Process Technology for Cyclic Butylene Terephthalate

We deliver the complete process chain for the automated production of fiber-reinforced-composites made with Cyclic Butylene Terephthalate!

This offer includes analysis along the value chain, cost calculations, the theoretical background, pilot plants and process technology for mass production.

Thermoplastic-composites with continuous fiber-reinforcement could be manufactured in cycles of a few minutes!

The main motivation for an innovative process chain is the combination of a novel manufacturing technology with a novel polymer. This symbiosis leads towards a drastic reduction of cycle time. A very low melt viscosity of the polymer allows a super-fast impregnation of the fiber architectures. Within the production, a high molecular weight thermoplastic macromolecule, Polybutylene terephthalate (PBT) is formed (in-situ polymerization).

The polymer
Cyclic Butylene Terephthalate (CBT®) is a cyclic oligomer, which is converted into a high molecular weight, semi-crystalline thermoplastic material (PBT) by an entropy-driven ring-opening poly addition using a catalyst.

Possible process chains (extract)

The interval hot press (IHP) is working in a semi-continuous step-mode and can be described as a technology between a discontinuous press and a continuously operating double band press. A feed unit clamps the support materials, including semi-finished products and ensures a sequential transport of all materials during the stepwise opening. In the pressing stage, the column press builds up the consolidation pressure. The temperature transfer is via the contact of the pressing surfaces and can be fully controlled with several heating and cooling zones.
In contrast to the double belt press, various tool geometries can be represented by the vertical movement of the column press. As a consequence, the technology is not limited to flat panels. U-profiles or closed profiles with floating cores and continuous fiber-reinforcements can be manufactured continuously.

The static pressing with an inductively heated unit, supplied from RocTool consists out of two components: a conventional press and a temperature-controlled tool. Space next to the press, time-distance and pressure regulations, and the parallelism of both tool surfaces are the only special requirements to implement the technology. This novel technology is based on the company developed and patented method of heating and cooling. RocTool uses an electromagnetic inductor and only the functional surface of the tool in combination with the skin-effect. Once the inductor is turned off, the tool can be cooled rapidly by using cooling channels filled with conventional cooling liquids just below the surface.

The major advantage for users is the very rapid heating and cooling rates. Depending on the configuration of the tool and the generator, heating and cooling rates of 100-350 K / min can be realized.

The result
In an economic process model the production costs for a primary unit of “organic sheet” (1000 mm length, 640 mm width, made ​​up of 5 layers of prepreg with an areal weight of 620g/m²) in various processing technologies were analyzed. Furthermore, the economic study highlights the differences between the manufacturing of classic PBT and reactive CBT.

Comparison of the production costs

The combination of modern processing technologies and the use of novel polymers allows to halve the production cost.

Steeg, M.: Prozesstechnologie für Cyclic Butylene Terephthalate im Faser-Kunststoff-Verbund. In: Prof. Dr.-Ing. Peter Mitschang (Hrsg.): IVW Schriftenreihe Band 90. Kaiserslautern: Institut für Verbundwerkstoffe GmbH, 2010