| Work Detail |
Austrian researchers tested thermoplastic polyolefin (TPO) encapsulants as an alternative to conventional ethyl vinyl acetate (EVA) copolymer and polyolefin elastomers (POE) to evaluate their use in glass-glass modules. They report that all TPO samples outperformed EVA and POE, especially the TPO-3.5 encasulants.
Austrian researchers evaluated the degradation potential of thermoplastic polyolefin (TPO) encapsulants for use in glass-glass modules, as an alternative to conventional ethyl vinyl acetate (EVA) copolymer and polyolefin elastomers (POE). .
“TPO films are currently used for niche products such as colored double glass modules and building-integrated photovoltaic modules. Double glass modules require encapsulants with significantly less reactive byproduct. Unlike cross-linked EVA and POE encapsulants, TPO materials facilitate processing and recycling,” Martin Tiefenthaler, a researcher at Johannes Kepler University Linz (JKU), told pv magazine , adding that TPO films do not They do not contain peroxides or vinyl acetate comonomer units, which are prone to hydrolytic degradation.
In the study, the team prepared double glass laminates, 25 mm × 25 mm × 7 mm, using three TPO film adhesives, each with a different formulation, TPO-3.5, TPO-UV, TPO-F, and supplied by the Austrian Borealis. Two other samples made of EVA and POE were used as reference.
Before the compression shear test, the experimental specimens were exposed to ultraviolet (UV) irradiation of 40 W/m2, at temperatures of 65 C and a relative humidity of 10% for a maximum of 3,000 h. Visual, optical, mechanical and chemical analysis of the changes could be performed using various instruments, such as microscopy, UV-visible-near-infrared spectroscopy, compression shear testing, as well as differential scanning calorimetry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The team analyzed and ranked the results in order of importance.
The team analyzed and classified the results. They found that the TPO variation with the best results was TPO-3.5, followed by TPO-UV, TPO-F, EVA, and POE. “While the aged and fractured laminates of EVA, POE, TPO-F and TPO-UV showed carboxylic acid signatures different in intensity, no carboxylic acid residues were detected on the fractured surface of TPO-3.5,” stated the equipment.
Additionally, TPO-3.5 had a “lower melt index,” which translates to “a higher average molar mass” compared to TPO-F and TPO-UV. “For cross-linked EVA and POE, the test temperature was already within the melting range of the non-cross-linked, polyethylene-rich phase of these peroxide-cross-linked encapsulants,” the academics specified.
The team concluded that the “obtained results clearly indicate that special attention should be paid to TPO-3.5 encapsulants for double-glass PV modules” in future research. “The next step will be the evaluation of the effect of moist heat and UV aging of TPO-glass laminates on the long-term performance,” said Tiefenthaler, adding that the positive results at the sample level have to be validated and investigated by the expansion to photovoltaic module sizes.
The research results were presented in “ Effect of UV aging on debonding of double glass laminates based on different crosslinking and thermoplastic PV encapsulants ” thermoplastics and cross-linking), published by Solar energy materials and solar cells . The researchers came from Johannes Kepler University Linz, the Christian Doppler Laboratory for Superimposed Mechanical-Environmental Aging of Polymeric Hybrid Laminates and Borealis.
Last year, another research group at the Johannes Kepler University in Linz carried out long humidity-heat tests on double-glass solar modules made with UV-transparent EVA and POE encapsulants for more than 10,000 hours, discovering several advantages of using of POE encapsulants compared to EVA materials. |
