Preparation Of Nano-SiO₂ Transparent And Abrasion-Resistant Coating And Study On Its Properties

Over the past ten years research into the special functional properties of nanometer materials have become a hot topic in many countries worldwide. The combine of inorganic nanometer materials with organic polymers carries its significance in producing abrasion-resistant coatings with high transparency. Applied to wooden furniture, floorboards and resin lens etc, such properties are especially desirable.In this thesis, we first look at the use of steric acid in the surface treatment of nano-SiO₂. Steric acid reacts with hydroxide groups on the surface of nano-SiO₂ and such surface-treated nano-SiO₂ is combined with alkyd to produce transparent and abrasion resistant coatings. The best result is achieved with the addition of 5wt% of nano-SiO₂, which has increased the abrasion resistance by 99%. Scratch-resistance and hardness are also improved, the latter reaching 2H in the Wolff-Wilborn Pencil Test.Discussions are then given to the relation between the particle volume concentration (PVC) and the abrasion resistance, scratch resistance and hardness of the coating. It is determined that a PVC of about 2.06% (5wt%) is a critical value at which many of the coating's properties show abrupt change, thus confirming that the nanometer material coating follows the CPVC theory obeyed by ordinary coatings. The mechanism through which the nano-material improves the coating's abrasion resistance is examined, including the choice of resin and nano-particles and the mechanism of lubrication.The aqueous dispersion of nano-SiO₂ is then investigated. This covers the type of dispersant, dispersant dosage, pH value, dispersion time, dispersion method and the influence of the nano-particle concentration on dispersion effectiveness. A stable dispersant is produced using a 4wt% nano-SiO₂ dispersant, pH 5, 4wt% nano-SiO₂ and with an ultrasonic dispersiontime of 20 minutes.Finally, a certain amount of aqueous nano-SiO₂ dispersant is added to aqueous Acrylester to produce a transparent, abrasion resistant nano-coating. A coating with 4wt% nano-SiO₂ has its abrasion resistance enhanced by a factor of 2.4; when the added nano-SiO₂ reaches a concentration of 5wt% the scratch resistance doubles and the hardness is improved from 2H to 3H.