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Impact of Eco-Friendly Flame-Retardant Water-Blown Rigid Polyurethane Foams Containing Recycled Polyols for Insulation Applications.

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Title: Impact of Eco-Friendly Flame-Retardant Water-Blown Rigid Polyurethane Foams Containing Recycled Polyols for Insulation Applications.
Authors: Santiago-Calvo, Mercedes1 (AUTHOR) mersan@cidaut.es, Amundarain, Izotz2 (AUTHOR), Gómez-Alonso, José Luis1,2 (AUTHOR), Ballestero, Jesús2 (AUTHOR), Arnaiz, Sixto2 (AUTHOR), Cañibano, Esteban1 (AUTHOR), Fernández, María-Teresa1 (AUTHOR)
Source: Polymers (20734360). Apr2026, Vol. 18 Issue 7, p856. 16p.
Subjects: Polyols, Fire resistant materials, Fireproofing agents, Urethane foam, Electric insulators & insulation, Thermal conductivity
Abstract: The need to reduce polyurethane (PU) foam waste has encouraged the development of sustainable foam formulations based on recycled raw materials and environmentally friendly additives, addressing both waste management and comparable foam properties to those based on fossil resources. In the present investigation, more sustainable water-blown rigid PU foams were investigated using recycled polyol and halogen-free flame retardants (FRs) for fire-resistant insulation applications. Two series of foam formulations were prepared: a first series with virgin polyol and the inclusion of a halogen-free FR additive (6 wt%) and a second series with recycled polyol (10% added respect to the total polyol) and halogen-free FR additives (6 wt%). Two types of FR were used: FR900, specifically identified as 3,9-Dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide, in powder form with 24% phosphorus content and reactive polyol based FR140, an oligomeric ethyl ethylene phosphate, in liquid form with 19% phosphorus content. The density, cellular structure, aged thermal conductivity, dimensional and hydrolytic stability, fire properties, and mechanical properties were characterized for novel foamed systems. Rigid foamed materials with very low densities around 50 kg/m3 were obtained. On the one hand, the inclusion of FR900 into the PU formulation containing virgin polyol generated foam with the lowest thermal conductivity (36.10 mW/mK) due to the smaller open cell content (11.7%) and cell size reduction (433 microns). On the other hand, the inclusion of recycled polyol reduced the foam density by 6 kg/m3 (44.1 kg/m3), increased the cell size average (848 microns) and open cell content (15.1%), maintained thermal conductivity (38.73 mW/mK), slightly improved the fire properties, and worsened the mechanical properties in comparison with the PU reference containing only virgin polyol. The results obtained by the foam containing recycled polyol and 6% FR900 are remarkable, presenting an increase in density (50.3 kg/m3) and in open cell content (73%), but a very high reduction in cell size (465 microns) and thus a low value of thermal conductivity of 37.04 mW/mK with respect to the reference material containing recycled polyol. Moreover, this PU foam containing recycled polyol and FR900 offered improved fire resistance (148.2 kW/m2 of Maximum Average Rate of Heat Emission (MARHE), 179.1 kW/m2 of Maximum Heat Release Rate (HRRmax), and 24.6 MJ/m2 of Total Heat Release (THR)) and mechanical properties (6.97 MPa of Young's modulus and 0.24 MPa of collapsed stress) for the construction sector. The inclusion of FR140 does not improve the properties of the foam system containing recycled polyol, mainly due to the deterioration of the cellular structure (in the open cell content and cell size). [ABSTRACT FROM AUTHOR]
Copyright of Polymers (20734360) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Group: Ti
  Data: Impact of Eco-Friendly Flame-Retardant Water-Blown Rigid Polyurethane Foams Containing Recycled Polyols for Insulation Applications.
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  Data: <searchLink fieldCode="AR" term="%22Santiago-Calvo%2C+Mercedes%22">Santiago-Calvo, Mercedes</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> mersan@cidaut.es</i><br /><searchLink fieldCode="AR" term="%22Amundarain%2C+Izotz%22">Amundarain, Izotz</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Gómez-Alonso%2C+José+Luis%22">Gómez-Alonso, José Luis</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Ballestero%2C+Jesús%22">Ballestero, Jesús</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Arnaiz%2C+Sixto%22">Arnaiz, Sixto</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Cañibano%2C+Esteban%22">Cañibano, Esteban</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Fernández%2C+María-Teresa%22">Fernández, María-Teresa</searchLink><relatesTo>1</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Polymers+%2820734360%29%22">Polymers (20734360)</searchLink>. Apr2026, Vol. 18 Issue 7, p856. 16p.
– Name: Subject
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  Data: <searchLink fieldCode="DE" term="%22Polyols%22">Polyols</searchLink><br /><searchLink fieldCode="DE" term="%22Fire+resistant+materials%22">Fire resistant materials</searchLink><br /><searchLink fieldCode="DE" term="%22Fireproofing+agents%22">Fireproofing agents</searchLink><br /><searchLink fieldCode="DE" term="%22Urethane+foam%22">Urethane foam</searchLink><br /><searchLink fieldCode="DE" term="%22Electric+insulators+%26+insulation%22">Electric insulators & insulation</searchLink><br /><searchLink fieldCode="DE" term="%22Thermal+conductivity%22">Thermal conductivity</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: The need to reduce polyurethane (PU) foam waste has encouraged the development of sustainable foam formulations based on recycled raw materials and environmentally friendly additives, addressing both waste management and comparable foam properties to those based on fossil resources. In the present investigation, more sustainable water-blown rigid PU foams were investigated using recycled polyol and halogen-free flame retardants (FRs) for fire-resistant insulation applications. Two series of foam formulations were prepared: a first series with virgin polyol and the inclusion of a halogen-free FR additive (6 wt%) and a second series with recycled polyol (10% added respect to the total polyol) and halogen-free FR additives (6 wt%). Two types of FR were used: FR900, specifically identified as 3,9-Dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide, in powder form with 24% phosphorus content and reactive polyol based FR140, an oligomeric ethyl ethylene phosphate, in liquid form with 19% phosphorus content. The density, cellular structure, aged thermal conductivity, dimensional and hydrolytic stability, fire properties, and mechanical properties were characterized for novel foamed systems. Rigid foamed materials with very low densities around 50 kg/m3 were obtained. On the one hand, the inclusion of FR900 into the PU formulation containing virgin polyol generated foam with the lowest thermal conductivity (36.10 mW/mK) due to the smaller open cell content (11.7%) and cell size reduction (433 microns). On the other hand, the inclusion of recycled polyol reduced the foam density by 6 kg/m3 (44.1 kg/m3), increased the cell size average (848 microns) and open cell content (15.1%), maintained thermal conductivity (38.73 mW/mK), slightly improved the fire properties, and worsened the mechanical properties in comparison with the PU reference containing only virgin polyol. The results obtained by the foam containing recycled polyol and 6% FR900 are remarkable, presenting an increase in density (50.3 kg/m3) and in open cell content (73%), but a very high reduction in cell size (465 microns) and thus a low value of thermal conductivity of 37.04 mW/mK with respect to the reference material containing recycled polyol. Moreover, this PU foam containing recycled polyol and FR900 offered improved fire resistance (148.2 kW/m2 of Maximum Average Rate of Heat Emission (MARHE), 179.1 kW/m2 of Maximum Heat Release Rate (HRRmax), and 24.6 MJ/m2 of Total Heat Release (THR)) and mechanical properties (6.97 MPa of Young's modulus and 0.24 MPa of collapsed stress) for the construction sector. The inclusion of FR140 does not improve the properties of the foam system containing recycled polyol, mainly due to the deterioration of the cellular structure (in the open cell content and cell size). [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Polymers (20734360) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.3390/polym18070856
    Languages:
      – Code: eng
        Text: English
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      Pagination:
        PageCount: 16
        StartPage: 856
    Subjects:
      – SubjectFull: Polyols
        Type: general
      – SubjectFull: Fire resistant materials
        Type: general
      – SubjectFull: Fireproofing agents
        Type: general
      – SubjectFull: Urethane foam
        Type: general
      – SubjectFull: Electric insulators & insulation
        Type: general
      – SubjectFull: Thermal conductivity
        Type: general
    Titles:
      – TitleFull: Impact of Eco-Friendly Flame-Retardant Water-Blown Rigid Polyurethane Foams Containing Recycled Polyols for Insulation Applications.
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            NameFull: Santiago-Calvo, Mercedes
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            NameFull: Amundarain, Izotz
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            NameFull: Gómez-Alonso, José Luis
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            NameFull: Ballestero, Jesús
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              Text: Apr2026
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              Y: 2026
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