COMPATIBILITY OF HALS-NITROXIDES WITH POLYOLEFINS

The solubilities and diffusion coefficients of some nitroxy derivatives of hindered amine light stabilizers (HALS-NO) have been measured in polypropylene (PP), high density polyethylene (HDPE), low density PE (LDPE) and linear low density PE (L-LDPE). The results are compared with the values for the corresponding HALS and it is shown that nitroxides are always less soluble than the parent amines. Quantitative measurement of non-extractable stabilizer indicates that 1-2% of the stabilizer is bonded to the polymer chains after thermal aging (60-80-degrees-C). The diffusion behaviour of nitroxides is strongly dependent on the polyolefin type and differences of up to two orders of magnitude have been observed between PP and LDPE.