MATERIALS | ADDITIVES
matrix, promoting the formation of a network that leads to improved melt strength, even at very low loadings.
Above: BASF’s IrgaCycle solutions address recycled resin quality issues and can improve processability, long-term thermal
stability and outdoor weathering protection
toxicology knowledge and regulatory support. He stresses the group’s ability to be a partner to the mechanical recycling industry and that this value chain collaboration is important in driving the sustainability changes that are needed. The first five IrgaCycle grades from BASF are:
IrgaCycle PS 030 G, which enhances long-term thermal stability in rigid applications and is intended mainly for recycled HDPE, polyolefins and mixed polymers; IrgaCycle PS 031 G for improving processing and long-term thermal stability of recycled LDPE and LLDPE for incorporation into films and related flexible packaging applications; IrgaCycle PS 032 G, which provides processing stability and long-term thermal protection for recycled PP and polyolefin blends containing impurities; IrgaCycle UV 033 DD, which combines weathering stability with enhanced thermal and processing stability for reclaimed HDPE and PP blends for re-use in outdoor goods; and IrgaCycle XT 034 DD, which is said to rejuvenate processing, improve long-term heat stability and to help neutralise impurities to improve mechanical properties.
Right: Fraunhofer LBF says novel additive solutions are needed to successfully recycle plastic parts such as car battery cases
BASF says one advantage of the IrgaCycle additives lies in their ready-to-use granulated non-dusting product form, which ensures safe and easy dosing during converting or compounding. The group is continuing its research investigations into recyclates, for example to increase its under- standing of properties after repeated cycles in the mechanical recycling process. Improvement of properties in polyolefins containing recyclate — specifically high melt strength PP — is the goal for the latest additive introduction from Cray Valley. Dymalink 9200 is an acrylate functional zinc salt that reacts with aliphatic polymers to form a carbon-carbon covalent link. The company says the polar zinc cations tend to assemble into ionic clusters within the polymer
54 PLASTICS RECYCLING WORLD | October 2021
High melt strength PP (HMS-PP) is most com- monly used for extrusion of foams and thermo- formable sheet. Thermoforming in particular can produce a large amount of scrap, which can be added back to the original compound. But be- cause the regrind has lower low melt strength than the virgin polymer, only a relatively modest amount can be incorporated back into the base compound. Dymalink 9200 is said to combat this. Experi- ments carried out at Cray Valley simulated regrind material by passing a commercially available HMS PP through a twin-screw extruder up to four times. This was then compounded with Dymalink 9200 at 1%, 1.5% and 2% addition levels before specimens were cut from compression moulded sheets and tested on a TA Instruments DHR-2 using an SER3 elongational viscosity fixture. Elongational viscosity testing was performed at 180°C using a constant strain rate of 0.1s-1. In the first stage of testing, one pass through the
extruder was enough for the HMS-PP to see a reduction in melt viscosity of 90%. During this study the 1.5% loading of Dymalink 9200 proved to be optimum for the material and increased the elongational viscosity by more than 800%, from 125,000 to 1,139,000 Pa.s. In the second stage, the regrind sample contain- ing 1.5% Dymalink was blended into virgin HMS PP and compared against compounded regrind containing no Dymalink. The regrind addition was increased by 5% increments up to 25% of the total compound. The elongational viscosity of the 95/5 base compound/regrind control was measured at 587,000 Pa.s. With 1.5% Dymalink 9200, an elongational viscosity of 687,000 Pa.s was achieved with 25% regrind. The Dymalink-modified regrind at 5% level achieved a higher melt viscosity than
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IMAGE: SHUTTERSTOCK
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