PHYSICAL LOSS OF HINDERED AMINE LIGHT STABILIZERS FROM POLYETHYLENE

The diffusion of oligomeric HALS was measured by permeation through swollen LDPE film. It was found that only about 4% of the oligomer permeated the film. Based on previous data the diffusion parameters of the oligomer were extrapolated. The data obtained showed that oligomer molecules containing only one structural unit can diffuse through a LDPE matrix at a rate comparable to low molecular weight stabilizers. Measured and extrapolated diffusion and solubility data were used to estimate the efficiency of the stabilizers according to a model for physical loss of additives. However, the results were not satisfactory when compared with the real effectivity of HALS. The decreasing efficiency of oligomeric HALS with increasing molecular weight is discussed in view of the extrapolated diffusion parameters.