That's an excellent and practical question! As someone who's watched public bins fade from dark green to pale gray, I've wondered the same. The direct answer is: it depends entirely on the plastic material and manufacturing process, but most modern urban bins are moderately to highly resistant, thanks to specific additives.
Standard plastics like untreated polyethylene will degrade under prolonged UV exposure. The sun's ultraviolet rays break down the polymer chains, making the plastic brittle, causing cracks, fading, and eventual failure. You might see this in cheap, thin bins that become chalky and crack after a few seasons.
However, responsible municipalities and manufacturers use UV-stabilized plastics. This involves compounding additives like carbon black (which also gives the black color), UV inhibitors, and absorbers into the plastic resin during production. These additives act as a "sunscreen," absorbing or scattering UV radiation before it can damage the polymer structure. High-density polyethylene (HDPE) bins, common in cities, are often well-stabilized.
So, how resistant? A quality, commercially-produced urban bin is engineered to withstand 5-10 years of constant outdoor exposure before significant brittleness sets in. Fading will occur sooner, but that's often cosmetic. The key is thickness (thicker walls degrade slower) and color—dark colors like black, dark green, or brown generally offer better inherent UV protection than light colors.
To maximize lifespan, placement matters slightly. A bin in constant, direct desert sun will degrade faster than one in dappled shade. But overall, while not indestructible, today's plastic urban bins are surprisingly resilient solar warriors, designed to take the heat and light for the long haul.