Effect of low-frequency melt vibration on HDPE morphology

BACKGROUND: A low-frequency vibration-assisted injection-molding (VAIM) device was developed to explore the morphology of high-density polyethylene (HDPE) injection moldings. Scanning electron microscopy, wide-angle X-ray diffraction and differential scanning calorimetry were used to characterize structure-property relationships of final products prepared under different VAIM processing conditions (vibration frequency and vibration pressure amplitude) with conventional injection molding for comparison. RESULTS: It was found that increasing the vibration frequency at constant vibration pressure amplitude was beneficial for obtaining 'shish-kebab' structures in the core region of VAIM specimens, and increasing the vibration pressure amplitude at constant vibration frequency was a prerequisite for achieving HDPE specimens with large-scale lamellas, more pronounced orientation and high crystallinity. CONCLUSION: Both preferred orientation lamellas and increased crystallinity allow one to obtain strong injection moldings with the application of the melt vibration technique. (C) 2009 Society of Chemical Industry