In the recent years different types of dampers for structural control in civil engineering have been developed, where one of the most promising solutions are viscoelastic dampers. In this paper we demonstrate that by utilizing knowledge on the effect of inherent hydrostatic pressure on the time- and frequency-dependent behavior of polymers it is possible to design and build the ultimate insulation systems for civil engineering applications. An optimal solution is achieved by using highly pressurized multimodal granular polymeric materials. The results on case material, Thermoplastic Polyurethane, showed that by increasing inherent pressure of the material from 1bar to 2000bar the frequency at which material exhibits its maximal damping properties was shifted from 37kHz, at P=1bar to 235Hz at P=2000bar. At the same time, the increase of inherent hydrostatic pressure from 1 bar to 2000 bar changes material stiffness up to 2.5 times, while the damping properties increase up to 5.2 times.
B.04 Guest lecture
COBISS.SI-ID: 13174555Polyoxymethylene 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.
B.04 Guest lecture
COBISS.SI-ID: 13175067Rector's award for the Best Innovation of University of Ljubljana is organized with the aim to support innovations and innovative business ideas to enter the market, either in a framework of own company or in any other form, for example in the form of sales or licensing of the patent or knowledge. Technology dissipative granular materials allows optimum utilization of the damping properties of polymeric materials and thus the maximum reduction of vibration and noise. For a project of Technology of dissipative granular materials, the research team received third place at Rector's award for the Best Innovation of University of Ljubljana.
E.01 National awards
COBISS.SI-ID: 13347867