Temperature dependency of the long-term thermal conductivity of spray polyurethane foam

2021 ◽  
pp. 174425912110454
Author(s):  
Neal Holcroft
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Cellular Structure ◽  
Gas Diffusion ◽  
Temperature Dependent ◽  
Blowing Agent ◽  
Closed Cell ◽  
Wall Assembly ◽  
Cell Foam

The thermal properties of closed-cell foam insulation display a more complex behaviour than other construction materials due to the properties of the blowing agent captured in their cellular structure. Over time, blowing agent diffuses out from and air into the cellular structure resulting in an increase in thermal conductivity, a process that is temperature dependent. Some blowing agents also condense at temperatures within the in-service range of the insulation, resulting in non-linear temperature dependent relationships. Moreover, diffusion of moisture into the cellular structure increases thermal conductivity. Standards exist to quantify the effect of gas diffusion on thermal conductivity, however only at standard laboratory conditions. In this paper a new test procedure is described that includes calculation methods to determine Temperature Dependent Long-Term Thermal Conductivity (LTTC(T)) functions for closed-cell foam insulation using as a test material, a Medium-Density Spray Polyurethane Foam (MDSPF). Tests results are provided to show the validity of the method and to investigate the effects of both conditioning and mean test temperature on change in thermal conductivity. In addition, testing was conducted to produce a moisture dependent thermal conductivity function. The resulting functions were used in hygrothermal simulations to assess the effect of foam aging, in-service temperature and moisture content on the performance of a typical wall assembly incorporating MDSPF located in four Canadian climate zones. Results show that after 1 year, mean thermal conductivity increased 15%–16% and after 5 years 23%–24%, depending on climate zone. Furthermore, the use of the LTTC(T) function to calculate the wall assembly U-value improved accuracy between 3% and 5%.

Effect of the cellular structure on thermal conductivity of rigid closed-cell foam polymers during long-term aging

1999 ◽  
Vol 35 (2) ◽  
pp. 129-138 ◽  
Author(s):  
A. G. Dementyev ◽  
M. A. Dementyev ◽  
P. A. Zinger ◽  
I. R. Metlyakova
Keyword(s):  
Thermal Conductivity ◽  
Cellular Structure ◽  
Closed Cell ◽  
Cell Foam

scholarly journals Microstructural and Chemical Analysis of Polyurethane and Polyisocyanurate Foam Insulations

2021 ◽  
Author(s):  
Umberto Berardi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Cell Structure ◽  
Polymer Degradation ◽  
Chemical Characterization ◽  
Aging Behavior ◽  
Blowing Agent ◽  
Closed Cell ◽  
Physical Attributes ◽  
Cell Foam

For some closed cell foam insulation products, the thermal conductivity increases at low temperatures, contrary to single thermal resistance values provided by manufacturers. This phenomenon has been demonstrated in various polyurethane and polyisocyanurate insulations. The reduction in thermal performance has been attributed to the diffusion of air and blowing agent through the foam and to the condensation of blowing agent. Aging processes such as freeze-thaw cycling, moisture accumulation, and polymer degradation further increase thermal conductivity. The initial cell structure plays a role in dictating the thermal performance. To further understand the loss of thermal performance in closed cell foams, microstructure and chemical characterization was performed in this study. The aging behavior of foam insulations was analyzed by imaging foams with SEM and by measuring foam. Changes in the polymer physical attributes were identified and compared to increases in thermal conductivity. This project also used gas chromatography and quantified changes in pentane concentration in polyisocyanurate foams that have undergone aging

scholarly journals Microstructural and Chemical Analysis of Polyurethane and Polyisocyanurate Foam Insulations

2021 ◽  
Author(s):  
Umberto Berardi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Cell Structure ◽  
Polymer Degradation ◽  
Chemical Characterization ◽  
Aging Behavior ◽  
Blowing Agent ◽  
Closed Cell ◽  
Physical Attributes ◽  
Cell Foam

For some closed cell foam insulation products, the thermal conductivity increases at low temperatures, contrary to single thermal resistance values provided by manufacturers. This phenomenon has been demonstrated in various polyurethane and polyisocyanurate insulations. The reduction in thermal performance has been attributed to the diffusion of air and blowing agent through the foam and to the condensation of blowing agent. Aging processes such as freeze-thaw cycling, moisture accumulation, and polymer degradation further increase thermal conductivity. The initial cell structure plays a role in dictating the thermal performance. To further understand the loss of thermal performance in closed cell foams, microstructure and chemical characterization was performed in this study. The aging behavior of foam insulations was analyzed by imaging foams with SEM and by measuring foam. Changes in the polymer physical attributes were identified and compared to increases in thermal conductivity. This project also used gas chromatography and quantified changes in pentane concentration in polyisocyanurate foams that have undergone aging

scholarly journals Properties of polyurethane foam with fourth-generation blowing agent

e-Polymers ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 763-769
Author(s):  
Vladimir Yakushin ◽  
Ugis Cabulis ◽  
Velta Fridrihsone ◽  
Sergey Kravchenko ◽  
Romass Pauliks
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Cellular Structure ◽  
Fourth Generation ◽  
Low Density ◽  
Technological Parameters ◽  
Blowing Agent ◽  
Foam Properties ◽  
Rise Direction ◽  
Foam Production

Abstract Climate change makes it imperative to use materials with minimum global warming potential. The fourth-generation blowing agent HCFO-1233zd-E is one of them. The use of HCFO allows the production of polyurethane foam with low thermal conductivity. Thermal conductivity, like other foam properties, depends not only on the density but also on the cellular structure of the foam. The cellular structure, in turn, depends on the technological parameters of foam production. A comparison of pouring and spray foams of the same low density has shown that the cellular structure of spray foam consists of cells with much less sizes than pouring foam. Due to the small size of cells, spray foam has a lower radiative constituent in the foam conductivity and, as a result, a lower overall thermal conductivity than pouring foam. The water absorption of spray foam, due to the fine cellular structure, also is lower than that of pouring foam. Pouring foam with bigger cells has higher compressive strength and modulus of elasticity in the foam rise direction. On the contrary, spray foam with a fine cellular structure has higher strength and modulus in the perpendicular direction. The effect of foam aging on thermal conductivity was also studied.

Effect of Filler Types on Properties of the Natural Rubber Closed Cell Foam

2019 ◽  
Vol 886 ◽  
pp. 213-218
Author(s):  
Ekaroek Phumnok ◽  
Jakkrit Boonphang ◽  
Orrachorn Bourkaew
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Precipitated Calcium Carbonate ◽  
Elongation At Break ◽  
Blowing Agent ◽  
Compression Set ◽  
China Clay ◽  
Closed Cell ◽  
The Difference ◽  
Cell Foam

In this research, effects of filler types and their loading on properties of the natural rubber closed cell foam were investigated. The azodicarbonamide was used as a blowing agent in 4 phr loading. The filler types that are the N-330 grade of carbon black, precipitated calcium carbonate and rubber grade china clay, their loading was varied from 0 to 50 phr (part per hundred dried rubber). The physical properties of the rubber foam that are the difference torque from the oscillating disk rheometer, hardness, tear strength, 300% modulus, tensile strength, elongation at break and compression set were analyzed. The results were found that the carbon black was yielded the highest of all properties in every loading. In conclusion, the suitable filler for closed cell rubber foam is the carbon black.

scholarly journals Thermal Insulating and Mechanical Properties of Cellulose Nanofibrils Modified Polyurethane Foam Composite as Structural Insulated Material

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 200 ◽  
Author(s):  
Weiqi Leng ◽  
Biao Pan
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Cellulose Nanofibrils ◽  
Thermal Insulating ◽  
Foaming Process ◽  
Wood Construction ◽  
Closed Cell ◽  
Foam Composite

Cellulose nanofibrils (CNF) modified polyurethane foam (PUF) has great potential as a structural insulated material in wood construction industry. In this study, PUF modified with spray-dried CNF was fabricated and the physical and mechanical performance were studied. Results showed that CNF had an impact on the foam microstructure by increasing the precursor viscosity and imposing resistant strength upon foaming. In addition, the intrinsic high mechanical strength of CNF imparted an extra resistant force against cells expansion during the foaming process and formed smaller cells which reduced the chance of creating defective cells. The mechanical performance of the foam composite was significantly improved by introducing CNF into the PUF matrix. Compared with the PUF control, the specific bending strength, specific tensile strength, and specific compression strength increased up to three-fold for the CNF modified PUF. The thermal conductivity of PUF composite was mainly influenced by the closed cell size. The introduction of CNF improved thermal insulating performance, with a decreased thermal conductivity from 0.0439 W/mK to 0.02724 W/mK.

Effect of Blowing Agent and Polyethylene Glycol on Cellular Structure and Mechanical Properties of Chloroprene Rubber

2012 ◽  
Vol 217-219 ◽  
pp. 517-521 ◽  
Author(s):  
Hong Ling Yi ◽  
Ting Wei ◽  
Lin Heng ◽  
Bai Cun Zheng
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Zinc Oxide ◽  
Polyethylene Glycol ◽  
Cellular Structure ◽  
Foaming Agent ◽  
Blowing Agent ◽  
Swell Ratio ◽  
Closed Cell ◽  
Chloroprene Rubber

In this paper the closed-cell sponge of chloroprene rubber(CR) were produced by foaming agent Azodicarbonamide (AC) and Oxybis (benzene sulfonyl) hydrazide (OBSH). The blend blowing agent AC/OBSH was more effective than the pure AC as it could produce chloroprene foam with greater cell porosity, more uniform and better cell distributions. The CR foam prepared with AC/OBSH had better tensile strength and tear strength than pure AC, but higher Shore C hardness. The Polyethyene glycol (PEG) modified Zinc Oxide (ZnO) could accelerate curing and foam process simultaneously. Increase the content of PEG, CR foam has bigger swell ratio, smaller cell size, and better softness.

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