Polyurethane Foams: Past, Present, and Future

Gama, Nuno; Ferreira, Artur; Barros‐Timmons, Ana

doi:10.3390/ma11101841

Cited by 591 publications

(468 citation statements)

References 236 publications

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“…The value of the extinction coefficient of the solid polymer (K W = 600 cm −1 ) was obtained from the literature. 7 The values of the Glicksman extinction coefficients (K G ) calculated using Eqn (6) are presented in Fig. 7.…”

Section: Extinction Coefficient Modelling: Glicksman Extinction Coeffmentioning

confidence: 99%

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: Extinction Coefficient Modelling: Glicksman Extinction Coeffmentioning

confidence: 99%

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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“…They are also used as a protection during the transport of goods [4,5]. The production of polyurethane foams (PUF) is still dependent on petroleum [6]. The concerns relate primarily to the harmful health effects and environmental problems of oil-based PU and future crude oil shortage [7].…”

Section: Introductionmentioning

confidence: 99%

“…The concerns relate primarily to the harmful health effects and environmental problems of oil-based PU and future crude oil shortage [7]. The development of new technologies motivates searching for solutions based on natural and renewable raw materials with such chemical structure that it will allow their quick and easy degradation [4][5][6][7][8]. The need 2 of 23 to develop a more ecological polyurethane material from renewable sources is also associated with an increasing amount of waste from PU.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of Photodegradation and Biodegradation of RPU/PIR Foams Modified by Natural Compounds of Plant Origin

et al. 2019

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Four types of rigid polyurethane-polyisocyanurate foams (RPU/PIR) were obtained. Three of them were modified by powder fillers, such as cinnamon extract (C10 foam), green coffe extract (KZ10), and cocoa extract (EK10) in an amount of 10 wt %. The last foam was obtained without a filler (W foam). The basic properties and thermal properties of obtained foams were examined. All foams were subjected to degradation in the climatic chamber acting on samples of foams in a defined temperature, humidity, and UV radiation for 7, 14, and 21 days. The physico-mechanical properties of foams were tested. The compressive strength of degraded foams after 7, 14, and 21 days was compared with the compressive strength of nondegraded foams (0 days). The chosen properties of degraded foams, such as cellular structure by scanning electron microscopy (SEM) and changes of chemical structure by FTIR spectroscopy were compared. The obtained foams were also subjected to degradation in a circulating air dryer in an increased temperature (120 °C) for 48 h. Additionally, W, C10, ZK10, EK10 foams were placed in a soil environment and subjected to 28 days biodegradation process. The biochemical oxygen demand (BOD), the theoretical oxygen demand (TOD), and the degree of biodegradation (Dt) of foams were determined in this measurment. Test results showed that the compressive strength of foams decreased with the longer time of foam degradation in the conditioner. The foam subjected to degradation darkened and became more red and yellow in color. The addition of natural compounds of plant origin to foams increased their susceptibility to biodegradation.

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“…Furthermore, the effects of manufacturing in a continuous process remains to be explored. (b) PU foams can be tailored through modifications in the chemical formulation [22][23][24]. However, details on the chemical formulation of the PU are rarely documented in the studies found in the literature and they may or may not match those of PU insulated pipes.…”

mentioning

confidence: 99%

Anisotropy in Polyurethane Pre-Insulated Pipes

2019

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The polyurethane foam in district heating pre-insulated pipes has a critical role to play both as thermal insulation and as load bearing element, as it serves as bond between the medium pipe and the casing. Hence, knowledge on how the foam behaves under multiaxial stresses is of great importance for the design as well as for aging predictions of the network. It is known that cell shape anisotropy in polymeric foams leads to anisotropy in its mechanical properties. In this study, we evaluate and quantify the microstructural anisotropy of PU foam from pre-insulated pipes as well as its mechanical behaviour under compression in the three orthogonal directions. We cover rigid and flexible PU foam, batch and continuous manufacturing, and different pipe diameters. The results were compared with those predicted by available rectangular and Kelvin cell shape models. We have found that PU from pre-insulated pipes is orthotropic and present stronger anisotropy than that typically found in PU slabs. The traditional bonded pipes under consideration behaved in a similar way. However, when comparing the two flexible pipes in this study, despite no significant differences in cell shape anisotropy were found, a significantly different behaviour for the E modulus ratio was observed. This shows that while the manufacturing process exerts the main influence on cell shape anisotropy, to explain the difference in stiffness behaviour other factors need to be taken into consideration, such as cell size and cell size variability.

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Polyurethane Foams: Past, Present, and Future

Cited by 591 publications

References 236 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

Assessment of Photodegradation and Biodegradation of RPU/PIR Foams Modified by Natural Compounds of Plant Origin

Anisotropy in Polyurethane Pre-Insulated Pipes

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