Rigid polyurethane foams with infused nanoclays: Relationship between cellular structure and thermal conductivity

Estravís, Sergio; Tirado‐Mediavilla, Josías; Santiago‐Calvo, Mercedes; Ruiz‐Herrero, J.L.; Villafañe, Fernando; Rodríguez‐Pérez, Miguel Ángel

doi:10.1016/j.eurpolymj.2016.04.026

Cited by 99 publications

(77 citation statements)

References 54 publications

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“…Their thermal conductivity (14.5 mW m –1 K –1 for CO 2 and 12 mW m –1 K –1 for CP at 20 °C) is very low, but these gases slowly diffuse out of the cells, being substituted by atmospheric air, whose thermal conductivity (25.6 mW m –1 K –1 at 20 °C) is higher. The CP is retained in the cells for longer periods of time compared to CO 2 ; CO 2 leaves the foam in a time period less than 30 days …”

Section: Resultsmentioning

confidence: 99%

“…The extinction contribution depends on the cell size ( ϕ ), foam density ( ρ f ), solid PU density ( ρ s ), mass fraction in the struts ( f S ) and a constant related to the cell geometry (4.10). A value of 0.7 for the mean mass fraction in the struts is considered for this type of foam . The cell wall contribution is valid for foams containing thin cell walls ( δ < 30 μm, around 2 μm in our foams) and includes the hypothetical extinction coefficient for a uniform material which occupies the entire volume of the foam, whose attenuation is the same as those of thin cell walls.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the use of blowing agents with low thermal conductivities is one of the key strategies to improve the thermal properties of RPU foams. Moreover, the addition of fillers to the RPU matrix may also decrease the cell size and/or block infrared radiation, reducing the radiation contribution to the thermal conductivity …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Santiago‐Calvo

Tirado‐Mediavilla

Ruiz‐Herrero

et al. 2019

Polymer International

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An understanding of the long‐term thermal conductivity of rigid polyurethane (RPU) foams presents great interest in the building field considering the conservation of energy efficiency. In this study, the effect of different types of particles (talc, diatomaceous earth and non‐porous silica) on the thermal conductivity of RPU foams blown with cyclopentane and water as blowing agents was investigated during 3 years of aging. The characterization of the cellular structure shows how the addition of particles causes a cell size reduction of the foams, and consequently an enhancement of the thermal properties just after production. However, this initial reduction is not maintained, because each foam shows a different thermal conductivity evolution with time. We have found, for the first time, a relationship between the slope of the thermal conductivity versus time at the first measurements and the internal temperature reached during the foaming process. The evolution of the RPU foams in which higher internal temperatures were reached is more pronounced than in those RPU foams where lower foaming temperatures were observed. This effect is related to the kinetics of the diffusion of the gas occluded inside the cells and imposes a new criterion for the selection of particles to reduce the thermal conductivity of RPU foams; these additives should ideally decrease the temperature reached during the foaming process. Moreover, the effect of aging on the thermal conductivity is explained by using theoretical models. © 2019 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Santiago‐Calvo

Tirado‐Mediavilla

Ruiz‐Herrero

et al. 2019

Polymer International

Self Cite

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“…The effect of EG on the thermal conductivity of RPUF can be inferred from the data collected in Table . The thermal conductivity is measured when the carbon dioxide produced in the blowing reaction has been substituted by atmospheric air (approximately 2 weeks after production) . The data in Table show how the addition of increasing amounts of EG produces an increase in the thermal conductivity, compared to that of the reference materials.…”

Section: Resultsmentioning

confidence: 99%

Impact of expandable graphite on flame retardancy and mechanical properties of rigid polyurethane foam

et al. 2018

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Flame retardant (FR) and mechanical performance properties of two different rigid polyurethane foams (RPUFs) containing expandable graphite (EG) as FR additive were studied. The impact of EG on the foam properties were evaluated. Cellular structures were less homogeneous in foams containing EG. Thermal conductivities of RPUF increased slightly with EG addition. FR properties of the foams were evaluated by limiting oxygen index (LOI) test, vertical burning test (UL94), and cone calorimeter test. The addition of EG improved the FR performance and increased the density of the foams. For example, LOI value was increased from 18.4 to 25.2 in EG10PU1, whereas for EG10PU2, LOI increased from 19.2 to 29.8. In UL94 test, EG10PU1 reached V‐1 rating, while EG8PU2 passed V‐0 rating. Results from cone calorimeter test showed that the EG in the RPUF effectively reduced heat release rate, total heat released, total smoke production, and mass loss rate with increase in EG. This improvement was more efficient for the higher density foam. In addition, low loading of EG in PU1 increased the compression performance but decreased as the amount of EG was further increased. POLYM. COMPOS., 40:E1705–E1715, 2019. © 2018 Society of Plastics Engineers

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“…These additional advantages are strongly affected by the filler‐to‐resin ratio, extent of dispersion, and particle size of the filler . Different types of mineral fillers such as calcium carbonate, talc, and nanoclay have been considered to improve the properties of PU foams. Czupryński et al incorporated various particulate fillers in rigid polyurethane‐polyisocyanurate foams and analyzed their effect on the properties of the rigid foam.…”

Section: Introductionmentioning

confidence: 99%

Investigation on flammability of rigid polyurethane foam‐mineral fillers composite

2019

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Summary This study investigates the incorporation of castor oil–based rigid polyurethane foam with mineral fillers feldspar or kaolinite clay in order to enhance the mechanical, thermal, and flame retardant properties. Influence of mineral fillers on the mechanical strength was characterized by compressive strength and flexural strength measurement. Thermogravimetric analysis (TGA) was performed to diagnose the changes in thermal properties, while cone calorimeter test was performed to ascertain the flame retardancy of the mineral filler–incorporated rigid polyurethane foam composites. Results showed that the foams incorporated with mineral filler demonstrated up to 182% increase in compressive strength and 351% increase in flexural strength. Thermal stability of these composite foams was also found to be enhanced on the incorporation of kaolinite clay filler with an increase in 5% weight loss temperature (T5%) from 192°C to 260°C. Furthermore, peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) were also found to decreased on the incorporation of mineral filler in the rigid polyurethane foam. So mineral fillers are ascertained as a potential filler to enhance the mechanical, thermal, and flame retardant behaviors of bio‐based rigid polyurethane foam composites.

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Rigid polyurethane foams with infused nanoclays: Relationship between cellular structure and thermal conductivity

Cited by 99 publications

References 54 publications

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Impact of expandable graphite on flame retardancy and mechanical properties of rigid polyurethane foam

Investigation on flammability of rigid polyurethane foam‐mineral fillers composite

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