Evaluating Degradation Mechanisms in Post-Consumer Polyolefin Flake
Polyolefin degradation evaluation requires coupling multi-load melt flow testing and OIT analysis to quantify chain scission and restabilize flake lots.
Melt Filtration Continuous Screen Pack
Meaning
A filtration device continuously removes solid contaminants and gels from polymer melts during extrusion or compounding without interrupting the flow of material. This filtration setup, utilizing a melt filtration continuous screen pack, automatically advances a fresh wire mesh screen into the melt stream as pressure builds up behind the blocked filter. It ensures consistent melt pressure and product quality during long production runs.
Mechanical Operation
The continuous filter utilizes a ribbon of wire mesh that moves slowly across the flow channel of the extruder. As the screen captures contaminants like unmelted polymer gels, wood, and paper fibers, the pressure drop across the screen increases. An automated drive mechanism advances the mesh band when the pressure reaches a preset limit.
This incremental movement introduces clean screen area to the melt flow, maintaining a stable operating pressure.
Quality Improvement
Fluctuations in melt pressure cause variation in extrudate thickness and part weight, which can lead to out-of-specification parts. By stabilizing the pressure of the melt stream, this filtration method reduces part variation during long injection or extrusion cycles. It also eliminates the risk of introducing large contaminant particles that act as stress concentrators.
Economic Impact
Manual screen changes require stopping the extruder, which results in lost production time and significant material waste during restarts. Utilizing a continuous screen system allows the compounding line to run uninterrupted for several days. This continuous operation lowers the labor cost per kilogram of recycled plastic produced.