Thermal expansion of the crystalline lattice of polyamides

X-ray structural analysis is used to study the thermodynamics of the crystalline lattice of isotropic polyamide samples: polyhexamethyleneadipamide, polycaproamide, polyhexamethylenesebacinamide and polydodecaneamide. It is shown that change in the parameters of the lattice with rise in temperature is of a non-linear character. Break points in the dilatometric curves are observed at 100–120 and 180–200°C. In the first temperature region heavy rupture of the hydrogen bonds in the crystalline lattice begins with phase transition in the second to the haxagonal structure.