PETpla.net Insider 10 / 2013

MATERIAL / RECYCLING 37 PET planet insider Vol. 14 No. 10/13 www.petpla.net At its K 2013 press conference, BASF Plastics Additives introduced an additive designed to be used in the recycling of PET. The additive, known as Joncryl ADR, is claimed to help recyclates to achieve high performance characteris- tics, superior even to virgin product: The keyword is upcy- cling instead of downcycling. Downcycling through pro- cessing and re-processing The polymer chains of a recycled plastics material are exposed to harsh conditions, not just at the reprocess- ing stage but even the original com- pounding and processing can lead to a reduction in the average molecular weight. There are the further stresses to which they are exposed during their “active life”, for example, reactions due to ageing , hydrolysis and contact with acids, laundry detergents or other aggressive media. For these reasons, neither fresh recyclates nor even scrap and faulty batches from the manufacturing process have generally been able to compete with the material properties of virgin material itself. A special case is PET, a plastic not actually produced by BASF. All over the world PET bottles are col- lected, comminuted, washed and pelletised on a huge scale. The pel- lets obtained are remarkably uncon- taminated with other types of plastic. This is why mechanical PET recy- cling makes a lot of sense compared with some other plastics where this level of purity can only be achieved at significantly greater expense and inconvenience. Nonetheless, even the use of recycled PET polyester was for a long time limited to simple applications such as fibre produc- tion; melt strength was not sufficient to manufacture high-grade packag- ing because of the shortened chain lengths of the molecules. The result is downcycling of the material which means that it is only suitable for use in applications of lower quality. The problem with insufficient melt strength of PET recyclates can be solved by using functional addi- tives from BASF such as Joncryl ADR. These are chain extenders, i.e., molecules that attach to the ends of broken polymer chains. They act like an adhesive which sticks the split polymer chains back together again and so repairs or “heals” them at a molecular level. Not only are the original chain lengths and hence melt strengths restored as a result; the molecular chains produced can be even longer than in the original material, depending on the amount of additive incorporated. Consequently, the restored material can be used not only to make bottles again, but it can also be processed into sheets that are thermoformable into packaging - such as cups for the food industry. In addition, Joncryl ADR additives can also endow the recycled polyester with completely new and desirable prop- erties. Chain extenders having multiple reactive sites can link polyester frag- ments together to form highly branched polymers of high molecular weight which are completely unobtainable initially via conventional poly-condensation reac- tions; they then also display correspond- ingly interesting mechanical properties. Joncryl ADR 4300 equips recycled PET for example with increased tensile strength useful in packaging straps or high-tenacity fibres. PET with glass fibre Exclusively in the USA, BASF offers Petra 7030, a special easy-flow injection-moulding PET with 30% glass fibre content, based on recycled mate- rial. Petra 7030 combines high strength and stiffness with very good dimen- sional stability, low creep and good high-temperature properties. Because of its good flow properties, the prod- ucts fabricated from the material have a high-quality surface finish even with- out painting. Petra 7030 has already come to be used in the 111 Navy Chair, manufactured by the furniture maker Emeco and presented during the design competition of the North Ameri- can plastics fair NPE 2012. It is made from recycled PET bottles. www.plasticadditives.basf. com