IEC 62788-1-6-2020 Measurement procedures for materials used in photovoltaic modules – Part 1-6: Encapsulants – Test methods for determining the degree of cure in Ethylene-Vinyl Acetate.
This part of IEC 62788 defines the terminology, test equipment, test environment, specimen preparation, test procedures, and test report for measuring the degree of cure of Ethylene-Vinyl Acetate (EVA) encapsulation sheet used in photovoltaic (PV) modules. The differential scanning calorimetry (both residual enthalpy and melt/freeze protocols) and gel content methods are included herein. This procedure can be used by material- or module-manufacturers to verify that the cross-linking additive is present and is active. The procedure can also be used to verifty the module manufacturing (lamination) process for the purposes of quality- and process-control.
The procedure can also be used to assess the uniformity of the EVA formulation within a roll as well as to compare variation of the EVA formulation from roll to roll. This procedure can be applied to uncured or recently cured EVA sheet as well as uncured or recently cured EVA from PV modules.
This test procedure can also be applied to cross-linking ethylenic co-polymers other than EVA.
The temperatures identified for the calorimetry measurements in this procedure have been optimized for EVA. Therefore, if the test procedure is applied to other encapsulation materials,the range of the test temperatures can have to be adjusted based on the active temperature of the curing agent and/or the melt/freeze temperature of the base material.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references， the latest edition of the referenced document (including any amendments) applies.
IEC 61215-1, Terrestrial photovoltaic (PV) modules – Design qualification and type approval – Part 1: Test requirements
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories
ISO 291:2008, Plastics – Standard atmospheres for conditioning and testing
ISO 6427:2013，Plastics 一Determination of matter extractable by organic solvents (conventional methods)
IsO 6721-1, Plastics – Determination of dynamic mechanical properties – Part 1: General principles
ISO 11357-1:2009，Plastics – Differential scanning calorimetry (DSC) – Part 1: General principles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
●IEC Electropedia: available at http://www.electropedia.org/
●ISO Online browsing platform: available at http://www.iso.org/obp
NOTE Calculations related to these definitions are given in 5.5.
3.1 degree of cure
G unitless parameter that characterizes the extent of cross-linking within EVA
Note 1 to entry: Unlike the cross-link density, which is a physical quantity defined by the theory of rubber elasticity, the degree of cure in a polymer may be assessed by any experimental method that distinguishes partially cured specimens with respect to one another or with respect to a reference material. The degree of cure can be correlated to the gel content, which is the mass percentage of insoluble material (assumed to be cross-linked) within the specimen.IEC 62788-1-6 pdf download.