In this blog post, I present to you the processing temperatures of high performance polymers for injection molding.
For processing
of high performance polymers equipment is needed which is capable of dealing with temperatures
up to 450°C for the plasticizing unit and 250°C for the moulding tool (oil
heating).
The figure below shows the mould and processing temperatures of the most used high performance polymers, together with the processing shrinkage values.
 |
| Figure: processing temperatures of high performance polymers for injection molding |
Important to
note is that certain wall cross sections and flow length ratios need to be
fulfilled. Polymers such as PAI have a high viscosity. Therefore, wall
thicknesses below 1.5 mm should be avoided. A wall thickness of 1 mm is
possible with unreinforced PEEK. In case the part has a wall thickness of 10
mm, additional ribs prevent sink marks.
Commodity
and engineering plastics show high processing shrinkage values. However, with high
performance polymers, shrinkage values are much lower compared to engineering
and commodity plastics. PEEK shows shrinkage values below 2.5 %. In general,
shrinkage is in flow direction lower than cross flow direction. Additionally, it
is important to have sufficient draft angels (around 2°).
Furthermore,
attention needs to be paid to the forming of weld lines in the cavity, since
high performance polymers have a high viscosity and this may result in a lower
strength at weld lines (less entanglements).
Thank you for reading and
#findoutaboutplastics
Herwig Juster
Literature:
[1] Sachtling Kunststoff-Taschenbuch
No comments:
Post a Comment