Hindered Amine Stabilizers (HAS) are well known stabilizers against the UV-degradation of polymers. Nowadays these stabilizers are also promoted as long-term heat stabilizer for polypropylene (PP). However, their ability to reduce the thermo - oxidative degradation of polypropylene is different from that of the traditionally used phenolic antioxidants (PAOs). It already was shown that the effectivity of HAS is more pronounced at lower (<120 deg C) than at higher temperature (150 deg C). It also was shown that the decline of the mechanical properties for HAS (gradually with degradation time) and phenolic antioxidants (long period without changes followed by a fast drop) containing PP is totally different.
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