Blow Moulding

Also called: Extrusion blow moulding, injection blow moulding, stretch blow moulding, EBM, ISBM

Blow moulding makes hollow plastic products such as bottles and cans by inflating a heated plastic tube or preform inside a mould.

Blow moulding is a process for making hollow products. A heated tube of plastic, called a parison, or a moulded preform is placed in a mould and inflated with air until it takes the mould shape. The main types are extrusion blow moulding, used for HDPE and PP bottles, cans and drums, and stretch blow moulding, used for PET bottles.

Why it matters when buying recycled plastic

• Extrusion blow moulding needs high melt strength so the parison does not sag, which means low MFI grades.
• Gels and contaminants can cause pinholes or weak spots in thin walls, so filtration quality matters.
• Recycled HDPE from bottles is often a good match for new blow-moulded products, while injection-grade HDPE usually is not.
• Recycled PET for bottles needs suitable intrinsic viscosity and, for food contact, approved processing.

Common products

Bottles, jerry cans, drums, containers for detergents and lubricants, fuel tanks and hollow toys. Many processors also use a share of their own trimmings as regrind.