These are cross-linked by nucleophilic attack from amino groups in the hardener, forming rigid bonds that prevent crystallisation, and instead form a complex, amorphous, 'glassy' structure with a high glass transition temperature (𝑇 𝑔 ). The yield behaviour of this thermoset (below its 𝑇 𝑔 ) is identical to that of uncross-linked glassy thermoplastics .