Elastomers and Composites Vol. 46, No. 1, pp. 29~36 (March 2011)

* ** , * , **

(2011 1 12), (2011 1 20), (2011 1 26)

Introduction to Thermal Insulating Materials and Silica Aerogels

Jinho Hong, Il Kim*, Ju Ho Yun**, and Sang Eun ShimDepartment of Chemical Engineering, Inha University

253 Yonghyundong, Namgu, Incheon, S. Korea 402-751*The WCU Center for Synthetic Polymer Bioconjugate Hybrid Materials, Department of

Polymer Science and Engineering, Pusan National University, Pusan 609-735 Korea**Enviromental Materials & Components R&D Center,

Korea Automotive Technology Institute, Chungnam 330-912 Korea(Received January 12, 2011, Revised January 20, 2011, Accepted January 26, 2011)

(thermal insulating materials)

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ABSTRACTThe term 'thermal insulating materials' describes a class of materials which can improve the thermal efficiencyby reducing the thermal conduction, convention and radiation between the inside and outside of the system. As a thermalinsulating material, numerous industrial applications are possible including the automobile, aerospace, aviation, and petro-chemical. Especially, the silica aerogel, with their superior thermal insulating behavior, has been widely used as thermal insulating materials. Because the mechanical properties of the silica aerogel cannot meet the industrial demand, use of the silica aerogel is limited. This article aims to review the thermal insulating materials and silica aerogel, and to introducethe silica aerogel/polymer composites.

Keywordsthermal insulating materials, silica aerogel, thermal insulation, polymer composite.

E-mail: seshim@inha.ac.kr

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30 Jinho Hong et al. / Elastomers and Composites Vol. 46, No. 1, pp. 29~36 (March 2011)

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Table 1. Service Temperature Range of Commercial Insulating Materials1

Introduction to Thermal Insulating Materials and Silica Aerogels 31

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(kg/cm2) . . . . > > ,

Table 1 .1

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Table 2. Precursors, Solvents, and Catalysts Used in Solgel Reaction3

TMOS EtOH/water HClMTMS MeOH/water Oxalic acid, NH4OHPEDS Ethyl acetate HFPEDS EtOH/water HFPFAS/PEDS EtOH/water HFMTES CH2Cl2/water TFATMOS Ionic liquid HCO2HTMOS Aceton/water HCO2HTMOS MeOH/water CH3CO2H/NH4OHTMOS EtOH/water HNO3/H2SO4/oxalic acidTMOS MeOH/water NH4OH/HClTMOS EtOH/water NH4OH/HClTEOS EtOH/water HCl PEG

32 Jinho Hong et al. / Elastomers and Composites Vol. 46, No. 1, pp. 29~36 (March 2011)

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droplet silyl group (Figure 2). 3 .

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Introduction to Thermal Insulating Materials and Silica Aerogels 33

Figure 1. Drying process of silica aerogel.4

Figure 2. Springback phenomenon happening at the drying proc-ess of silica aerogel.4

Table 3. General Properties of Silica Aerogel4

0.003-0.35 g/cm3 0.1 g/cm3

600-1000m2/g % 0.13-15% 5% (95% ) 20nm BET 2-5nm electron microscopy reflective index 1.0-1.08 2.0-4.010-6 ultrasonic dielectric constant~1.1 0.1g/cm3 100m/s 0.07g/cm3

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-OH -OH methoxy (-OCH3)x (Figure 3).

34 Jinho Hong et al. / Elastomers and Composites Vol. 46, No. 1, pp. 29~36 (March 2011)

Figure 3. Water droplet on hydrophobic silica aerogel.4

4. /

dielec-tric constant, , .

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1998 M. Schmidt .4

. , aerogel/epoxy . , di-electric constant . aerogel/epoxy , , dielec-tric . Clay aerogel/polymer

areogel . / 1998 M. Schmidt .5 insulator, chemistry, kinetic energy absorber, elec-tronics, pharmacy, agriculture filler . 1998 M. Schmidt polyvinylbutyral (PVB) (0.120 W/mK) / .

Figure 4. The effect of the amount of silica aerogel on the thermal conductivity of aerogel/PVB composites.5

Figure 5. Heat transportation path upon the mixing method: (a) dry mixing and (b) wet mixing.6

(Figure 4) .

. 2003 (wet, dry, dual mixing) PVB /PVB , .5

dry mixing . dry mixing close packing wet mixing PVB (Figure 5). 2008 2009 /epoxy . 2008 Gupta

Introduction to Thermal Insulating Materials and Silica Aerogels 35

Figure 6. SEM morphology of silica aerogel/epoxy composite (a) at low magnification, and (b) at low magnification.7

Silica aerogel volume fraction (%)

Figure 7. The effect of the content of silica aerogel on the thermal conductivity of epoxy composites.8

epoxy resin mixing curing . ep-oxy mixing . Figure 6 .

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Teh epoxy mixing curing . Teh aromatic amine aliphatic amine 0-40 vol% . Aromatic amine .

. .7

2009 Ge /epoxy . trimethyl-chlorosilane (TMCS) epoxy mix-ing . 40-80 vol% (Figure 7) .

0.20 W/mK 0.04 W/mK

.

.8

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/ . (-OH)

. , clay . methoxy ([-OCH3)x]) . silane coupling agent .

. coupling agent

36 Jinho Hong et al. / Elastomers and Composites Vol. 46, No. 1, pp. 29~36 (March 2011)

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4. M. Schmidt and F. Schwertfeger, Applications for silica aerogel products, J. Non-Cryst. Solids, 225, 364 (1998).

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6. N. Gupta and W. Ricci, Processing and compressive properties of aerogel/epoxy composites, J. Mater. Process. Tech., 198, 178 (2008).

7. P. L. Teh, M. Mariatti, A. N. R. Wagiman, and K. S. Beh, Effect of curing agent on the properties of mineral silica filled epoxy composites, Polym. Composite., 29, 27 (2008).

8. D. G