Atmospheric Polymeric SiOx Films Used in Printing Plates (Part One)

[Abstract] In this paper, hexamethylene disiloxane (HMDSO) was used as the monomer, and the polymer synthesis was carried out in the atmospheric environment using a DBD plasma gun. The discharge characteristics and polymerization effects of two different sample injection methods were compared and found. The discharge characteristics of the two sampling methods are the same. The only difference is that the torch length of the discharge plasma downstream of the plasma region increases first and then decreases when the flow rate is low, and the torch length of the direct plasma injection mode in the plasma area directly reaches arc starting. Maximum value. FTIR showed that the different input modes of monomer had little effect on the structure of the polymer film, but had a significant effect on the deposition rate of the polymer film. The film formation rate of the monomer downstream of the plasma zone was significantly faster than that of the monomer directly into the plasma area. Scanning electron microscopy (SEM) gave the surface morphology of the polymer film. The surface energy test showed that the contact angle was up to 110 degrees. The ink pushing experiment showed that the polymer film used in the downstream area of ​​the plasma had good ink repellency and could be used as a waterless offset plate. .

Key words: plasma chemistry; polymerization; sample introduction method; SiOx film; DBD plasma gun

Packaging and printing materials are widely used, the market is huge, and there is room for various technologies. Plasma technology is promising as a new technology in the packaging industry. The synthesis of SiOx film using plasma polymerization technology is not only widely used in barrier packaging, but also due to its lower surface energy, it can be applied to new waterless offset printing plates.

Plasma polymerization is the use of plasma means to generate electrons, ions, reactive groups, chemical reactions in the gaseous or substrate surface, deposited in the form of thin film or powder on the surface of the substrate, plasma chemistry is an important research direction. Its application scope is expanding, such as textiles, preparation of nanomaterials, medical polymer materials, and functional film scraping. Traditional non-equilibrium plasmas (or cold plasmas) are produced under a pressure of 1 气压, and the large investment in equipment and the limited scale of production limit the application of plasma polymerization in industry. Therefore, non-equilibrium plasma chemistry under atmospheric conditions is used. Polymerization has become the development direction of special-purpose polymerization reactions. In 1998, the University of California, USA E. Babayany et al. published a paper on plasma deposition and deposition of SiOx thin films under atmospheric pressure, but the discharge method was glow discharge between two electrodes, and the uniformity of the discharge limited the application of the plasma gun. Under the atmospheric DBD discharge, plasma with an ion number density of the order of 10 -9/cm 3 can still be measured at 15 cm from the ionization zone. Therefore, using a high-frequency dielectric barrier discharge plasma gun, the plasma polymerization in the atmosphere has the advantage of being free from the limitations of vacuum conditions and more uniform discharge.

Hollow copper tubes were used as internal electrodes for atmospheric plasma gun polymerization. Two different sampling methods can be used, namely direct injection in the plasma zone and injection downstream in the plasma zone. Their device structures and polymerization principles are all different. In order to understand the effect of different injection methods on the polymerization film formation, the discharge characteristics of the plasma guns of the two injection methods were compared and the polymer film FYIR was compared and the surface morphology of the polymer film was given.

1 test device and sample preparation

Using the laboratory-made DBD plasma gun, the gun consists of three parts: a single input system, a DBD plasma gun body and a power supply system. The monomer input system consists of a gas source and a valve, a flow meter, and a conduit. The gun body consists of inner and outer electrodes and quartz glass as a dielectric layer. The power supply adopts an adjustable voltage power supply with an output voltage of 0 to 12000V. The frequency is 16kHz and the functional film is polymerized between 20 and 100W. The working gas is argon and the monomer is hexamethyldisiloxane. When the electric field strength formed by the voltage of 9bJ30 is higher than the required field strength for gas breakdown, discharge occurs and a plasma is formed in the chamber. When gas is blown from the inlet, plasma is blown from the muzzle and a plasma torch is formed. The cross-sectional area of ​​the plasma gun discharge chamber is shown in Figure 1.

In the input method in which a single cell is directly input into the plasma zone, the input cell is brought into the plasma zone by the carrier gas between the inner electrode and the glass tube. The method for the monomer to enter the plasma downstream region is to divide the argon into two channels. One is ionized between the inner electrode and the medium to form a plasma, the other is used as a carrier gas, and the monomer is carried through the hollow inner electrode to reach the plasma region. Downstream, the plasma generated by the ionized argon gas acts to polymerize. The reaction mechanism and its device structure diagram are as follows: Direct plasma injection:

(to be continued)