1. Scope

Keywords

Rationale

Please find below a draft for a New Practice for the Accelerated Weathering of Aromatic Plastics. This is a designed exposure, for a specific class of materials, to reproduce a specific exposure result that happens during outdoor exposure testing. This new practice is specifically for aromatic plastics, which due to their unique chemistry erode and can leave surface deposits such as pigment particles as part of the weathering process. The deposits are not from the atmosphere, but are formed as the material degrades. These deposits are removed when the materials are exposed outdoors, due to rainfall similar to benchmark locations such as South Florida and Arizona, and/or periodic surface washing (field rinsing) as required by many outdoor weathering standards. If these surface deposits are not removed during accelerated weathering, the continuation of weathering is different than if those deposits are removed. Different results are obtained between washed and unwashed specimens. There is no accelerated laboratory method currently that simulates this specific effect. Xenon arc testing is extremely good at simulating the exposures, but most currently accepted cycles are lower in water spray durations, and do not include surface washing. Using a newer high moisture cycle improves correlation, and periodic washing of the specimens reproduces the erosion effect. Together these modifications give good agreement to outdoor weathering of aromatic plastics in a South Florida exposure test. A new focused method is required to fill this need. Committee D20 is the logical place to have a specific standard for accelerated weathering of plastic material. Currently this method has only been demonstrated as effective for this combination of material type, and exposure practice. The Scope of this new practice confirms its application to this limited field of use. Anyone interested in further information will find a full list of references at the end of the draft.