Thermal and dielectric properties of polycarbonatediol polyurethane

Abstract

Ortiz Serna, MP.; Carsí Rosique, M.; Redondo Foj, MB.; Sanchis Sánchez, MJ.; Culebras, M.; Gomez, CM.; Cantarero, A. (2015). Thermal and dielectric properties of polycarbonatediol polyurethane. Journal of Applied Polymer Science. 132 (22) ABSTRACTThe dielectric relaxation behaviour of a segmented polyurethane has been studied using Broad-Band Dielectric Spectroscopy in the frequency domain, 10 -2 -10 9 Hz, and in the temperature range of -120 to 140 ºC. The spectra show three secondary processes (,  and β) followed by the  relaxation and conductive processes. The Havriliak-Negami (HN) phenomenological equation was used in order to characterize all the processes. The ,  and  relaxations are probably associated with (i) local motions of the main chain (ii) motions of the carbonate group in the soft phase and (iii) reorientational motions of the water molecules. The microphase-separated morphology associated with soft and hard domains is reflected in the dielectric spectra, at high temperatures, by the presence of the Maxwell-Wagner-Sillars (MWS) interfacial polarization process.

Composites prepared from the waterborne polyurethane cationomers-modified graphene. Part II. Electrical properties of the polyurethane films

“…The software Origin v.8.0 and WinFit of Novocontrol was used to present and analyze the results of the measurements. The generic complex equation Havriliak–Negami (H-N) equation was applied to set basic relaxation functions’ parameters in frequency, which described the changes of dielectric permittivity in frequency function [10, 11]:where k is the total number of partial ( k  = 1 for low-frequency component HN1 and k  = 2 for high-frequency component HN2); N is the coefficient of conductivity character;is the polarizability, the difference between static permittivity (low frequency) ( ε 0 ) and optical high-frequency permeability ;Δ ε k is the polarizability; τ k is the relaxation time;is circular frequency; f is vibration frequency; α , β are the constants of the equation H-N; and σ 0 is the parameter of AC conductivity.…”

Optimization of mechanical and dielectric properties of poly(urethane–urea)-based dielectric elastomers via the control of microstructure

“…In addition, even though many literature investigated the dielectric properties of PU/PUUs, [19][20][21][22][23][24] the effects of microstructure of PUUEs on dielectric and mechanical properties still have less been understand, so far. For example, how the hydrogen bonding structure and crystallinity of hard domains and microphase separated network structures contribute to the dielectric constant, dielectric loss and breakdown strength of PUUs?…”

Transparent thermoplastic polyurethanes based on aliphatic diisocyanates and polycarbonate diol

“…The one located around 50 C is related to enthalpic relaxation of hard segments with short-range-ordered structures 9 probably formed during ageing. 27,28 The melting endothermic peaks appearing around 90 C and 100 C correspond to the crystalline melting temperature of long-range-ordered structures as hard segment components dispersed in the soft region 20,27,28 As observed in Figure 2, the increase in HDI prepolymer content increases the melting temperature and enthalpy. The aliphatic diisocyanate linear structure, HDI, induces crystallization with a more ordered structure thus reducing soft/hard segments mixing and values of T gS leading to a better microphase separation.…”