Design and development of an embedded system for thermal conductivity measurement of polymer thin films

Abstract

In recent years, majority of thermal conductivity measurement techniques employ steady-state technique. This is for the reason that it is well suited for measuring low thermal conductivity in thin films. Keeping this in view point, the present study focuses at the design of an instrument to evaluate the thermal conductivity of thin polymer films employing the steady-state technique. Experimental set-up is developed in the laboratory for the measurement of thermal conductivity of thin films. The set-up consists of a heat source in the form of copper slab. The sink is also made up of a copper slab of same dimensions as that of the source slab. The thin film is placed between the two slabs. Water circulation system is designed to maintain the sink at constant temperature. A constant current source designed in the laboratory supplies current to the heater assembly that was embedded inside the source. Temperature sensors were also embedded in the slabs to evaluate the source and sink temperatures. The output of temperature sensors are signal conditioned using special circuitry designed and developed in the laboratory. The data acquisition and thermal conductivity measurements are accomplished using an embedded system that has built around the ATmel AVR 8535 microcontroller. The design system was calibrated using standard polymer thin films (PVC, PMMA, PP and PTFE). In order to validate the instrument developed in the present work, thermal conductivity measurement has been carried out on three new polymer samples (Soy Flour-Glyoxal films, Carboxy Methylated Cellulose sodium salt film (CMC), Hildigardia populifolia Fabric).