Factors that affect the EVA encapsulant discoloration rate upon accelerated exposure

摘要: Several factors that affect the discoloration rate of ethylene-vinyl acetate (EVA) copolymer encapsulants used in crystalline-Si photovoltaic (PV) modules upon accelerated exposure have been investigated primarily by employing UV-visible spectrophotometry, spectrocolorimetry, and fluorescence analysis. A variety film samples including two typical (unprimed) EVA formulations, A9918 15295, were studied. The films laminated, cured, exposed to either a concentrated 1-kW Xe or an enhanced-UV light source. results indicate extent can be affected general categories: chemical physical. In category, degradative include (1) formulation, (2) presence concentration curing-generated, UV-excitable chromophores depend on type curing agent used, (3) loss UV absorber, Cyasorb 531TM, (4) conditions, (5) photobleaching reactions due diffusion air into laminated films. physical involve (6) intensity, (7) UV-filtering effect glass superstrates, (8) gas permeability polymeric (9) thickness, (10) lamination-delamination (maybe and/or mechanical effect, too). Photodecomposition was first verified cyclohexane solutions then Elvax 150TM (EVX) (the without any additives agent). decomposition rates are exponentially proportional but greatly reduced free-radical scavenger, Tinuvin 770TM, furthermore antioxidant, Naugard PTM. increases with increasing 531 is faster for greater generated from slower than 15295 fast cured. general, absorber yellow brown follow sigmoidal pattern. reasonably good correlation changes transmittance at 420 nm, yellowness index, peak area (or intensity ratio) obtained as progresses. No observed EVX contain no stabilizers curing-generated chromophores. both types largely superstrates remove UV< 320nm. Photobleaching responsible non-discoloration unlaminated EVA, visually clear perimeter around edges samples, gas-permeable polymer superstrates. Delamination top superstrate after prolonged exposure.