Synthetic preparations, thermal properties and crystallization characterization of PLLA‐PPG block copolymers/clay nanocomposites

Abstract

In this study, intercalation of the polymer or pre‐polymer from solution was used to blend different proportions of polylactic acid‐propylene glycol (LPG) copolymers (polypropylene glycols (PPG) of : 700, 1000, 2000) and lipophilic montmorillonite (clay) in order to investigate the melting and the crystalline nature of LPG copolymers/clay nanocomposites via a differential scanning calorimeter (DSC). In addition, changes in the intermolecular force and crystal morphology of the nanocomposites under different crystallization conditions were also studied. For the results, it was observed from a thermogravimetric analyzer that increasing the clay content elevated the weight loss temperature. In non‐isothermal experiments using a DSC, it was discovered that the melting temperature and crystallization temperature of the LPG copolymers also increased with increasing amounts of added clay. The crystallinity of LPG2000 + 1.5 wt% clay was enhanced by 17.00%; in addition, it was found in the crystallinity study that adding clay slowed down the crystallization rate of the LPG copolymers. Moreover, it was found via X‐ray diffractometer (XRD) that the intensity of the diffraction peaks of the 1.5 wt% specimen was stronger than that of the 0.5 wt% specimens. The results imply that copolymers with a longer chain length provide greater space for the crystals to grow, thus making it easier for larger crystals to grow. Conversely, the added clay generates an inhibitory effect in copolymers, reducing the d‐spacing (d) in the XRD. Therefore, adding clay would change the crystallization behavior and the morphology of the LPG copolymers. Copyright © 2015 John Wiley & Sons, Ltd.