Trexel Inc. (Wilmington, MA), the company that developed and commercialized the MuCell process for the production of microcellular foamed parts in injection molding, blowmolding and extrusion, announced that it will now offer TecoCell, a chemical foaming agent (CFA), to its customers.

Trexel long believed that CFAs could not produce a consistent microcellular structure needed for foaming thin-wall parts. However, in the course of Trexel's research and development with Polyfil's EcoCell product line, it was able to identify process conditions that did, indeed, create generally consistent microcellular structures within certain parts and with specific materials. This now enables Trexel to offer multiple high-performance foaming products to its customers, depending on their exact requirements, by applying Trexel's expertise in designing and molding foamed parts with the TecoCell chemical agent.

TecoCell is Trexel's brand name for Polyfil's EcoCell. "We want to distinguish this product for our activities in the injection and blowmolding markets versus Polyfil, which is serving the extrusion market with its EcoCell," said Levi Kishbaugh, VP Engineering for Trexel, in an interview with PlasticsToday. "It differentiates the companies between markets."

Originally developed by Polyfil, this chemical foaming technology has only one reaction point. Unlike most foaming additive systems, TecoCell does not produce corrosive byproducts or require scavenger technology. Trexel has exclusive rights to commercialize TecoCell for all injection molding and automotive blowmolding applications, while Polyfil will market its EcoCell line of CFAs for extrusion.

TecoCell has a reaction temperature of 200°C (393°F), at which point the system releases CO₂ to create a microcellular structure in the range of 20 to 80 microns. As with all foaming systems, the optimal size of the cell will depend on process conditions and the type of material used as well as part geometry. This system is targeted at injection molding across all industries and specifically at automotive blowmolding applications. Weight reductions of 30 to 35% for blowmolding and 7 to 10% for injection molded parts are typical for this additive package. The blowmolding applications have seen excellent property retention, according to the company.

Kishbaugh explained that Trexel has supported the automotive market for blowmolded components, primarily vehicle ductwork, with the MuCell process for a number of years. Now it also will offer the TecoCell chemical foaming process, which features some property benefits as well as cost savings. "The accumulated blowmolding process using MuCell requires some material modifications based on the fact that if you incorporate enough nitrogen to get good cell nucleation in the part, the parison melt strength is compromised," he said. "TecoCell serves as both the foaming agent as well as nucleating agent."

For injection molding, especially in unfilled olefins—and HDPE in particular—Kishbaugh explained that the tendency is to see a drop-off in impact properties. "Running a relatively high nitrogen level to get good nucleation reduces the impact strength," he said. "The self-nucleating feature of TecoCell means that we maintain better impact strength, particularly with HDPE materials."

TecoCell, which is produced through a specialized and patented process, creates a homogeneous gas/cell matrix by utilizing uniform size CaCO₃ particles of 0.08 microns. The CaCO₃ nano particles distribute themselves evenly in the material system, resulting in a strong and consistent cell structure throughout the blowmolded or injection molded part. The uniformity of the cell gives the user a lightweight part with low warpage, faster cycle times, better stiffness and higher heat distortion properties.

In addition to automotive applications, TecoCell will offer an excellent alternative for injection molded thin-wall packaging. Packaging applications will benefit both in terms of material costs and material flow. TecoCell, which may be added at levels ranging from 1 to 3%, involves relatively low capital investment but has high annual operating costs. For example, a 2% additive level may result in an additional cost of $0.06 per pound of end product.

TecoCell will save on upfront investment costs, however, because no special equipment is needed, such as the nitrogen system that is required for the MuCell process. "We have customers that have volumes that don't justify the investment in the MuCell system," Kishbaugh noted. "TecoCell is an excellent alternative foaming method for a low-volume application."