成果報告書詳細
管理番号20110000000694
タイトル*平成22年度中間年報 革新的ノンフロン系断熱材技術開発プロジェクト 革新的断熱技術開発 超低熱伝導率構造部材に必要な物性と構造の同定とその創製のための基盤研究
公開日2011/7/28
報告書年度2010 - 2010
委託先名国立大学法人京都大学
プロジェクト番号P07019
部署名環境部
和文要約平成22年度は、低熱伝導度を長期的に継続させるための技術検討を深化させた。具体的には、低熱伝導度を実現し、かつその長期性を担保するための手法として、発泡によるナノセルラーの創製、バイモーダルセル構造の実現、さらにキセロゲル・エアロゲルとポリマーのハイブリッドからの高空隙率の多孔体の実現を検討した。
英文要約The results we obtained for the first items were as follows:
(1)Nanocellular foams
Plastic foam with a nano-scale cell structure was prepared from poly(ether ether ketone) (PEEK)/para-diamine poly(ether imide) (p-PEI) as well as PEEK/meta-diamine poly(ether imide) (m-PEI) blends by a temperature quench foaming method with CO2. The difference in chemical configuration between m- and p-PEI gave rise to a prominent change in the higher-order blend morphology and cell structure of the respective foams. The bubble nucleation site and bubble size were controlled by templating the morphology of the PEEK/p-PEI blend, which shows an immiscible and unique strip-patterned crystalline morphology. The properties influenced by the immiscibility of the PEEK/p-PEI blend were investigated using SEM, thermal analysis and rheology and compared with the properties of the miscible PEEK/m-PEI blend. The bubble size and location were highly controlled in the PEI disperse domain that was aligned between the PEEK crystalline layers in the PEEK/p-PEI blend.
We further extended this blend morphology templating method to prepare nanocellular foam from polypropylene (PP) with a crystalline nucleating age. The batch foaming experiments were conducted by changing the pressure release rate and the foaming temperature. The effects of these factors on cell morphology were investigated. The experiments showed the existence of the transition temperature at which the cellular size changes from nano to micro scale. Thermal conductivity could be reduced by increasing the porosity with nano- and micro pores and the relationship between porosity and thermal conductivity could be expressed by the multilayer models.
(2)Bimodal cellular foams
In-situ preparation of a cross-linked poly(methyl methacrylate) (PMMA) and polystyrene (PS) blend and its foaming were investigated for creating a bimodal cellular structure in the foam. Methyl methacrylate (MMA) monomer was dissolved in PS under supercritical CO2 at a temperature of 60 °C and a pressure of 8 MPa, and the polymerization of MMA was conducted at 100 oC and 8 MPa CO2, with a cross-linking agent in PS. The blend was successively foamed by depressurizing the CO2. CO2 played the roles of plasticizing the PS and enhancing the monomer dispersion in PS during the sorption process and as a physical blowing agent in the foaming process. The cross-linking agent was used for controlling the elasticity of polymerized PMMA domains and differentiating their elasticity from that of the PS matrix. The difference in elasticity delayed the bubble nucleation in the PMMA domains from that in the PS and made the cell size distribution bimodal, in which the smaller cells ranging from 10-30 μm in diameter were located in the wall of large cells of 200-400 μm in diameter. The effects of the initial MMA content, the concentration of cross-linking agent, and the depressurization rate on the bimodal cell structure and bulk foam density were investigated.
(3)Marine bio mass gel
Highly porous β-chitin structure was successfully fabricated by combining solvent- exchange-induced phase separation and supercritical-CO2 drying processes. The resulting structure consists of porous chitin particles together with a fribrillar network. The nitrogen adsorption was used to determine mesoporous nature of the structure: the pore size distributed in the range of 5-20 nm and the surface area was 400 m2 g-1. The change in crystalline structure was also investigated by X-ray diffraction method and a conversion of β-chitin to α-chitin crystalline structures in the fabrication and drying processes was detected.
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