Every DFHB Pipe has to meet structural, mechanical and chemical requirements according to its type and to comply with national standards. The major reinforcing material used for DFHB Pipes to achieve the recommended mechanical properties in the axial and circumferential direction is glass fiber. There are some layers in the wall structure of a DFHB Pipe in which the fibers are the main component and responsible for the excellent mechanical properties of every DFHB Pipe.

Resin

Very detailed specifications have been compiled for Unsaturated Polyesters intended for use in pipe production by centrifugal casting in order to ensure the process ability (gel, exothermic and curing times, viscosity), the compound performance (elastic modulus, tensile and bending strength/strain, glass transition) and the service performance of the pipe during its life cycle (chemical resistance, molecular weight, acid number, heat deflection temperature).

This complete set of specifications is available from DFHB Engineering GmbH and guarantees that the quality of the UP resins, even if from different suppliers, meets the high level of requirements.

Reinforcing Materials

Generally it is possible to mix unsaturated polyester resins with various reinforcing materials of natural or artificial origin. These reinforcing materials are used to achieve certain mechanical properties (stiffness) and also to reduce resin consumption during production.

Typical reinforcing types used in the DFHB process are calcium carbonate CaCO³ powders, such as limestone, marble or dolomite. Limestone is a semi-crystalline material with an age of approximately 110 to 150 million years, whereas marble is highly crystalline dating back some 300 to 500 million years. Both materials are of completely biogenetic origin and are to be found nearly all over the world. Typical sand types for the DFHB process are, similar to filler carbonate or quartz (Si0²),aggregates with a grain size up to 1 mm.

Rubber

Filling the gap between the pipe and joint requires a material which can be deformed reversibly in order to ensure tightness of the pipeline, even if there is relative movement between the pipe and joint. The material sought must be water-resistant and also resistant to a wide variety of chemicals which may be transported together with the water. For that purpose an EPDM (ethylene propylene diene polymer) is the perfect choice. Its excellent ability to restore its shape after having been stressed and relieved and its good chemical resistance are of major importance when being used for sealing profiles.