Physical Description
Polymeric compound applied as a liquid state formulation to encapsulate delicate sensing assemblies before curing into a rubbery elastomer layer. A viscoelastic potting matrix dampens mechanical vibration transmitted through housing walls and isolates internal strain gauges from differential thermal expansion between dissimilar substrates. Curing proceeds through platinum catalyzed addition reactions or moisture cure mechanisms depending on the base silicone or polyurethane chemistry specified for the application.
Viscosity profiles prior to gelation dictate flow behavior around wire bonds and microelectronic components during the dispensing phase. Crosslinking density determines the glass transition temperature and the modulus of elasticity across the operational temperature range defined by the manufacturer.
Mechanical Attenuation
Shear stress absorption depends on the loss factor calculated from dynamic mechanical analysis testing under sinusoidal loading conditions. Oscillating forces transferred from external mountings encounter phase lag within the elastomeric network, converting mechanical energy into dissipated heat rather than transmitting shock waves to the active sensing element. Compressive set resistance prevents permanent deformation under sustained static loads applied during long deployment cycles in industrial environments.
Strain relief is quantified by measuring the reduction in transmitted acceleration amplitude between the outer enclosure and the internal transducer diaphragm. Calibration drift caused by mechanical preloading of piezoresistive elements decreases when the dampening layer absorbs transient impact energy before reaching the silicon die.
Thermal Drift
Coefficient of thermal expansion mismatches between the ceramic substrate and the metallic housing generate mechanical stress that alters output voltage measurements without any change in the physical variable being monitored. Temperature cycling tests establish the bounds within which the elastomer accommodates dimensional changes without delaminating from lead wires or solder joints. Heat conduction pathways through the cured mass affect the thermal time constant of the sensor during rapid ambient temperature shifts.
Glass transition boundaries restrict low temperature deployment because modulus values increase sharply below that threshold, converting the dampening layer into a rigid solid that transmits stress rather than absorbing it.
Environmental Protection
Moisture barrier performance is evaluated by measuring water vapor transmission rates through standardized sample thicknesses cured under production conditions. Chemical resistance data defines degradation thresholds when exposure occurs against hydraulic fluids, cleaning solvents or saline atmospheres common in marine or aerospace installations. Dielectric strength ratings govern the maximum voltage potential the cured layer withstands before electrical breakdown occurs between adjacent circuit traces.
Adhesion strength to aluminum and polybutylene terephthalate substrates is verified through peel tests conducted after accelerated aging exposure in humidity chambers.
