystallinity than its cast film.