The most common outdoor plastics found in construction projects are polyvinyl chloride (PVC), high-density polyethylene (HDPE), and polycarbonate (PC). These construction plastics can be found in applications such as windows, pipes, doors, seals, flooring, and insulation.
The construction industry is the second largest user of plastic, swallowing up around 25% of all plastic used across all industries. This is for good reason as it is so versatile and adaptable for so many products that are used in the construction and building industry.
Construction plastics are prolifically used within the construction industry because they are so versatile. Their strength-to-weight ratio makes them easy to transport and manoeuvre within the building site. Plastic is also resistant to corrosion and has very good weather resistance. The ability to form and shape plastics gives them the advantage of maintaining their integrity, however, where joints are required, and they have excellent sealing properties due to the ability to solvent weld many types together to create a permanent bond.
In order to review material suitability to products, let’s have a look at some typical products and evaluate the different materials that may be suitable.
Pipes are one of the most common uses for construction plastics because there are just so many applications! Sewage, general plumbing, electrical conduits, gas, and the list goes on. Each of these applications requires different plastic properties, so let’s see which polymers might be good options for which use.
There are generally three main types of plastic used in water pipe manufacturing, PVC, CPVC, and PEX. Let’s explore each and the specific properties that make them suitable for use with water.
Polyvinyl Chloride (PVC)
Polyvinyl Chloride, or PVC, is predominantly used to carry mains water throughout a building. It has a very high moisture resistance giving it a long life expectancy without degradation. It has a relatively low melting temperature and will start to deform at around 140℉ making it unsuitable for the transfer of hot water. It does, however, have a low operating temperature of around -20℉ which makes it suitable for cold water transfer.
Typical applications for PVC pipes:
- Mains water supply
- Cold water transfer
- Sprinkler systems
Chlorinated polyvinyl chloride (CPVC)
CPVC is a chlorine-treated PVC material which gives it greater performance over standard PVC. With a higher melting temperature than PVC, CPVC can handle temperatures up to 200℉ making it capable of transferring hot water, and can also withstand greater pressures than standard PVC.
Typical applications for CPVC pipes:
- Hot and cold water transfer
- Fire sprinkler systems
Cross-linked polyethylene (PEX)
PEX has very good thermal resistance at both cold and hot temperatures (-20℉ to 200℉) making this a very good material for the plumbing of hot and cold water throughout a building. It is dimensionally stable over an extended period of time and does not corrode or degrade with time. It can also withstand high pressures and is suitable for pressurized water systems throughout a building.
Typical applications for PEX pipes:
- Hot and cold water transfer
- High-temperature water transfer through underfloor heating systems
- Fire sprinkler systems
Here, safety is paramount and material choice for transferring natural gas is critical because there is zero room for error. There can be no leaks, cracked pipes, degradation of joints over time, or any other potential faults that could result in gas escaping and cause an explosion and fatalities.
There is one plastic that meets all these criteria and that is Polyethylene (PE).
MDPE & HDPE
The gas pipe, always yellow in color for easy identification, is produced in either medium-density polyethylene (MDPE) or high-density polyethylene (HDPE) and is produced in a continuous extrusion and wound onto large diameter drums.
Image source: https://www.watersandfarr.co.nz/product/gas-imperial-polyethylene-pe-pipe-10200-mm-id/
HDPE yellow gas pipes are suitable for systems with a pressure of less than 125 psi.
Advantages of HDPE for gas pipes:
- Lightweight plastic makes it easy to transport and manoeuvre on-site and during project construction.
- Easy to join with heat fusion technology – this is also a safety critical element and all joints need to be 100% error-free.
- Excellent impact resistance making this suitable for construction projects and being able to withstand the impacts during installation of pipes
- Chemical resistance as well as excellent corrosion resistance over a long period of time.
- A life expectancy of fifty years or more makes HDPE a material that does not require maintenance or replacement during its lifecycle.
Disadvantages of HDPE:
- Low to medium pressure installations only, HDPE cannot withstand high pressures.
Windows and Doors
Here we can look at the different sections of a door or window, the framework, the door panel, and the window pane. Let’s have a look at each of these and consider which construction plastics are suitable for which application.
Window or Door Frames
There are many advantages of using plastic as opposed to wood for window and door frames, they are more cost-effective, need very little maintenance during their lifespan, they do not expand or contract in hot or cold weather to the point they will not close or let in a draft of air. For double glazed windows and doors, they offer greater cost savings over time as they are more efficient at controlling room temperatures.
So what material is used to create these frames?
The main plastic for window and door frame construction is Unplasticized Polyvinyl Chloride or UPVC which is a strong stiff plastic that can be easily extruded into complex cross sections that maintain their dimensional stability over time.
Advantages of UPVC:
- Easy to extrude with complex cross-sections
- Weather and UV resistant
- Requires very little maintenance
- Good thermal operating range
- UPVC is inherently flame retardant
- Can construct different shapes and size frames
- High impact resistance provides good security
- Can be colored to replicate other materials such as wood grain
Disadvantages of UPVC
- Low resistance to solvents and can cause stress cracks
- Become brittle at 40℉ so not ideal in extremely cold areas – to improve this, UPVC can be modified so it has a greater temperature range
- Maximum upper-temperature range of 120℉
Window Pane or Glass Replacement
There are two plastics that dominate the glass-replacement space, Polymethyl methacrylate or PMMA, which is best known as acrylic, and polycarbonate or PC.
We have looked at both of these materials in this guide [link], but here is a summary of both plastics:
In sheet form, it is branded and known as plexiglass acrylic sheet and is a popular alternative to glass window panes for a multitude of reasons.
- Cost Effective: The cost to manufacture sheets of acrylic is far less than it is to manufacture glass, it takes less energy to produce. Due to being lighter than glass, it is cheaper to transport.
- Strength: with excellent impact strength up to 17 times greater than glass, acrylic takes a lot more force to break.
- Safety: when glass breaks, it shatters into tiny pieces and these pieces of glass can be extremely sharp and dangerous. Acrylic on the other hand does not shatter the same way as glass when it is broken, it tends to break into larger sections which are less dangerous.
- Stability: Acrylic is more stable with its integral strength for larger window panes. The larger the dimensions, the more traditional glass becomes difficult (almost impossible) to manoeuvre and the risk of damage and breakage increases, whereas with acrylic, creating larger size panes is not an issue, the weight makes it easier to manoeuvre and has a reduced risk of damage or breaking.
Despite the fact that polycarbonate is more expensive than acrylic, its superior properties compensate for that fact. Let’s have a look at some of these properties which make it a better option than both glass and acrylic.
- Strength: PC is 250 times stronger than traditional glass and up to 30 times stronger than acrylic. Because of its excellent impact strength, polycarbonate is the preferred plastic for security glass, bulletproof windows and for buildings that need to withstand extreme weather conditions.
- Safety: as we mentioned, polycarbonate is 250 times stronger than glass and will not break. Even in the most extreme cases, polycarbonate will not shatter or break into pieces which makes this a very safe plastic as a glass alternative.
- Adaptability: polycarbonate can be modified during the manufacturing process to improve or alter the performance of the finished sheet, it can be tinted to have a reflective side to deflect heat from the sun, it can have anti-static properties added if required and it can be formed and shaped without heat making it ideal for applications that need window panes formed onsite during installation.
Summary for Plastics in the Construction Industry
The building industry is a harsh environment for plastics to function in, however, some of the construction plastics used last as long as a building is standing without any maintenance or replacements. The key thing here is the plastic choice and the application.
Pipes play a major part in the construction industry, from supplying clean water to transporting that water around a building and then removing the dirty water out of the building. Water is not the only commodity being utilizing pipes in a building, gas it also piped around a building. Both of these commodities need to be securely moved under pressure with the slightest of leaks.
The three main plastics used for water are:
- Polyvinyl Chloride (PVC) – used for mains and cold water distribution
- Chlorinated polyvinyl chloride (CPVC) – used for cold and hot water distribution
- Cross-linked polyethylene (PEX) – used for high-temperature water distribution
As for gas pipes, there is basically one predominant plastic used in the industry, Polyethylene in either medium density or high-density variation (MDPE) and (HDPE).
When it comes to other plastic parts used within building construction, we look at all sorts of parts, however, the plastic most consumed in the production of building parts, including window and door frames is Unplasticized Polyvinyl Chloride or UPVC which is a strong stiff plastic that can be easily extruded into complex cross sections that maintain their dimensional stability over time.
When it comes to glass window pane plastic replacements we are looking at two primary candidates, Poly(methyl methacrylate) or PMMA, which is best known as acrylic, and polycarbonate or PC. Both of these plastics have excellent clarity, are lighter than glass and withstand impacts better. However, if you are looking for something more ‘bulletproof’ then polycarbonate should be your plastic of choice. In fact, the PC is used as a bulletproof material in many applications that require that level of impact resistance.