From PVDF Transparency To Aluminum Moisture Barriers

Hangzhou First, one of the leading encapsulation and backsheet manufacturers, has contributed data for 7 products to the fluoropolymer section of the TaiyangNews Backsheets and Encapsulation Market Survey 2024/25. The product range covers transparent backsheets with PVDF and FEVE coatings, grid variants for bifacial applications, and aluminum-backed models designed for enhanced moisture protection. Introduced in 2021, BEC-303TM appeared in our report for the first time in 2023. It is a transparent backsheet with a PVDF film of 25 μm on the outside and a 10 μm inner coating, with a 275 μm PET core. The product has a tensile strength of 150 MPa. It has a high transmittance of 92% and is available with a mesh option in white or black. The product exhibits good adhesion with EVA/POE, achieving an EVA peel strength of 10 N/mm.

BEC-301TM is another transparent backsheet from the company that is offered with a grid. Like the 303, this backsheet can also be opted with either a white or a black grid and is available as a plain transparent backsheet without a grid, BEC-301T in this case. In fact, most of the specs for these two backsheets are identical, except that BEC-301TM is somewhat of an older model released in 2019 and is built with an outer coating film of 20 μm.

TPC structure in which a 25 μm Tedlar film is used as the outer protective layer, a PET core layer, and a fluoroethylene vinyl ether (FEVE) inside coating, making up for an effective thickness of 310 μm. The product is designed for a 1,500 V partial discharge and 1.8 g/m²/d for moisture ingression. It has a tensile strength of 160 MPa and a tear strength of 80 N/mm. HANGZHOU FIRST is mainly promoting this product for applications that require high resistance to sand abrasion.

BEC-301TM comes with FEVE on both sides and has a thickness of 10 μm on the cell side and 20 μm on the air side, with a 275 μm PET in between, all amounting to an effective thickness of 305 μm. The backsheet is provided with an additional FEVE mesh of 20 μm towards the cell side to fill the cell gaps in bifacial modules using a transparent backsheet. They are designed for a 1,500 V partial discharge with 1.8 g/m²/d for moisture ingression. Like BEC-306D, BEC-301T and BEC-301TM have a tear strength of 80 N/mm.

BEC-301, which outlines the company’s basic backsheet configuration, features a 5 μm FEVE coating on the cell side and 20 μm on the air side, while the PET core film has a thickness of 255 μm, resulting in an effective thickness of 280 μm. Originally introduced in 2008, this model has a partial discharge of 1,000 V tested in air and is rated for a water vapor permeability of 1.8 g/m²/d. The backsheet has a white outer layer, while the inner side can either be white or black. It has a reflectivity of 80% within the wavelength range of 400 to 700 nm (see HANGZHOU FIRST Adds Coextruded Films To Non-EVA Encapsulant Range).

BEC-301T is the transparent version of BEC-301, suitable for bifacial applications. It has a PET layer that is 275 μm thick, while the FEVE layer measures 10 μm for an effective thickness of 305 μm. It follows the same construction down to the individual layers. Apart from being transparent, the major technical difference associated with this model over the BEC-301 is an EVA peel strength of 8 N/mm, about half of the other model at 14 N/mm.

BEC-303 is yet another solution, apart from the above-mentioned BEC-303TM, for module makers that insist on having a fluoropolymer film on the outer side of the backsheet. This backsheet has a 5 μm FEVE coating and a 20 μm thin PVDF film attached to a 275 μm PET sheet, amounting to an effective thickness of 305 μm. The product is offered in white and black. The bond between the EVA and FEVE coatings evaluated via EVA peel strength is given as 14 N/mm, and the peel strength of the inner layers, which is not applicable for purely coating-based products, is given as > 0.4 N/mm.

The majority of the mechanical properties for the above products (except BEC-303TM and BEC-301TM) are identical. They all have the same tensile strength of 160 MPa in the MD as well as the TD direction. The elongation is 130% in the MD direction and 120% in the TD direction, while the tear strength is 80 N/mm in both directions. The specs for dimensional stability and shrinkage are also the same for all models – 0.3% in the MD direction and 0% for the TD direction. Water vapor permeability is also the same for the entire range at 1.8 g/m²/d.

While it is acceptable to have such a level of water permeability for the above backsheets, the value is somewhat higher for BEAL-304. This backsheet comes with an extra layer of aluminum, typically used for better moisture-barrier properties. In addition to the 5 and 20 μm FEVE coatings and 255-μm PET films, this backsheet includes a 20-μm aluminum film, giving the product a total thickness of 305 μm. The mechanical properties of this backsheet are the same as the set above. Similar to the company’s other products, this backsheet is also supplied in rolls and sheets and can be stored at less than 35°C and relative humidity of 80% for up to 1 year. The company’s entire product range is offered with a standard width of 1,260 mm.

 For more fluoropolymer offerings from Hangzhou First, refer to the product description section of the report. The text is an excerpt from the latest TaiyangNews Market Survey on Backsheets & Encapsulation Materials 2024/25, which can be downloaded for free here.