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F. Kamleitner, B. Duscher, T. Koch, S. Knaus, V. Archodoulaki:
"Melt functionalisation of polypropylene as an innovative up-cycling process";
Poster: EUROMAT 2017, THESSALONIKI; 2017-09-17 - 2017-09-22; in: "EUROMAT 2017", EUROMAT 2017, (2017), Paper ID A3-P-TUE-P1-5, 1 pages.

e-mail corresponding author: vasiliki-maria.archodoulaki@tuwien.ac.at
Polypropylene (PP) with a share of 19.2% on European plastic demand is the second most important polymer. Nearly half of the produced PP ends up after a short period of use as post-consumer waste [1]. Recycling rates of PP are increasing since years, but converting PP-waste into a valuable resource is still a challenge and needs scientific research from a dif-ferent perspective.
In this work, a novel and innovative concept of PP post-consumer waste treatment is pre-sented: Long chain branching (LCB) - a well-known industrial process - was used to increase the molar mass, broaden the molar mass distribution, improve the melt strength and intro-duce strain hardening to the material [2]. The occurrence of strain hardening and higher melt strength was verified by dynamic and extensional rheology measurements, the branch-ing number was calculated from HT-SEC measurements.
This feasibility study focussed on two possible influences on the melt modification. We start-ed to investigate the influence of polymeric impurities like polyethylene (PE) - especially PE-HD an inherent part of PP-waste - first. Model mixtures from PP containing 10% PE-HD were prepared, chemically modified and compared with PP without impurities. The same study was repeated with real post-consumer material from household plastic waste [4]. Interest-ingly the melt properties were improved in any case independent of the PE-HD in the blend. However, the mechanical properties showed mixed results, especially in the case of the post-consumer feedstock, the material suffered from the formation of highly branched gel parti-cles.
The second part focused on the influence of different PP types and therefore different molar masses on the LCB formation itself. PP-types with higher molar masses, like for water pipe systems, show lower yield of LCB compared to an injection moulding PP-type with low molar mass.