One of the most significant processing advancements in thermoplastic injection molding is the development of “hot runner” or “runnerless” melt delivery systems which eliminate the cold runner and sprue by never allowing these flow paths to cool. Hot runners are often utilised in production programmes where volumes exceed 200,000 units per year, reducing scrap by as much as 80%, for a very large savings in material costs.
Tests in hot runner systems confirm that these time and money saving techniques can be used with Victrex materials with no degradation to the polymer.
Husky Hot Runner. © Courtesy: Husky 2015
High performance materials for efficient hot runner production: Thermal stability is key
While hot runners seem like an obvious choice, many polymers are limited by their sensitivity to thermal degradation when exposed to heat for long periods of time. Thermal degradation dramatically affects both mechanical properties and cosmetic properties of the molded part, so engineers must give serious consideration to the thermal stability of a material when selecting hot runner processing.
Unlike many other engineering plastics, VICTREX™ PEEK polymers offer a solution to both the properties and processing challenges of many consumer electronics parts with their high temperature performance, broad chemical resistance, and excellent thermal stability.
A range of VICTREX™ PEEK polymer grades were successfully processed using a Husky hot runner system with a Husky VX valve gate. A drop in molecular weight could lead to embrittlement or other loss of mechanical properties. Testing by Gel Permeation Chromatography (GPC) shows essentially no change in the polymer’s molecular weight after processing in the Husky system, even with processing temperatures of up to 400°C and extended residence time.
We have processed VICTREX PAEK high performance polymers with our Husky hot runners and controllers and have achieved great results. With proper molding guidelines in place, we are able to run a very consistent process to produce parts with exceptional mechanical properties and cosmetic appearance. Furthermore, we did not have any thermal degradation issues which can often be a problem when using some other engineering resins.
By working together, we have proven that utilizing our hot runner systems and controller to mold VICTREX PAEK parts can reduce waste by 50-80%. This innovative, eco-friendly solution means significant cost savings for our customers.