ADDITIVES | ANTIOXIDANTS & STABILISERS
Right:
Ampacet’s Agristab 372 UV stabilising masterbatch offers better greenhouse film perfor- mance where sulphur fumigation is used
MFI after even a single extrusion following oven ageing,” Marshall says. “Adding additional antioxi- dant during recycling (following the oven ageing) does help retard further increases in MFI during subsequent multiple extrusion, but it does not eliminate the differences observed in the first post-ageing extrusion, nor does it undo any damage already done to the polymer.” This is shown in Figures 1a and 1b. Everspring’s work has demonstrated that the
presence of sufficient levels of active hydroperoxide decomposers (its Everfos 626 and 9228 for exam- ple) in the polymer as it is being melted for recycling is important to maintain the polymer’s properties. “This is because hydroperoxides, which form during the service life of the polymer in air, are relatively stable at ambient temperatures but rapidly decom- pose causing a surge in oxidation reactions while the polymer is being heated for reprocessing but before any additional antioxidant can be blended in to the polymer melt,” Marshall says.
Agricultural options Moving to products with lifetimes measured in years rather than weeks and months, Ampacet has introduced Agristab 372, which it describes as a highly effective UV-stabilising masterbatch that outperforms conventional HALS and NOR HALS stabilisers typically used in greenhouse film when pesticides are heavily used. “Typical greenhouse film containing conven- tional NOR HALS stabilisers is designed for maximum 3,000 ppm sulphur content and three years, or four seasons, of effectiveness, while the market tends to require greenhouses with longer life-spans and higher pesticide usage, to withstand up to 5,000 ppm sulphur for a duration of more than three years,” the company says. Sulphur evaporators are one of the most commonly-used methods to fumigate greenhous-
es. But the use of sulphur fumigation leads to a loss of UV stabilising properties of the greenhouse film as photo-oxidation of sulphur deposited on the greenhouse film surface can yield acidic species, deactivating HALS stabilisers. Ampacet says Agristab 372 provides greenhouse film with outstanding resistance to pesticides, allowing usage of up to 5,000 ppm sulphur for a green- house that can last for more than three years. It does not affect the colour of the film and offers very high light transmission. Solvay has introduced Cyasorb Cynergy Solutions M528 light stabiliser, specifically devel- oped for masterbatch producers. “Its value lies in the additional formulation flexibility and increased production efficiency that it imparts by enabling the masterbatch producers to produce either super- concentrates or combi-batches, resulting in lower let-down and higher profits,” says Andrea Landuzzi, Global Marketing Director, Technology Solutions – Polymer Additives, at Solvay Technology Solutions. This new UV stabiliser is part of Solvay’s M
Series, which the company says ensure good long-term quality protection for general PE durable injection and blow moulded articles – crates, boxes,
Figure 1a and 1b: Recycling presents greater challenges for polymer stabilisation. A system that works well to protect virgin PP through multiple reprocessing steps (Figure 1a) can be far less effective when the material has a previous service exposure history (simulated in Figure 1b by oven ageing).
40 COMPOUNDING WORLD | September 2018
Source: Everspring Chemical
www.compoundingworld.com
PHOTO: AMPACET
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