Silicon oxynitride coatings on glass and polyethylene terephthalate (PET) film have been fabricated by thermal annealing of inorganic polymer perhydropolysilazane (PHPS) between 60 °C and 200 °C. The chemical structure, thermal behavior and structural evolution of PHPS were investigated. The coatings obtained on glass possess pencil hardness as high as 9H, high transparency above 90% in the visible wavelength range, good adhesion to the substrate and a hydrophobic property with water contact angle above 98°. The PHPS coated PET film has pencil hardness above 4H, water contact angle 102° and a high scratch resistance property with no obvious scratches after a 50 cycles scratch test under a load of 2 kg. All these data imply the great potential of PHPS as a hard coating for optical devices. © 2015 Society of Chemical Industry

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Highly transparent and durable superhydrophobic hybrid nanoporous coatings with different surface roughnesses were fabricated via a simple solidification-induced phase-separation method using a liquid polysiloxane (PSO) containing SiH and SiCH═CH2 groups as precursors and methyl-terminated poly(dimethylsiloxane)s (PDMS) as porogens. Owing to the existence of SiCHn units, the hybrid material is intrinsically hydrophobic without modification with expensive fluorinated reagents. The roughness of the coating can be easily controlled at the nanometer scale by changing the viscosity of PDMS to achieve both superhydrophobicity and high transparency. The influence of surface roughness on the transparency and hydrophobicity of the coatings was investigated. The enhancement from hydrophobic to superhydrophobic with increasing surface roughness can be explained by the transition from the Wenzel state to the Cassie state. The optimum performance coating has an average transmittance higher than 85% in the visible-light range (400-780 nm), a water contact angle of 155°, and a slide angle lower than 1°. The coatings also exhibit good thermal and mechanical stability and durable superhydrophobicity, which paves the way for real applications of highly transparent superhydrophobic coatings.

Heating mechanisms of ultrasonic welding for thermoplastics were studied via numerical simulation and experiment. Relationship between dynamic modulus and static relaxation modulus of thermoplastics was theoretically analyzed. Segment time—temperature equivalency equation for different temperature ranges and a method for directly separating viscoelastic heat from strain energy were used in the simulation. Temperature measurement tests with poly(methyl methacrylate) specimens were carried out to verify the simulation results. Results of simulation and experiment reveal that interfacial friction rather than viscoelastic heat initially start the whole welding process. Viscoelastic heating becomes dominant when temperature reaches Tg (glass transition temperature) of the material. And viscoelastic heat provides most required heat during welding.

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