High Density Polyethylene (HDPE) and Polypropylene (PP) Polyblend: An Experimental Approach

The present research focuses to evaluate a complete outlook of virgin high density polyethylene
(HDPE) and polypropylene (PP) polyblends. Virgin PP of 10, 20, 30, 40 and 50 weight % is
compounded with virgin HDPE. Tensile, Flexural and impact test specimens of virgin HDPE, Virgin PP
and HDPE-PP composites are prepared via twin screw extruder and injection moulding methods as
per ASTM D638-02a (Type-I), ASTM D790 and ASTM D256-A standards respectively. The
mechanical properties like tensile strength, flexural strength, Izod impact strength are examined.
Polymer sheets are fabricated using a two roll milling machine and compression moulding; and its
electrical properties like dielectric strength, surface resistivity, volume resistivity are examined
according to ASTM-D 257 standard. The study also includes effect of strain rate on tensile properties
of the prepared composite at a cross head speed of 30, 40, 50, 60 and 70 mm/min. Design of
experiment is conducted to find parameters dominating the tensile strength. All experiments are
carried out at room temperature of 23°C and absolute humidity of 54%. Scanning electron microscopy
(SEM), Atomic force microscopy (AFM) and polarised light microscopy (PLM) are used to observe the
surface and crystal morphology. X-ray diffraction (XRD), Fourier transform infrared spectroscopy
(FTIR) tests verify the non compatibility of both polymers. Differential scanning calorimetry (DSC) and
thermogravimetric analysis (TGA) techniques are used to study the thermal behaviour of composites.
The results manifest dielectric strength and volume resistivity decreases with addition of PP to HDPE;
whereas surface resistivity increases. Co-occurring spherulites are seen for polyblends; indicating the
composite to be a physical blend of continuous and dispersed phases, but on the other hand PP
improves the tensile and flexural properties of HDPE.