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

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...

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Bibliographic Details
Published in:Polymer international 2019-10, Vol.68 (10), p.1826-1835
Main Authors: Santiago‐Calvo, Mercedes, Tirado‐Mediavilla, Josías, Ruiz‐Herrero, José Luis, Villafañe, Fernando, Rodríguez‐Pérez, Miguel Ángel
Format: Article
Language:English
Subjects:
Additives
Aging
Blowing agents
Cell size
Cellular structure
composites
Cyclopentane
Diatomaceous earth
Energy conservation
Evolution
Fillers
Foaming
foaming temperature
foams
Heat conductivity
Heat transfer
Organic chemistry
Plastic foam
Polyurethane
Polyurethane foam
Reaction kinetics
Silica
Silicon dioxide
Size reduction
Structural analysis
Talc
Thermal conductivity
Thermodynamic properties
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Summary: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 The long‐term thermal conductivity of water‐cyclopentane blown rigid polyurethane composite foams has been studied during 3 years of aging. The initial measurements of filled foams showed an improvement of the thermal properties due to a decrease in the radiation contribution. However, this initial reduction was not maintained, because each foam showed a different thermal conductivity evolution with time, which has been related to the foaming temperature reached during the foam production.
ISSN:0959-8103
1097-0126
DOI:10.1002/pi.5893