GB/T 29848-2018 in English

《GB/T 29848-2018光伏组件封装用乙烯-醋酸乙烯酯共聚物（EVA）胶膜》由TC203（全国半导体设备和材料标准化技术委员会）归口，主管部门为国家标准化管理委员会。

ChinaStandards.net is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.

This standard is drafted in accordance with the rules given in GB/T 1.1-2009.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.

This standard was proposed by and is under the jurisdiction of the National Technical Committee on Semiconductor Equipment and Materials of Standardization Administration of China (SAC/TC 203).

Ethylene-vinyl acetate copolymer (EVA) film for encapsulant solar module

1 Scope

This standard specifies the terms and definitions, requirements, test methods, inspection rules, packaging, marking, transportation and storage of ethylene-vinyl acetate copolymer (EVA) film for ground encapsulant solar module (hereinafter referred to as "EVA film").

This standard is applicable to the film used for encapsulant solar module, formed by melt processing, with EVA as the main raw material and added with various additives.

2 Normative references

The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced documents (including any amendment) applies.

GB/T 1033.1-2008 Plastics — Methods for determining the density of non-cellular plastics — Part 1: Immersion method liquid pyknometer method and titration method
GB/T 1410-2006 Methods of test for volume resistivity and surface resistivity of solid insulating materials
GB/T 1695-2005 Rubber, vulcanized — Determination of electrical breakdown strength and voltage resistant at commercial power frequency
GB/T 2410-2008 Determination of the luminous transmittance and haze of transparent plastics
GB/T 2423.3-2006 Environmental testing for electric and electronic products — Part 2: Testing method — Test Cab: Damp heat, steady state
GB/T 2790 Adhesives, 180° peel strength test method for a flexible-bonded-to-rigid test specimen assembly
GB/T 2828.1 Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
GB/T 2918 Plastics — Standard atmospheres for conditioning and testing
GB/T 6672 Plastics film and sheeting — Determination of thickness by mechanical scanning
GB/T 19394-2003 UV test for photovoltaic (PV) modules
ASTME 313 Standard practice for calculating yellowness and whiteness indices from instrumentally measured color coordinates

3 Terms and definitions

For the purpose of this document, the following terms and definitions apply.

3.1
ethylene-vinyl acetate copolymer (EVA) film
film used for ground encapsulant solar module, formed by melt processing, with EVA as the main raw material and added with various additives

3.2
crosslinking degree
degree to characterize the crosslinking of polymer chains
Note: Generally, the crosslinking degree of EVA film is expressed by gel content, i.e. the percentage of crosslinking polymer chain in the total EVA.

3.3
shrinkage rate
percentage of the length reduction of a material after treatment (water immersion, heat setting or resin treatment, etc.) in its original length

4 Requirements

4.1 Specifications

The specifications of a single roll of products shall meet those specified in Table 1.

Table 1 Specifications
No. Item Specification
1 Thickness/mm 0.2~0.8
2 Density (g/cm3) 0.95~0.96
Note: Special specifications may be implemented as per contracts.

4.2 Appearance

The products shall be smooth in the appearance, without visible impurities or bubbles and with clear embossing.

4.3 Physical properties

The physical properties of products shall meet those specified in Table 2.
 
Table 2 Physical properties
No. Item Indicator
1 Content of vinyl acetate (mass fraction/%) 26~34
2 Light transmittance
% EVA film for battery front Wavelength: 380 nm~1,100 nm ≥ 90
Wavelength: 290 nm~380 nm As agreed between the supplier and the purchaser
EVA film for battery back Wavelength: 380 nm~1,100 nm As agreed between the supplier and the purchaser
Wavelength: 290 nm~380 nm ≤ 30
3 Crosslinking degree
% ≥ 75
4 Peel strength
N/cm > 50
5 Shrinkage rate
% < 3.0 in the machine direction (MD)
< 1.5 in the transverse direction (TD)
6 Volume resistivity
Ω·cm > 6.0 × 1013
7 Electrical breakdown strength
kV/mm > 28.0
8 Accelerated aging resistance by ultraviolet lamp Change in yellowness indice < 5.0
Glass peel strength > 25 N/cm
9 Steady-state damp-heat aging resistance Change in yellowness indice < 5.0
Glass peel strength > 25 N/cm

5 Test methods

5.1 Sampling method

After 3~5 layers are removed from the outer layers of EVA film roll for inspection, take the EVA film section wound evenly in the middle of the roll as the specimen film under inspection.

5.2 Requirements for specimen

5.2.1 Atmospheres for conditioning and testing specimen

The atmospheres for conditioning and testing specimen shall be in accordance with GB/T 2918, at an ambient temperature of 23 °C ± 2 °C and a relative humidity of 50% ± 5%. Keep the specimen on a horizontal plane for not less than 24 h and conduct a test under this condition. 
5.2.2 Back board for specimen

The back board for tests in this standard shall meet the following requirements: its surface is made of fluorine-contained materials, and the water vapor transmission rate is less than 2.5 g/(m2·d); after an accelerated aging test by ultraviolet lamp at an irradiation intensity of 120 kW·h/m2, the yellowness indice of the back board is changed by less than 2.0, and the back board is free of interlayer separation after steady-state damp-heat aging test.

Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Requirements
5 Test methods
6 Inspection rules
7 Packaging, marking, transportation and storage
Annex A (Normative) Content determination of VA in EVA film by hydrolysis and back titration method