Melt stabilization of polyethylene with natural antioxidants: comparison of a natural extract and its main component

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.

Pomegranate extract for the processing stabilization of polyethylene

“…Even hindered phenolic antioxidants discolor the polymer slightly, but the use of a phosphorous antioxidant sufficiently compensates for the effect. Natural antioxidants are either colored themselves [ 12,20,22,23 ] or their reaction products give the polymer a strong color. [ 21 ] The extract, as mentioned in the experimental part, has a slight yellowish color; thus, we might have expected only weak color in the product.…”

“…The direct use of a natural extract for stabilization would be more advantageous, and a recent study showed that the natural extract of silymarin was a more efficient stabilizer than the main component of the extract, silybin. [23] Pomegranate (Punica granatum L.) is cultivated throughout the world in subtropical and tropical areas, mainly in Mediterranean and Asian countries and in several countries of North and South America. [24] Pomegranate is produced in large quantities in India, China, Iran, and Turkey; India is the main exporter of pomegranate in the world.…”

Processing Stabilization of Polyethylene with Grape Peel Extract: Effect of Extraction Technology and Composition

“…However, the number of studies and, thus, scientific papers on the use of natural antioxidants for the stabilization of plastic products continuously increases. Flavonoids produced by plants, such as quercetin [ 15 , 16 , 17 ], rutin [ 18 ] and dihydromyricetin [ 19 ], proved efficient stabilizers in polyethylene, and the comparison of a natural extract, silymarin, to its main component, silybin, showed that extracts could be more efficient than purified single compounds [ 20 ]. Recently, pomegranate peel extract was used for the processing stabilization of polyethylene, and its efficiency exceeded that of the commercial hindered phenolic antioxidant, Irganox 1010 (I1010) [ 21 , 22 ].…”

Structural Insights into LDPE/UHMWPE Blends Processed by γ-Irradiation

“…However, the different morphological aspects of components led to modifications in the compatibilization features ( Figure 9 ). The effects of inorganic materials, such as Hap [ 65 ], as well as polyphenol types of natural antioxidants [ 66 ], cause different thermal responses related to interface cohabitation, where crystalline islands are spread through amorphous material. The presence of Hap in the composites led to a decrease in Xc values compared with the LDPE/UHMWPE composites at all the irradiation doses.…”