Sunlight and weathering

Polyethylene is the lowest-cost plastic commercially available. Mechanical properties are generally poor, particularly above 50°C (120°F), ana pipe must be hilly supported. Carbon-filled grades are resistant to sunlight and weathering. 

Other factors which can affect impact behaviour are fabrication defects such as internal voids, inclusions and additives such as pigments, all of which can cause stress concentrations within the material. In addition, internal welds caused by the fusion of partially cooled melt fronts usually turn out to be areas of weakness. The environment may also affect impact behaviour. Plastics exposed to sunlight and weathering for prolonged periods tend to become embrittled due to degradation. Alternatively if the plastic is in the vicinity of a fluid which attacks it, then the crack initiation energy may be reduced. Some plastics are affected by very simple fluids e.g. domestic heating oils act as plasticisers for polyethylene. The effect which water can have on the impact behaviour of nylon is also spectacular as illustrated in Fig. 2.80. 

Polysulphide systems were found to be durable over long periods and to be resistant to ozone, sunlight and weathering. 

Properties Poor resistance to sunlight and weathering, generally good resistance to bleeding and to chemicals. 

Features Not for proionged outdoor appiics. as sunlight and weather will cause pigment to decompose... 

The advantages of neoprene include its good chemical resistance, heat resistance to 200°F/93°C, good oil resistance, better resistance to ozone, sunlight, and weather than natural rubber, its excellent abrasion resistance, and the fact... 

Resistance Excellent resistance to sunlight and weathering poor resistance to acids and alkalies resistant to water. 

Under normal conditions PBT polymers can be stored for unlimited periods. Even at elevated temperatures (e.g. 40-45 °C) in air, and under the action of sunlight and weather, no decomposition reactions occur. PBT is not a hazardous material and it poses no risk to... 

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