IR SPECTROMETRIC DETERMINATION OF CONCENTRATIONS OF SOLUBLE AND INSOLUBLE FRACTIONS OF BIS(2,2,6,6-TETRAMETHYL-4-PIPERIDINYL) SEBACATE IN POLYMERS - APPLICATION TO LDPE FILMS

The method described is based on the shift of the carbonyl absorption in the IR spectrum of the ester groups of this hindered aliphatic amine stabilizer when it is soluble or bloomed as a surface solid phase. It is shown that the values of the extinction coefficient to be used for the calculation of these concentrations are: epsilon(solute) = 589 cm(-1) mol(-1) litre at lambda(max) = 1736 cm(-1). and epsilon(solid) = 945 cm(-1) mol(-1) litre at lambda(max) = 1718 cm(-1). Quenching of the films after processing or any other heat treatment may lead to higher, non-equilibrium values of the soluble part of this additive. The resulting annealing effect must not be overlooked. Ir measurements were done at room temperature (23 +/- 2 degrees C) on extruded blown films obtained from mixtures of low density polyethylene (LDPE) pellets with this powder additive (less than or equal to 0.5 wt%).