Abstract

Aluminium-27 solid state NMR spectroscopy has been applied to investigate the interaction at the molecular level of various aluminium based tanning salts with leather. High resolution and variable temperature ²⁷Al-solid state NMR studies, combined with differential scanning calorimetry and kinetic studies of the shrinking of Al-tanned hide powder and sheepskin samples have clearly shown that shrinking is a kinetically controlled process, during which the synthetic crosslinks remain intact. The shrinkage temperature is determined by the size of the formed crosslinked macromolecular moieties which in turn depends on the kinetic stability of the interactions of the tanning agent with collagen.