Singapore Institute of Manufacturing Engineering SIMTech

Singapore, Singapore

Singapore Institute of Manufacturing Engineering SIMTech

Singapore, Singapore
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Hayat M.D.,University of Auckland | Li T.,Singapore Institute of Manufacturing Engineering SIMTech | Wen G.,University of Auckland | Cao P.,University of Auckland
International Journal of Advanced Manufacturing Technology | Year: 2015

Due to environment-friendly nature, water-soluble binder systems have received much attention in recent years. Polyethylene glycol (PEG) and polymethyl methacrylate (PMMA) binder system is one such example and has been widely reported in the literature. In this paper, a comprehensive investigation of PEG/PMMA binder system has been carried out. Feedstocks were made using stainless steel 17-4PH powder, and subsequently, conventional and micrometal injection moulding (μMIM) processes were carried out. Differential scanning calorimetry (DSC) and fracture surface analysis of moulded samples were performed for complete evaluation. It was found that despite great potential, there are certain drawbacks associated with this binder system. The main problem is the formation of shrinkage voids during solidification. It is proposed that this binder system is more suitable for μMIM process that has an inherently higher cooling rate. © 2015, Springer-Verlag London.


Hayat M.D.,University of Auckland | Li .,Singapore Institute of Manufacturing Engineering SIMTech | Cao P.,University of Auckland
Materials and Design | Year: 2015

In spite of its great potential, the polyethylene glycol (PEG) and polymethyl methacrylate (PMMA) binder system was found susceptible to void nucleation, as the rigid PMMA chains hinder PEG volumetric shrinkage upon cooling. We previously reported that this void formation could be minimized by either using a higher cooling rate or by incorporating a crystallization inhibitor in the binder system. In this paper, efforts have been made to increase the workability of this binder system for conventional metal injection molding (MIM) by adding the crystallization inhibitor, polyvinylpyrrolidone (PVP). Differential scanning calorimetry (DSC), rheological property measurements, solvent and thermal debinding behavior, and fracture surface analysis of the molded samples were performed. Incorporation of PVP into the PEG/PMMA binder system is successful in that high quality void-free MIM components have been produced while maintaining the clean nature of the PEG/PMMA binder system. © 2015 Elsevier Ltd.


Hayat M.D.,University of Auckland | Wen G.,University of Auckland | Li T.,University of Auckland | Li T.,Singapore Institute of Manufacturing Engineering SIMTech | Cao P.,University of Auckland
Journal of Materials Processing Technology | Year: 2015

To study the effect of different surfactants on the metal-and-binder interaction that has not been reported before, polyethylene glycol (PEG) and polymethyl methacrylate (PMMA) were used as the major and backbone constituents in the binder system. Three different surfactants - stearic acid (SA), peanut oil and castor oil - were chosen to prepare feedstocks of 60 vol% solid loading. Rheological properties analysis, fracture surface, and flexural strength studies were carried out to identify the suitable surfactant that yields feedstock with excellent mouldability. It is found that castor oil as surfactant results in excellent overall properties of feedstock by enhancing metal-and-binder interaction. The reason of this higher interaction lies in the chemistry of castor oil, which has more polar ester functional groups, which latch on the metal powder surface via dipole-dipole attractive forces. Therefore a better powder dispersion and higher powder-binder interaction is achieved. © 2015 Elsevier B.V. All rights reserved.

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