Weather-induced degradation tests of polymers usually require weeks or months to complete. However, the Micro-UV Irradiator-GC/MS system, which uses a xenon lamp with UV light intensity about 200 times stronger than the deuterium lamp, significantly reduces the time necessary to acquire data on the degradation of polymers to a few hours.
Today, paint manufacturers are integrated Micro-UV/Pyrolysis-GC/MS, which uses the micro-furnace pyrolyzer into their day to day analytical protocols due to the efficiency and effectiveness of this technique for weathering testing.
The micro-furnace is a multi-functional pyrolyzer. Virtually any material (solid or liquid) can be chemically characterized using an array of techniques, which are designed into the micro-furnace. These techniques are Evolved Gas Analysis (EGA), multi-step Thermal Desorption (TD), Pyrolysis (PY), Double-Shot (TD followed by PY), Heart cuts, UV irradiation, and conventional sorbent based thermal Desorption. The micro-furnace directly connects to the GC injection port and directly deposits all pyrolyzates on-column in a single step process for a continuous-mode analysis. The continuous-mode process allows low and high molecular-weight as well as polar compounds to be detected and analyzed. The absence of any transfer line is also critical in the ability of this device to detect heavy and polar pyrolyzates as well as additives.
In this technical note, the Micro-UV Irradiator is used to irradiate two acrylic samples, one with and the other without UV absorber and HALS. The degree of deterioration of each sample was then examined by evolved gas analysis (EGA-MS) mode of operation using the micro-furnace.
Background: Acrylic coatings are widely used on the exterior walls of houses because of their excellent color development and long-term stability. Exposure to sunlight can cause photodegradation of the acrylic coatings; consequently, UV light absorbers and hindered amine light stabilizers (HALS) are routinely added as additives to improve the durability of the coatings.
Experimental: The samples were acrylic coatings. Sample A contained UV absorber (Tinuvin 400) and HALS (Tinuvin 292), while sample B contained no additives. Each sample was placed in a sample cup (side-hole Eco-Cup UV), attached to the end of the optical fiber, and then introduced to the micro-furnace set at 60 ºC. UV irradiation was performed for 1 to 20 hours in the air using a Micro-UV irradiator (UV-1047Xe) with a mercury xenon lamp as a light source. EGA-MS analysis of the sample was performed before and after irradiation under He carrier gas. [1]
Results: The EGA thermograms of Samples A and B before, during, and after UV irradiation are shown in Fig. 1. In sample A, the peak apex temperature and full-width at half-maximum (FWHM) did not change significantly before, during, and after UV irradiation. This can be attributed to the effectiveness of the UV light absorber and HALS to keep the photostability over 10-hour irradiation. The results for Sample B are much different. The peak apex temperature shifted -8 ºC after 10 hours of UV irradiation. Also, the FWHM approximately doubled (31 to 70 ºC) as the irradiation time increases. Fig. 2 shows that samples do not show remarkable changes in FWHM after 10 hours and the total change is less for Sample A, i.e., more durable, than Sample B. [1]
To learn more about the micro-furnace pyrolyzer, its modes of operations, and how the UV irradiator can be used for your weather-induced degradation testing of polymers, simply connect with us.
References: This technical note was developed by Frontier Laboratories Ltd. 4-16-20 Saikon, Koriyama, Fukushima, 963-8862 JAPAN. www.frontier-lab.com