Every aerogel datasheet on the market seems to promise a thermal conductivity around 0.020 W/(m·K). Yet published measurements of the same class of material range from under 0.002 W/(m·K) to well above 0.036 W/(m·K) — a spread of more than twenty times. The numbers are not lying; they were simply taken under different conditions. A look at how Chinese testing labs, instrument makers, and industry researchers actually measure aerogel blankets explains most of the confusion, and offers a practical protocol for buyers who need to know what a blanket will do in their service, not on a slide.
The same blanket, very different numbers
Start with a clean baseline. In a documented heat flow meter test following ASTM C518, an aerogel blanket measured 0.024 W/(m·K) at a 20°C mean temperature — closely matching the manufacturer's claimed 0.023 W/(m·K) at 100°C. The small discrepancy was attributed to test temperature and ambient humidity during measurement. That is what a good result looks like: measured and claimed values within a few percent.
Now widen the lens. A technical paper published by Chinese insulation-industry researchers on the problems of measuring ultra-low thermal conductivity in aerogel materials reports equivalent conductivity values of 0.0123 and 0.0114 W/(m·K) for aerogel blanket under low-temperature, large-temperature-difference conditions — and 0.0014 to 0.0016 W/(m·K) under high vacuum. Neither figure is comparable to a 0.020 W/(m·K) datasheet claim, because neither test replicates ambient-pressure, moderate-ΔT conditions. The lesson: a conductivity number without its test conditions is not data.
What actually moves the measured number
Chinese industry literature points to four variables that dominate the gap between lab values and installed performance:
- Mean temperature. Chinese product test reports conventionally list conductivity at a 25°C mean and again at 300°C, with conforming grade-A products required to stay at or below roughly 0.021 and 0.036 W/(m·K) respectively. Radiative heat transport grows sharply with temperature, so the elevated-temperature value is the one that matters for steam and process piping.
- Pressure and atmosphere. Aerogel's nano-pores suppress gas-phase conduction, but only fully below the mean free path of air molecules. The 0.0014–0.0016 W/(m·K) figures cited above only appear under vacuum; at atmospheric pressure, gas conduction sets a floor near 0.013–0.018 W/(m·K) for good material, which is why Chinese securities-industry research describes silica aerogel's practical room-temperature conductivity as reaching about 0.013 W/(m·K) — below still air's 0.025.
- Compression and thickness. A blanket measured uncompressed will not behave like one clamped between flanges or crushed at a pipe support. Over-compression collapses the pore structure and pushes conductivity up; under-compression leaves convective paths at joints.
- Moisture. Chinese manufacturers routinely claim hydrophobicity above 99% and market it aggressively, precisely because water ingress is the dominant in-service degradation mechanism. Wet insulation can lose a large share of its thermal performance — and in industrial service it brings corrosion under insulation with it.
Why Chinese test conditions differ from Western ones
China's steady-state reference method, GB/T 10294-2008 (protected hot plate), is the counterpart of ASTM C177, while GB/T 10295 (heat flow meter) parallels ASTM C518. Instruments marketed into the Chinese and Taiwanese lab market for blanket testing follow the ASTM C518-style workflow — parallel plates held at a fixed temperature difference (for example 10°C and 30°C), automatic thickness measurement under a defined plate pressure, and conductivity computed from the calibrated heat flux. Reported accuracy in that class of instrument is around 3%, with repeatability better than 1%.
The practical consequence for buyers: a "0.020 W/(m·K)" claim from a Chinese producer tested to GB/T 10294 at a 25°C mean, a "0.023 W/(m·K)" claim from a Western producer tested at 100°C mean, and a 300°C conformance value of 0.036 W/(m·K) can all describe the same blanket. None of the three is inflated; they answer different questions.
A due-diligence protocol borrowed from Chinese practice
The most useful habit from Chinese project practice is demanding a conductivity curve, not a point. Industrial buyers in China's petrochemical sector typically ask suppliers for measured values at two or three mean temperatures spanning the service range, tested to a named method, plus the declared density and thickness tolerance. A blanket that holds its conductivity across the temperature range is telling you its fiber reinforcement and opacifier loading are well engineered; one that only quotes a room-temperature number is hiding the temperature sensitivity.
Second, insist on the moisture angle. Ask how hydrophobicity was measured (contact angle versus water absorption tests give different assurance), and whether the supplier has aging data showing hydrophobicity retention after thermal exposure. Chinese technical commentary on in-service insulation failures repeatedly identifies water ingress — through cladding damage or terminations — as the leading cause of performance loss, not the blanket itself.
Third, sanity-check against thickness math. Chinese industry reports summarize the value proposition as: to achieve the same insulation effect, an aerogel blanket needs roughly one-third the thickness of rock wool and one-fifth that of expanded perlite. If a supplier's conductivity claim implies dramatically better thinness ratios than that under your design conditions, the claim deserves independent verification before it enters your heat-loss calculations.
Bottom line
Chinese test data — from national-standard conformance reports to instrument makers' application notes to independent research papers — converges on one message: aerogel's headline conductivity is real, but it is a property of material plus conditions. Buyers who record mean temperature, method, compression state, and moisture exposure alongside every number they collect will find the datasheet-versus-reality gap largely disappears.