Extrusion blow molding is one of the most widely used processes in the plastics industry for manufacturing hollow products, such as bottles, jugs, drums and packaging in general. In this guide, SICEMAR explains how the process works, its advantages, the materials used and the main applications.
What is extrusion blow molding
It is a thermoplastics transformation process in which the material is melted and extruded into the shape of a tube — called a parison — which, while still hot, is enclosed within a mold and inflated with air. The air pressure pushes the plastic against the mold walls, giving rise to the hollow product in the desired shape.
How it works, step by step
- Plasticizing and extrusion: the polymer is melted in the extruder screw and shaped into a tube (parison).
- Mold closing: the mold closes around the parison. On high-performance blow molding machines, this is done with a toggle-type clamping system, which ensures uniform force distribution.
- Blowing: compressed air is injected, expanding the material to the shape of the cavity.
- Cooling: the part cools while maintaining its final shape.
- Extraction and finishing: the mold opens, the part is removed and excess material (flash) is trimmed.
Materials: HDPE and PP
The most common materials in this process are HDPE (high-density polyethylene) and PP (polypropylene). Both offer good chemical and mechanical resistance, making them ideal for consumer, industrial and pharmaceutical packaging. Multilayer technologies (up to 6 layers) make it possible to combine materials to achieve superior barrier properties and performance.
Advantages of the process
- High productivity and competitive cost per part.
- Volume flexibility — from small bottles to large-capacity drums.
- Compatibility with multi-cavity molds for large scale.
- Excellent finishing and precision at the neck of the packaging.
Applications and products
Extrusion blow molding is used to produce a wide variety of items:
- Bottles for detergent, cosmetics, food and chemical products;
- Water jugs, lubricating oil containers and pesticide containers;
- Plastic drums and barrels;
- Pharmaceutical packaging and special hollow products.
See SICEMAR's complete line of Meper blow molding machines and the types of packaging produced.
Frequently asked questions
What is extrusion blow molding?
It is a manufacturing process for hollow plastic products in which the material is extruded into the shape of a tube (parison) and then inflated with air inside a mold, taking on the desired shape.
Which materials are used in blow molding?
The most common are HDPE (high-density polyethylene) and PP (polypropylene), used in consumer, industrial and pharmaceutical packaging.
Which products can be manufactured?
Bottles, water jugs, drums, lubricating oil containers, pharmaceutical packaging and many other hollow plastic products.