Thermal, mechanical and rheology of EVA/wax and wax/LLDPE blends as a carrier vehicle for investment casting pattern

ABSTRACT

Different ratios of wax/ethylene vinyl acetate (EVA) and wax/linear low-density polyethylene (LLDPE) blends were prepared using one-step extrusion process to investigate their potential as carrier vehicles for pattern material for investment casting. The thermal, mechanical and rheological properties were characterised. Thermal analysis was done by thermogravimetric analysis (TGA) and differential scanning calorimetry. Mechanical properties were characterised by three-point bending and thermomechanical analysis, whereas the rheological properties were characterised by oscillatory rheometry. The TGA analysis showed that the incorporation of EVA or LLDPE into wax matrix improved the thermal stability properties of the blend. This can be attributed to an enhanced phase adhesion. The melting and solidification behaviour of the blends had intermediate temperatures between wax and EVA. The EVA/wax blends displayed evident viscosity shifts as compared to the viscosity of wax. The incorporation of EVA into wax significantly altered its mechanical properties. Fourier transform infrared spectrometry for both wax/EVA and wax/LLDPE showed a predominant presence of CH₂ and carbonyl group in the blend, and the mechanical properties of neat wax were improved when EVA and LLDPE were incorporated into wax.

KEYWORDS:

• Wax/EVA
• wax/LLDPE
• rheology
• thermal analysis
• three-point bending

Acknowledgements

The authors gratefully acknowledge financial support from the Technology Innovation Authority (TIA), South Africa. Any findings and opinions and conclusions based on this research are those of the authors and therefore TIA does not accept any liability with regard thereto. The authors also acknowledge the help of Professor Walter Focke of University of Pretoria, Institute of Applied Materials, for his guidance all through the experiments. The authors also acknowledge thermal analysis assistance provided by Dr Isbe Van der Westhuizen, rheology assistance by Dr Shatish Ramjee and Dr Benjamim Mapossa for the SEM analysis and compounding.

Disclosure statement

No potential conflict of interest was reported by the authors.