The Impact of Atmospheric Parameters on the Dielectric Permittivity Values of SikaBlock®-M150 and Other Rigid Polyurethane Foams Measured with a Capacitive One-Side Access Sensor

Abstract

A shortage of research on the impact of atmospheric parameters on the measured dielectric permittivity values of rigid polyurethane (PU) foams was identified. Therefore, the impact of temperature, pressure, and relative humidity of air in the test room on the measured values of dielectric permittivity of rigid PU foams of different densities as well as monolithic polyurethane was investigated in a year-long experimental research study with a capacitive one-side access sensor. It was shown that relative humidity has the highest correlation with the dielectric permittivity values of rigid PU materials. The detected values of parameters were linked to the water vapour mass in ambient air and its correlation with permittivity of the investigated materials was determined. The warm-up drift and warm-up time of the spectrometer were estimated experimentally. A novel methodology was demonstrated to determine the true permittivity spectrum of rigid PU foams without any involvement of the environmental chamber, desiccators, or saturated salt/water solutions. A relative increase in the measured dielectric permittivity value was estimated numerically for the entire density range of rigid PU foams, i.e., 33–1280 kg/m3 (including monolithic PU).

Electric Susceptibility at Partial Coverage of a Circular One-Side Access Capacitive Sensor with Rigid Polyurethane Foams

“…Rigid closed-cell petrochemical PU foams were made at apparent core densities of 30 kg/m 3 < ρ < 80 kg/m 3 , in blocks, according to the formulation in [8,26,27]. The apparent core density (density) was determined in correspondence with ISO 845:2006 [28].…”

“…Permittivity was measured with an experimental dielectric spectrometer equipped with a capacitive sensor of the one-side access (OSA) type [3,8,26,27]. The dielectric sample was placed on the active area of the sensor, Figure 1, and excited via electrodes, by an electrical field generated by sinusoidal voltage signals.…”

“…PU foam is a "Polymer-gas" composite, which has the same matrix-monolithic polyurethane, in the whole range of densities, i.e., 30-1280 kg/m 3 [23][24][25]. For light-weight PU foams (density of 30 kg/m 3 ), permittivity ε ≈ 1.065, for medium weight (550 kg/m 3 ), ε ≈ 2.10, and for monolithic polyurethane (1280 kg/m 3 ), ε ≈ 3.35 (all at a frequency of 1 kHz) [8,26,27]. Rigid polyurethane (PU) foams [23,24] exhibit low dielectric interference and nearly non-dispersive permittivity; therefore, excellent dielectric performance can be ensured in a wide frequency range.…”

Microwave Cavity Sensor for Measurements of Air Humidity under Reduced Pressure

“…The combination of high sensitivity and low inertia in the microwave methods determines the prospects of using microwave sensors for the measurement and monitoring of gas humidity under low pressures. Even a small amount of moisture in a gas can significantly affect the technological processes and the physical phenomena observed in laboratory studies in the field of vacuum technology and engineering [ 15 ]. The problems of measuring and monitoring humidity in the atmosphere at various altitudes are of special interest.…”

Construction of Dielectric Model of Nonaqueous Reactive Polyurethane Grouting Materials

“…Beverte et al conducted a one-year experimental study using a capacitive single-side access sensor to investigate the effects of air temperature, pressure, and relative humidity on the measured permittivity of rigid polyurethane foamed plastics and integral polyurethane of different densities. The results showed that the humidity had the greatest effect on the permittivity [20,21]. Al-Qadi used the data obtained from 12 different road sections by two GPR systems, and used the air-coupled GPR system to calculate the complex permittivity of hot mix asphalt in the frequency range of 750~1750 MHz [22].…”