GB/T 29848-2018Ethylene-vinyl acetate copolymer (EVA) film for photovoltaic modules (English PDF)

5.5.1 Luminous transmittance

5.5.1.1 Instrumentation Spectrophotometer: It is equipped with an integrating sphere, the diameter of which shall be greater than 90 mm.

5.5.1.2 Preparation of specimen Take a piece of EVA film which has a size of 50 mm × 50 mm.From top down, sequentially superimpose the front-panel material, the non-adhesive film, the EVA film, the non-adhesive film, the back-panel material.Place it into the vacuum laminating machine, allowing the front-panel to face downwards. According to the curing temperature and time as required for the product, carry out curing and crosslinking.Then take it out.Place it into a desiccator to cool it to room temperature.Prepare for use.For the specimen as taken from the non- adhesive film, the upper and lower surfaces shall be flat; the thickness shall be uniform; the crosslinking degree reaches above 75%.The number of specimens for each group is not less than 3.

Note 1: The front-panel material and the back-panel material shall be consistent with the materials used in the actual PV modules.

Note 2: The non-adhesive film does not react with EVA film during the lamination process.It can withstand temperatures above 200 °C.It may use the surface-untreated ETFE film; the thickness of which ranges 50 µm ~ 125 µm.

5.5.1.3 Test method Test the specimen according to the spectrophotometer method of GB/T 2410- 2008.Set the wavelength range of the spectrophotometer to be 290 nm ~ 1100 nm.Respectively calculate the average values of the luminous transmittances W2 - The mass of the specimen-contained bag, in grams (g); W3 - The mass of the specimen package after solvent extraction and drying, in grams (g).

5.5.3.2 Differential scanning calorimetry (DSC method) 5.5.3.2.1 Instrumentation The instrumentation is as follows:

a) Micro-electronic balance: Accurate to

0.01 mg; the range is greater than 1 g;

b) Differential scanning calorimeter (DSC): The temperature accuracy is ± 0.05 °C; the calorimetric accuracy is ± 0.2%; the temperature sensitivity is 10 µW; the temperature measurement repeatability is ±0.1%; the temperature-rising rate is 5 °C/min ~ 30 °C/min; the temperature measurement accuracy is ±0.1 °C; the baseline curvature and baseline drift are less than 10 µW. 5.5.3.2.2 Preparation of specimen The specimen preparation process is as follows:

a) Respectively cut the un-laminated EVA film and the EVA film as laminated according to

5.5.1.2 into 7 mg ~ 10 mg of test samples (hereinafter referred to as uncured sample and cured sample, respectively).The accuracy of weighed sample is within 1%.Prepare 3 sets of specimens;

b) Place the uncured and cured samples in two sample crucibles, respectively.Press and pack it on the sample packaging machine. 5.5.3.2.3 Test method The test method is as follows:

a) Turn on the DSC instrument.Set the parameters.The test shall be carried out under the atmosphere of protective gas (including nitrogen, helium, argon).The gas flow rate is 20 mL/min ~ 50 mL/min.The initial temperature is 30 °C.The termination temperature is 250 °C.The temperature-rise rate is 10 °C/min;

b) Put the sample crucible and the reference crucible into the furnace, respectively.Close the furnace cover;

5.5.5 EVA/glass peel strength

5.5.5.1 Instrumentation and supporting materials Instrumentation and supporting materials are as follows:

a) Tensile testing machine;

b) Laminating machine;

c) Ultra-white embossed tempered glass: The surface shall be clean and flat, without stain; the thickness is

3.2 mm; the transmittance in the 380 nm ~ 1100 nm band is above 91.5%;

d) Flexible back-panel: The surface shall be clean and flat, without wrinkles, scratches, delamination, air bubbles, etc.The transmission rate of water vapor shall be less than

2.0 g/(m2 - 24 h).The back-panel itself does not separate between layers.The breaking force is greater than 300 N;

e) Floating-plate semi-tempered glass: The surface shall be clean and flat, without stain; the thickness is

5.5.5.2 Preparation of specimen The procedures for the preparation of specimens are as follows:

a) Prepare two pieces of uncured EVA film, one piece of glass, one piece of flexible back-panel which have a size of 300 mm × 150 mm;

b) Superimpose the glass/EVA film (two pieces)/flexible back-panel sequentially.Put it in the vacuum laminating machine.According to the curing temperature and time as required for the product, carry out curing and cross-linking.In the laminated and cured sample, the EVA film shall not have air bubbles.Prepare 3 specimens;

c) In the width direction, at an interval of 5 mm, cut the flexible back- panel/EVA film layer into the specimens which have a width of 10 mm ±

0.5 mm.Use them for the test of peel force between EVA and glass.

Note: The glass for preparing the transparent EVA sample is ultra-white embossed tempered glass.The glass for preparing white EVA sample is floating flat semi-tempered glass.The non-tin surface is facing EVA. The instrumentation is as follows:

5.5.9.1 Preparation of specimen Take uncured EVA film.Follow the requirements of

5.5.1.2 to laminate it.Cut off the specimen which has a size of 30 mm × 30 mm from the location where the surface is flat and free from air bubbles and impurities.Superimpose multiple samples, to obtain one group of specimens which have a thickness of at least 3 mm.Prepare 5 groups of specimens.

5.5.9.2 Test method According to the provisions of GB/T 4207-2012, prepare the solution A.On the surface of the specimen, at a rate of 30 s ± 5 s, add 50 drops or 100 drops of the solution A.Observe and record the appearance of the 5 groups of specimens.According to the provisions of GB/T 4207-2012, judge the tracking resistance index (PTI) or the contrast tracking index (CTI) of the specimen.

5.5.10 UV-aging resistance

5.5.10.1 Purpose Use the ultraviolet accelerated aging test to check the performance of the atmospheric light-aging performance of the cured EVA film which is exposed to

5.5.10.5 Test procedure It is according to the provisions of

4.10 of IEC 61215-2:2016.The test procedure is as follows:

a) Allow the glass side of the specimen to face the light source, place it in the effective irradiation area of the UV-aging test chamber.Test conditions are as follows: 1) Ultraviolet spectral distribution: The irradiation intensity between the wavelengths of 280 nm and 400 nm is 50 W/m2 ~ 150 W/m

2.The illumination uniformity at the surface of the test sample is within 15%. Irradiation in the 280 nm ~ 320 nm band accounts for 3% ~ 10% of the total irradiation; 2) While the ultraviolet irradiation is being performed, the surface temperature of the specimen in the test chamber is maintained at 60 °C ± 5 °C; 3) Accumulation of irradiation power: It is accumulated according to the actual exposure of the specimen's surface.

b) Test time: It is calculated based on the accumulated dosage of the radiation power, 120 kWh/m2.

c) After the test, remove the specimen.At an open environment of temperature 23 °C ± 5 °C and relative humidity of less than 75%, restore it for 2 h ~ 4 h.Check the appearance.There shall be free from appearance defects.The light-exposed surface of the white EVA is free from embrittlement or powdering.

d) Respectively for the laminated specimen before and after the test, follow the requirements of ASTM E313-2010 to measure the yellowing index YI. For each specimen, make measurement for at least 3 points.The yellowing index YI of the specimen is taken as the average of the measured points.Record the difference between the yellowing index YI after aging and the yellowing index YI before aging, which is the yellowing index DeltaYI.For laminates which use the flexible back-panel materials, use the test method of

5.5.5 to measure the peel strength between the film and the glass in the laminates before and after the tests.

5.5.11 High-temperature high-humidity aging performance

5.5.11.1 Purpose Measure the aging resistance of the cured film under high-temperature high- humidity constant damp heat conditions. it for 2 h ~ 4 h.Check the appearance.There shall be free from appearance defects.

d) Respectively for the laminated specimen before and after the test, follow the requirements of ASTM E313-2010 to measure the yellowing index YI. For each specimen, make measurement for at least 3 points.The yellowing index YI of the specimen is taken as the average of the measured points.Record the difference between the yellowing index YI after aging and the yellowing index YI before aging, which is the yellowing index DeltaYI.For laminated specimens which use the flexible back-panel materials, use the test method of

5.5.5 to measure the peel strength between the film and the glass in the laminates before and after the tests.

5.5.14 PCT aging performance (optional item)

5.5.14.1 Purpose Determine the aging resistance of the cured film under constant damp heat conditions of high-temperature, high-humidity, high-pressure.

5.5.14.2 Instrumentation and supporting materials Instrumentation and supporting materials are as follows:

a) High-temperature high-pressure cooking aging test chamber;

c) Tensile testing machine;

d) Supporting material, same as 5.5.10.3.

5.5.14.3 Preparation of specimens Take two pieces of 300 mm × 300 mm EVA film.Follow the requirements of

5.5.10.4 to prepare the laminated specimens.Prepare 3 laminated specimens.

5.5.14.4 Test procedure The test procedure is as follows:

a) Put the specimen into the PCT aging test chamber.Set the test conditions: Temperature 121 °C ± 0.5 °C, relative humidity 99% ~ 100%;

b) Test time: 48 h;

c) After the test, remove the specimen.At an open environment of temperature 23 °C ± 5 °C and relative humidity of less than 75%, restore it for 2 h ~ 4 h.Check the appearance.There shall be free from of the product, which may affect the performance of the product;

c) When the production is restored after suspension for more than 1 year or when it is produced by new machine;

d) When the national quality supervision and inspection agency proposes the requirements for type inspection;

e) When the exit-factory inspection result is significantly different from the previous type inspection result.

7.1 Packaging

7.1.1 The product is in the unit of rolls.Each roll of products uses moisture- proof and dust-proof package.

7.1.2 Each roll of product is accompanied by a certificate of conformity, the items include: product model, specification, batch number, production date.

7.2 Marking Each box of products shall, during exit-factory, be marked of the name of the manufacturer, product name, model, specification, quantity, date of manufacture, implemented standards.

7.3 Transportation The transportation of products shall be protected from light, heat, moisture, throwing or stacking in open air.It shall not bend or damage the product.

7.4 Storage

7.4.1 Storage location The product shall be stored indoors.The temperature is controlled within the range of 0 °C ~ 30 °C.The relative humidity is less than 60%.Avoid direct exposure to sunlight.Do not be close to heating equipment or expose to dusty places.

7.4.2 Storage requirements Storage requirements are as follows:

a) Before unpacking, check the packaging box of the stored product, which shall be intact; ......