HALIZA JAYA, MOHD FIRDAUS OMAR, HAZIZAN MD AKIL, ZAINAL ARIFIN AHMAD, NIK NORIMAN ZULKEPLI, MOHD MUSTAFA AL BAKRI ABDULLAH, IOAN GABRIEL SANDU, PETRICA VIZUREANU EFFECT OF SURFACE MODIFICATION ON SAWDUST REINFORCED HIGH DENSITY POLYETHYLENE COMPOSITES UNDER A WIDE RANGE OF STRAIN RATES In this study, the alkali treatment of sawdust (SD) using different concentration (1%, 3%, 5%, and 7%) of sodium hydroxide (NaOH) was performed. The phases change due to alkali treatment on sawdust particles was examined using Fourier Transform Infrared (FTIR) spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). Result shows that the treatment with 5% NaOH on sawdust particles improved the surface roughness of the filler with 21.1 % diameter reduction. Both treated and untreated sawdust particles were reinforced in HDPE matrix using an extrusion method. For comparison purpose, both treated and untreated high density polyethylene/sawdust composites were tested under static and dynamic loading up to 1100 s-1 using the universal testing machine and the split Hopkinson pressure bar apparatus, respectively. Results indicate that the treated high density polyethylene/sawdust composites with better filler/matrix interlocking characteristic shows better mechanical performances as compared to untreated high density polyethylene/sawdust composites under a wide range of strain rate investigated. Apart from that, the mechanical properties of both treated and untreated polyethylene/sawdust composites also show great dependency on the strain rate applied where yield stress, compression modulus and ultimate compressive strength were steadily increased with increasing strain rate. Unfortunately, the yield strain shows the contrary trend. While for the fractographic analysis under dynamic loading, the untreated composite specimens had undergone a severe catastrophic deformation and damages than that of treated composite specimens.