| Poly(ethylene-co-vinyl acetate), or EVA, is widely used as a solar cell encapsulant. The key property for such an encapsulant is light transmission. Light transmission over 90% is highly desired to increase the efficiency of photovoltaic panels and their associated electrical output. Thus, increasing the transparency of the encapsulant is key to increasing energy generation. The main goal of this thesis was to assess the impact of additives on the light transmission of a high transparency EVA resin containing 33 wt% VA (AT3324A TM, Celanese). This study focused on the use of two novel nanoclays (Perkalite F100 and F100S from AkzoNobel Polymer Chemicals LLC) and a novel polyethylene nucleating agent (HyperformRTM HPN20E from Milliken Chemical). The crystallinity of EVA alone and in the presence of varying concentrations of the aforementioned additives was studied using differential scanning calorimetry (DSC) and x-ray diffraction (XRD) to quantify the effects of these additives on the microstructure of the polymer. Optical measurements were also made in order to evaluate the influence of these additives on macroscopic properties. Finally, other properties of critical importance in this application (volume resistivity, tensile properties) were evaluated as well. The results showed that the Hyperform HPN-20E nucleating agent was incompatible with the 33 wt% VA containing EVA resin causing a significant decrease in visible light transmission below the 90% level targeted for the application. For the Perkalite F100 and F100S nanofillers, both showed good compatibility with the resin. The average transmission for samples containing nanofillers was consistently above 90% in the visible range, and additionally displayed better UV blockage at the 350 nm cutoff. However, the volume resistivity was deteriorated below the targeted specification (1014 &OHgr;· cm) by at least one order of magnitude. Nevertheless, these two nanofillers can be used with 33 wt% VA containing EVA in applications in which such high electrical resistivity are not required and other properties such as permeability, fire retardancy, UV blockage and the like are more important. |
