Dielectric Permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies
- Ilze Beverte1,*, Vairis Shtrauss1, Aldis Kalpinsh1, Uldis Lomanovskis1, Ugis Cabulis2, Irina Sevastyanova2, Sergejs Gaidukovs3
1 Institute for Mechanics of Materials, University of Latvia, Riga, LV-1006, Latvia
2 Latvian State Institute of Wood Chemistry, Riga, LV-1006, Latvia
3 Faculty of Materials Science and Applied Chemistry, Institute of Polymer Materials, Institute of Applied Chemistry, Riga Technical University, Riga, LV-048, Latvia
* Corresponding Author: Ilze Beverte. Email: Ilze.Beverte@lu.lv
(This article belongs to this Special Issue: The 10th Conference on Green Chemistry and Nanotechnologies in Polymeric Materials (GCNPM 2019))
2 Latvian State Institute of Wood Chemistry, Riga, LV-1006, Latvia
3 Faculty of Materials Science and Applied Chemistry, Institute of Polymer Materials, Institute of Applied Chemistry, Riga Technical University, Riga, LV-048, Latvia
* Corresponding Author: Ilze Beverte. Email: Ilze.Beverte@lu.lv
(This article belongs to this Special Issue: The 10th Conference on Green Chemistry and Nanotechnologies in Polymeric Materials (GCNPM 2019))
Received 16 February 2020; Accepted 20 May 2020; Issue published 03 August 2020
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 εg ≈ 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 Sika JSC and General Plastics Manufacturing Co.
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/m3 and the mentioned biofoams, comprising the
renewable rapeseed oil polyol, up to densities 230–250 kg/m3
. 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.
Keywords
Polyurethane foams; rapeseed oil polyol; biofoams; dielectric permittivity; capacitive sensor; one-side access; low frequencies
Cite This Article
Beverte, I., Shtrauss, V., Kalpinsh, A., Lomanovskis, U., Cabulis, U. et al. (2020). Dielectric Permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies. Journal of Renewable Materials, 8(9), 1151–1170.
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