Abstract
The efficiency of the natural extract, silymarin, was compared to its main component, silybin in the processing stabilization of polyethylene. The two compounds were applied as primary antioxidants in the concentration range of 0–500 ppm in combination with 1000 ppm Sandostab PEPQ phosphorous secondary stabilizer. The efficiency of the stabilizers was determined by the measurement of the concentration of unsaturated groups, the amount of residual PEPQ, melt flow rate (MFR), oxidation induction time and color of polymer samples taken after consecutive extrusion steps. The comparison showed that at large concentrations, the extract is more efficient than the pure compound; the vinyl group content and MFR of the polymer are preserved more in the presence on the extract than with silybin. The residual stability of the polymer containing silymarin is also slightly better at the same additive content than that prepared with silybin. Larger efficiency is explained by the smaller bond dissociation enthalpies of the most active phenolic hydroxyl groups of some of the components of the extract. The larger solubility of silymarin resulting from its amorphous character and the presence of the accompanying components of the extract also contributes to its better efficiency. At small concentrations, silymarin proved to be inferior to silybin, which was explained by the interaction of the components. The use of the extract seems to be more advantageous because it is more efficient and significantly cheaper than its pure main component. On the other hand, the stabilizing efficiency of silymarin and the related compounds is inferior to other flavonoids like quercetin, dihydromyricetin or rutin.
Highlights
Most polymers must be protected against degradation during their processing and very often during their use as well
The comparison of the stabilizing efficiency of a natural extract of flavonolignans to its main component showed that the extract is more efficient than the pure compound at large concentrations
The residual stability of the polymer containing silymarin is slightly better at the same additive content than that prepared with silybin
Summary
Most polymers must be protected against degradation during their processing and very often during their use as well. Polyolefins, including polyethylene (PE) undergoes thermooxidative degradation caused by radical chain reactions. Polyethylene is stabilized routinely by the combination of a phenolic antioxidant and a secondary stabilizer, usually a phosphite or phosphonite. Light stabilizers might be added to the additive package, in case the application requires it. The current stabilization practice is well-established, very few new stabilizers appeared on the market recently, and no new concept at all. Some years ago, concerns were raised about the possible environmental and health hazard of phenolic antioxidants and most of the related questions have not been answered yet [1]. Natural antioxidants are already extensively used in the food industry, and they might offer a new way of stabilization for polymers
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
