Stretch-induced bidirectional polymorphic transformation of crystals in poly(butylene adipate)

Stretch-induced structural changes of poly(butylene adipate) at various temperatures were systematically investigated by X-ray diffraction method. It was found that tensile deformation could lead to both occurrence of α to β and β to α crystal transition via solid–solid process. Experimental results shows that either α or β form can be adopted as the stable phase for PBA crystal depending on the competition between tensile strain and temperature. Higher temperature favors β to α crystal transformation, while larger strain would result in α to β crystal transformation. Due to the conversion of crystal stability during stretching, a unique “β to α to β” transformation phenomenon of PBA appears at appropriate temperature for original β spline. This study provides evidence that both temperature and tensile strain can alter the relative stability of polymorphic crystals of semi-crystalline polymers.