Uniaxial stretching behavior of polylactide with long chain branching

Abstract

The investigation about the uniaxial stretching behavior of fully crystallized poly(L-lactide)s (PLLA) containing long chain branching (LCB) is carried out by two dimensional wide angle X-ray scattering (2D-WAXS) and differential scanning calorimetry (DSC). The controlled sample is the linear PLLA containing nucleating agents which owns the similar degree of crystallinity and crystalline morphologies as that of PLLA LCB. The results show that much more chain entanglements in the amorphous area of PLLA LCB make the LCB sample be able to bear much larger stress and then reach larger elongation when it breaks. Although the original lamellae are more difficult to be damaged in PLLA LCB due to the more chain entanglements compared with linear PLLA, the final crystal orientation is much better for it. The higher melting point indicates that the extended chain crystals in this stretched LCB sample are more perfect, especially at high drawing temperature. The original topological structure of chains is supposed to be the governing factor which determines the different evolution of crystalline structures under strain.