WEATHERING PERFORMANCE OF STABILISED RECYCLED PIGMENTED POLYPROPYLENE CRATE MATERIAL.

In the reported experiments, the photostabilizing effciencies of various light stabilizer systems in recycled pigmented polypropylene crate materials, that had previously been in use for six to seven years, were examined using the standard carbonyl index and time to embrittlement methods. A large number of polymer film samples with and without additional stabilizers were prepared and exposed in both a Xenotest-150 and Microscal apparatus. Of all the stabilizer systems examained the hindered-piperidine type were found to be the most effective followed by the nickel complexes and then the 2-hydroxybenzophenones and hydroxybenzotriazoles. Antioxidants appear to have an important influence on the overall order in weathering performance of the stabilizer systems. A comparison of the two artificial weathering units indicated that humidity is an important factor in the photostabilization of pigmented polypropylene by hindered-piperidine stabilizers.