Dear colleagues, the protective hot plate method is the standard method for testing the thermal conductivity of insulation materials. The core logic is "constructing a one-dimensional thermal flow field+precise stability control+quantitative calculation". The entire process strictly follows the GB/T 10294-2008 standard, which is implemented in six steps:

The first step is sample pretreatment and preparation. According to the standard requirements, the sample needs to be placed in an environment of 23 ± 2 ℃ and 50 ± 5% RH for ≥ 72 hours to achieve equilibrium moisture content. The processing size needs to match the measuring hot plate, commonly 100mm × 100mm or 300mm × 300mm, with a thickness of 10-50mm and a surface roughness of ≤ 0.8 μ m. Measure the thickness three times with a 0.01mm precision caliper and take the average value to ensure that the sample is flat and not tilted, avoiding affecting heat flow conduction.

The second step is instrument calibration and parameter setting. Calibration is required before testing: the temperature difference between the measuring hot plate and the protective hot plate should be ≤ 0.1 ℃, the accuracy of the temperature sensor should be calibrated to ± 0.05 ℃, and the full-scale error of the power sensor should be ≤ ± 1%. Set the hot plate temperature (50 ℃, 70 ℃, or 85 ℃) and the cold plate temperature to be 20-50 ℃ lower than the hot plate. Enter basic data such as sample thickness and effective heat transfer area to ensure accurate parameters.

Step three, sample installation and cavity sealing. Place the sample in the center between the measuring hot plate and the cold plate, and apply a thin layer of thermal paste with a thermal conductivity coefficient of ≥ 1.5W/(m · K) (thickness ≤ 0.1mm) when the fit is not tight, to reduce the contact thermal resistance. Low thermal conductivity materials (λ ≤ 0.03W/(m · K)) need to be evacuated to 10 ⁻³~10 ⁻⁴ Pa to eliminate air convection interference, and then the chamber should be sealed.

Step four, start temperature control and heat flow stabilization. Turn on the heating and cooling system, measure the constant temperature of the hot plate, and synchronously control the temperature of the protective hot plate to compensate for lateral heat dissipation - this is the core advantage of this method, which forces heat to pass vertically through the sample to avoid errors in heat dissipation, and requires patient waiting for thermal steady state.

Step five, thermal steady state determination and parameter acquisition. According to the standard judgment: Within 30 consecutive minutes, the fluctuation of heating power is ≤± 1%, the fluctuation of temperature difference on both sides of the sample is ≤± 0.1 ℃, and the temperature difference between the two hot plates is ≤ 0.1 ℃. Automatically collect three sets of key data after steady state: heating power (Q), temperature difference (Δ T), sample thickness (d), and heat transfer area (A).

Step six, data calculation and report output. According to Fourier's law of heat conduction, calculate automatically according to λ=Q × d/(A × Δ T), and take the average of 3 sets as the final result (with 4 significant digits retained). The report should include pre-processing records, vacuum degree data, steady-state curves, and standard numbers to ensure data compliance and traceability, and meet the requirements of engineering acceptance and product quality control.