Material-Preserving Extrusion of Polyamide on a Twin-Screw Extruder

Area of Science:

• Polymer Science
• Materials Science
• Chemical Engineering

Background:

• Plastics recycling involves repeated melting and extrusion, often causing material degradation and affecting product properties.
• Additives like chain extenders can mitigate damage by promoting post-polymerization during processing.
• Linear chain extension is crucial to avoid uncontrolled property changes from branching and crosslinking.

Purpose of the Study:

• To investigate the effectiveness of specialized linear chain extenders for polyamides during multiple extrusion cycles.
• To evaluate the impact of chain extenders on the molar mass distribution of polyamide-6 after reprocessing.

Main Methods:

• Polyamide-6 was subjected to five extrusion cycles without additives.
• The plastic was then processed two additional times with varying concentrations of linear chain extenders using a twin-screw extruder.
• Molar mass distribution was analyzed after each extrusion cycle.

Main Results:

• Chain extenders effectively prevented molar mass degradation in polyamide-6 during multiple reprocessing steps.
• A material buildup, rather than degradation, was observed with the appropriate additive concentrations.
• The polydispersity of the molar mass distribution remained consistent throughout the extrusion cycles.

Conclusions:

• Reactive extrusion with suitable linear chain extenders enables multiple reprocessing cycles for polyamides without significant molar mass loss.
• This approach can substantially increase the recyclability of plastics, reducing the need for virgin materials.
• Ensuring a pure material flow is essential for maximizing the benefits of repeated plastic reprocessing.