Synthesis and properties of oxetane-based polysiloxanes used for cationic UV curing coatings

Syntheses and Characteristics of Urushiol-Based Waterborne UV-Cured Wood Coatings

The manufacture and properties of waterborne UV-cured coatings (WUV coatings) by acetone process based on urushiol for wood finishing were investigated. Firstly, epoxide urushiol (EU) was prepared by reacting urushiol with epichlorohydrin. Secondly, the EU was reacted with acrylic acid to obtain acrylic epoxide urushiol (AEU). Next, the prepolymers were synthesized by the reaction of AEU, 2,2-Bis(hydroxymethyl)propionic acid (DMPA), and isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), respectively, using acetone as a solvent. The prepolymers were further neutralized by triethylamine (TEA) to obtain ionomers and dispersed in the water. After removing the acetone by vacuum distillation, the polyurethane dispersions (PUDs) were obtained. Finally, the WUV coatings were performed by adding a photoinitiator (Irgacure 2959). The products in the synthesized processes and the properties of the WUV coatings were examined. The results showed that the EU, AEU, prepolymers, and ionomers could be synthesized stably. The PUDs synthesized by the IPDI and HDI had a similar solid content of 25.2% and 26.2%, and similar pH values of 7.8 and 7.6. However, the IPDI-containing PUD displayed lower viscosity, smaller particle size, and a more even polydispersity index. The IPDI-containing WUV film displayed a higher hardness, gloss, and lightfastness. The HDI-containing WUV film possessed superior impact resistance. Both IPDI-containing and HDI-containing WUV films showed excellent adhesion, bending resistance, and mass retention, and demonstrated a potential for wood finishing.

Polysiloxane Functionalized Carbon Dots and Their Cross-Linked Flexible Silicone Rubbers for Color Conversion and Encapsulation of White LEDs

In this work, aminopropylmethylpolysiloxane (AMS) functionalized luminescent carbon dots (AMS-CDs) were prepared via a one-step solvothermal method. AMS-CDs could be self- or co-cross-linking with AMS to form 3D flexible transparent silicone rubbers (SRs) where CDs acted as cross-linking points, so the loading fraction of AMS-CDs could be adjusted from 10 to 100 wt %, thus modulating fluorescence properties and flexibility of silicone rubbers. Because of the self-curing property and high thermal stability, AMS-CDs were also studied in white LEDs (WLEDs), serving as a color conversion and encapsulation layer of GaN based blue LEDs simultaneously that would avoid the traditional problem of poor compatibility between emitting and packaging materials. And the color coordinate of AMS-CDs based WLEDs (0.33, 0.28) was very close to the pure white light. In addition, the obtained CDs cross-linked SRs had good transparency (T > 80%) at 510-1400 nm and high refractive indexes (1.33-1.54) that could meet the need of commercial packaging materials and optical application. AMS-CDs were also promising to be used in the UV LEDs based WLEDs according to their wide wavelength emission and flexible optoelectronic device.

High-performance transparent solvent-free silicone resins with stable storage and low viscosity based on new hyperbranched polysiloxanes

Five new hyperbranched polysiloxanes, for example, methylhydrogen siloxanes (MHSis), with varying concentrations of silicon–methyl (Si-Me) groups were synthesized and characterized, and then a series of MHSi/poly(methylphenylvinylsilicone) (PSi) resins were prepared to investigate the influence of the structures and concentrations of MHSi on the integrated properties of both uncured and cured MHSi/PSi resins. The results show that the compatibility between MHSi and PSi is closely related to the concentration of Si-Me groups in the MHSi as well as the molar ratio of MHSi and PSi. If MHSi has a suitable concentration of Si-Me groups, and the molar ratios of MHSi to PSi are appropriate, transparent MHSi/PSi resins with stable compatibility can be obtained. In addition, these compatible resins show good thermal stability with dynamic mechanical and dielectric properties. They exhibit a great potential for use as high-performance solvent-free silicone resins in either vacuum pressure impregnating process or liquid-molding techniques.