IEC 62788-1-6-2020 pdf free download – Measurement procedures for materials used in photovoltaic modules – Part 1-6: Encapsulants – Test methods for determining the degree of cure in Ethylene-Vinyl Acetate.
5.1.4lnstrument calibration
The instrument should be calibrated routinely according to the instrument manufacturer’sspecification,using the instrument supplier’s recommended calibration methods.Accuracycalibration should be performed using standard substances, for example, indium or tin, as the
temperature and heat-flow verification material. Sapphire may be used to quantify the baseline(curvature) of the instrument drift The instrument should specifically be recalibrated if the testrate, type of pan, or test atmosphere has been changed before DsC measurements.
NOTE The importance，performance，and considerations related to DSC instrument calibration are descoribsed_ furtherin D.ChenA. Green,D. Dollimore，”“DSC: the l/mportance of Baseline Calibration’，Thermochimica Acta。284 (2)，1996,429-433.
5.2Specimen preparation for the secondary method5.2.1Sampling and storage
5.2.1.1 Because the results for the secondary method may depend on the make of EVA, test
results may only be directly compared for the same formulation of EVA. Therefore,testspecimens should come from the same manufacturer(s) and fabrication batch- for the samefabrication lay-up configuration (backsheet/EVA combination). Changes in the encapsulant that
affect the curing process, including but not limited to a change of the material supplier, would
require validating the correlation between G% and the degree of cure. For example，if thepercentage vinyl acetate content in the EVA resin changes, a new correlation betweenG andthe degree of cure (from a secondary method) should be obtained because the percentage vinyl”
acetate content is known to significantly affect the viscoelastic-dependent cure characteristicsof the encapsulant.
5.2.1.2 Additional experimentation shall be performed using uncured EVA to establish abaseline for the uncured state (for both the Dsc residual enthalpy and meltfreeze methods) and
a previously cured (“maximum cured””)EVA used to establish a baseline for the final cured state(for the melt/freeze method).
lf the experiment is intended to monitor a production process, the “maximum cured” samplesshould be taken from a laminated module or test sample subjected to the thermal history used in lamination. lf the experiment is intended to monitor the complete consumption of peroxide(which often does not occur during the lamination of a PV module), additional processing (time
or temperature) may be required
5.2.1.3 Operators should wear clean gloves when preparing and handling samples.
5.2.1.4 When storage is required, the EVA should be packaged in a marked, sealed bag forlater use.
5.2.1.5Specimens should be kept dry (stored at below 50 % relative humidity), maintainedat ambient temperature, and not exposed to light.
lt is recommended to verify that the results of the secondary method do not change with storagetime.
5.2.2Preparation procedures
5.2.2.1Weigh the empty specimen crucible and empty reference crucibles.The use of aluminium crucibles is recommended for use with EVA.
5.2.2.2 Prepare EVA specimens 5 mg to 9 mg in size (or of a size recommended by the Dsc instrument manufacturer).obtained from a single sheet of material. The accuracy of themeasurement of the specimen mass should be at least 1 %.
5.2.2.3A minimum of 2 samples shall be used from each roll of EVA for process control.5.2.2.4 Place each specimen in a separate crucible, and seal the crucible with a lid.
A non-hermetic aluminium crucible meets the requirement for this test.IEC 62788-1-6 pdf download.