Degradation of VIP barrier envelopes exposed to alkaline solution at different temperatures

Huiqiang Li, Huisu Chen, Xiangyu Li, Wenhui Duan

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7 Citations (Scopus)

Abstract

As covering layers, barrier envelopes of VIPs are always exposed to severe environmental conditions,including high temperatures, alkaline environments and local stress concentration when used as thermal insulation material in concrete structures. This study investigated the time-dependent degradationsof three types of commonly used envelopes (aluminium film, metallized film and metallized film coatedwith alkali-resistant (AR) fibreglass mesh) and VIPs covered by these three envelopes by simulating environmental conditions with four types of alkaline solutions (NaOH solution with pH = 7, 11, 13 andsaturated Ca(OH)2), two different temperatures (20C and 60C) and local stress concentration. The results showed that stress and high temperature accelerated the degradation of envelopes and that suchdegradation became more serious with increased pH value and temperature. It was also observed that the thermal conductivity of VIPs increases quickly when they are exposed to higher alkalinity com-bined with high temperatures. After 6-week submerged in saturated Ca(OH)2solution at 60C, thethermal conductivity of VIPs increased from 4.413 mW/m K to 13.049 mW/m K for aluminium foil, from 5.375 mW/m K to 10.982 mW/m K for metallized film, and from 5.786 mW/m K to 8.110 mW/m K for ARfibreglass mesh-reinforced film, respectively
Original languageEnglish
Pages (from-to)208 - 216
Number of pages9
JournalEnergy and Buildings
Volume93
DOIs
Publication statusPublished - 15 Apr 2015

Keywords

  • Vacuum insulation panels
  • Barrier envelopes
  • Alkali
  • Stress
  • Temperature
  • Degradation
  • Thermal conductivity

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