MATERIALS | COMPATIBILISERS
a batch of pellets mainly processed from used ropes and nets that were recovered from the ocean. The composition of the ocean plastics was approximately 1:1 weight ratio of HDPE and iPP. They displayed brittle mechanical properties, and break upon stretching without much elongation. By adding 2 wt.% of the compatibilisers developed by Intermix, toughness was significantly improved to over 800% elongation at break. Lin says compatibilised HDPE/iPP blends “now become promising materials which could be reprocessed into products, regardless of the composition and inseparability of the recycled HDPE/iPP blends. This can significantly decrease the cost for plastics recycling and enhance the recycle efficiency.” Intermix Performance Materials is collaborating with toll manufacturers to scale up the productivity of the compatibilisers from gramme scale to kilogramme scale. “Products made of recycled HDPE/iPP blends may soon be realised,” says Lin. Nexam Chemical has developed a product con- cept it calls Reactive Recycling for improved performance in mixed recycled polymer streams that are difficult to recycle. One example is recycled PP containing HDPE. ”Nexamite R201 provides compatibilisation of PP and PE by reacting the polymers together creating a PP/PE hybrid,” says Chief Marketing Officer Lars Öhrn. “Tensile testing is showing less variations when R201 is added to an 85% rPP and 15% rHDPE mix.”
Tensile testing of tensile bars composed of (left) uncompatibilised ocean plastics (note the break at the middle of tensile bar), and (right) ocean plastics compatibilised with 2 wt.% compatibilisers developed by Intermix Performance Materials Source: Intermix
Another example is PE containing polyamide.
Tensile testing has shown improved mechanical performance and surface appearance when adding Nexamite R405 to a mix of 93% HDPE and 7% PA 6, yield stress is improved, and break strength is on a par with pure HDPE. Öhrn says details of the reactive chemistry are confidential, saying only that “it functions in polyolefins but can also bridge and react with
Comparisons of properties of blends with and without Nexamite compatibilisers Yield Stress (MPa) 25.6 23.7 27.3
100% HDPE 93% HDPE /7% PA6 88% HDPE/7% PA6/ 5% Nexamite R405 (%)
Yield Strain (%) 12.9 10
10.6 100% rPP 100% rHDPE 85% rPP/15% rHDPE
80% rPP/15% rHDPE/5% Nexamite R201 Source: Nexam
Photos of tapes extruded with different materials, extruded on a Brabender lab 25D, 20 mm, single-screw extruder. Images show sections of tape approxi- mately 3.75cm across
28
11.3 8.8
10.2 12.5
(MPa) 33.1 30.3 24.9 30.1
(%) 632 747 505 648
Break Strength (MPa) 42.7 34.2 42.6
Yield stress Yield strain Break Strength Break Strain Break Strain MFI (MPa) 27.6 34.7 27.1 27.2
123 150 18
2.5 1.2 2.4 1
Std dev (g/10min) 62
100% HDPE
Mix of 93% HDPE, 7% PA6
Mix of 88% HDPE, 7% PA6, 5% Nexamite R405
PLASTICS RECYCLING WORLD | May/June 2022
www.plasticsrecyclingworld.com
IMAGE: NEXAM
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