February 2016

Improved Surface Appearance for Medical Housings

Today’s medical device OEMs and their customers demand appealing surfaces for housings and functionality with the opportunity to reduce manufacturing costs. To meet this demand, Covestro has developed the perfect response: hot molds, cool designs.

To evaluate the effect of rapid heating and cooling technology for improved surface appearance, Covestro recently installed a water-based dynamic mold temperature controller at the Pittsburgh-based North American headquarters. The dynamic temperature controller contains a hot and cold water circuit that allows the user to adjust each circuit temperature to optimize the heating and cooling of the mold during all phases of the injection molding process. It works by heating the surface of the cavity prior to injection, and then cooling it throughout the holding and cooling phase of the cycle.

With the help of this technology, it is possible to eliminate surface defects like visibility of material fillers, weld lines and surface blush, while also being able to generate high- and low- gloss parts, all within a single cavity. A broad range of Makroblend® polycarbonate+polyester (PC+polyester) and Bayblend® polycarbonate+acrylonitrile butadiene styrene (PC+ABS) grades by Covestro can be molded with rapid heating and cooling to deliver high-quality surfaces and style designs that offer medical OEMs and molders countless possibilities and significant cost savings.

Bayblend® T88GF10, a 10% glass-filled PC+ABS, was used to mold the above parts, both with and without the rapid heating and cooling process. The rapid heating and cooling example was not only able to hide the presence of the glass fiber on the surface, but also eliminated cosmetic issues like weld lines, surface blush and read through. It also exhibited higher gloss on the polished areas of the part, while providing lower gloss on the textured areas of the part due to the better replication of the mold steel.

The above part was molded with Bayblend® T85HG, an inherently high-gloss PC+ABS. The rapid heating and cooling process allows for designers and molders to control the amount of gloss through different texturing and polishing methods, as well as the temperatures used during processing. Despite being high-gloss, a matte finish was achievable through the use of laser texturing and micro-etching on a portion of the cavity, while still maintaining the mirror-like, high-gloss finish on the polished portion of the cavity.

For more information, visit solutions.covestro.com/en/materials/plastics or email plastics@covestro.com.

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