noncrosslinked

Noncrosslinked describes polymers or materials in which polymer chains are not connected by permanent covalent crosslinks to form an extended network. In such materials, the chains may be linear or branched but lack a chemically bound network, though physical entanglements can still influence properties.

Because they do not form a covalent network, noncrosslinked polymers are typically soluble in suitable solvents and melt-processable. They generally do not exhibit the elastic, rubbery plateau seen in crosslinked networks and tend to have lower modulus and strength, with greater creep under sustained load. Their mechanical performance and dimensional stability are more temperature- and solvent-dependent, and they often show well-defined glass transition temperatures or melting points.

Formation and processing are key distinctions: noncrosslinked polymers arise from polymerization without crosslinking agents, or from thermoplastics that avoid irreversible linking. Processing methods include casting, extrusion, and injection molding, which enable reshaping and recycling, in contrast to thermosetting networks that cannot be remelted.

Common examples include linear or branched thermoplastics such as polyethylene, polypropylene, polystyrene, and poly(methyl methacrylate). These materials are widely used in films, coatings, fibers, packaging, and consumer products where reprocessability is advantageous.

Terminology and measurement often reference crosslink density. A truly noncrosslinked material has negligible chemical crosslinks, zero gel fraction, and high swelling or solvent uptake relative to a network. In practice, many polymers exhibit partial or transient interactions that can affect properties without forming a permanent network.