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PAP Backsheet

PAP : PEN/ AI Foil/ PET: what is it?

PAP is the abbreviation of PEN/ AI Foil/ PET film which is a composite layer film that is used as a backsheet material in solar modules.  

Backsheet material

The backsheet consists of multiple layers of barrier films and adhesives. Certainly, the construction of the backsheet is instrumental in protecting the solar cells from different environmental conditions like moisture, UV exposure and other performance threats while also improving solar module efficiency by aiding the reduction of partial discharge. To accomplish this, the solar panel material should be of a robust construction, typically a three layer laminate, and possess high dielectric properties. Most backsheets consist of combinations of films chosen for their different properties. Examples of standard films include: PET or EVA, Tedlar and Kynar. Combinations can be TPT (Tedlar/PET/Tedlar), KPK (Kynar/PET/Kynar) or PPE (PET/PET/EVA) among other combinations.   What is PEN? It is the Polyethylene naphthalate polypropylene. Most importantly, PEN (Polyethylene naphthalate) resin became popular in many industries after U.S. company Amoco Chemicals started commercial producing of NDC (naphthalenedicarboxylic acid) a raw material of the PEN resin, in 1995. Also, PEN is manufactured in a similar process to that of PET (polyethylene terephthalate), another typical polyester used commonly as a backsheet in solar panels. PEN is used in solar panels as backsheet material, besides that it is used in other products as bottles, plateware, containers and medical product containers. PEN is commonly used in products that require transparency, chemical and heat resistance.

PAP use in solar panels

It is used to produce the solar panel backsheet material. PAP has many properties that makes attractive to use in backsheets. Mainly, high transparency, higher thermal resistance compared to PET-based products, longer lifetime than PET products, and high chemical resistance. PAP has one of the lowest water vapor permeability rate compared to other polymers which makes it withstand the different factors which cause the aging of PV modules including Corrosion of metal frames, delamination of encapsulant polymers and physical damage from external environmental weather conditions like wind, rain and snow.

Alternatives to PAP backsheet

PAP has different alternatives as a backsheet. PET or PEN-based material are used by manufacturers to replace the more expensive Tedlar-based material. Besides PEN, polyimide, and polyamide-based materials are also being considered as potential candidates. To sum up, for backsheets, a variety of materials and substructures can be used. For instance, that includes the whole range of Tedlar based polymer which include: TPT, TPE, TAT and TPAT. Glass is even sometimes used to replace polymer backsheets to provide a lower quality and cheaper option with lower properties.  
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