Most polymers must be protected from degradation during processing and often during use. Polyolefins, including polyethylene (PE), are subject to thermo-oxidative degradation caused by free radical chain reactions. Polyethylene is usually stabilised by a combination of phenolic antioxidants and co-stabilisers (usually phosphite or phosphite). Light stabilisers can also be added to the additive package if required by the application.
Current stabiliser practice is well established and as a result few new stabilisers have recently appeared on the market and there are few new concepts. However, a few years ago concerns began to arise about the potential environmental and health hazards of phenolic antioxidants and most of the related questions have not yet been answered. Natural antioxidants are already widely used in the food industry and they may also offer a new stabilisation method for polymers.
Antioxidant 1076 Cas 2082-79-3
Plants produce and use a large number of antioxidants very efficiently. These can have different structures, functions and efficiencies. A significant number of them have been tried as stabilisers in polymers with varying success. Natural oils, carotenoids, curcumin, vitamin E , lignans and many other compounds have been shown to have greater or lesser stabilising activity in a range of polymers, but mainly in polyolefins. Recently, interest in natural antioxidants has increased considerably and a large number of papers have been published on them.
Most of this work suggests that, at least in polyethylene, flavonoids are the most effective natural stabilisers. To date, only a few of the approximately 6000 flavonoid families have been tested as stabilisers, but they have proven to be very effective indeed in PE. Quercetin, dihydromyricetin and rutin already provide sufficient melt stability for PE at 50-100 ppm and residual oxidative stability at 250 ppm. All three are more effective than the phenolic antioxidants that are currently the most heavily used in industrial practice.
Antioxidant 1010 CAS 6683-19-8
Although natural antioxidants are very effective, they have several disadvantages; their melting temperatures can be very high, above the processing temperature of PE, they have low solubility and can discolour polymers.
Silymarin is another member of the flavonoid family. It is a natural extract with a standard composition and is widely used in human therapy, mainly for the treatment of diseases related to alcoholism. Silymarin protects and regenerates the liver through its antioxidant and anti-inflammatory effects, but there are other beneficial results from its use. Its main component is silymarin, which is also used in the treatment of cancer. In an earlier study, we investigated the stabilising effect of silymarin compared to quercetin . The use of natural mixtures for stabilisation is well founded, as many synthetic and natural compounds are used in industrial practice as mixtures due to their increased efficiency or lower price.
However, the poor performance of silymarin has raised some questions about the benefits of using pure compounds rather than extracts. Therefore, the goal of this work was to compare pure compound silymarin with natural extracts. We used the same techniques as before and determined the effect of both products on PE degradation and stability.
