Micromoulding: process measurements, product morphology and properties

The growth in Micro Electro-Mechanical Systems (MEMS) and demand for functional devices at smaller and smaller length scales has placed increasing demands on industry for product miniaturisation. Consequently, the micro-injection moulding (micromoulding) technology has evolved for the mass production of minute, intricate, polymer and composite components. Although there has been significant growth in the technology, there is little understanding of the effects of the process dynamics on product properties. This paper presents details of a programme of work conducted within these laboratories with the objectives of enhancing the understanding of polymer processing-property interaction. More particularly, the effects of microscale processing on the rheological, mechanical and tribological properties of engineering and commodity polymers, nanocomposites, metal and ceramic injection moulded feedstock and biomaterials are being explored. Simple analysis reveals that process conditions are potentially more severe on melts than those encountered during conventional moulding. High shear and rapid cooling rates combined with a large surface area to volume ratio may have a much greater influence over the resultant properties of a micromoulded product. A Battenfeld Microsystem50 micromoulding machine has been instrumented with a variety of sensors and data acquisition equipment, producing process data for a number of different cavity geometries. A novel microinjection compounding (MIC) machine has also been developed minimising the process stages and reducing material exposure to excessive residence times. This paper gives details of the effects of micromoulding process conditions on component surface morphology and mechanical properties measured using SEM, atomic force microscopy and nano-indentation techniques.