A program for investigation of the resistance of plastic film materials to solar radiation and weathering under distillation conditions was carried on through the use of accelerated laboratory tests as well as outdoor exposure tests. Sample containers affording protection of the film specimens while subjecting them to distillation conditions were developed, and an accelerated testing device constructed which appears suitable for rapid screening of materials, though direct correlation with outdoor exposure can not be established as yet.nThe program was subsequently extended to include preliminary design, construction, and initial testing of suspended envelope stills in modular unit form. A design was. developed which utilizes commercially available structural elements requiring a minimum amount of fabrication into still modules. Available plastic materials having superior resistance to exposure presented extensive problems in effective sealing.
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