Plastic Lumber Capabilities
HDPE (High Density Polyethylene), a member of the polyethylene family, is one of the most widely used plastics world wide. Global demand in 2009 exceeded 23 million tons or 131 semi truckloads per hour. A broad range of useful physical properties are responsible for its popularity, particular in the packaging, transportation and construction industries.
HDPE can be used at a maximum temperature of 240 degrees Fahrenheit and a minimum of – 140 degrees Fahrenheit. Low moisture absorption, high rigidity and very good chemical resistance make HDPE a prime choice for applications from gas tanks to shampoo bottles, from natural gas pipes to buckets, from wear plates to plastic lumber. In addition, HDPE offers good impact resistance and high tensile strength and there is nothing in HDPE that micro organisms can use as food or leaches out that could harm the environment.
This sounds all great, but like all materials HDPE has also its weak sides. HDPE is not a good choice for assemblies that require gluing. Due to its inertness HDPE refuses to combine with other materials including glue. Strong, dependable connections can only be made by mechanical means such as screws or bolts etc. Or by welding. The most common and least demanding (from a perspective of required skill level and initial investment) is hot air welding. This method can produce assemblies as strong as the individual parts.
Normally HDPE has a poor resistance to UV, a segment of sun light. Milk jugs are made from HDPE and designed for a short shelf life. After all, they are made to contain perishable food. The whitish, translucent appearance is the natural color of HDPE. If milk jugs are left outside for a few months, even worse in direct sun light, they will degrade to such an extend that you can crumble them easily with your hands. Things change for the better when during manufacturing colorant has been added. The small platelets of the colorant prevent the harmful UV to penetrate deep into the plastic. However, the color of the colorant has a major impact on the protection that is achieved.. If the manufacturer included a generous amount of white colorant, items such as white buckets used around the garden can last for quite some time. Carbon black is the most effective screen against UV and perhaps the best weathering stabilizer available. If black is not an option, light stabilizers should be added that either absorb light or quench the detrimental chemical reaction caused by UV.
All MAXiTUF plastic lumber is made from recycled products that have been designed for a long shelf life. Therefore colorant and UV stabilizers have been already added once by the original manufacturer. To achieve the desired color and durability of our MAXiTUF plastic lumber, we add more colorant and UV stabilizers in our manufacturing process. Even with all these precautions taken, HDPE will still degrade ever so slowly if exposed to the environment. A gray prototype park bench, that we built about 20 years ago, serves as a good example. The original gray has faded to a lighter gray and if one scratches the surface the darker original gray is exposed. The layer of the powder-like substance has a thickness of a few thousands of an inch on surfaces most exposed to direct sun light. In other areas with less exposure to direct light, this layer is thinner or non-existent.