The technology for the cyclic butylene terapthalate CBT produced by US start-up Cyclics (Europe: NL 4600 AC Bergen op Zoom; www.cyclics.com) was developed by GE Plastics and acquired by Cyclics´ shareholders in a management buyout in 1999. Starting material for the versatile polymer is polybutylene teraphthalate (PBT) with a melting point of 195 °C. With the help of an initial catalyst, the PBT chains are first converted into ring molecules. A polymerisation catalyst then opens the ring and transforms the material back into PBT.

A distinct feature of CBT is its water-like viscosity, which Cyclics says “promotes easy processing in a variety of applications.” It can be processed alternatively as a thermoset or a thermoplastic. In the lower viscosity range, glass fibre mats can be impregnated faster and safer than is possible with the honeycomb-like structure of thermoplastics, the company says. In contrast to polyolefins, CBT is claimed to be suitable for painting.

The price for a kilogramme of ready-to-process CBT is under EUR 10 and thus in the region of PA 11 and PA 12, or PPS. The company currently supplies two grades. The standard “CBT 100” and “CBT 200” are for low processing temperatures (170-240 °C) and longer processing time. Materials with higher flame-retardancy, for contact with food, along with higher rigidity, are being developed.

According to Cyclics, the viscosity of CBT can be increased for use in rotational moulding. After this polymer has been fully commercialised, the company plans to pursue cyclic modification of other polyester grades as well as polycarbonate. Patents for these applications were acquired in 1999 in the buyout.

• e-Service:
Data sheet for CBT 100 as PDF document (41 KB)
Data sheet for CBT 200 as PDF document (41 KB)