Nanoscale physics

Structural anisotropy of ethylene vinyl acetate film
Kislyuk V.V.1, Vorona I.P.2, Trachevskij V.V.3, Kotrechko S.O.1
1 G.V.Kurdyumov Institute of Metal Physics, NAS of Ukraine, 36 Academician Vernadsky Boulevard, UA-03142 Kyiv, Ukraine. E-mail: viktor.kislyuk@gmail.com
2 V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, 41 pr. Nauki, 03028, Kyiv, Ukraine.
3 Technical Center, NAS of Ukraine, Pokrovsʹka St., 13, UA-04070, Kyiv, Ukraine. 

Eethylene vinyl acetate (EVA) film used widely as encapsulant for photovoltaic modules [1] was found to demonstrate rather strong anisotropy (as to the axis of its rolling) both at macrolevel (mechanical tensile creep testing) and nanolevel (paramagnetic resonance spectra - EPR). 
Tensile testing. The film oriented parallel to the rolling direction have several orders of magnitude longer time of creep than that of the sample oriented perpendicularly at the same conditions of the. 
EPR spectra (Fig. 1) contain wide bands and narrow triplet series (with a suppressed component) attributed to hindered amine stabilizer. The former is sensitive to the orientation of samples as to the constant magnetic field and to their line of rolling while production. The series of the stabilizer resonances remains almost unchanged and used for quantitative analysis.
	Figure 1. EPR of the EVA film cut parallel (1) and perpendicular (2,3) to the rolling direction and placed in the resonator with H in-plane (2) and out of plane of the film (1,2) (with 90 and 0 angle between H and normal, respectively);
(4) – zoomed-in fragment corresponding to triplet of hindered amine stabilizer. 	
1.	Kislyuk V.V., Shyvaniuk V.M., Trachavskij V.V., Ostapyuk S.M., Kotrechko S.O., PV encapsulant material mechanical properties (peculiarities and their microscopic mechanisms) // Macromol. Res. 2021 – in press.