The use of a shut-off nozzle or valve gating, as well as the screw position control, is advantageous to prevent premature foaming. Our experience has shown that the following adjustments are effective: • The gates and runners should be designed to achieve a quick and uniform filling of the mold • The melt flow should be directed from thin- walled to thick-walled sections • It is important for the mold to have good venting at the end of the flow path, in “dead-end” recesses and at the ejection pins The tooling strength for foam injection molds need not be as high as for solid injection molds as the internal pressure is now lower, due to the reduced viscosity of the base polymer, when the dissolved gases plasticize it. The foaming system typically employs shut-off nozzles and/or valve gates to keep pressure on the melt and keep the gas solubilized.

reSound™ Ultra-Low Carbon Footprint TPEs: These TPE formulations offer an industry-first cradle-to-gate negative, neutral, or near-zero product carbon footprint (PCF) while delivering comparable performance to traditional TPEs. 

The PA6 grade contains 76% PIR, and the PA66 grade contains 78% PIR content, resulting in up to 81% lower cradle-to-gate product carbon footprint (PCF) than traditional alternatives made without recycled content.

Gates Choc Brown GPCX7500

Gates Orange UN2239

Proper positioning of the gate, or mold opening, and proper mold design can minimize flaws. In the mold, use general purpose nozzles (not tapered nozzles) and large, free-flow gates. Runners should be designed with a full round gate and no sharp corners.1

Relocate the gate to minimize the flow length to thickness ratio

In contrast, the bio-derived grade offers greenhouse gas emissions at 2.35 kg CO2e / kg product, a nearly 25 percent lower cradle-to-gate product carbon footprint (PCF) than Avient’s standard Versaflex HC BT218 grade.

Avient’s technical representatives worked with the tool maker to provide insight on venting, gate placement and other tool design concerns to minimize the potential for any tool-related problems.

By incorporating all the parameters (part design, tool layout, processing requirements, and material selection) there is an opportunity to proactively adjust the gate and runner location and size to ensure quality parts are consistently produced.  Ask your material supplier for more information about startup, processing temperatures, shutdown, drying, gate size, gate types, flow rates, purging, regrind, etc.