Results to date-development of new EVA-based encapsulants, faster-curing and flame-retardant types

This research focuses on development of "faster-curing" and "flame-retardant" EVA-based (ethylene vinylacetate copolymer) encapsulants. Cure kinetics measured by moving die rheometry determined that cure time reductions of /spl sim/70% were accomplished, achieving full cure (80% or greater gel content), versus commercial "fast-cure" EVA-based encapsulant. Prototype 60-watt polycrystalline silicon modules were manufactured using 5 and 6 minute lamination cycles in a Spire 240A laminator. The implications of a successful development are significant, as reductions in process time increase a PV module throughput and overall plant capacity allowing lower-cost processing and gains realized by avoided cost of capital equipment, floor space, labor, etc., thereby reducing PV module manufacturing costs. Other efforts focused on reformulating the substrate EVA encapsulant layer to afford a UL 1703 Class A flammability rating on PV modules employing a single glass superstrate and polymeric backsheet. Early experimental formulations proved that UL 1703 Class B flammability ratings are achievable on prototype 60-watt polycrystalline silicon modules. Further reformulation yielded laboratory results that demonstrate EVA-based encapsulants resistant to combustion upon direct flame-impingement exceeding 2 hours, without evidence of dripping, flame spread or smoke generation. These encouraging results for both technologies are detailed herein, including processing conditions and current results from accelerated aging and qualification testing.