Abstract
Multilayer packaging materials find nowadays a broad range of applications due to their exceptional tensile and barrier properties. However, it is challenging to recycle such materials as the layers need to be separated prior to recycling. Thus, from the point of view of sustainability, we need to shift to mono-material multi-layer flexible packaging. Poly-ethylene (PE) can be a material of choice for this type of packaging as its material properties can vary depending on the synthesis (HDPE, LDPE, LLDPE), processing, and post-processing.
Conventionally, the outer layer of multilayer flexible packaging is made from non-PE materials which can provide ad-equate stiffness and barrier properties to the overall package. The stiffness of PE films can be enhanced significantly by Machine Direction Orientation (MDO) process. During the MDO process, the polymer film is stretched in the ma-chine direction at a certain temperature which depends on the polymer’s chemical nature.
In this work, we study the influence of the molecular properties (average molar mass) and MDO process parameter (stretch draw ratio) on the final morphology and mechanical properties of MDO-PE films which is intended as the out-er layer of multilayer material.
Four grades of PE were film-blown and subjected to MDO process to obtain the final films. One selected polymer was processed at different speed stretch-ratios while keeping other process parameters constant. Furthermore, we dry-blended different grades of PE prior to film blowing and MDO treatment to study the influence of molar mass and dis-persity on the tensile properties. The results showed that the increase in the MDO process stretch-draw ratio leads to better fibrillation and increased crystallinity. Consequently, the tensile modulus and stiffness increase as well. From the molecular properties point of view, the higher molar mass and the molar mass distribution provide a better possibility for uniform stretching and relatively easier processing.
Thus we showed that the MDO-PE films with enhanced stiffness can indeed provide sufficient stiffness for the design of multilayer mono-material packaging with the enhanced recyclability.
Conventionally, the outer layer of multilayer flexible packaging is made from non-PE materials which can provide ad-equate stiffness and barrier properties to the overall package. The stiffness of PE films can be enhanced significantly by Machine Direction Orientation (MDO) process. During the MDO process, the polymer film is stretched in the ma-chine direction at a certain temperature which depends on the polymer’s chemical nature.
In this work, we study the influence of the molecular properties (average molar mass) and MDO process parameter (stretch draw ratio) on the final morphology and mechanical properties of MDO-PE films which is intended as the out-er layer of multilayer material.
Four grades of PE were film-blown and subjected to MDO process to obtain the final films. One selected polymer was processed at different speed stretch-ratios while keeping other process parameters constant. Furthermore, we dry-blended different grades of PE prior to film blowing and MDO treatment to study the influence of molar mass and dis-persity on the tensile properties. The results showed that the increase in the MDO process stretch-draw ratio leads to better fibrillation and increased crystallinity. Consequently, the tensile modulus and stiffness increase as well. From the molecular properties point of view, the higher molar mass and the molar mass distribution provide a better possibility for uniform stretching and relatively easier processing.
Thus we showed that the MDO-PE films with enhanced stiffness can indeed provide sufficient stiffness for the design of multilayer mono-material packaging with the enhanced recyclability.
Original language | English |
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Title of host publication | Book of Abstracts, International Conference on Polymer Process Innovation | PPI 2023 |
Number of pages | 1 |
Publication status | Accepted/In press - Sept 2023 |
Keywords
- circular plastics
- Circular economy (CE)
- flexible packaging
- mechanical recycling
- sustainability
- Design for recycling