Ageing and Weathering

Environmental Impact of Ambient Ozone. Ozone can be toxic to plants, animals, and fish. The lethal dose, LD q, for albino mice is 3.8 ppmv for a 4-h exposure (156) the 96-h LC q for striped bass, channel catfish, and rainbow trout is 80, 30, and 9.3 ppb, respectively. Small, natural, and anthropogenic atmospheric ozone concentrations can increase the weathering and aging of materials such as plastics, paint, textiles, and mbber. For example, mbber is degraded by reaction of ozone with carbon—carbon double bonds of the mbber polymer, requiring the addition of aromatic amines as ozone scavengers (see Antioxidants Antiozonants). An ozone decomposing polymer (noXon) has been developed that destroys ozone in air or water (157). 

Sealants for insulated glass windows are based on butyl polymers. These sealants have excellent weathering and ageing, low-moisture vapour transmission and are non-fogging [66]. 

Cellulosic They are tough, transparent, hard or flexible natural polymers made from plant cellulose feedstock. With exposure to light, heat, weather and aging, they tend to dry out, deform, embrittle and lose gloss. Molding applications include tool handles, control knobs, eyeglass frames. Extrusion uses include blister packaging, toys, holiday decorations, etc. Cellulosic types, each with their specialty properties, include cellulose acetates (CAs), cellulose acetate butyrates (CABs), cellulose nitrates (CNs), cellulose propionate (CAPs), and ethyl celluloses (EC). 

Polysulfide resins combine with epoxy resins to provide adhesives and sealants with excellent flexibility and chemical resistance. These adhesives bond well to many different substrates. Tensile shear strength and elevated-temperature properties are low. However, resistance to peel forces and low temperatures is very good. Epoxy polysulfides have good adhesive properties down to -100°C, and they stay flexible to -65°C. The maximum service temperature is about 50 to 85°C depending on the epoxy concentration in the formulation. Temperature resistance increases with the epoxy content of the system. Resistance to solvents, oil and grease, and exterior weathering and aging is superior to that of most thermoplastic elastomers. 

DIN 53 387 (1989). Artificial weathering and ageing of plastics and elastomers by exposure to filtered xenon arc radiation. Deutsches Institut fiTr Normung e.V., 10772 Berlin, Germany (E-mail postmaster din.de). ... 

Using standardized phytotoxicity test methods, Rocheleau et al. [40] investigated the effects of TNT, TNB, 2,4-DNT, and 2,6-DNT freshly amended (following a 24-h moisture equilibration period) or weathered and aged (13 weeks) in SSL soil. Tests... 

Specific mechanisms of changes in the toxicity following weathering and aging of EMs in soil are not well understood. Compounds produced due to TNT degradation... 

Rocheleau S et al., Phytotoxicity of nitroaromatic energetic compounds freshly amended or weathered and aged in sandy loam soil, Chemosphere, 62, 545, 2006. 

Kuperman RG et al., Weathering and aging of TNT in soil increases toxicity to potworm... 

Kuperman RG et al., Toxicities of dinitrotoluenes and trinitrobenzene freshly amended or weathered and aged in a sandy loam soil to Enchytraeus crypticus, Environ. Toxicol. Chem., 25, 1368, 2006. 

Effects of Weathering and Aging on Energetic Compounds Bioaccumulation... 

Note F = freshly amended soils W/A = material weathered and aged in soils. a Value units are mg kg-1. 

Growth (Shoot Fresh Mass) Toxicity Benchmarks (EC20 mg kg-1) for Munition Constituents (MC) Freshly Amended or Weathered and Aged in Sassafras Sandy Loam Soil for Selected Test Species... 

Notes Values listed as fresh/weathered and aged exposure treatments. All values (mg kg-1, dry soil mass) are based on acetonitrile extractable concentrations in soil (USEPA Method 8330). NT = not tested. a Greatest concentrations tested. 

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