{"id":1890,"date":"2024-10-04T19:44:59","date_gmt":"2024-10-04T10:44:59","guid":{"rendered":"https:\/\/c-mng.cwh.hokudai.ac.jp\/aml.eng\/Root\/?p=1890"},"modified":"2024-10-04T19:44:59","modified_gmt":"2024-10-04T10:44:59","slug":"schematic-graphs-for-understanding-foamed-plastics-fiber-insulations-degradation-mechanisms","status":"publish","type":"post","link":"https:\/\/c-mng.cwh.hokudai.ac.jp\/aml.eng\/Root\/researches\/schematic-graphs-for-understanding-foamed-plastics-fiber-insulations-degradation-mechanisms.html","title":{"rendered":"Schematic graphs for understanding foamed plastics\/fiber insulation’s degradation mechanisms"},"content":{"rendered":"
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Introduction<\/h3>\n\n\n\n

Architectured Materials Laboratory at the Faculty of Engineering, Hokkaido University, is one of the few(if not the only) laboratories that is researching the durability and long-term performance of foamed plastic insulation materials from a materials chemistry perspective. Based on the literature surveys and experimental results from our laboratory, we would like to summarize what we have come to understand, with the aim of writing a rough draft of a review manuscript.<\/p>\n\n\n\n


\uff11.Diffusion of Various Gases and Changes in Cell Pressure<\/h3>\n\n\n\n

(1) Diffusion of air, moisture and foamed gas (Reference 1)
In the case of foamed plastic insulation, the gas that was sealed in as a foamed gas and the gas from the atmosphere are involved. In other words,
\u30fbAir and moisture diffuse from the outside to the inside
\u30fbFoamed gas diffuses from the inside to the outside.
The change in the partial pressure of the various gases at this time is thought to be diffused according to the general diffusion law.

(2) Change in gas pressure (Reference 2)
Assuming that the gas pressure changes according to the diffusion law, it is thought that diffusion basically occurs according to the gradient of partial pressure (fraction of substance amount), so
\u30fbThe atmosphere diffuses until the gas pressure inside and outside is equal
\u30fbThe foaming gas diffuses until it disappears, as it often does not exist in the atmosphere (except for CO2 gas in urethane)
As a result of (3), (1) and (2), the total pressure inside the cell changes in various ways while maintaining a state where the pressure is higher than atmospheric pressure. In general, there are often times when the internal pressure temporarily increases from the time of manufacture.<\/p>\n\n\n\n


\uff12. Changes of cell structure based on polymeric changes <\/h3>\n\n\n\n

(1) A cell in foamed plastics has a thin film which has several microns to submicrons. As a polymeric product, it is very thin, and therefore, it undergoes the same changes as other polymeric films. For example, it is affected by foaming gas, atmospheric gas and moisture.
Additinalliy, it undergoes parallel changes such as oxidation, cross-linking scissession (Ref. 3), swelling due to moisture (Ref. 4), delayed reactions of unreacted agents, polymerization (Ref. 5), and dimensional changes (Ref. 6). As a result, it is thought that the mechanical properties (Young’s modulus, tensile strength, shear strength, etc.) will change. Therefore, material properies inevitably continue to change. Conversely, it is impossible to provide evidence that it will remain “unchanged”.

(2) Based on general foam engineering, it is thought that \u201cshear failure\u201d occurs due to generation of multidirectional stress concentration around multi-branched struts and around interfaces with heterogeneous materials, which cause cracks and micropores. This has been reported based on changes in gas adsorption results and XCT results (Ref. 7)
(3) As micro-pores expand, the cells around the pores come to be fused into one larger cell (Ref. 8)
(4) Even if fusion of cells in a insulation material are progressed, it takes place locally, therefore, it takes takes time for the pores to become continually conected to outside.
<\/p>\n\n\n\n

3.Changes in cell structure due to other effects<\/h3>\n\n\n\n

(1) Fillers
They cause changes in rigidity of cell films. In general, they cause shear failure at the interface, but they are thought to play a role in mechanism mentioned in Chapter 2.<\/p>\n\n\n\n

(2) Skin layer
Skin layer is a heterogeneous surface layer, but the mechanism of change is the same mentioned in Chapter 1 and 2.<\/p>\n\n\n\n

(3) Secondary foaming and chemical changes due to moisture and temperature can also occur due to unreacted components after initial foaming. (Ref. 9)
<\/p>\n\n\n\n

\uff14.Summary: Understanding changes in physical properties as a result of material changes<\/h3>\n\n\n\n

As the chapters mentioned above, cells can be physically changed. Therefore, physical properties like “thermal conductivity” should be understood based on changes of complex physical factors in foamed plastics. Gas diffusion to outside is partly contributed to the change of thermal conductivity, but we should discussed it under the understanding of comprehensive changes of physical changes of cells.<\/p>\n\n\n\n

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Supplementary Note 1: Issues with measurement methods<\/h3>\n\n\n\n

For example, we have the starndard for measuring thermal conductivity, but it forcuses on evaluating the initial thermal conductivities of insulation materials, but it never assumes evaluating degradated insulation materials left in a building for a long time and absorbed moisture or changed in size. Therefore, when measuring the thermal conductivity of insulation materials collected from a construction site, there are cases where the materials are measured after being collected and left to stabilize in atomosphere for a long time in accordance with the measuring standard (Ref. 10). Additionally, in some cases the materials are dried out first before being measured. Probably, the transient state until it stabilizes may be a state of moisture loss until it reaches equilibrium with the measurement environment. In that case, it may not an appropriate measurement method that actually embodies the state of being placed inside a building. In a society that will more precisely recognize energy-saving buildings in the future, additional consideration will be necessary.<\/p>\n\n\n\n


Supplementary note 2: The discussion of long-term durability is not limited to foamed plastic. The same perspective should be applied to fiber-based materials as well<\/h3>\n\n\n\n

The physical properties and material stability of fiber-based insulation materials are achieved by binding fibers together with an adhesive to form a cotton-like material that prevents air from moving through it. Conversely, if the adhesive that holds the fibers together deteriorates, the physical properties will change. Of course, as with foam plastic insulation, it is thought that this will not cause any particularly significant changes, but in order to understand the long-term performance, which requires tracking changes over a period of several decades, it is essential to understand the long-term performance of polymers in the same way as for plastic foam.<\/p>\n\n\n\n

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Reference<\/h3>\n\n\n\n
    \n
  1. Bae, M.; Ahn, H.; Kang, J.; Choi, G.; Choi, H. Determination of the Long-Term Thermal Performance of Foam Insulation Materials through Heat and Slicing Acceleration. Polymers 2022, 14, 4926. https:\/\/doi.org\/10.3390\/polym14224926<\/li>\n\n\n\n
  2. Choi, HJ., Kang, JS. & Huh, JH. A Study on Variation of Thermal Characteristics of Insulation Materials for Buildings According to Actual Long-Term Annual Aging Variation. Int J Thermophys 39, 2 (2018). https:\/\/doi.org\/10.1007\/s10765-017-2318-3<\/li>\n\n\n\n
  3. Valentina Pintus et. al., What about phenol formaldehyde foam in modern-Contemporary art? Insights in to the unaged and naturally aged material by a multi-analytical approach, Polymers 13 (2021) 1964, https:\/\/doi.org\/10.3390\/polym13121964<\/li>\n\n\n\n
  4. Jedediah B. Alvey et al., Experimental study on the effects of humidity and temperature on aerogel composite and foam insulations, Energy and buildings 144 (2017) 358-371, https:\/\/doi.org\/10.1016\/j.enbuild.2017.03.070<\/li>\n\n\n\n
  5. Wanli Li et al., Reducing the contents of free phenol and formaldehyde in phenolic foam, Journal of applied polymer science Vol. 90 (2003) 2333-2336, https:\/\/doi.org\/10.1002\/app.12828<\/li>\n\n\n\n
  6. Kondo Y., IWAMAE A., NAGASAWA Y., FUJIMOTO T., KIKUCHI Y., TASAKA T., Experiments on influence of moisture on thermal performance change of insulations -Long term thermal performance of building insulation materials- Part2, J. Environ. Eng., AIJ, Vol. 75, No.649, 261-269, Mar. 2010, https:\/\/doi.org\/10.3130\/aije.75.261<\/li>\n\n\n\n
  7. Y. LEEM, R. KITAGAKI, D. TAKAHASHI, W. KANESHIKA, \u201cMicrostructure analysis based on gas isotherms of N2, H2O, and CO2 and 3D imaging Using X-ray CT into extruded polystyrene foam adding graphite\u201d, Macromolecular Symposia, 413, 2300241, (2024), https:\/\/doi.org\/10.1002\/masy.202300241<\/li>\n\n\n\n
  8. Y. LEEM, R. KITAGAKI, T. ISHIDA, H. HAGIHARA, \u201cLong-term stability and water vapor induced degradation of physico-chemical properties of XPS and PF\u201d, Developments in the Built Environment, 100429, (2024) https:\/\/doi.org\/10.1016\/j.dibe.2024.100429<\/li>\n\n\n\n
  9. Y. LEEM, R. KITAGAKI, T. ISHIDA, H. HAGIHARA, \u201cLong-term stability and water vapor induced degradation of physico-chemical properties of XPS and PF\u201d, Developments in the Built Environment, 100429, (2024) https:\/\/doi.org\/10.1016\/j.dibe.2024.100429<\/li>\n\n\n\n
  10. Y. LEEM, R. KITAGAKI, N, KOGURE, T. NAGAYOSHI, N. MIHARA, Y. HIRATSUKA, \u201cEstimation method of temperature and humidity under the floor of wooden house using PLS analysis\u201d, The 42nd Japan symposium on Thermophysical properties, (2021)<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

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