What isyour application? Does it have to look pretty? I'd expect no UV protectant if not stated but not certain. I'd expect " few years" with no UV protectant and a few years with (OK maybe 3-5.) NZ is VERY harsh UV wise. If there is a will to do so you could make plastic sheet last much longer than it probably will. Probably 10-15 years if you really wanted. UV protectants diffuse out of the target material with time, setting one of several upper limits on lifetime Real people blow multiple layers of disparate plastics as an apparent single sheet to get desired results. 2 & 3 common. 4 I've seen. More + may exist. Probably PE. May be PP - lss likely. May be other but less likely again. You want both a UV stabiliser turned to the absorbtion peaks of you plastic AND a HALS (hindered amine light stabiliser) that absorbs the breakdown radicals when they do occur. You want to see what BASF have to say. They are THE biggest chemical company in the world and know their IV stuff. CIBA Geigy were very very good too - but BASF bought them about 2 years ago= .. CIBA do the Tinuvin range of UV protectants. Beware the "like Tinuvin xxx" or same formula as Tinuvin xxx. This may in fact be true but even then they seem to get better results. All "identical" plastics are not created equal The wonderful Gaisma Nothing on UV but adds to your information base. http://www.gaisma.com/en/location/denver-colorado.html Altitude 1600m will have some effect. You'd expect an increase in clearaness factor from that but the 0.5x or so isn't stunning. Here's Bamiyan for comparison http://www.gaisma.com/en/location/bamiyan.html Kudahuvadhoo http://www.gaisma.com/en/location/kudahuvadhoo.html Both chosen for hoped for clearness factor. Oh yes! Amundsden-Scott - 0.73! http://www.gaisma.com/en/location/amundsen-scott--permanent-station-of-the-= us.html Denver Variable I II III IV V VI VII VIII IX X XI XII Insolation, kWh/m=B2/day 2.03 2.87 4.06 5.09 5.87 6.34 6.28 5.50 4.56 3.43 2.37 1.88 Clearness, 0 - 1 0.49 0.51 0.53 0.53 0.54 0.55 0.56 0.55 0.55 0.54 0.52 0.5= 0 Temperature, =B0C -3.00 -1.25 2.80 7.27 13.00 17.55 20.72 19.29 14.95 8.40 0.90 -3.31 Wind speed, m/s 8.01 7.57 7.54 7.45 6.64 6.01 5.48 5.51 5.97 6.46 7.00 7.61 Precipitation, mm 13 18 34 42 71 40 53 40 30 24 22 15 Wet days, d 5.5 5.9 8.7 8.1 10.5 8.7 9.3 9.3 6.9 5.0 5.4 6.0 On 30 December 2011 09:22, YES NOPE9 wrote: > > If a roll of 6 mil black plastic does not say it is UV resistant ....... > Does one presume it is not ? If it does say it is UV resistant, > what kind of lifetime will it have in Denver, CO ? ( sunny most days , high altitude ) > 99guspuppet > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .