@Article{jrm.2020.010215,
AUTHOR = {Ilze Beverte, Vairis Shtrauss, Aldis Kalpinsh, Uldis Lomanovskis, Ugis Cabulis, Irina Sevastyanova, Sergejs Gaidukovs},
TITLE = {Dielectric Permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies},
JOURNAL = {Journal of Renewable Materials},
VOLUME = {8},
YEAR = {2020},
NUMBER = {9},
PAGES = {1151--1170},
URL = {http://www.techscience.com/jrm/v8n9/39624},
ISSN = {2164-6341},
ABSTRACT = {Early investigations of dielectric permittivity of rigid polyurethane
foams at low frequencies were made on petrochemical-origin foams, mainly by
means of parallel plate capacitors. In the present investigation biopolyol was
synthesized from Latvia-grown rapeseeds’ oil by the transesterification method
with triethanolamine, in an environmentally friendly process, without emission
of harmful substances, at temperatures 175°C ± 5°C. Rigid, closed-cell rapeseed
oil polyol polyurethane biofoams and petrochemical foams were made ensuring
content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.
Dielectric permittivity of the polyurethane foams and the underlying monolithic
petrochemical-origin polyurethane and biopolyurethane was measured with a
non-destructive dielectric spectrometer equipped with a capacitive sensor of
one-side access type at 16 discrete frequencies distributed geometrically over
the band 10 Hz, … , 330 kHz. Permittivity value of the gaseous phase in the
closed-cells was estimated to be ε<sub>g</sub> ≈ 1.001 that corresponds to the values, characteristic for the most of gases. Dielectric permittivity of petrochemical polyurethane
foams and the mentioned biofoams was compared with permittivity of polyurethane
foams from industrial producers <i>Sika JSC</i> and <i>General Plastics Manufacturing Co.</i>
Polyurethane foams of the developed formulation exhibit competitive, low dielectric permittivity, not exceeding that of the foams from industrial producers: petrochemical foams up to 550 kg/m<sup>3</sup> and the mentioned biofoams, comprising the
renewable rapeseed oil polyol, up to densities 230–250 kg/m<sup>3</sup>
. Considering petrochemical-origin polyurethane foams as a heterogeneous media “Polymer—gaseous
phase”, the applicability of the rule of mixture and Maxwell–Garnett equation to
model mathematically the dependence of effective dielectric permittivity on the
volume fraction of phases was showed.},
DOI = {10.32604/jrm.2020.010215}
}