Evaluation Of Thermal History
Of Plastics Using Additive Markers
Background
Thermoplastic resins are regarded as important materials for realizing a sustainable society.However, thermoplastic resins are weakened by thermal history addition in physical properties such as strength and elongation. Therefore, it is important to control and grasp the thermal history of polymer recycle. So, the purpose of this application was to evaluate the thermal history, directly and rapidly.
Samples
Polypropylene pellet; 1) Virgin pellet, 2) 3x recycled pellet
Methods
Samples were cut into about 1 mm square, and then placed into the ionRocket copper sample pot. A temperature gradient of 100ºC/min from room temperature to 600ºC was applied (total run time: 7 min.)
Results
TIC and MS spectra of measured at 260ºC were shown in Figure 1 and Figure 2.
Regarding the TIC, no significant difference was detected between the samples, and similar thermal decomposition patterns were observed. However, regarding the MS spectra, Irgafos 168 and its oxidized compound were detected. In comparing the intensity ratios of the oxidized Irgafos 168 and pure Irgafos 168 between the samples, the ratio of the 3x recycled pellet was higher than that of the virgin pellet. This confirmed that the 3x recycled pellet increased oxidized Irgafos 168 by recycle. In addition, in comparing the extracted ion current grams for Irgafos 168 between the samples (Figure 3), the 3x recycled pellet showed less than the virgin pellet. This confirmed that Irgafos 168 was consumed by recycle. In summary, by using this method, additives contained in a polypropylene pellet and the polypropylene polymer matrix were detected independently and directly by gradient thermal heating. This method can be a useful way to evaluate the thermal history of recycled thermoplastic resins quickly and easily, by using the antioxidants contained in the thermoplastic resins as markers. Moreover, this method could be applied to quality control for thermoplastic resin products, such as containers and parts.
Figure 1. MS TIC
Figure 2. MS spectra of measured at 260ºC
Figure 3. Extracted ion current grams of Irgafos 168
Target
Recycled Plastics / Thermal History / Antioxidant