1.1.6　Crosslinked Polymers

A crosslinked or network polymer（交联或网状聚合物）is one in which chemical bonds exist between the chains，as showed in Figure 1.2.The materials can be usually swelled（溶胀）by "solvents"， but they can't be dissolved.In fact，this insolubility can be used as a cautious criterion of a crosslinked structure.Actually，the amount of the swelled polymer in a solvent depends on the crosslinking density.The bigger crosslinking density presents，the smaller the amount of swelled polymer is.If the crosslinking degree is high enough，the material may be a rigid，high-melting，unswellable solid.Light crosslinking of chains favors the formation of rubbery elastomeric（弹性的）properties.