TY - BOOK

T1 - Material data determination of liquid silicone rubber: characterization methods for a reliable injection moulding simulation

AU - Azevedo de Freitas, Mauricio

N1 - no embargo

PY - 1800

Y1 - 1800

N2 - Silicones, or poly(siloxanes), are distinguished by their thermal stability, flexibility, and resistance to environmental degradation; qualities that render them ideal for numerous engineering applications, particularly in scenarios demanding robust performance materials. The simulation of liquid silicone rubber (LSR) injection moulding (IM) is complex due to the material's unique properties and behavior under processing conditions. This thesis systematically explores the critical properties of LSR relevant to improving the accuracy of IM simulations: flow behaviour (viscosity), thermal characteristics (specific heat capacity, thermal conductivity, and specific volume), and curing kinetics. Distinct experimental methodologies to characterize these properties are critically and systematically compared, aiming to achieve important insights about material data characterization for IM simulation. Concerning the flow behaviour of liquid silicone rubber, the focus was on detailing how viscosity responds to temperature and shear rate changes, employing different methodologies. It was discovered that steady shear-based techniques are adept at capturing the microstructural transformations of LSR, crucial to account for the presence of structuring fillers in the silicone matrix. Next, the study delves into thermal properties variations with temperature and curing state. The results underscore that specific heat capacity is mainly influenced by temperature rather than curing state, also being dominated by the presence of fillers, facilitating more precise energy conservation modeling in simulations. Besides, different methodologies were able to reach similar results for the thermal properties. The curing kinetics investigation compares different methodologies for determining LSR's crosslinking behaviour. The findings reveal that calorimetry and rheology provide different insights, with calorimetry supporting an autocatalytic model and rheology indicating an n-th-order model. Finally, the simulation trials integrate these insights into injection moulding simulations, assessing the impact of varying material datasets on simulation outcomes. The simulations highlighted that oscillatory measurements of viscosity under large amplitude oscillation can be compared to high pressure capillary rheometer data, but with important differences concerning the injection phase in terms of pressure. Furthermore, distinct specific heat capacity data affected mostly the curing phase, with differences concerning curing onset. Finally, via applying distinct curing kinetics parameters, the compared simulations reached different curing behaviours, but the curing time at a practical ejection point was not significantly changed.

AB - Silicones, or poly(siloxanes), are distinguished by their thermal stability, flexibility, and resistance to environmental degradation; qualities that render them ideal for numerous engineering applications, particularly in scenarios demanding robust performance materials. The simulation of liquid silicone rubber (LSR) injection moulding (IM) is complex due to the material's unique properties and behavior under processing conditions. This thesis systematically explores the critical properties of LSR relevant to improving the accuracy of IM simulations: flow behaviour (viscosity), thermal characteristics (specific heat capacity, thermal conductivity, and specific volume), and curing kinetics. Distinct experimental methodologies to characterize these properties are critically and systematically compared, aiming to achieve important insights about material data characterization for IM simulation. Concerning the flow behaviour of liquid silicone rubber, the focus was on detailing how viscosity responds to temperature and shear rate changes, employing different methodologies. It was discovered that steady shear-based techniques are adept at capturing the microstructural transformations of LSR, crucial to account for the presence of structuring fillers in the silicone matrix. Next, the study delves into thermal properties variations with temperature and curing state. The results underscore that specific heat capacity is mainly influenced by temperature rather than curing state, also being dominated by the presence of fillers, facilitating more precise energy conservation modeling in simulations. Besides, different methodologies were able to reach similar results for the thermal properties. The curing kinetics investigation compares different methodologies for determining LSR's crosslinking behaviour. The findings reveal that calorimetry and rheology provide different insights, with calorimetry supporting an autocatalytic model and rheology indicating an n-th-order model. Finally, the simulation trials integrate these insights into injection moulding simulations, assessing the impact of varying material datasets on simulation outcomes. The simulations highlighted that oscillatory measurements of viscosity under large amplitude oscillation can be compared to high pressure capillary rheometer data, but with important differences concerning the injection phase in terms of pressure. Furthermore, distinct specific heat capacity data affected mostly the curing phase, with differences concerning curing onset. Finally, via applying distinct curing kinetics parameters, the compared simulations reached different curing behaviours, but the curing time at a practical ejection point was not significantly changed.

KW - Flüssigsilikonkautschuk

KW - Spritzgießen

KW - Simulation

KW - Materialdaten

KW - Rheologie

KW - Vernetzungskinetik

KW - thermische Eigenschaften

KW - liquid silicone rubber

KW - injection moulding

KW - simulation

KW - material data

KW - rheology

KW - curing kinetics

KW - thermal properties

M3 - Doctoral Thesis

ER -