Frequently Asked Questions
Do Nextel™ Ceramic Fibers pose any health risks?
Nextel™ Ceramic Fiber diameters are greater than 6 microns and therefore considered nonrespirable with no chronic health effects. They can however cause mechanical irritation of the eyes and skin and it is recommended that measures to minimize eye and skin contact be taken. For more detailed information. More about Health and Safety of Nextel™ Ceramic Fibers (PDF, 116Kb)
What is the difference between 312, 440, 550, 610, and 720?
The fiber nomenclature is used to indicate various compositions. The different fiber chemistries and resulting properties make them uniquely suited for specific applications. For more detailed information see the Table of Applications for Nextel™ Woven Fabrics.
What is sizing?
Sizing is a coating applied during the manufacture of the fibers. The coating protects the fibers during handling and textile processing by increasing lubricity and bundle integrity.
Do I need heat cleaning or heat treating?
Heat cleaning is recommended if the fiber or fabric is to be used in one of the following: resin prepreg, silicone rubber coated fabric, electrical insulation for thermocouples or heaters, in reducing atmospheres or vacuum, or when adequate ventilation does not exist for the initial burn-off of sizing in the application. Heat treating is recommended for Nextel™ Fabric 312 that will be used in hot wet environments or in areas where chemicals are present that could be detrimental to the strength of the fabric. Heat treating can also be used to reduce the stress of the fiber and minimize the unraveling in the cut ends of braided sleeving or fabrics.
How do I select the appropriate fabric or fiber?
The family of Nextel fibers were developed to serve a variety of needs. Nextel™ Fibers 312, 440 and 550 are designed for non-structural applications where their primary purpose is to insulate or to act as a flame barrier. Nextel™ Fibers 610 and 720 are composite grade fibers designed for load bearing applications in metal, ceramic, and polymer matrices. The industrial fibers, Nextel™ Fiber 312 and 440 are made from Al2O3, SiO2, and B2O3 at varying percentages. These compositions have both crystalline and glassy phases. The glassy phase helps the fiber retain strength after exposure to high temperature. However, the glassy phase also weakens the fiber when stressed at high temperature. Nextel™ Fiber 550 does not have a glassy phase. Its strength is lower than Nextel™ Fiber 440, but it retains strength better at temperature. The composite grade fibers, Nextel™ Fibers 610 and 720 have more refined crystal structures based on alpha-Al2O3 and do not contain any glassy phases. This allows them to retain strength to higher temperatures than the industrial fibers. Nextel™ Fiber 610 has essentially a single-phase composition of alpha-Al2O3. It has the lowest strength retention at temperature even though it starts with the highest strength at room temperature. Nextel™ Fiber 720, which is alpha-Al2O3 with SiO2 added (forming alpha-Al2O3/mullite), has better strength retention at temperature and lower creep.
When selecting the fiber type for a particular application, it is important to consider all these factors. If the fiber/fabric will not have to support a load at temperature, the lower-cost industrial grade fibers may be appropriate. However, if the fiber will be load bearing at temperature as in ceramic matrix composites, then one of the composite grade fibers would be a better choice. Of course there may be other factors, such as corrosion, chemical resistance, or atmospheric conditions that may require trade-off in the selection process.
More information and data can be found in the Nextel™ Technical Notebook.
All literature is in pdf (Adobe Acrobat) format. For a free copy of Adobe Acrobat visit: http://www.adobe.com/products/acrobat/readstep.html
Technical Literature and Papers
New High Temperature Oxide Fibers Published in High Temperature Ceramic Matrix Composites, 4th Int. Conf. on High Temperature Ceramic Matrix Composites, ed. W. Krenkel et. al., Wiley-VCH, 2001.
Statistical Tensile Strength of Nextel™ 610 and Nextel™ 720 Fibers D.M. Wilson, 3M Metal Matrix Composites.
High Performance Oxide Fibers for Metal and Ceramic Composites. D. M. Wilson and L. R. Visser, 3M Specialty Fibers and Composites. Paper presented at the Processing of Fibers & Composites Conference, Barga, Italy, May 22, 2000.
Ceramic Oxide Fibers, Building Blocks for New Applications. T. L. Tompkins, 3M Ceramic Fiber Products Program. Ceramic Industry, April, 1995.