Comparison of chromatographic, spectroscopic, thermal, and mechanical measurement techniques for polyethylene recyclate characterization
Sprache des Titels:
Polymer Meeting 14 Book of Abstracts
The new regulation of the European commission sets high goals on the recycling of plastic
1 Plastic pipe products might take up high amounts of the resulting
recyclates, especially in lower performance/non-pressure applications. While packaging
products usually are short-term applications and are therefore sparingly stabilized, pipe
products should withstand environmental influences for several decades. Furthermore,
PE-HD packaging products are mostly injection- or blow-molded and therefore require
different flow properties than pipe materials.
In this study, three commercially available polyethylene post-consumer recyclates (rPE-1,
rPE-2, and rPE-3) produced from packaging waste streams are characterized in terms of
stabilization and flow properties and compared to a virgin pipe grade PE-HD of the
Two methods were used for stabilization characterization, high pressure liquid
chromatography with ultraviolet detection (HPLC-UV) and oxidation induction
temperature (TOX) measurement. For characterization of flow properties melt flow rate
measurements (MFR) were performed. Furthermore, tensile tests of injection-molded
specimens and molar mass measurement via gel permeation chromatography with infrared
detection (GPC-IR) were conducted and correlated with the flow properties.
The three recyclates show significant differences in stabilization to the virgin PE100-RC.
While the stabilizer contents (active and unconsumed Irganox 1010 and Irgafos 168) of the
recyclates range from 0.01 ppm to 0.08 ppm, PE100-RC contains in total 0.20 ppm of these
stabilizers. TOX measurements show a similar trend with the recyclates ranging from
228 °C to 242 °C, while PE100-RC delivers values of up to 261 °C.
The characterization of flow properties showed a wide range of properties for the recyclates
and substantiate the differences between packaging and pipe PE-HD. The MFRs of the
recyclates range between 0.8 g/10 min and 2.5 g/10 min, while the PE100-RC showed a
much lower MFR of 0.23 g/10 min. The strain-at-break values of the recyclates range
between 35 % and 120 %, while PE100-RC already broke at 21 % strain. Finally, the mass
average molar masses (Mw) of the recylates range between 142,000 and 168,000 g/mol,
while PE100-RC shows a higher Mw of 188,000 g/mol.
Both methods for stabilization characterization succeed in differentiating between the
tested materials and correlate to each other. While the MFR correlates to the strain-at-break
for all recyclates and the virgin polymer, the GPC results of the recyclates follow no trend.
Despite its higher MFR, rPE-1 shows a higher Mw than the other recyclates.