The effect of ultraviolet radiation on ultrasonic properties of polyurea

Abstract

Polyurea is used in military and civilian applications where exposure to the sun is commonly of long duration, which can deteriorate its mechanical performance to suboptimal levels. This study reports on the ultrasonic properties of polyurea as a function of ultraviolet radiation exposure duration and temperature. Six sets of samples were continuously exposed to ultraviolet radiation for different durations up to 15 weeks. Control samples were also tested that did not receive UV exposure. The ultrasonic properties were measured using high-frequency contact ultrasound transducers in pitch-catch configuration. All exposed samples exhibited significant color changes from transparent yellow to opaque light brown. Changes of color were observed as early as 3 weeks of UV exposure. Nonetheless, crazing was only observed in samples of 6, 9, 12, and 15 weeks of continuous exposure. The size of the surface cracks increased as the duration of exposure continued. The effect of extended UV radiation on the acoustic properties was noted to be minimal, where elastic and shear moduli decreased monotonically after an initial increase during the first 3 weeks of exposure. The attenuation properties were measured at 23°C and 40°C. The p-wave attenuation did not show any notable change, while the s-wave attenuation monotonically decreased as the temperature and UV exposure duration increased.

Effect of Die Head Temperature at Compounding Stage on the Degradation of Linear Low Density Polyethylene/Plastic Film Waste Blends after Accelerated Weathering

“…Elzubair and Miguez Suarez [39] showed that waste content does not affect the stress values even in the presence of additives and fillers in recycled HDPE. This could be attributed to the crystallinity of the polymers constituting each blend at room temperature and the change in their amorphous region due to processing conditions, especially when considering the number of polymers each blend possesses [5,40,41]. This also indicates that on a molecularly level the crystallinity of the B2 formulation is higher than the other examined blends, which is due to it exhibiting a higher stress at break as observed in Figure 3 mechanical properties) when such blends are employed in product development stages, considering that all recycled formulations show a comparable stress at break with the examined commercial products (C1 and C2, Figure 3), with less than 5% mean deviation among the values.…”

Synthesis and characterization of elastomeric polyurea foam

“…Grujici and coworkers attributed the ability of polyurea to exceptionally perform in such loading scenarios to the underlying molecular structure . In addition, polyurea was investigated in response to different environmental and operating conditions such as temperature, humidity, and ultraviolet radiation, all of which confirmed its superior overall properties …”

Investigations on Aging Behavior and Mechanism of Polyurea Coating in Marine Atmosphere

“…Youssef [14] investigated the effect of UV radiation on the dynamic mechanical properties of polyurea samples and found that the dynamic creep modulus increased with an increase in the UV exposure duration. Whitten [15] studied the color change from white to deep tan after extended exposure to ultraviolet radiation. Youssef [16] investigated the effect of UV radiation on the ultrasonic properties of polyurea and concluded that the acoustic wave speeds and p-wave attenuation were found to exhibit minimal change, while shear attenuation showed convergence as the temperature and ultraviolet exposure duration increased.…”