The OIT and Lifetime of Composite Deck Boards

The oxidative degradation capacity of tillers, inorganic (metal oxides, particularly free metal-containing) colorants, and other additives in WPC is greatly underestimated by many researchers and manufacturers of composites. Composite materials generally require much more antioxidants compared to neat plastics, particularly when an energy-intense compounding is employed. 

All observations of actual decks in the southern United States have shown that the larger the OIT, the longer the lifetime of the decks before crumbling is noticeable (if it is ever noticeable). For GeoDeck decks in Arizona, OIT in the range of 

8 min resulted in the boards crumbling in about 12-20 months. Boards with the OIT around 1.0 min lasted for about 2 years. Boards with OIT above 2-3 have not been crumbling in a 3-year observation period. These data are related mainly to hollow composite boards, though solid boards with the same OIT values can behave similarly. 

OF WOOD-PLASTIC COMPOSITE DECK BOARDS AVAILABLE IN THE CURRENT MARKET 

The OIT values of composite materials reflect two principal factors (a) how much of the antioxidants is present in the material and (b) how resistant is the material itself to thermal oxidation. The OIT values of the commercial composite materials determine the sensitivity of the deck boards to oxidative degradation, hence, the lifetime of the boards, first of all in the south. If they are heat/UV stable in the south, no need to worry in the north. 

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