Test and application of corona treatment equipment

Test and application of corona treatment equipment on plastic surface (I)

now plastic flexible packaging has been widely used in various fields of commodity packaging. The most commonly used non-polar films such as polyethylene and polypropylene in flexible packaging belong to non-polar materials, with dense and smooth surface, which is an inert surface, and the surface free energy is relatively low, only (2.9 ~ 3.0) × J/cm2。 Theoretically, the surface free energy is less than 3.3 × The film of j/cm2 cannot make any known adhesive wet, so the surface free energy of the film must reach (3.8 ~ 4.0) through surface treatment first × J/cm2, which is beneficial to obtain good composite strength. There are many commonly used methods of film surface treatment, among which corona treatment is the most commonly used method

the three gravure printing machines used in our factory are equipped with corresponding corona treatment equipment. When treatment is needed, just put the film between the electrode rollers in order. The treated film directly enters the printing unit, and the ink has a good adhesion effect on the film

the installation of corona treatment equipment on the dry compounding machine is an aspect of our plant's technical transformation, which aims to improve the surface tension of polyolefin film and the adhesion fastness of composite products. Our factory has achieved good results after equipping the dry compound machine with the corresponding EDM processing equipment according to the actual situation. The corona treatment equipment equipped is sdcd type plastic surface corona treatment equipment produced by Dalian Radio No. 9 factory. After corona treatment, the surface tension of the film can reach 3.8 × Above n/m, the height can reach 4.0 × N/m, which greatly improves the peel strength of the composite film and can completely meet the quality requirements. Installing the corona treatment equipment is very helpful for aluminum coating, especially BOPP aluminum coating, but the installation and wiring of the equipment should be changed. The following will discuss the corona treatment principle, surface tension detection method, equipment installation and wiring and common troubleshooting

I. corona treatment principle

1 Electric shock or breakdown

under the action of high-voltage electric field, the electron flow makes a strong impact on the plastic film. Jinan Shijin milk fiber tensile testing machine can make the film surface hairy, rough and increase the surface area. When the adhesive is in contact with its surface, it can produce a good infiltration, and the adhesive will penetrate into the roughened grooves. By "anchoring" effect, the film is firmly bonded, which is a physical effect. Under the high-power magnifying glass, the surface of the treated film is obviously uneven and rough compared with the untreated film

the electric shock intensity can increase with the increase of voltage and current

2. Increase the polarity of the film

under the action of high-voltage electric field, oxygen in the air turns into ozone, which in turn decomposes into oxygen and new ecological oxygen atoms. The new ecological oxygen atom is a strong oxidant, which can α- Carbon atoms are oxidized to form carbonyl or hydroxyl groups. With this structure, the polarity of film molecules increases, the surface tension increases, the affinity for adhesives increases, and the bonding fastness between composite films improves. In addition, due to the production of carbonyl, new compounds will be produced in the molecular chain α- Carbon atom, active hydrogen appears. This kind of active hydrogen energy reacts with isocyanate (-nco), the active group in the polyurethane adhesive, so that a solid chemical bond is formed between the bonded material and the adhesive, which further increases the bonding fastness. From the infrared spectrum detection, it is found that there are carbonyl or hydroxyl absorption peaks on the surface of the treated polyolefin film, which proves the existence of the above chemical effects

second, surface tension detection methods

there are three commonly used detection methods

1. Peel off with BOPP single-sided tape

Paste BOPP single-sided tape on the surface of the film to be tested, compress it, and then tear it apart. If the surface tension of the film meets the use requirements, the peeling is very hard and the sound is low; On the contrary, it is easy to peel off, accompanied by a "rustle" sound

2. Use the dyne test pen to test

when the film surface tension value meets the requirements (bopp:3.8xn/m, pet:5.n/m, nylon: 5.2xn/m), the liquid mark at the place where the test stroke is passed is uniform, without fracture mark and shrinkage; Otherwise, the test fluid will shrink. If one part shrinks and the other part does not shrink, it means that the treatment is not enough

it is worth mentioning that when testing pet and nylon, it is necessary to select a larger test pen. The common specifications of surface tension test pen are: 3.8 × N/m、4.0 × N/m、4.2 × N/m、4.4 × N/m、4.8 × 5 kinds of n/m (for measuring aluminum foil)

3. Self prepared surface tension test solution

see the attached table for the formula of some surface tension test solutions. The test method is to dip a cotton ball with a little test solution and apply it on the treatment surface. The judgment method is roughly the same as point 2

the treated film should not be stored for a long time, up to 7 days. The longer the time, the more obvious the reduction of the surface tension value of our professional manufacturers. If it needs to be placed for a long time, the initial value of surface tension should be increased (2 ~ 4) when processing the film × N/m。

III. installation method on dry-type compound machine

sdcd corona treatment equipment is composed of impact electrode frame, high-voltage transformer and control device

the mechanic of our factory placed the high-voltage transformer on a small platform made of angle iron on the drying channel and fixed it with 4 screws. The small platform is specially equipped with high-voltage transformers, which shall be placed stably and without shaking. The transformer has three incoming terminals, which are respectively connected with the three high-voltage terminals of the control device. The output end is a live line and a zero line, which are respectively connected with the positive and negative poles of the impact electrode frame. The positive pole is connected with the positive pole and the negative pole is connected with the insulating guide roller

the function of the impact electrode frame is to corona treat the film, which must be installed at the upper end of the feeding part of the compounding machine, preferably about 2m away from the ground. When refitting, the mechanic of our factory first welded an angle iron frame according to the size of the impact electrode frame at the installation position, locked it at the mechanical screw port of the drying Road, and then put the impact electrode frame on it. In fact, the impact electrode frame is half suspended in the air. In this way, no matter how high the speed of the dry-type compound machine runs, the impact electrode frame will not fall off and the corresponding valve will be designed

the control device is placed on the ground, and our factory has specially made a counter to place it for the convenience of compound personnel

when corona treating different films, be sure to pay attention to the correct wiring (referring to the wiring of live wire and zero wire on the impact electrode frame). When dealing with VMCPP and vmopp, the positive and negative electrodes on the electrode frame must be adjusted, and the electric spark will be sent out from the silicone rubber roller after the adjustment

when corona treatment is carried out, different treatment intensities can be obtained by adjusting the voltage, which generally does not exceed 15kV (pointer). When the machine is shut down, the impact spark must be turned off to prevent the material from burning and fire at the same time. When corona treatment is carried out, two people must cooperate, and the jaw of the hydraulic universal testing machine should observe the impact condition at any time after temporary use. Generally, the electric spark should be turned on slowly from small to large. It is required that the electrode aluminum bar discharge evenly without red flame