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  • Selection of appropriate polyoxymethylene based binder for powder injection moulding feedstock material : plenary 7
    Gonzalez-Gutierrez, Joamin ...
    Polyoxymethylene copolymer (POM) is considered a high performance engineering polymer with many applications primarily in the automotive industry, due to its very good mechanical properties such as ... high modulus, stiffness, hardness, fatigue and creep resistance. Currently, POM has also found uses in powder injection molding (PIM) technology. PIM is one of the most versatile methodsfor the manufacturing of small complex shaped components from metal or ceramic powders for the use in many industries, like automotive, electronics and medical devices. PIM consists of mixingpowders with a polymeric binder, injecting this mixture in a mould, debinding and then sintering. The main advantage of using POM in PIM technology is the faster debinding rates compare to polyolefinbased feedstock materials, since POM sublimates into its monomer directly when exposed to an acidvapour.The feedstock material for PIM has two main contradictory requirements; on one hand it must have low viscosity in order to facilitate the injection molding process, but once the molded part solidifies it must have sufficient mechanical strength so that it does not break or deform during handling and debinding. POM-based feedstock materials have indeed superior mechanical streghth in the solid state, but the main problem is their high viscosity, which can in fact difficult the injection moulding process. For this reason it was decided to prepare POM copolymers with different average molecular weights and investigate the effect of the average molecular weight on the viscosity and solid mechanical properties, in order to select the correct copolymer to be used as binder for PIM feedstock. In this work, POM materials of different molecular weights have been prepared and characterized in terms of oscillatory viscosity and impact toughness. As expected, both properties increase as the average molecular weight increases. However, the Newtonian viscosity of POM increases with average molecular weight following a power law function, as it is the case with other linear entangled polymers. While the increase in impact toughness does not follow a simple relationship with molecular weight and it appears that there is a plateau at small molecular weights. With the information here gathered, it is possible to suggest that a POM copolymer with an average molecular weight of around 24000 g/mol could be used as the main component of a binder used for PIM. As compared to the currently available POM-based binder, using POM with the suggested molecular weight can lead to adecrease in viscosity of 200 times, while reducing toughness only by 10 times; this can be considereda significant improvement on the performance of POM-based binders for PIM.
    Vir: Ic-rmm1 : book of abstracts (Str. 15)
    Vrsta gradiva - prispevek na konferenci
    Leto - 2013
    Jezik - angleški
    COBISS.SI-ID - 13175067

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