PVC is one of the most widely used plastics, particularly in the building sector. After all, your home has a drainage, sewage, and water system. Did you know that PVC pipes make up most of the pipes in these systems? What would happen in an accidental fire since PVC is plastic? Is PVC flammable, though?
Before answering whether PVC is flammable, we first define PVC. We also answer what happens to PVC in a fire, including what it releases, its flashpoint, if it is toxic, and whether it can be recycled. We conclude by explaining the properties and uses of PVC.
What is a PVC Pipe?
Polyvinyl chloride, or PVC, is a type of chlorinated hydrocarbon polymer. It is a combination of vinyl and plastic. PVC is widely used for making water pipes, among other things. Heated PVC is pushed into hollow pipes using an extruder. These PVC pipes are highly durable and practically unbreakable. Schedule 40Pvc and schedule 80Pvc PVC pipes are the two most well-known types.
PVC is hard and brittle without the addition of chemicals that boost its malleability and resistance to high temperatures. Plasticizers, heat stabilizers, and UV stabilizers are a few of the additives.
PVC pipes are classified into four main categories for various applications.
- C-Pvc: Chlorinated Pvc pipes are perfect for water piping systems in commercial and residential systems because they can withstand various temperatures. These pipes are more ductile and completely recyclable.
- Pvc-U: Unplasticized Pvc, which means that there is no plasticizer additive. It’s the most common Pvc for making all types of pipes. Its best qualities are high chemical resistance, durability, and mechanical performance.
- Pvc-O: The unclear structure of Pvc-U is transformed into a layered structure by molecularly oriented Pvc. Pvc-O improves the impact and fatigue resistance, flexibility, and hydraulic capacity of Pvc-U. They are best suited for underground pipes.
- Modified Pvc(Pvc-A, Pvc-HI, Pvc-M): These thermoplastic alloys are produced by combining Pvc with the required modifying chemicals. As a result of the agents’ increased Pvc durability, thinner-walled PVC pipes are made with less material.
- Pvc-HI is High Impact Pvc. Pvc-U is added as an impact modifier to increase the pipes’ resistance to outer blows. Natural gas and hydrogen can be transported with ease using these pipes.
Is PVC Pipe Flammable?
The PVC pipe is not flammable. Because a PVC pipe doesn’t burn until a flame is present, it is regarded as self-extinguishing. A PVC pipe is naturally fire-resistant due to its chemical structure’s high concentration of chlorine ions. When exposed to heat, chlorine ions are particularly difficult to separate. Additives and the limiting oxygen index are other factors that make PVC pipe not to be flammable.
Although a Pvc pipe can eventually catch fire, its flames burn slowly. Pvc pipe is treated with additives such as d-limonene, borax, and glycol to reduce its flammability. Burning the Pvc pipe triggers water release, slowing the burning process. Another byproduct of Pvc burning, hydrogen chloride, slows burning by preventing oxygen from reaching the PVC surface.
The limiting oxygen index is another factor that makes Pvc not flammable. The oxygen index of PVC is 48. The oxygen index is the lowest oxygen concentration at which a material will begin to burn when exposed to a mixture of nitrogen and oxygen. A compound with a high limiting oxygen index is difficult to burn.
What Happens to PVC in a Fire?
Pvc ignites and quickly begins to burn. It starts to soften at around 200°F (93°C) before becoming a thick liquid at temperatures of 350°F (178°C). The Pvc will burn if exposed to any hot flame that reaches such temperatures. The surrounding environment is protected from heat when the Pvc melts, producing a carbonaceous layer.
There are several stages that Pvc goes through when burning. Here is a demonstration:
Is PVC Toxic?
At standard temperatures, Pvc does not release any toxic gases. Pvc, however, releases fumes at temperatures of 140°F (60°C). Burning Pvc produces the harmful byproduct formaldehyde, a key ingredient of acetaldehyde, a known carcinogen. The more hazardous substances released by Pvc include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, and nitroaromatic hydrocarbons (nitrates).
When Pvc burns, volatile organic compounds (VOCs) such as xylene, toluene, and benzene are also produced. To improve the quality of Pvc, various chemicals are frequently added. These additives include phthalates, lead, fungicides, and other toxic substances. Sadly, these compounds wash off PVCs fast, making them deadly for anybody who comes into contact.
Unfortunately, harmful chlorine-based chemicals are released during Pvc’s production, usage, and disposal. These chlorine-based chemicals, also known as organochlorines, are present in our food, water, and environment. Organochlorines are resistant to breaking down and are not excreted by humans or animals. The pollutants can remain in the environment for many years.
As a result, the toxins cause harm to people, animals, and plants, which results in problems such as the ones listed below:
- Impaired childhood development,
- Hormonal disruption,
- Immune system damage,
- Mental health issues.
Flashpoint of PVC
Pvc has a flashpoint of 736°F (391°C). A substance’s flashpoint is the lowest temperature at which a vapor or liquid produces enough heat to ignite. Pvc has an almost 150°C higher flashpoint than wood. The flashpoint of Pvc with additives is higher than that of standard Pvc. Pvc undergoes softening, melting, flowing, and pyrolysis at high temperatures.
What Does PVC Release When Burned?
Pvc releases water (H2O), carbon dioxide (CO2), and hydrogen chloride (HCI). Pvc is a plastic with a long hydrocarbon chain. Plastic primarily consists of hydrogen and carbon. Dihydrogen monoxide (water) is released when hydrogen is burned. Carbon dioxide and carbon monoxide are produced when carbon is burned. Even though Pvc contains chlorine ions, burning it does not produce chlorine gas.
Water may not cause any harm, but hydrogen chloride reacts with water to form hydrochloric acid. The corrosive acid spreads faster than the flames and overpowers the people around the burning area. Unless it takes the place of oxygen in your breathing system, carbon dioxide is not harmful. Carbon monoxide kills because it binds to the blood at the oxygen receptor and cannot be expelled.
However, when chlorine-based materials burn, dioxin and dioxin-like chemicals, persistent organic pollutants (POPs), are released. Unfortunately, Pvc is the source of most environmental dioxin compounds. Dioxin is typically released as ash and soot in fires involving Pvc.
Can PVC Be Recycled?
If Pvc is made of a single material, recycling it becomes simpler. Burning Pvc is not the best method of recycling due to the numerous toxic chemicals it releases, and letting it decompose naturally can harm the environment. Fortunately, Pvc can be recycled more than six times and last up to 600 years.
Pvc can be recycled in two ways:
- Mechanical recycling: Before cleaning the wastes, PVC is mechanically processed by being ground into small particles. Then, the particles are remelted and reshaped to manufacture the same product or a new one. It is optional to include fresh material.
- Chemical recycling: The Pvc waste transforms using specialized chemical methods like hydrolysis or pyrolysis. The end products are either added to other manufacturing processes or used to create new Pvc.
Find out if your neighborhood recycling facility takes waste Pvc before placing it in your recycling containers. By calling them, you can ask whether to deliver the PVC waste to their facility or have them pick it up.
Read: Is Helium Flammable?
Properties and Uses of PVC
Pvc are naturally white and brittle. The addition of additives improves the properties of Pvc. Hence we have the rigid and flexible Pvc. Each Pvc form has various uses across multiple industries.
Properties of PVC
Pvc properties are summarized in the table below.
|Properties of Pvc
|-It can be molded with heat, making it easy to work.
|-Resistant to corrosion, weathering, abrasion, shock, and chemical rotting.
|-Resistant to all inorganic chemicals such as diluted alkalis, aliphatic hydrocarbons, and acids.
|High dielectric strength
|-A good insulation material.
|-Self-extinguishing due to high chlorine content.
|-Needs low maintenance and has excellent cost-performance benefits.
Uses of PVC
Due to its strong fire resistance, Pvc is widely used in interior and exterior building components. Here are a few examples:
- Pvc water supply pipes supply water to residential and commercial buildings for plumbing and drainage purposes. Due to their resistance to bacterial contamination, water companies frequently use Pvc pipes.
Pvc pipes are often used in large irrigation networks to supply water. Using Pvc pipes for irrigation saves water and avoids salinizing, swamping, and cold soil flooding. The pipes are underground, resulting in a high land usage rate.
For the drainage of rainfall from roofs and other structures, underground Pvc pipes with a bigger bore and thicker walls are employed. Additionally, they can be used to develop sprinkler systems for landscaping and fire sprinkler systems for buildings.
- PVC sanitation sewer networks: It is the ideal material for sewer networks due to ease of installation, cost efficiency, chemical resistance strength, and a wider range of available diameters.
- PVC electricity and telecommunications systems: Used in making electrical cables, wire coverings, switch boxes, insulating tapes, cable coverings, and protecting tubes for power and telecommunication cables.
- PVC for heating and cooling systems: PVC is the best material for Heating, Ventilation, and Air Conditioning (HVAC) because it resists corrosion and rust. PVC is resilient, strong, and resistant to a variety of factors. Due to its insulation capabilities, the house won’t lose heat in freezing temperatures.
As a form of a chlorinated hydrocarbon polymer, PVC is inflammable. Chlorine ions, a limiting oxygen index, and additives slow down PVC burning. Burning PVC, however, releases many dangerous chemicals and should be avoided.
There are two approaches to recycling Pvc to create the same product or one completely different. Pvc is used widely in many industries because of its various properties.