Multi layer blow moulding or co-extrusion blow moulding enhance the quality container than those produced from conventional single layered blow moulding process. The various combinations available are listed below:
No of Layers = 2 (Double layer)
Combination of Layers= Virgin - Recycled
Application :
- Economical due to usage of recycled material.
- Strong containers due to double layer structure. Ecco-friendly due to recycled material
Combination of Layers= Natural - Colored
Application:
- Cost reduction due to less usage of additives.
- Suitable for special packaging for sensitive materials where the color additives should not directly in contact with material to be packed.
Combination of Layers = HDPE/PP – Recycled - HDPE/PP
Application :
- Economical due to usage of recycled material.
- Strong containers due to multi layer structure.
- Ecco-friendly due to recycled material
- Btter aesthetics due to recycled material is sandwiched between virgin layers.
Combination of Layers = Virgin HDPE - Recycled with carbon black - Virgin HDPE
Application :
- Best suitable for light sensitive products like milk.
- Improves shelf life considerably.
Combination of Layers = Nylon - Adhesive - HDPE/PP
Application :
- For pesticides and similar hazardous chemicals, solvents etc.
- Reduce the evaporation of product filled.
Combination of Layers = Nylon - Adhesive - Regrind/recycled - HDPE/PP
Application :
- For pesticides and similar hazardous chemicals, solvents etc.
- Reduce the evaporation of product filled.
- Regrind from the machine is used for economy.
- Recycled material also possible to process.
Combination of Layers = HDPE/PP - Adhesive - Barrier resin - Adhesive - Regrind - HDPE/PP
Application:
- For food packaging for long shelf life and aroma retention.
- For Plastic Fuel Tank in Automobiles.
Barrier Resins:
For enhancing packaging properties of blow molded containers, barrier resins are used. They have better barrier properties from gas, moisture etc. than normal polyolefin’s (HD and PP). The most common barrier resins are:
- Nylon
- EVA
- EVOH
Adhesive Resins:
When non-related materials with different characteristics are to be combined for better quality, an adhesive material is required, which can bond with both of the material. These are used to bond the barrier layer to holding layer of polyolefin’s. Barrier resins like Nylon or EVOH normally do not bond with HDPE or PP. Specially developed adhesives bond to both the barrier and carrying layer. The adhesive resin should be selected in accordance to the layers to be bonded. Some commercially available brands are:
- Bynel from DuPont
- Plexar from Equistar Chemicals
- Admer from Mitsui Chemicals
- Modic from Mitsubishi Chemical
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