Differential thermal lens temperature scanning approach to glass transition analysis in polymers: application to polycarbonate

Abstract

In this paper, mode mismatched thermal lens spectrometry is applied to determine the thermal and optical properties of polycarbonate as a function of temperature. The focus of the experiments was in the temperature range between 120 °C and 170 °C, where the sample glass transitions occurs. In order to validate and evaluate the sensitivity of the proposed method we have also carried out conventional differential scanning calorimetry measurements. The results showed that the temperature dependence of the signal amplitude of the thermal lens provided a better definition in locating the glass transition compared to the differential scanning calorimetry data. In addition, a sharp decrease in the thermal diffusivity values at the beginning of the sample glass transition was observed. According to the Debye model, this change was attributed to the variation of the sample elastic constant throughout the glass transition. Finally, we propose this procedure, called the differential thermal lens temperature scanning approach, as a new method for the investigation of phase transitions in transparent polymers.} \fnm{3}{Author to whom correspondence should be addressed.

Thermal lensing in poly(vinyl alcohol)/polyaniline blends

“…Using ds / dT values and supposing ( n − 1)(1 + ν)α = 5.02 × 10 −5 K −1 , as calculated with PVC data,15 we estimated dn / dT = −1.5 × 10 −4 K −1 . These values are similar to those obtained from TL measurements in PVC 11. Because dn / dT is negative for most polymers, thermal expansion and dn / dT contributions to ds / dT have opposite signs (eq 9).…”

“…We verified that the nonlinearity in this regime had a thermal origin for both doped and undoped blends. Once the origin of the nonlinearity was identified, we employed the time‐resolved mode‐mismatched TL technique8–11 to determine the optical path change with temperature ( ds / dT ) and the thermal diffusivity coefficient ( D ). We verified that the values of D increased from 1.1 to 2.1 × 10 −3 cm 2 /s as the sample aged in the 20–90 °C range.…”

A review on the mechanical, electrical and EMI shielding properties of carbon nanotubes and graphene reinforced polycarbonate nanocomposites

“…Though PC is being a stronger polymer and this has large number of applications as reported in literature. . However, the combination of PC with conductive nanofillers such as CNTs and graphene has led to several very interesting properties in nanocomposites, which made these nanocomposites as one of the most important material in industrial research.…”

“…Though PC is being a stronger polymer and this has large number of applications as reported in literature.. [191][192][193] However, As a result, the inexpensive plastic was used to make optical discs with features in military aircrafts to shield them against buildup of electrical charges and pulses, which can lead to significant failures. Additionally, by modifying the amount of CNTs added to the PC-nanotube mix, the EC of the nanocomposite could be increased from that of silicon…”

Thermo-optical properties measurements in chalcogenide glasses using thermal relaxation and thermal lens methods

“…These are determined by measuring the thermal diffusivity, D, the temperature dependence of the optical path length change, ds/dT, and the specific heat, c p [8,9]. In the last few years, these properties have been measured in glasses, crystals, and polymers, also as a function of temperature, by using the thermal lens (TL) technique and thermal relaxation calorimetry (TRC) [10][11][12][13].…”