PET Bottle/Jar Stretch Blow Molding

• Heat and soften PET preform -- heater;
• Blow high pressure air into preform and form bottle -- stretch blow molding machine, blow mold, air compressor, air purifier.

Stretching blow molding is also called biaxial orientation blow molding. It is a kind of package container producing method stretching preform in axes by mechanical device and in radial by compressed air ( air should be cleaned by air purifier if necessary) when material is under high elasticity condition. This is widely used for PET, PE,  PVC and etc.

Orientation can improve product's mechanical property, solvent resistance, transparency and anti-permeability. Polymer molecule is unbalanced long-chain structure. Orientation happens when stretching. Orientation means molecule arrange along stretching direction parallelly.

Stretching blow molding brings biaxial orientation effect to the products. To cool products quickly means high orientation degree.

The glass transition temperature of PET is 82⁰C, and its best orientation temperature is 105⁰C.

PET stretch blow molding machine is a kind of container making method that stretches PET preform in axes by mechanical device and in radial by compressed air when PET preform is under high elasticity condition.

Orientation can improve products' mechanical property, solvent resistance, transparency and antipermeability. Polymer molecule is long-chain structure which is unbalanced. Orientation happens when stretching. Orientation means molecule chains arrange along stretching direction parallel.

Stretching blow moulding brings biaxial orientation effect to the products. To cool products quickly means high orientation degree. So to reach satisfactory orientation effect, we can raise stretch speed, increase polymer's molecular weight or lower stretching temperature.

In orientation molecular chain can move freely along pulling force temperatures for four different materials.

There are two methods to estimate orientation degree:

• Gauge tensile strength of PET slice cut from bottles to estimate its orientation degree. In terms of theory tensile strength after orienting equals its tensile strength before orienting multiplied corresponding draw ratio approximately. If gauged value is 14MPa less than calculated value, it means orientation not enough.
•  There is another quick and simple method. Cut the bottle and tear it in axes and radial by hand. It means orientation not enough when the bottle be torn smoothly. On the contrary it means good orientation when the bottle is not easy to be torn.

Thickness of carbonated drink bottles is required to be 0.45~ 0.55mm. But for stretched and blown bottles 0.25~0.38mm will be okay because orientation will improve products' quality.