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Optical properties of polypropylene upon recycling
Felice De Santis1, Roberto Pantani
1Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II, 132-84084 Fisciano, Italy.
Thescientificworldjournal
|November 30, 2013
Summary
Recycling polypropylene (PP) films increases their opacity, especially with more alpha phase and larger spherulites. This impacts optical properties crucial for food packaging applications.
Area of Science:
- Polymer Science
- Materials Science
- Physical Recycling
Background:
- Physical recycling of polymers is gaining interest.
- Recycling impacts polymer properties, but optical changes are less studied.
- Optical properties like opacity are vital for food packaging.
Purpose of the Study:
- To investigate the effect of recycling steps on the opacity of isotactic polypropylene (i-PP) films.
- To correlate changes in opacity with polymer crystallinity and morphology.
Main Methods:
- Commercial isotactic polypropylene (i-PP) was repeatedly extruded to simulate recycling.
- Films were produced by cooling extruded samples at various rates.
- Opacity, crystallinity, and morphology of the films were analyzed.
Main Results:
- Opacity of i-PP films generally increased with the amount of alpha phase present.
- For a constant alpha phase content, opacity increased with larger spherulite size.
- Recycling steps significantly influenced the crystalline structure and thus opacity.
Conclusions:
- The study quantifies the impact of physical recycling on polypropylene film opacity.
- Understanding these changes is crucial for maintaining optical quality in recycled food packaging.
- Crystallinity and spherulite size are key factors governing opacity changes during recycling.
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