Influence of a new chemical crosslink system on the morphology and crystallite size of nylon-12

Special polyamide chains of desirable structure were polymerized such that they already contained reactive sites at the chain ends. The degree of crosslinking is determined by the chain structure and the amount of a specific epoxide silane, which causes crosslinking by formation of condensed silicon centres. The influence of the chain structure and the amount of epoxide silane on the morphology and the crystallite size were investigated by transmission electron microscopy using electron spectroscopic imaging and differential scanning calorimetry. A three-component structure was observed, consisting of crystalline and amorphous regions with a transition region between them. The lamellar thickness of the crystallites (5–7 nm) was independent of the chain structure and of the amount of epoxide silane, i.e. independent of the degree of crosslinking. Conversely, the lamellar length of the crystallites was dependent on the chain structure. For the material containing linear chains it was usually greater than 100 nm; for the material containing highly branched chains it varied from about 100 nm down to a block-like structure. The width of the transition region, in which the chains are under stress, was about 2 nm. The condensed silicon centres (crosslink points) were randomly distributed with respect to the resolution of the transmission electron microscope. RuO₄ is a good staining agent for nylon-12.