The fracture surfaces can basically be divided into two types:

• brittle fractures are characterised by smooth surfaces and indicate poor or insufficient welding
• ductile fracture surfaces have a stretched structure and indicate good welding

Brittle fracture

Ductile fracture

The molecular chains of smooth fracture surfaces could not or only to a very small extent intermingle in the interfaces of the two join partners (e.g. by join partners that were too cold because of insufficient heating temperatures/-times, environmental effects, too long relocating times, too low jointing pressures etc.) or a sudden load of the seam occurred.

In ductile fractures, the molecular chains, which are well intermingled in the interfaces, were literally torn apart. The stretchings themselves can be fairly different in size depending on the type of polyethylene. However, they mostly show a white colouring (white fracture).