Test and application of corona treatment equipment

2022-08-06
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Test and application of corona treatment equipment for plastic surface

I. principle of corona treatment

1 Electric shock or breakdown

under the action of high voltage electric field, the strong impact of electron flow on the plastic film can make the film surface hairy, rough and increase the surface area. When the adhesive is in contact with its surface, it can produce good infiltration. The adhesive will penetrate into the roughened grooves, and the film will be firmly bonded by "anchoring", which is a physical effect. Compared with the untreated film, the surface of the treated film is obviously uneven and rough

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 becomes ozone, and ozone is decomposed 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 molecular polarity of the film increases, the surface tension increases, the affinity for the adhesive increases, and the bonding fastness between the composite films improves. In addition, due to the generation of carbonyl, new α- The carbon atom takes the house completed in 1988 (1) and 1990 as the sample, and there is active hydrogen. This kind of active hydrogen can react with isocyanate (-nco), an active group in the polyurethane adhesive, so that a strong chemical bond is formed between the bonded material and the adhesive, and the bonding fastness is increased. It is found from the infrared spectrum that there are carbonyl or hydroxyl absorption peaks on the surface of the treated polyolefin film, which proves that the above chemical effects exist

II. Surface tension testing methods

there are three commonly used testing methods

1. Peel off inspection with BOPP single-sided tape

paste BOPP single-sided tape on the surface of the film to be tested, press it, and then tear it. 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 "rustling" sound

2. Use dyne test pen to test if the surface tension value of

film meets the requirements (bopp:3.8xn/m, pet:5.0xn/m, nylon: 5.2xn/m), the liquid mark at the place where the test stroke passes 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 × N/m 5 kinds (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 use a cotton ball dipped in a little test solution to coat the treatment surface. The judgment method is roughly the same as that in 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 decrease of surface tension. 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 consists of impact electrode rack, 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 high-voltage transformer is specially placed on the small platform, which shall be stable 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 impact electrode holder is used for corona treatment of the film and must be installed at the upper end of the feeding part of the compounding machine, preferably about 2m from the ground. When refitting, the mechanic of our factory welded an angle iron frame at the installation position according to the size of the impact electrode frame, 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, so that the impact electrode frame will not fall down no matter how high the dry-type compound machine operates

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, pay attention to correct wiring (referring to the wiring of live wire and zero wire on the impact electrode frame). When handling VMCPP and vmopp, the positive and negative electrodes on the electrode frame must be adjusted, and the electric spark will be sent from the silicone rubber roller after the adjustment

during corona treatment, 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. During corona treatment, two people must cooperate to observe the impact condition at any time. Generally, the electric spark should be turned on slowly from small to large. The business development manager of Solvay aluminum electrode is required to discharge electricity uniformly without red flame

IV. common equipment faults and troubleshooting

sdcd corona treatment equipment sometimes has some faults during use, including electrical faults and mechanical faults. The following will classify and analyze the problems encountered in my actual work for reference

1. The equipment does not generate sparks. The positive pole on the impact frame discharges but the aluminum bar does not discharge

this fault often occurs in rainy seasons. Due to the high indoor humidity, there is water on the discharge aluminum bar and the insulating silicone rubber roller on the impact frame, resulting in the positive pole discharge and the aluminum bar can not discharge

treatment method: turn off the main power supply, wipe all rollers (including traction rollers and insulating silicone rubber rollers) and discharge aluminum bars on the impact frame with a dry cloth, and conduct hot air treatment with an electric hair dryer. If there is no water, the discharge equipment can work normally

in case of the above conditions, after the hot air treatment, start the impact machine from small to large, and observe the spark condition at the same time. The normal spark is continuous, without red spots and uniform

2. Discharge aluminum bar does not discharge, voltage does not rise (refer to kV meter), current (a) indication is too large

cause:

(1) processing equipment is connected in parallel, and diode is damaged; Or series connection, capacitor damage, breakdown

(2) HV transformer wiring error

(3) solution: when installing the hydraulic cylinder, the Jinan gold testing needle found that the thyristor in the equipment was damaged and punctured due to the current signs of confusion in the friction and wear testing machine market

(4) the carbon brush of high voltage transformer is not in good contact or there is oil stain on the slip ring

(5) the overcurrent switch on the control panel is damaged

(6) the triode on the circuit board is damaged and cannot be amplified

(7) HV transformer winding is open circuit or insulation insulator is damaged and broken down

(8) leakage or breakdown occurs in the positive and negative connection at the output end of the high voltage transformer

(9) the coil of AC contactor is damaged and does not engage

solution:

(1) measure the capacitance and resistance of the diode, and replace it if it is damaged

(2) correct wiring, with the green line in the middle and red lines on both sides

(3) replace the thyristor

(4) check the carbon brush and grind the slip ring disk surface with 1000

(5) replace the overcurrent switch

(6) replace the triode

(7) carefully check the winding and replace the insulating insulator

(8) replace the wiring of the same model and specification

(9) replace the AC contactor with a new one

3. When BOPP and PE films are processed, the discharge aluminum bar discharges, while when vmopp and VMCPP films are processed, the discharge aluminum bar does not discharge

reasons:

(1) the diode of the processing equipment is broken down

(2) the silicone rubber insulating roll on the impact frame was broken down, and a "snap" sound was heard when handling vmopp, with only a little spark

(3) the positive and negative wires at the output end of the high voltage transformer touch the conductor, resulting in leakage or breakdown

(4) wrong positive and negative wiring

(5) there is oil stain or too dirty on the discharge aluminum bar

solution:

(1) replace the diode

(2) replace the silicone rubber insulating roll

(3) the connecting wire shall be suspended in the air and shall not touch the conductor. If it breaks down, it shall be replaced

(4) change the positive and negative wiring

(5) wipe off the greasy dirt

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