Nonfusible

Nonfusible is an adjective meaning not capable of fusing or melting to form a liquid or fused mass under the temperatures or conditions to which the material is exposed. The term is used across several fields with related but distinct implications.

In metallurgy and ceramics, nonfusible materials are those that resist melting or fusing during high-temperature processing. They are used to line furnaces and crucibles, or as refractory components, to withstand contact with molten metals and chemical attack. Common nonfusible refractory materials include alumina, silica, magnesia, and zirconia. Their lack of fusion ensures structural integrity and prevents contamination of the contents.

In textiles and garment manufacturing, nonfusible refers to interfacing or fabrics that do not melt, fuse, or bond when heated. Nonfusible interfacing provides stiffness through mechanical attachment (stitching) or a non-melt adhesive, and is preferred for delicate fabrics that could be damaged by heat. Nonfusible materials are also used in protective clothing designed to resist heat and melt-through.

In some contexts, nonfusible is used to describe components or materials that should not fuse under expected service conditions, including certain high-temperature insulations and coatings. The opposite term is fusible, used for materials designed to fuse or bond when heated.

Etymology derives from non- plus fusible, from Latin fusus meaning melted or poured.