Overall, poly lumber is a durable, recycled plastic known for its longevity. Most grades of poly are resistant to water, but not every type of poly lumber will be a good fit for outdoor furniture. It is vital to understand the different strength levels of each kind of poly before purchasing plastic furniture or doing your own projects.
PVC (Polyvinyl Chloride)
PVC is a standard grade of poly that is widely used in many industries across the world. It’s used for piping in the plumbing industry. It is also a common material for medical devices. Due to its high chlorine content, PVC is fire-resistant. However, when exposed to continual sunlight PVC becomes brittle. It is often used because it is lightweight, but in a windy region, that may not be a preferable quality for outdoor furniture.
Polystyrene is also a lightweight plastic, however, it is considered a low-strength material in comparison to the other grades of poly. It is easily molded and is mainly used for things outside of poly lumber – such as disposable bags and seals. This plastic is also prone to turning brittle in extreme temperatures and UV radiation. While there is some PS furniture, Polystyrene is not often considered the best option long-term.
This plastic variation is stronger and rigid in form. Polypropylene is often associated with automotive parts, food packaging, and common household appliances. The FDA considers this to be one of the safer options for plastic containers. While it is uncommon as poly lumber, it is still found in some outdoor furniture and deck material.
Low-Density Polyethylene (LDPE)
LDPE is a softer and bendable variation of poly. That is why it is often used for squeeze bottles, marine bumpers, lab equipment, and various other caps, components, and closures. This grade is also not well known as a material for poly lumber. It tends to be weak against fluctuating and extreme temperatures. LDPE also does not handle UV concentration as well as other plastics.
High-Density Polyethylene (HDPE)
This grade of poly is often the preferred material for outdoor furniture and decking. It isn’t indestructible, but its weight and resistance to the elements make it a highly sought-after plastic. If exposed to freezing temperatures or left in UV radiation for a substantial amount of time, you will witness it wearing down. However, it lasts longer in comparison to many other poly variants. While its weight may not make it suitable for all poly purposes, it makes for great furniture that will resist fading, cracking, peeling, and low-impact damage.
As a whole, HDPE’s qualities make it the smartest choice for durable poly lumber. While other grades have great qualities for other products, none of them are as loved in the furniture industry as HDPE.