materials feature | Additives for PET
Developments in PET
additives will continue to
create opportu- nities in a variety of
applications
Compatibilized recyclate has higher strength, greater elongation at break and improved low-temperature impact toughness. Recyclate can, the company maintains, be used to injection mould high-perfor- mance, thin-walled containers. Entira additives are also used to simplify construc- tion of some food packaging. The materials can be modifiers in CPET (crystalline) and APET (amorphous) trays. In CPET they improve low-temperature impact properties in frozen (down to -40°F) foods and promote cross-linking. In APET they increase impact strength in refrigerated trays.
trade association, says that more PET is recycled in Europe than any other polymer type, and that more than 60 billion PET bottles were recycled across the region in 2012. In North America, more than 400,000 tonnes of PET was recycled in 2012, according to the region’s PET and plastics recycling associations. This is good news for suppliers of additives that are
used to maintain or improve key resin properties, such as transparency, oxygen barrier and impact strength, allowing recyclate to be used in more demanding applications. One problem in recycling is commingled resins, and
DuPont is targeting this issue with a new line of additives, Entira EP, designed to compatibilize incom- patible polymers. The initial grades are ethylene copolymers that have been optimized for mixed polyolefin streams, primarily polypropylene and polyethylene. Jose Torradas, senior technical consultant, says the company is developing versions that will compatibilize other commingled resins. These include PE and polyamide, PE and ethylene vinyl alcohol, and HDPE and PET. This last reflects the extensive use of HDPE caps, closures and seals in PET beverage bottles and rigid containers. DuPont reports that Entira EP is formulated for
efficient compounding with reground recyclate in twin-screw and single-screw extruders. Depending on its formulation tailoring, Entira additives yield compounds with almost the same properties as the major blend fraction. Resulting materials are suitable for injection moulding, blow moulding and extrusion, and can be used in virgin blends, as a core layer, or even by themselves in some applications. It is claimed that the additive also minimizes melt-filter cleaning operations during compounding. The ethylene propylene compatibilizers generate
strong adhesive bonds to one or both mixed resins, and are effective at loadings down to 4%, DuPont says.
64 COMPOUNDING WORLD | March 2014
Sustainable trends Compounders and others can expect recycling to benefit in coming years from further developments in additive technology. One area that is bound to be active is bio-based PET. “There is interest in producing bio-PET,” affirms Torradas. “It’s not a reality yet, but somebody will figure out how to make [bio-based versions] of the co-monomers.” When that happens, DuPont and other suppliers will
follow suit with bio-based additives. “We would develop bio-modifiers in place of petrochemical-based materi- als,” he adds. DuPont might already be on the leading edge of such
research. In 2011, the company acquired Danisco of Denmark, whose products and technologies comple- ment the chemical giant’s interest in biomaterials and sustainable technologies. “Anything involving biopolymers or green materials
is hot,” remarks Kulkarni of Americhem. His company offers masterbatches with colorants for recycled PET fibre compounds. Adding colour and other properties to the recyclate eliminates the need for chemical dyes and water during fibre spinning. “It’s a greener way of colouring,” he says, “and a good sell for recyclate.” Based on these observations, it is clear that
developments in additives for recycling and other uses promise enhancements to PET compounds that will maintain market momentum in all of the resin’s forms and create opportunities for new and at times radical applications.
Click on the links for more information: ❙
www.americhem.com ❙
www.ampacet.com ❙
www.aschulman.com ❙
www.colormatrix.com ❙
www.dupont.com ❙
www.invista.com ❙
www.polyone.com ❙
www.sukano.com
www.compoundingworld.com
PHOTO: POLYONE
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