Thermogravimetric analysis of thermal stability of poly(methyl methacrylate) films modified with photoinitiators

Films of poly (methyl methacrylate) (PMMA) were prepared by the addition of photoinitiator to the polymer. The influence of five organic photoinitiators on thermal stability of poly(methyl methacrylate) was studied by thermogravimetric analysis. Next, the PMMA films doped with these photoinitiators were UV irradiated and investigated in terms of changes in their thermal stability. It was found that the photoinitiators had accelerated thermal degradation of non-irradiated PMMA films due to the action of free radicals coming from the additives’ thermolysis. For UV-irradiated specimens, the effect of photoinitiator on PMMA thermal stability depended on the chemical structure of organic compound modifying the polymer. In general, thermal stability of irradiated samples was higher in the presence of additives. Thermal destruction of modified PMMA can be explained by the formation of resonance structures in aromatic photoinitiators and consumption of energy in dissipation processes.     

Salen impregnated silica gel as a new sorbent for on-line preconcentration of cadmium(II)

A new sorbent – salen impregnated silica gel – was prepared and characterised for application as a minicolumn packing for flow-injection on-line preconcentration of cadmium(II). The system was coupled with flame atomic absorption spectrometer (FI-FAAS). The optimal pH for Cd(II) sorption was in the range of 7.4–8.8 and nitric acid (1%, v/v) was efficient as eluent. Sorption was most effective within the sample flow rate up to 7?mL?min^?1. Sorption capacity of the sorbent found in a batch procedure was 26.3?µmol?g^?1 (2.95?mg?g^?1). Enrichment factor (EF) and limit of detection (LOD) obtained for 120-second loading time were 113 and 0.26?µg?L^?1, respectively. The sorbent stability in the working conditions was proved for at least 100 preconcentration cycles. The evaluated method was applied to Cd(II) determination in various water samples.