Density and melt index (MI) are the most important properties of high density polyethylene (HDPE) in industrial manufacturing.In this work

density and MI of commercial grade HDPE were detected by Raman spectrum

based on the partial least squares (PLS) method.The short-branch degree was found to be inversely proportional to the density

according to the PLS analysis of the characterization spectra in the range 2700—2970 cm-1.A regression model between short-branch degree and density was built up.The correlation coefficient (r)

average relative deviation (ARD) and standard error of the prediction (SEP) for density prediction were 0.950

0.09% and 1.02

respectively.And the density regression model gave a better result than those obtained by near-infrared spectrum and Raman spectrum based on phase structure analysis.Furthermore

the vinyl content was found to be proportional to the MI value.A regression model between vinyl content and the MI of HDPE was established by analyzing the characterization spectra in the range from 1288 cm-1 to 1650 cm-1.And the values of r

ARD and SEP for MI prediction were 0.966

8.61% and 0.99

respectively.Comparing with the results measured by near-infrared spectrum

Raman spectrum showed higher precision for MI estimation.