ADDITIVES | PROCESSING AIDS


spiral channel testing mould. The results demonstrated that flow can be significantly increased by using wax additives, with the best result of 15% longer than the control Blank 1 achieved with Cevo- process J-4418. The flow extension with Waradur E was around 8% and for both calcium stearate and amide wax between 5.0 and 5.5%. The results are shown in Table 1.


Ejection gains In another study, ejection force reduction enabled by the use of montan waxes in PBT (polybutylene terephthalate) was examined. Montan wax Waradur


E acts as a thermally stable and low volatile release agent in PBT, with typical additions of 0.3-0.5% recommended for unfilled PBT resins and up to 1.0% for filled or reinforced formulations. The PBT formulations (Table 2) were compounded using a Brabender twin screw extruder and pre-dried at 110°C to a residual moisture content of 0.03%. The moulding trials were carried out on an Arburg Allrounder 420C 1000 at a melt temperature of 240°C and the ejection forces calculated from 20 measured injection mould cycles once the process had stabilised. The force required for ejection was measured using a 5kN load cell from Hottinger Baldwin Messtechnik that was axially integrated into the ejector rod. An injection moulding tool with a particularly high shell surface was selected and the precise ejection force calculated using Katman software. The results showed that ejection forces were reduced by approximately 20% using Waradur E. PETS and calcium stearate only reduced the ejection forces by 8% and 11% respectively.


Beyond lubrication


Figure 4: Cycle time reduction and flow improvement – spiral flow injection moulding trials Source: Voelpker


Figure 5: Ejection force results comparing Waradur E montan wax with alternatives Source: Voelpker


With a customer base focused on either innovation, performance or adapting to regulatory change, US-based Hybrid Plastics says that it is seeing a demand for processing aids that offer value beyond traditional lubrication. “For example, processing additives that provide desirable rheological effects in conjunction with modulus enhancement, nucleation capability or dispersion capability are common requests,” says Joe Lichtenhan, Vice-President, New Business Development. “These innovation-based customers are focused on using smart or multi-effect additives to achieve new material performance levels and manufacturing simplifications that improve bottom- line economics. We are also see growing interest in processing aids that do migrate and that do not contain low molecular weight volatiles. Customers in this area most often are seeking regulatory compliance or aesthetics.” There is a real and growing demand for low addition level products. “Additives that can be utilised at low percentages to expand the


Table 2: Ejection force analysis of montan wax and alternatives in PBT. Test formulations Matrix


SHINITE D201NA


(PBT Base polymer grade) + Irganox 1010 [0.5 wt.%]


Source: Voelpker 66 COMPOUNDING WORLD | April 2019 www.compoundingworld.com


Additive None


WARADUR E PETS


Calcium stearate


Additive [phr] 0.0 0.4 0.4 0.4


Comments


Reference/blank Montan ester wax Pentaerythritolester


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