EFFECT OF THERMOOXIDATION ON TINUVIN-783 IN LDPE FILMS - CHARACTERIZATION BY UV AND FTIR SPECTROSCOPY

The effect of thermooxidation on Tinuvin 783 which is a hindered amine light stabilizer in LDPE films has been investigated by UV and FTIR s pectroscopy. Initially, a standard curve describing the variation of t he concentration of Tinuvin 783 in LDPE films was plotted using the me thod of integration of the band area. The relation obtained was: band area = 19.6249 x [Tinuvin 783]. This equation was then applied to meas ure the variation of the concentration of Tinuvin 783 in the 0.2%(wt) stabilized samples which have undergone thermooxidation at 90 degrees C for 98 days. The results showed a considerable decrease in the conce ntration of Tinuvin 783 by 35% during the first 30 days due to probabl y the formation of nitroxyl radicals. After this, the concentration wa s observed to be unchanged and may correspond to the phase of nitroxyl radical regeneration. On the other hand, no chemical change in the st abilized LDPE films was observed by FTIR spectroscopy at 90 degrees C during 98 days while the band characteristic of ketone soups (1720 cm( -1)) was detected for the unstabilized samples after only 11 days. (LD PE:low density polyethylene; HALS:hindered amine light stabilizer).