ADDITIVES | LUBRICANTS AND PROCESSING AIDS
And even if the market would accept a lower-quali- ty appearance, a PPRA can be important for reducing the pressure in the machine to improve output,” says Lowrie. “PPRA can be added to virgin resin by resin producers who want their materials to process well even when recycled. In addition, PPRA can be added by a compounder or as a masterbatch to help recyclers with processing and product appearance.”
Figure 3: Study showing % melt fracture as a function of elapsed time for blends of two LLDPE grades with and without PPRA additives (LLDPE 1 with no PPRA, LLDPE 2 with 500 ppm PPRA) Source: Arkema
melt index materials, he says. When used in recycled polymer compounds,
processing aids can also relieve processing variation and reduce degradation and discolora- tion. Arkema has come up with a new name for additives that provide these benefits and are intended to be added to a recycled polymer or one that is expected to be recycled — a polymer processing and recycling aid (PPRA). The company says PPRAs should not contain added per- or polyfluoroalkyl substances (PFAS) as these environmentally persistent organic chemicals are being regulated or phased out in many applica- tions, including recycling. Arkema says that its fluorinated processing aids — the Kynar Flex line of polyvinylidine fluoride [PVDF] copolymers — are manufactured without use of PFAS surfactants and so meet this requirement. “PFAS has not been used in manufacturing of
Kynar Flex PVDF since 2016,” says David Seiler, Americas Business Manager, Industrial and Fluoropolymers Global Advisor at Arkema. “PVDF is known to be nonreactive. It is used, for example, in pharmaceutical manufacturing equipment, and is FDA food-contact compliant.” Given the many pledges to increase recycled
content, particularly in plastics packaging, proces- sors are expected to be adding higher percent- ages of recyclate. “A lot of companies are blending in 10-20% recyclate now, but this percentage will go up. People are looking even at 100% recyclate,” says Lowrie. This shift is expected to affect product appear- ance and processability. “PPRA can help with the aesthetics of these high-recycled content products.
24 COMPOUNDING WORLD | April 2022
Proven benefits In a controlled experiment (Figure 3), the company compared an LLDPE containing 500 ppm PPRA to LLDPE with no PPRA by first extruding each into a monofilament, grinding, and extruding again into a pellet. The reprocessed materials were then extruded with a flat die to compare processing pressure and melt fracture of the pure materials and blends of the two. Having just 25% of the LLDPE containing PPRA in the blend had some effect on reducing melt fracture and extruder pressure. Increasing the level of the PPRA-contain- ing reyclate helped to more quickly reduce melt fracture and pressure. The Evonik range of processing aids are based
on organo-modified siloxane (OMS) chemistry and are designed primarily for compounds and master- batches going into film extrusion applications, including highly filled compounds and compounds containing recycled polymers. The additives act as internal lubricants to improve processing, aid homogenous dispersion of pigments and fillers, and to improve final part properties such as long-term scratch resistance, reduced coefficient of friction, enhanced haptic properties, increased hydrophobicity, and prevention of bloom over the lifetime of the polymer, says Ido Offenbach, Americas Segments Manager for Compounds & Adhesives at Evonik Interface & Performance. The company’s newest OMS polymer processing
aids (PPAs) for film extrusion include Tegomer 6810 (for PE) and Tegomer 6850 (for PP). They are being positioned as halogen-free PPAs that provide alternatives to fluorine-based elastomer PPAs. The company reports that the OMS PPA also functions as a permanent slip enhancer.
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.noracadditives.com �
www.clariant.com �
http://greenpolymeradditives.emeryoleo.com/additives/ �
www.greenmantra.com �
www.voelpker.com �
www.arkema.com �
www.evonik.com
www.compoundingworld.com
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