Polycrystalline mullite fiber is an alumina–silica fiber produced by sol–gel technology rather than by conventional melt-spinning. A high-purity precursor (typically about 72 % Al₂O₃ and 28 % SiO₂) is fiberized, dried, and then heat-treated so that the final product consists of fine mullite and alumina crystals, with a controlled fiber diameter of roughly 4–6 µm.
A representative grade is PCW1600, with a classification temperature of 1600 °C and a recommended continuous service temperature up to 1450 °C for blankets and bulk. For rigid boards, higher temperature grades such as PCW1700 and PCW1800 are available, designed for hot-face or structural insulation up to 1700–1800 °C.
Typical product forms include:
Bulk fiber – base material for vacuum-formed shapes, boards, papers, and specialty parts.
Blankets – flexible needled mats at 96–150 kg/m³ density for furnace linings and backup layers.
Modules – compressed blanket blocks with integrated anchors, used for rapid installation of furnace linings between 1300–1600 °C.
Boards – vacuum-formed rigid panels (PCW1600/1700/1800) with high density and strength for hot-face linings, structural insulation, and specialty components.
These products are designed to be functionally comparable to well-known commercial PCW brands used worldwide, offering a high-temperature upgrade over standard ceramic fiber and AES fibers.
Because of its unique balance of temperature capability, insulation performance, and stability, polycrystalline mullite fiber is widely used in:
Steel Industry: Reheating and annealing furnaces, walking beam and pusher furnaces, soaking pits and heat-treatment furnaces, backup or hot-face linings in high-temperature zones where bricks alone are not sufficient.
Glass Industry: Furnace crowns and superstructure, regenerators and port necks, forehearths and working end insulation.
Aluminum and Non-ferrous: Melting and holding furnaces, launders, filters, and dosing furnace covers (as backup insulation), high-efficiency linings where low shrinkage and chemical resistance to molten metal and fluxes are required.
Ceramics and Special Materials: Roller kilns, shuttle kilns, tunnel kilns, laboratory and testing furnaces operating above 1400 °C.
Petrochemical, Refining, and Energy: Cracking and reforming furnaces, incinerators and thermal oxidizers, high-temperature stacks and ducting.
Automotive and Aerospace: Exhaust and catalyst insulation systems, heat shields, thermal protection systems, and structural insulation around high-temperature components.
In many of these applications, PCW is used as the hot-face or near-hot-face layer, with lower-cost ceramic or bio-soluble fibers behind it as backup insulation.
Classification temperature (Tc) is determined by standardized tests (e.g., 24 h exposure at the rated temperature with a defined shrinkage limit).
Continuous use temperature is usually set 50–150 °C below Tc, depending on application severity, mechanical load, and atmosphere.
For PCW1600 blankets and bulk, Tc is 1600 °C, but continuous operation is typically recommended at ≤1450 °C to ensure low shrinkage over many cycles. Boards at 1700–1800 °C classification are similarly derated in design to ensure long-term reliability.
