Background

Nextel® 440 and Nextel® 312 are two similar materials - compositions of ceramic specially developed for the production of continuous filament yarns which are sufficiently flexible to manufacture conventional textile articles such as fabrics and sewing threads whilst retaining much of the high temperature and chemical resistance typical of ceramics. Nextel® 440 has somewhat better tensile properties and a higher upper working temperature but is less flexible than Nextel® 312 and is available from Goodfellow as a yarn.

The fibres are coated with finishes during manufacture which can be removed, if desired, by “heat cleaning” at about 550°C. If the best possible properties are required, further heat treatment at about 1215°C should be used. More details of recommended treatment methods are available on request.
Key Properties

Chemical Resistance










Acids - concentrated


Fair

Acids - dilute


Good

Alkalis


Poor-Fair

Electrical Properties










Dielectric constant


5.7 @ 9.4GHz

Mechanical Properties










Tensile modulus ( GPa )


185

Tensile strength ( MPa )


2000

Physical Properties










Density ( g.cm-3 )


3.05

Refractive index


1.62

Thermal Properties










Coefficient of thermal expansion ( x10-6 K-1 )


5 @ 20-1000°C

Specific heat ( J.K-1.kg-1 )


1000 @ 500°C

Sublimation point (°C )


1800

Upper continuous use temperature (°C )


1350-1650

Properties Alumina/Silica/Boria Fibre




Property








Value

Coefficient of thermal expansion - Longitudinal


x10-6 K-1





4.4

Density


g.cm-3





3.05

Modulus


GPa





180

Tenacity


GPa





2.0