3. Exposure conditions
Sample coupons were divided into three groups. The first group
of samples ([0] and [90]) were exposed up to 2000 h of combined
and individual accelerated aging using three chambers: (i) Moisture
and heat in a Tenney Benchmaster BTRS temperature and
humidity chamber, (ii) UV Radiation in a Q-Lab QUV/se accelerated
weathering chamber, and (iii) Salt spray and heat in a Bemco
P700XL chamber. UV radiation simulates natural sunlight using
fluorescent UV bulbs at a 340 nm wavelength. Intensity is monitored
by real-time UV irradiance sensors. One-half the samples in
the first group were exposed to individual exposures and the other
half were rotated every 48 h between two sets of chambers: salt
spray and UV chambers, and heat and humidity and UV chambers
to produce combined exposures. Because UV radiation exposure is
only on one side of the coupon in the QUV/se chamber, sample
sides were rotated every 24 h to receive uniform UV radiation. In
the temperature and humidity chamber, moisture was set at 85%
relative humidity (RH) and temperature at 35C. In the QUV ch