mechanical performance
As a direct barrier to protect the cell and package materials, the back panel of the photovoltaic crystalline silicon component plays a vital role in the safety, long-term reliability and durability of the components. To achieve the purpose of protection, the backplane must have good mechanical strength and toughness, weathering resistance, insulation, water vapor barrier, corrosion resistance and sand wear and other balance of performance.
And the realization of these key energy, and backplane materials are inseparable.
Since the the 1980s NASA crystalline Silicon Module research project has been completed, the glass front plate +eva+ double-sided TEDLAR®PVF Thin Film composite backplane of the classic PV module packaging structure through a variety of climatic conditions of practical testing, Back Plate and has been used to date. Among them, the Special Energy ® (tedlar®) PVF film as the only more than 30 years of extensive outdoor performance verification of the backplane material has been the system developers, financial insurance and other investment and financing institutions to provide long-term reliable protection of PV modules to ensure that investment returns.
Perfect materials must combine their own advantages and unique processing technology
The TPT backplane (Tedlar®/pet polyester film/tedlar®) made up of double-sided TEDLAR®PVF film has become the industry benchmark, although there are a variety of shanzhai products on the market, Back Plate but none can surpass its superior product performance.
So the question is, why is PVDF (PVF) thin film?
First, polyethylene (PVF) Thin film using two-way tensile manufacturing process, the prepared film in the transverse and longitudinal direction of two has been enhanced, the mechanical performance of the balance has no weakness. Because the PVF film processing temperature and decomposition temperature are close to the requirements of extremely high process control and investment, Back Plate which is the only DuPont can produce the main reason, thus ensuring the quality of tedlar® film product reliability and consistency.
In contrast, polyvinylidene fluoride (PVDF) films are mainly used in both blowing film and casting process. The films prepared by these two processes have different degrees of stretching in longitudinal direction, but the transverse tensile strength is weak or even without stretching, resulting in poor transverse mechanical properties. In addition, PVDF itself is difficult to film, must add other materials-no less than 30% PMMA, commonly known as acrylic, Back Plate inherent brittleness is very strong. After adding acrylic, it is easy to cause the defect of poor transverse mechanical performance of PVDF film, which mainly shows that the fracture elongation rate is low, generally less than 30%.
In order to compensate for this flaw, individual manufacturers add elastomer in the formula, so that PVDF films in the mechanical properties of the test produced a "lingering" effect to achieve a higher test results, but the actual outdoor anti-aging performance is not helpful. In addition, Back Plate because PVDF film processing difficulty and the threshold is relatively low, each of the process, formula and membrane structure also have a difference, resulting in different PVDF film performance is uneven. But it is difficult to distinguish different PVDF films from appearance or general composition analysis, so it is very difficult to supervise.
Poor mechanical performance can lead to cracking, which seriously affects component safety
It is well known that the mechanical properties and weatherability are the most important properties of the fluorine film used in the back plate, the PVDF film has a low transverse fracture elongation, which has been gradually exposed in the test and application. Although the addition of elastomer materials can help PVDF films in the initial mechanical performance test because of the high tensile strength of the fracture elongation, but after a slight aging test, all PVDF film transverse fracture elongation is lower than 10%, the basic loss of the polymer material due to toughness, very easy to crack.