What is BOPET film production process?

BOPET film, as known as biaxially oriented polyethylene terephthalate, is a polyester film made by stretching polyethylene terephthalate (PET) in its two primary directions to make a versatile engineered film.

It was developed by the British ICI company in the 1950s.

It has many benefits high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties, and electrical insulation.

After years of development, the product has evolved from the original single insulating film to the current capacitor film, packaging film, a photosensitive insulating film, etc.

  • Its thickness can be from 4.5um to 350 μm.
  • Its production process has also developed from simple kettle batch production to multiple stretching and simultaneous bidirectional stretching.
  • Its product form has also evolved from flat film to multilayer coextruded film, reinforced film, and coated film.

Polyester film has become one of the fast-growing film varieties in the market.

Dehui FIlm is one of bopet film suppliers in China. Currently, We mainly produce them by a two-step two-way stretching process. With the expansion of its application volume, the quality requirements of polyester films are getting higher and higher. Forcing us to improve the quality and enlarge the output.

BOPET film production process

Now, let’s introduce the bopet film production process. The general process is as follows:

PET resin drying → extrusion casting → longitudinal stretching of thick sheets → transverse stretching → winding → slitting and packaging → deep processing.

(1) Drying of PET resin

PET resin contains polar groups in the molecule. so it is highly hygroscopic. its saturated moisture content is 0.8%. The presence of moisture makes PET extremely prone to oxidative degradation during processing. Affect product quality.

Therefore, the water content must be controlled below 0.005% before processing. This requires sufficient drying of PET.

There are two general drying methods, namely vacuum drum drying and airflow drying.

The former drying method is better. Because PET is not in contact with oxygen during vacuum drying. It is conducive to controlling the high-temperature thermal oxygen aging of PET and improving product quality.

The vacuum drum drying conditions of PET are as follows:

vapor pressure0.3 ~ 0.5 MPa
vacuum degree98.66 ~ 101.325 kPa
drying time8 ~ 12h.

(2) PET melt-extruded cast sheet

After melt-extruded and plasticized the dried PET resin, and then mixed by coarse and fine filters and static mixer,It is transported to the machine head by the metering pump. Then cooled by the quenching roller Into thick slices for use.

The process conditions for extruding the cast sheet are:

the temperature of the conveying section of the extruder240-260 ° C,
the temperature of the melting plasticizing section265-285 ° C,
the temperature of the homogenizing section270-280 ° C,
the temperature of the filter (net)280-285 ° C.
the melt temperature270-275 ° C
the slab quenching roller temperature18-25 ° C.

(3) Extrusion of biaxially stretched

PET thick film Biaxial (direction) stretching is to stretch the film or sheet extruded from the extruder at a certain temperature. In the longitudinal and transverse directions to make the molecular chain.

The crystal face to be determined is oriented, and then heat-setting treatment is carried out in the case of stretching.

The biaxially stretched film, due to the orientation of the molecular segments, improves the crystallinity.

So it can significantly increase the tensile strength, tensile elastic modulus, impact strength, tear strength, improve cold resistance, transparency, airtightness, Electrical insulation, and gloss.
Most of the flat film adopts the plane-type successive biaxial stretching process.

I Hope is ususful for you to understand What is BOPET film production process?

BOPET Film Supplier

Besides the clear bopet film production, Dehui film also provides more other category PET films.Such as colored PET Film (Milky White PET film, Red PET film, Black PET film, Yellow BOPET film ), Metallized PET film, matte bopet film, transfer PET film, and so on.