Covering for sun-energy collector - from fluorinated plastic films with improved spectral characteristics and temp. stability

摘要

Cover film of fluorine plastic material for sun-energy collectors, has the following characteristics; a light transmittancy in the visible range of 90%, an infrared absorption in the range 7-10mum of 90%, stability in the range 0-150 degrees C and a density between 1.5-2.2 g/cm3. The film is made from (I) polyvinylidene fluoride (PVDF) or a mixed polymer contg. vinylidene fluoride and another polymerisable perfluorinated vinyl cpd., (II) a mixed polymer contg. chlortrifluorethylene and ethylenen (ECTFE), (III) tetrafluoroethylene (PTFE) and a non fluorinated vinyl cpd. of the formula CH2=CH-R where R=H, (ETFE) or can be a selected alkyl or aryl radical, (IV) PTFE or a mixed polymer consisting of PTFE with a fluorinated vinyl cpd. of the formula CF2=CF-R where R = a selected perfluorinated alkyl radical, (V) a mixed polymer of PTFE and a perfluorinated vinyl ether of the formula CF2=CF-O-R where R = a selected alkyl or aryl residue. The film may be reinforced with (in)organic fibres. The films have improved spectral characteristics relative to polyvinyl fluoride films and to glass plates. They have good weather, cold and heat stability, good mechanical properties. They are lighter and cheaper than glass, show less tendency to collect dirt, ice and snow and are easy to clean.