Commonly used five major ink characteristics and application areas 2

4 Application of Nano-Zinc Oxide in Coatings Nano-zinc oxide is a new type of high-functional and fine inorganic product facing the 21st century. Its particle size is between 1 and 100 nm, also known as ultra-fine zinc oxide. Nano-zinc oxide has special properties and new applications unmatched by general zinc oxide products in magnetic, optical, electrical, and sensitive applications. Among them, applications in coatings are:

(1) As a new sunscreen and antibacterial agent in cosmetics. Because they are non-toxic, odorless, non-irritating to skin, non-decomposing, non-deteriorating, and have good thermal stability, and nano-zinc oxide itself is white, it can be simply colored, inexpensive, and has strong ultraviolet absorption ability. 320-400 nm) and UVB (medium wave 280-320 nm) have a shielding effect and are widely used. In the sunlight, especially under ultraviolet radiation, nano-zinc oxide self-decomposes in the water and air (oxygen) to freely move negatively charged electrons (e-) while leaving positively charged holes (h+). This hole can activate the oxygen in the air to become active oxygen, has a strong chemical activity, can react with a variety of organic substances (including organic substances in the bacteria), thus killing most pathogens and viruses. Northwestern University has conducted a quantitative bactericidal test of nano-zinc oxide. When the concentration of nano-zinc oxide is 1% within 5 min, the killing rate of Staphylococcus aureus is 98.86%. The kill rate of E. coli was 99.93%. Therefore, the addition of nano-zinc oxide in cosmetics can not only shield the sun from UV rays, but also antibacterial and deodorant.

(2) Antibacterial coatings for telephones, microcomputers, etc. A certain amount of ultra-fine zinc oxide coating is applied to telephones and microcomputers and has good antibacterial properties.

(3) Because of the small size and large specific surface area of ​​nano-ZnO, the bonding state of the surface is different from that of the particles, and the coordination of surface atoms is incomplete. As a result, the active sites on the surface are increased, forming an uneven atomic step and increasing the reaction. Contact surface, therefore, nano-zinc oxide is also a good photocatalyst. Under ultraviolet light, it can decompose organic substances, antibacterial and deodorant. Photocatalysts having this property can be used in environmentally friendly coatings.

(4) Absorbing coating. The research of wave-absorbing materials is of great significance in national defense. The development and application of this "stealth material" is an effective means to improve the survival and penetration capabilities of weapon systems. Nano-powder is a very promising new type of military radar wave. Absorbent. Metal oxides such as nano-zinc oxide have become one of the hotspots in the research of wave-absorbing coatings due to their advantages of light weight, thin thickness, light color and strong wave-absorption ability.

(5) The conductivity of nano zinc oxide can impart antistatic properties to the coating.

5 Technology Key and Future Prospects Due to the relatively high surface activity of nanomaterials, how to disperse them into the coating matrix is ​​the key technology for the application of nanomaterials in coatings. The surface treatment of nanomaterials, the method of addition, and the choice of dispersing equipment directly affect the dispersion of nanomaterials in coatings. At present, there are mainly three types of dispersion.

(1) Chemical dispersion. Through the molecular design of nanomaterials, it has the following two characteristics, one is surface hydrophobicity, and the surface of the nanomaterials is coated with organic or inorganic compounds so that the treated nanomaterials are hydrophobic and the other is a surface. Amphiphilic, the selected treatment agent molecule has more than two functional groups, in addition to one reaction with the nanomaterial, the other is both hydrophilic and hydrophobic, the treated nanomaterial has amphipathic.

(2) Physical dispersion. Under the action of strong shear force, the nanomaterials are dispersed in the coating matrix, mainly including grinding and dispersing, ball milling and dispersing, sand grinding and dispersing, and high-speed stirring.

(3) Ultrasonic dispersion. In the actual operation process, various dispersion methods can be used in combination to uniformly disperse nanomaterials in the coating matrix. After the nanomaterials are added to the base material and formulated into paints, the stability of the dispersed state is also a common concern. On the one hand, to prevent the further agglomeration of nanomaterials, on the other hand, it is necessary to maintain the special functions of nanomaterials in coatings. This is one of the key technologies for the application of nanomaterials in coatings. Nano-materials added to the paint should have a certain amount of added. Inadequate additions do not produce the desired effect; excessive additions increase the cost and at the same time reduce the quality of the coating. Therefore, formulation research is also the key to the application of nanomaterials.

In summary, the application of nanomaterials in coatings has broad prospects. The current research is still in its infancy, and most of the studies are still in the laboratory stage in China, and there are still many key technical issues that need to be resolved. The development trend at home and abroad is to speed up the research and development of environmentally-friendly coatings and give full play to the weather resistance, decorative, anti-pollution, anti-bacterial, anti-electromagnetic wave interference, and other special functions of nanomaterials. At the same time, the application of nanomaterials in coatings is different. Because of the application of general materials in coatings, it belongs to a high technology and requires the joint efforts of nano-material R&D personnel and coating workers to put nano-materials into practical use as soon as possible.