Engel Advances In-Situ Polymerization of Polyamide Composites

Engel is significantly fine-tuning a potentially game-changing approach to the production of composite parts.

The overall technology is the anionic polymerization of caprolactam to polyamide 6, which allows full wetting without disturbing carbon or glass fiber placed in injection molds. The approach reflects a trend to recyclable composite components, and the use of the highly productive injection molding process, which allows molded-in features.  

Engel made a relatively low-tech demonstration of the technology at K2016, showing the production of a shovel. The mold was made by Schofer, Schwertburg, Austria, which is a specialist in the development of in-situ molds.  The demonstration showed that the technology had developed significantly since the first prototype machine was shown in 2012.

An evolution of the technology is disclosed in a U.S. patent application published yesterday. In brief, the new approach uses the sprue as a mixing chamber in an effort to overcome sealing problems. High pressure must be maintained in the sprue, and the use of a pressure sensor is recommended.

At K2016, pre-formed, dry reinforcement textiles were placed in the first cavity and infiltrated with the reactive matrix (εcaprolactam). The solid ε-caprolactam was melted and metered in the reactive aggregate. Since reactive processing takes place below the polymer’s melting temperature, the composite semi-finished product was transferred to the second cavity immediately after it was produced where it was functionalized by injection molding. Reinforcing ribs and contours made of short-glass-fiber-reinforced PA 6 were molded on.

Lead inventors of the new technology at Engel are Norbert Müller, development chief at Engel’s Center for Lightweight  Composite Technologies in St. Valentin, Austria and  Lorenz Reith, a reactive mixing expert. 

Patent drawing shows the position of the shut-off needles (13) in the closed position, directly sealing at the sprue (4). (USPTO)

About Doug Smock

Former Chief Editor at Plastics World and Senior Technical Editor Design News
Automotive, Carbon Composites, Carbon Fiber, Europe, Industrial, Injection Molding, Molds & Moldmaking, Polyamides , ,

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