Influence of Stabilization Additive on Rheological, Thermal and Mechanical Properties of Recycled Polypropylene

Abstract

To decrease the amount of plastic waste, the use of recycling techniques become a necessity. However, numerous recycling cycles result in the mechanical, thermal, and chemical degradation of the polymer, which leads to an inefficient use of recycled polymers for the production of plastic products. In this study, the effects of recycling and the improvement of polymer performance with the incorporation of an additive into recycled polypropylene was studied by spectroscopic, rheological, optical, and mechanical characterization techniques. The results showed that after 20 recycling steps of mechanical processing of polypropylene, the main degradation processes of polypropylene are chain scission of polymer chains and oxidation, which can be improved by the addition of a stabilizing additive. It was shown that a small amount of an additive significantly improves the properties of the recycled polypropylene up to the 20th reprocessing cycle. The use of an additive improves the rheological properties of the recycled melt, surface properties, and time-dependent mechanical properties of solid polypropylene since it was shown that the additive acts as a hardener and additionally crosslinks the recycled polymer chains.

Study on the processes and warpage of double‐injection‐molded parts containing PP recycled materials

“…The insignificant change in crystallinity may be due to the reduction of molecular weight, which increases the chain diffusion rate and promotes crystallization. On the other hand, it may be due to the formation of crystal defects, the destruction of the regularity of the molecular chain arrangement, and the inhibition of its crystallization 27 …”

“…On the other hand, it may be due to the formation of crystal defects, the destruction of the regularity of the molecular chain arrangement, and the inhibition of its crystallization. 27…”

Elucidating pathways of polypropylene chain cleavage and stabilization for multiple loop mechanical recycling

“…On the other hand, the foundational work on the importance of stabilization of polyolefins in recycling by Pfaendner et al has recently been reviewed. 11a Mihelčič et al investigated mechanical, thermal and rheological properties of recycled PP with and without stabilization, 22 and Bunjes et al additionally included additive analytics in their study of virgin and recycled PP. 23 Considering levels of 500-3000 ppm of stabilizers are commonly used to protect the polymers during the first loop, the levels of active species (e.g., phosphite) found in recyclates (Table 1) are often not sufficient anymore to protect the polymer from degradation during reprocessing and re-use.…”

“…On the other hand, the foundational work on the importance of stabilization of polyolefins in recycling by Pfaendner et al has recently been reviewed 11a . Mihelčič et al investigated mechanical, thermal and rheological properties of recycled PP with and without stabilization, 22 and Bunjes et al additionally included additive analytics in their study of virgin and recycled PP 23 …”

Polymers and the Environment: Some Current Feature Trends

“…Perše et al contributed to this issue with a valuable study on the influence of stabilizers on the rheological, thermal, and mechanical properties of recycled polypropylene [7]. In their article, the authors have shown that after twenty recycling steps by successive reprocessing of polypropylene, the well-known fact that the main degradation processes of polypropylene are based on oxidation and chain scission, which the addition of such stabilizer can efficiently delay.…”