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Polymers
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Polyurethane Foams: Current Advances and Future Perspectives
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Polyurethane Foams: Current Advances and Future Perspectives

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Networks".

Deadline for manuscript submissions: closed (20 April 2022) | Viewed by 18643

Special Issue Editor

Dr. Uģis Cābulis

E-Mail Website
Guest Editor
Polymer Laboratory, Latvian State Institute of Wood Chemistry, 27 Dzerbenes St., LV-1006 Riga, Latvia
Interests: polyurthane science and technology; polymers from renewable resources; thermal and cryogenic insulation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polyurethanes present a broad spectrum of materials that are produced to meet the needs for various applications, from automotive industry, building and construction, appliances, furnishing, marine and medicine. Foams are among the most important commercial polyurethane products that can be classified as rigid, semi-rigid and flexible. Applications of porous polyurethane materials are highly dependent on their polymer matrix and cellular structure.

In the 21st century, when it comes to the bioeconomy, a great deal of effort, research and investment will be made for the transition from a fossil-fuelled to renewables-driven economy. The polyurethane industry is not excluded from this trend; this industry has been under pressure to be more sustainable and find innovative solutions from an environmental and sustainability perspective. However, polyurethanes obtained via the conventional route are widely used—a major drawback of them is related to isocyanates toxicity. To solve these problems, a new range of nonisocyanate polyurethanes has been investigated and developed during the last few years. There are various synthetic pathways for nonisocyanate polyurethane foam production.

The purpose of this Special Issue is to bring together polymer scientists working with polyurethane foam materials, to reflect the current situation, not only in scientific laboratories, but also to update the requirements and settings of the industry. Authors are welcome to submit their latest results in the form of original full articles, communications, or reviews on this broad topic.

Dr. Uģis Cābulis
Guest Editor

Keywords

  • Rigid and flexible polyurethane foams
  • Nonisocyanate polyurethanes
  • Thermal and cryogenic insulation
  • Cellular, lightweight materials
  • Materials for construction, car and furniture industry
  • Foaming process, cell structure
  • Flammability, thermal stability and toxicity
  • Renewable and recyclable resources
  • Life cycle and biodegradability

Published Papers (6 papers)

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Research

14 pages, 5717 KiB  
Article
Natural Oil-Based Rigid Polyurethane Foam Thermal Insulation Applicable at Cryogenic Temperatures
by Katarzyna Uram, Aleksander Prociak, Laima Vevere, Ralfs Pomilovskis, Ugis Cabulis and Mikelis Kirpluks
Polymers 2021, 13(24), 4276; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13244276 - 07 Dec 2021
Cited by 18 | Viewed by 3465
Abstract
This paper presents research into the preparation of rigid polyurethane foams with bio-polyols from rapeseed and tall oil. Rigid polyurethane foams were designed with a cryogenic insulation application for aerospace in mind. The polyurethane systems containing non-renewable diethylene glycol (DEG) were modified by [...] Read more.
This paper presents research into the preparation of rigid polyurethane foams with bio-polyols from rapeseed and tall oil. Rigid polyurethane foams were designed with a cryogenic insulation application for aerospace in mind. The polyurethane systems containing non-renewable diethylene glycol (DEG) were modified by replacing it with rapeseed oil-based low functional polyol (LF), obtained by a two-step reaction of epoxidation and oxirane ring opening with 1-hexanol. It was observed that as the proportion of the LF polyol in the polyurethane system increased, so too did the apparent density of the foam material. An increase in the value of the thermal conductivity coefficient was associated with an increase in the value of apparent density. Mechanical tests showed that the rigid polyurethane foam had higher compressive strength at cryogenic temperatures compared with the values obtained at room temperature. The adhesion test indicated that the foams subjected to cryo-shock obtained similar values of adhesion strength to the materials that were not subjected to this test. The results obtained were higher than 0.1 MPa, which is a favourable value for foam materials in low-temperature applications. Full article
(This article belongs to the Special Issue Polyurethane Foams: Current Advances and Future Perspectives)
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19 pages, 9156 KiB  
Article
Polyurethane Foam Composites Reinforced with Renewable Fillers for Cryogenic Insulation
by Beatrise Sture, Laima Vevere, Mikelis Kirpluks, Daniela Godina, Anda Fridrihsone and Ugis Cabulis
Polymers 2021, 13(23), 4089; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13234089 - 24 Nov 2021
Cited by 11 | Viewed by 3326
Abstract
Sawdust, microcellulose and nanocellulose and their silanized forms were used to reinforce rigid polyurethane (PU) foam composites. The concentration of fillers was varied in the range of 0.5–1.5%. For rigid PU foam formulations, three polyols from recycled and renewable materials were used, among [...] Read more.
Sawdust, microcellulose and nanocellulose and their silanized forms were used to reinforce rigid polyurethane (PU) foam composites. The concentration of fillers was varied in the range of 0.5–1.5%. For rigid PU foam formulations, three polyols from recycled and renewable materials were used, among other components. Polyols were obtained from rapeseed oil, tall oil fatty acids and recycled polyethylene terephthalate. As rigid PU foam composites in literature have been described as appropriate thermal insulation material, the appliance of obtained composites for cryogenic insulation was investigated by determining the various physical-mechanical properties of composites. The physical-mechanical properties, such as the modulus of elasticity, compressive and tensile strength in both 293 K and 77 K, adhesion measurements with and without cryo-shock, apparent density, thermal conductivity coefficient, and safety coefficient were measured. The results showed that the addition of fillers did not give a significant improvement of characteristics. Full article
(This article belongs to the Special Issue Polyurethane Foams: Current Advances and Future Perspectives)
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14 pages, 2209 KiB  
Article
Identification and Evaluation of Hazardous Pyrolysates in Bio-Based Rigid Polyurethane-Polyisocyanurate Foam Smoke
by Sanita Reinerte, Vilhelmine Jurkjane, Ugis Cabulis and Arturs Viksna
Polymers 2021, 13(19), 3205; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13193205 - 22 Sep 2021
Cited by 9 | Viewed by 1723
Abstract
In this study, rigid polyurethane (PU) and polyisocyanurate (PIR) foam samples made from renewable material (tall oil fatty acid) based polyols were analyzed by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) to obtain information about the full relative smoke content, with a focus on [...] Read more.
In this study, rigid polyurethane (PU) and polyisocyanurate (PIR) foam samples made from renewable material (tall oil fatty acid) based polyols were analyzed by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) to obtain information about the full relative smoke content, with a focus on substance identification by their functional groups and hazardousness. The relative content of gaseous products produced during the thermal degradation was evaluated between the two samples, differenced by their assigned isocyanate (NCO) index value—150 and 300. The main thermal degradation components of the rigid PU-PIR foam were found to originate from the decomposition of isocyanate, primarily forming 4,4′-methylenedianiline, 3,3′-diaminodiphenylmethane, N-methylaniline, aniline, 4-benzylaniline and phenyl isocyanate. Hazard analysis revealed that the most common hazards were the hazards related to health: H315 (36%), H319 (28%), H335 (25%), and H302 (23%). The chemical compound with the highest relative content value—4,4′-methylenedianiline (45.3% for PU and 52.4% for PIR)—was identified to be a suspected carcinogen and mutagen. The focus of the study was identifying and evaluating the relative quantities of the produced gaseous products, examine their hazardousness, and provide information on the released thermal degradation products to form a renewable-source based rigid PU and PIR foam. Full article
(This article belongs to the Special Issue Polyurethane Foams: Current Advances and Future Perspectives)
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18 pages, 9647 KiB  
Article
Effect of Foaming Formulation and Operating Pressure on Thermoregulating Polyurethane Foams
by Angel Serrano, Ana M. Borreguero, Juan Catalá, Juan F. Rodríguez and Manuel Carmona
Polymers 2021, 13(14), 2328; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13142328 - 15 Jul 2021
Cited by 4 | Viewed by 3152
Abstract
The synthesis of rigid polyurethane (RPU) foams containing thermoregulatory microcapsules has been carried out under reduced pressure conditions with a new foaming formulation to reduce the final composite densities. These optimized RPU foams were able to overpass the drawbacks exhibited by the previous [...] Read more.
The synthesis of rigid polyurethane (RPU) foams containing thermoregulatory microcapsules has been carried out under reduced pressure conditions with a new foaming formulation to reduce the final composite densities. These optimized RPU foams were able to overpass the drawbacks exhibited by the previous composites over the studied temperature range, working as insulating and thermal energy storage materials. The change in the formulation allowed to decrease the final foam density and enhance their mechanical strength. The effect of the operating pressure (atmospheric, 800 mbar, and 700 mbar) and microcapsules content (up to 30 wt%) on the physical, mechanical, and thermal PU foam properties was studied. The reduction of the pressure from atmospheric to 800 mbar did not have any effect on the cell size, strut thickness, and compression strength 10% of deformation, the Young modulus being even higher at 800 mbar. Nevertheless, a strong impact on the microstructure and mechanical properties was observed for the foam composites obtained at 700 mbar. A deleterious impact on the RPU foams thermal conductivity was observed when using low-pressure conditions. Thermal analyses showed that a composite able to work as heat accumulator and thermal insulation both at transient and at steady state was achieved. Full article
(This article belongs to the Special Issue Polyurethane Foams: Current Advances and Future Perspectives)
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19 pages, 3206 KiB  
Article
Hardly Flammable Polyurethane Foams with 1,3-Pyrimidine Ring and Boron Atoms
by Elżbieta Chmiel-Szukiewicz
Polymers 2021, 13(10), 1603; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13101603 - 16 May 2021
Viewed by 1786
Abstract
This work presents the results of research related to the determination of application possibilities of new oligoetherols with 1,3-pyrimidine rings and boron atoms in rigid polyurethane foam production. Oligoetherols were obtained from 1,3-bis(2-hydroxyethyl)uracil, boric acid, and ethylene carbonate. Their structure was determined by [...] Read more.
This work presents the results of research related to the determination of application possibilities of new oligoetherols with 1,3-pyrimidine rings and boron atoms in rigid polyurethane foam production. Oligoetherols were obtained from 1,3-bis(2-hydroxyethyl)uracil, boric acid, and ethylene carbonate. Their structure was determined by instrumental methods (IR, 1H-NMR and MALDI-ToF spectra) and the physicochemical and thermal properties were examined. Obtained oligoetherols were used for synthesis of polyurethane foams. Some properties of the foams, such as apparent density, water uptake, dimensions stability, thermal stability, compression strength, thermal conductivity, oxygen index, and horizontal burning were investigated. The introduction of boron atoms into the foam structure reduced their flammability, but unfortunately it had a negative effect on the water absorption of the obtained materials—the water absorption was higher compared to the boron-free foams. The obtained foams showed good thermal stability compared to classic, rigid polyurethane foams. Full article
(This article belongs to the Special Issue Polyurethane Foams: Current Advances and Future Perspectives)
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23 pages, 5251 KiB  
Article
Polytetrafluoroethylene Films in Rigid Polyurethane Foams’ Dielectric Permittivity Measurements with a One-Side Access Capacitive Sensor
by Ilze Beverte, Ugis Cabulis and Sergejs Gaidukovs
Polymers 2021, 13(7), 1173; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13071173 - 06 Apr 2021
Cited by 9 | Viewed by 2127
Abstract
As a non-metallic composite material, widely applied in industry, rigid polyurethane (PUR) foams require knowledge of their dielectric properties. In experimental determination of PUR foams’ dielectric properties protection of one-side capacitive sensor’s active area from adverse effects caused by the PUR foams’ test [...] Read more.
As a non-metallic composite material, widely applied in industry, rigid polyurethane (PUR) foams require knowledge of their dielectric properties. In experimental determination of PUR foams’ dielectric properties protection of one-side capacitive sensor’s active area from adverse effects caused by the PUR foams’ test objects has to be ensured. In the given study, the impact of polytetrafluoroethylene (PTFE) films, thickness 0.20 mm and 0.04 mm, in covering or simulated coating the active area of one-side access capacitive sensor’ electrodes on the experimentally determined true dielectric permittivity spectra of rigid PUR foams is estimated. Penetration depth of the low frequency excitation field into PTFE and PUR foams is determined experimentally. Experiments are made in order to evaluate the difference between measurements on single PUR foams’ samples and on complex samples “PUR foams + PTFE film” with two calibration modes. A modification factor and a small modification criterion are defined and values of modifications are estimated in numerical calculations. Conclusions about possible practical applications of PTFE films in dielectric permittivity measurements of rigid PUR foams with one-side access capacitive sensor are made. Full article
(This article belongs to the Special Issue Polyurethane Foams: Current Advances and Future Perspectives)
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