A New Facile Method for Preparation of Nylon-6 with High Crystallinity and Special Morphology

In this study, we develop a new facile method to prepare nylon-6 with special features (denoted as vp-nylon-6). The key strategy for the method is to make the crystallization of nylon-6 be performed in a slow and near-equilibrium manner by diffusing the vapor of precipitator into a nylon 6/formic acid solution at ambient temperature and pressure. Differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD) have demonstrated that the crystallinity and crystalline perfection of vp-nylon-6 are significantly improved by the new method. Scanning electron microscope (SEM) observations have shown that vp-nylon-6 exhibits versatile morphological features including ribbon, bowknot, flower, semisphere, and dumbbell which are the result of the assembly of crystalline lamellae. The crystalline lamellae occur in a discrete fashion rather than being embedded in an amorphous matrix even if concentrated nylon solutions are used. Selected area electron diffraction (SAED) in transmission electron microscope (TEM) shows that the crystalline lamellae are composed of single crystals.