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Corona Roller for BOPP/BOPET film production line
Corona refers to the phenomenon of partial discharge on the surface
of the charged body in a gas or liquid medium, often occurring
around the high-voltage wire and near the tip of the charged body,
which can produce ozone, nitrogen oxide and other substances.
Most plastic films are non-polar polymers, the surface tension
generally 29-30mN/m, in theory, if the surface tension of an object
is less than 33mN/m, the currently known ink and adhesive can not
be firmly attached to the above, so the surface of the corona
method treatment.
The processing principle is to apply high frequency and high
voltage electricity to the processing equipment to generate high
frequency and high voltage discharge, resulting in small and dense
purple-blue sparks. Various ions produced after air ionization
accelerate and impact the plastic film in the treatment device
under the action of a strong electric field.
The chemical bonds of plastic molecules are broken and degraded,
increasing the surface roughness and surface area. The discharge
also produces a large amount of ozone, which is a strong oxidizing
agent that can oxidize plastic molecules and produce strong polar
groups such as carbonyl and peroxide, thereby improving its surface
energy.
When the plastic film surface is not treated, its surface tension
is low, in order to further improve the binding force between the
printing ink or vacuum aluminum plating layer and the surface of
the plastic film, and increase the adhesion fastness, it is often
necessary to surface treat the plastic film. Plastic film surface
treatment methods are: corona treatment method, chemical treatment
method, mechanical hair method, coating method, flame method, etc.,
the most commonly used is corona treatment method.
The basic principle of corona treatment method is: by applying a
high-frequency and high-voltage power supply between the metal
electrode and the corona roller (high temperature, ozone
resistance, high insulation silicone rubber roller), the discharge
is generated, so that the air is ionized and a large amount of
ozone is formed. At the same time, high-energy electrical sparks
impact the surface of the film. Under their combined action, the
surface of the plastic film is activated and the surface energy is
increased. The tension of polyolefin film can be increased to 38
dyne/cm by corona treatment. The surface tension of the polyester
film can reach 52-56 dyne/cm or more.
Because the corona roller is used in high voltage electric field
for a long time, the coating is required to have excellent
electrical insulation, arc resistance, corona resistance and flame
retardant. But the existing corona roller can not reach the ideal
effect, easy to produce reverse corona. The reverse corona may
produce the anti-sticking phenomenon of ink printing, the transfer
of aluminum plating layer will occur in aluminum plating, and the
transfer of adhesive layer will occur in glue coating, and the
ideal corona effect can not be achieved. Therefore, it is very
important to choose a high quality corona roller.
Huatao corona roller adopts imported special silica rubber, and the
corona roller is guaranteed by the high voltage test of 200,000
volts, which effectively increases the surface roughness of the
plastic film and makes the surface of the plastic film have higher
adhesion. Widely used in famous brand BOPP & BOPET film
production line. Effectively increase the surface roughness and
improve the surface energy of the film.
Product Parameters
Shell construction: 2OS Double-shell from Q345B
Shrinked and welded shafts from Q345B
surface: Silicone rubber coated, hardness apprx 70HRC
Disks and shafts 2-layer painting RAL
Out of roundness <=0.1mm
Cylindricity <=0.1mm
Dynamic balancing G2.5
Flow-system: Channels between inner and outer tube separated with
welded leading spirals
Shell construction | Double-shell from Q345B |
Surface treatment | Silicone rubber coated, hardness apprx 70HRC |
Disks and shafts | 2-layer painting RAL |
Out of roundness | <=0.1mm |
Cylindricity | <=0.1mm |
<=0.1mm | G2.5 up to max. line speed |
Dynamic balancing | Channels between inner and outer tube separated with welded leading spirals |