additives | Compatibilisers
react easily with the acid or hydroxyl functions of the matrix backbone, increasing the polymer molecular weight and enhancing melt strength and impact properties. The low Tg of the acrylic rubber core also has a positive effect on impact performance and limits crack propagation in the matrix. German distribution company Velox highlights the
Figure 2: Effect of SAG-008 on the flow properties of recycled polyamide Source: Velox/Fine-Blend Compatibilizer Jiangsu
Dow highlights the use of its acrylic impact modifiers
(AIMs) to upgrade recycled plastics, claiming benefits over alternatives such as SBS and MBS due to their more resilient structure and proven resistance to yellowing. Yannick Saint-Gerard, Sales Development Manager EMEAI for Engineering Plastics Additives, cites an application in recycled polycarbonate noting that the physical and mechanical properties of the polymer can be significantly degraded by recycling due to its thermal sensitivity, which translates into chemical backbone alteration even after a few processing cycles. The resulting material shows an increase of the melt flow rate, loss of impact strength and a lower molecular weight. Compounding with acrylic core-shell rubbers helps
to upgrade properties. “Core-shell rubbers have a pre-defined size and shape, typically well retained during the different steps of plastic processing, allowing the modifier to perform at same level even after a number of processing cycles,” says Saint-Gerard. “Additionally, the core-shell rubber particles disperse easily into the matrix and yield a uniform morphology independent of the processing conditions. This there- fore offers a wide processing window for compounders, which is an advantage when sourcing multiple resins with fluctuating quality.” Addition levels as low as 3 wt% of Paraloid EXL-2300
are usually sufficient to obtain high impact strength at ambient temperature starting from a lower quality material, Saint-Gerard claims (Figure 1). Applications have been developed based on automotive scraps, as well as recycled CDs and sprues. Paraloid EXL-2300 offers yellowness resistance in recycled PC applications even after several processing cycles. Paraloid EXL-2314 is an epoxy functional acrylic
core-shell rubber that can be compounded with recycled PET to upgrade impact strength and melt strength for applications not requiring transparency. The epoxy groups grafted on the shell of the rubber
48 PLASTICS RECYCLING WORLD | June 2017
Figure 3: Addition of 1% of Recycloblend 731 to a recycled PA results in a 20% improvement in tensile strength Source: PolyAd Services
www.plasticsrecyclingworld.com
Fine Blend range from Fine-Blend Compatibilizer Jiangsu, which it offers in most European countries. In particular, it cites styrene-acrylonitrile-glycidyl methacrylate (SAG) copolymers. “Fine-Blend SAG series show numerously advanced properties such as phase stability improvement and heat resistance of PC, polyesters and blends,” says Vanessa Haye, Product Manager in the company’s additive division. She says it can also be used as a chain extender in recycled polyesters, polycarbonate, as well as polyamides. The grade SAG-008 has a high concentration of epoxy groups, which can react with the terminal groups of the recycled polyester to prevent further degradation, increasing the melt viscosity and improving processing stability (Figure 2).
Progress with polyamides Quality improvement of recycled plastics through selected additives is one of the core topics at the Fraunhofer LBF Institute for Structural Durability and System Reliability. “Currently we dedicate substantial resources to the evaluation of the recyclability of halogen-free flame retarded plastics,” says division director Rudolf Pfaendner. The work is being carried out with funding from the Industrial Community Research of the AiF (German
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