Measurement of thermal conductivity of polymeric nanocomposite materials

A measuring device of the thermal conductivity of Polymeric nanocomposite materials is presented. This project is a continuation of a previous master student work. The goal of this project is to build a miniaturized version of the previous device in order to overturn certain limitations and improve its overall performance. The new device uses much smaller size samples, which ensures sample integrity/rigidity and saves material which in the case of nanoadditives may be expensive or scarce. In addition, the device is affordable and portable without compromising the operation convenience and precision/accuracy. As in the previous work, the device is based on the hot/cold tank principle, which is simple and easy to operate, is non-destructive to the sample, is safe to use and thermal conductivity is estimated through a simple mathematical model. The technique relies on recording the temperature evolution of a fluid in two separate tanks exchanging heat to each other. One tank contains a hot fluid (45-55°C), and the other a cold fluid (room temperature), while heat is being transferred through a sample placed in between the tanks. The development of the device is thoroughly described in this work. It starts from the apparatus conceptual design, its construction (including auxiliary units, e.g. for agitation, temperature measurement, data logging), preliminary tests to show proof of concept, technical and functional validation, (accuracy and precision when testing known polymeric materials), and ends with measuring the thermal conductivity of newly synthesized polymeric nanocomposite materials. Teflon samples are used first for the validation of the device's capacity, with the acquired results of thermal conductivity being in good agreement with literature values and also with measurements of the previous version of the device. Next, samples of polymeric nanocomposites of different nano additives concentrations are measured. Results demonstrate that the thermal conductivity of two types of epoxy resins (EPON828,827) increases with the addition of different concentrations of nano additives such as; Alumina (Al2O3), Boron nitride (BN), Silicone Carbide (SiC), Organoclay nanomere (I.30E), carbon nanotubes (CNT's) and different Silicone dioxide (SiO2) additives. It is found that some additives such as Alumina yield observable impact on the thermal conductivity of the epoxy resin whereas others such as multi-walled carbon nanotubes (MWCNT's) give a noticeable effect only at the higher examined concentrations. In the absence of additives, no impact on the epoxy resin thermal conductivity is observed when cured by different curing agents such as D2000, D230 and IPD. On the contrary, in the presence of additives, a clear effect of the curing agents D2000, D230 on the thermal conductivity of epoxy resin is observed. The significance of the nanocomposites curing process and the impact of achieving good degree of dispersion of the nanoadditives in the polymeric matrix is discussed