Shengping Yi

Facile fabrication of superhydrophobic coatings based on two silica sols

Superhydrophobic coatings were successfully fabricated by using two silica sols and fluorinated acrylate copolymers through the organic-inorganic hybrid method. The two silica sols contained different nanoparticles, namely, silica nanoparticles with many hydroxyl groups on their surfaces and silica nanoparticles with many long-chain alkyls on their surfaces. The integration of these two silica sols and fluorinated acrylate copolymers satisfied two necessary conditions of multi-scale nano/microstructures and low surface energy for fabricating superhydrophobic coatings. The superhydrophobic surfaces were constructed by using appropriate weight ratios of silica/copolymers and silica sol (methanol) contents. The superhydrophobic coatings displayed a water contact angle as high as 156.2° and contact angle hysteresis of 2.4°, which indicated their good self-cleaning capability. In particular, these coatings showed good mechanical properties and excellent thermal stabilities. The method is not only a facile and inexpensive way to achieve the lotus effect but could also create coatings with high values in practical application.

Modification of liquid silicone rubber by octavinyl-polyhedral oligosilsesquioxanes and silicon sol

To develop an efficient and bio-compatible way to improve the thermal and mechanical properties of addition type liquid silicone rubber (LSR), a series of modified LSR samples were prepared by introducing octavinyl-polyhedral oligosilsesquioxanes (VPOSS) and high purity silicon sol singly or in combination before vulcanization. Significant correlation was found between the loading rate of VPOSS and thermal properties. However, mechanical properties were negatively correlated with VPOSS content within the range experimented, which may be ascribed to material defect caused by uneven distribution and aggregation. Furthermore, test results approved that the introducing of silicon sol indeed affected the stabilities of the polymer by restraining the material defect caused by the aggregation of POSS molecules and improving cross link density. For example, adding 10%-20% of silicon sol into VPOSS(1.0%) modified LSR will increase tear resistance by 43.9%-85.7%, elongation at break by 31.7%-57.3%, residue at 800 °C in N2 atmosphere by 32.0%-37.9%, residue at 650 °C in air atmosphere by 70.9%-91.6%, respectively. This work proves that, to incorporate VPOSS into LSR by hydrosilylation, and to use silicon sol as dispersant and reinforce filler can become an efficient way to improve the mechanical property, thermal stability and bio-compatibility of LSR in the future.

The Preparation and Characterization of a Compatibilizer: Silicon Dioxide Nanoparticles Grafted with L-Lactic Acid Oligomer

It is found that the blending of inorganic materials and organic materials are usually thermodynamically immiscible with each other. The compatibility between the two blending materials can be enhanced by adding a component which is miscible with both parent materials. Therefore, the as-synthesized silicon dioxide grated by L-lactic acid (OLLA-g-SiO2) was used as a compatibilizer to enhance the compatibility of the PLLA and silicon dioxide (SiO2). In the paper, we prepared OLLA-g-SiO2 by using Tin (II) 2-octanoate Sn(Oct)2 as catalyst. Meanwhile, the surface-grafting reaction was characterized by Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TG). We also studied the mechanical properties of the composite PLLA/OLLA-g-SiO2/SiO2 films which can be used as package materials. It was found that the tensile strength of PLLA/SiO2 films could still be kept when OLLA-g-SiO2 were introduced, even if there were a large amount of SiO2 nanoparticles (>10 wt%) during blending. So the OLLA-g-SiO2 could be used as a compatibilizer in the films prepared by blending PLLA with SiO2.