Extrusion Blow Molding for 5 gallon PC water bottle

Extrusion blow molding is a type of blow molding in which molten Polycarbonate PC plastic comes out from die in the form of tube like shape. This tube like shape is called parison. Parison is captured by mold and then high pressure air form the shape.

Water bottles of PC 5 gallons (18.9 = 19 liter) are being produced by extrusion blow molding.

Processing temperature for PC is 300ºC.

The general properties can be summarized as follows:

1. Excellent physical properties
2. Excellent toughness
3. Very good heat resistance
4. Fair chemical resistance
5. Transparent
6. Moderate to high price
7. Fair processing

Extrusion blow molding is divided into two types

1. Continuous
2. Discontinuous

Low volume bottles are produced by continuous extrusion blow molding. In this type more two or more pair of molds work in synchronized manners.

Extrusion blow molding for 5 gallons Polycarbonate water bottle, consists of following steps.

1. Drying of raw material (Resin)
2. Mixing of resin, color and other additives and fillers
3. Plastification and melting of material
4. Parison forming
5. Mold closing
6. High pressure cool air through nozzle pin
7. Cooling
8. Mold open
9. Ejection of bottle

• Removal of flash at the bottom and upper part of the bottle.

Complete procedure

First of all resin is dried and then mixed with color and other additives. This material is then transferred to hopper of the extrusion blow molding machine. Extrusion blow machine provides better mixing of color than injection molding a homogenize mixture of molten is formed at the end of extruder. At the end of extruder screen pack and then die head assembly. Two types of dies are used:

1. Converging
2. Diverging

Molten plastic from die takes the shape of tube. When length of parison is more equal to the length of bottle (actual length is slightly more) blow pin comes in and mold closes. High pressure air from the blow pin pushes all the sides of parison and parison takes the shape of mold (Bottle).

Advantages

1. Extrusion blow molding in simple process
2. Very good mixing
3. Single step
4. Larger volume bottles can be produced easily

Disadvantages

1. Weight varies bottles to bottle
2. Uneven wall thickness
3. Lines on the surface of bottle

Difference between Extrusion Blow molding 5 gallon water bottle and Stretch blow molding 5 gallon water bottle

Difference between extrusion blown and stretch blown is seen on the bottom of the bottle. Extrusion blown bottles have flash marks at the bottom while stretch don’t have such mark but only injection point.