A lot of your expensive appliances such as a refrigerator, freezer, air conditioner, and coffeemaker in your home or office are made with plastic. Therefore, you think you might be at the risk of losing them to fire. Let’s look at if plastic is flammable.
Is plastic flammable?
YES. Plastic is flammable and burns almost immediately after it catches fire. Countries with fire and building codes have marked plastic as a flammable material. However, different plastics have unique qualities. Therefore, the rate at which they burn differs from each other.
It’s necessary you have some knowledge of what causes the plastic to burn. Also, you need to know about the different plastics that you might have around you, as well as their qualities.
This helps you in deciding your choice of devices and appliances and lessens/prevents the risk of losing them.
What causes plastic to burn?
Plastic is identified as a material, totally or partially synthesized, that contains polymers as the major constituent.
Plastic is made from chemicals gotten from fossil fuels (for example petroleum) and substances obtained from corn and cotton. These substances are highly flammable when ignited.
However, plastic is not instantly obtained from these substances. They subjected these substances to different processes to produce the desired plastic.
How is plastic made?
The first major step in the production of plastic is the linking or networking of different units of its starting materials, known as monomers. This process is referred to as polymerization.
The polymerized material is, however, not sold unaltered. Different materials, known as additives, are mixed with it to enhance its lifespan, tensile strength, appearance, and other properties.
These additives may include pigments, dyes, stabilizers, flame retardants, and plasticizers.
In some other cases, different polymerized materials are mixed to create a polymer blend with the combined properties of different polymers.
Plastics are grouped into several classes, but a major classification is into thermosetting plastics (thermosets) and thermoplastics based on the reversibility of the chemical processes involved in their production.
While thermoplastics are unchanged chemically when heated and can be molded repeatedly, thermosetting plastics break down chemically when heated. Thus, they can only take a solid shape once.
Therefore, the mixing of additives with thermosetting polymers comes with ease since they remain liquid after polymerization.
However, mixing additives with thermoplastics after polymerization requires the melting of these polymerized materials into molten form before mixing. This process occurs at a temperature range of 150 – 320 degrees centigrade.
The mixed materials are then processed into different shapes by different extrusion machines. These machines include those that use methods such as film blowing, blow molding, injection molding, and others.
Different plastics have unique properties, such as density, thermal resistance, and hardness, depending on the type of monomers and additives they are made from.
This influences their respective flammability and applicability. Let’s review some commonly used plastics in society and their properties.
Types of plastics
1. Polyethylene (PE): This is the most commonly used plastic in the world today. It has found use in detergent bottles, grocery bags, toys, as well as automobile fuel tanks.
It is classified as a thermoplastic and is also grouped as a commodity plastic because of its everyday use. Its starting material or monomer is ethylene, hence the name polyethylene.
The major polyethylene compounds include low-density polyethylene (LDPE), high-density polyethylene (HDPE), and linear low-density polyethylene (LLDPE).
These compounds differ in their chemical structures. This, therefore, affects their properties. While LDPE and LLDPE exhibit similar characteristics and are flexible materials, HDPE is of high strength and moderately stiff.
The melting point of LDPE is approximately 110 degrees centigrade while that of HDPE is found to be between the range of 120 – 130 degrees centigrade. Also, the thermal conductivity of LDPE is approximately 0.33W/mK while that of HDPE varies between 0.45-0.52W/mK
2. Polyvinyl chloride (PVC): This is recognized as the world’s second-most used plastic material. Because of its high tensile strength, it has been used to produce varieties of products such as hoses, water pipes, and blood bags.
It is classified as a thermoplastic and is also grouped as a commodity plastic due to its application found in everyday products.
The starting material of PVC is vinyl chloride, hence, the generic name. It has some crystallinity in its structure and thus exhibits its strength from this.
It can, however, be made flexible by using additives such as plasticizers. Therefore, it can exist in rigid or flexible forms.
The melting point of PVC is 85 degrees celsius and its thermal conductivity is found to be between 0.12-0.25W/mK.
3. Polypropylene (PP): This is the second-most widely produced plastic in the world today. It has high flexural strength and good impact strength and has thus been used to produce home appliances, toys, crates, bottles, pots, food trays, ropes, and pill containers.
It is also a thermoplastic and is grouped as a commodity plastic due to its application found in everyday products.
The starting material or monomer of PP is propylene, which belongs to the olefinic class ethylene. It has varying degrees of crystallinity in its structure, which determines its rigidity in nature.
Because of these structural varieties, it is divided into three distinct types based on the degree of crystallinity of each structure.
Isotactic PP has high crystallinity, syndiotactic one with less crystallinity and atactic PP is non-crystalline (amorphous) in nature.
The melting point of PP depends on the percentage of the crystallinity in its structure and is thus a varying entity. The thermal conductivity is found to be approximately 0.2W/mK.
4. Polyethylene terephthalate (PET/PETE): This has been found to be an easily recycled plastic. It has found applications in the production of disposable beverage bottles, fabrics, carpets, rugs, mats, and pillows.
It is a thermoplastic and a commodity plastic because of the application found in everyday products.
It is formed from the condensation polymerization of ethylene glycol (a diol) and terephthalic acid. Thus, the monomer is an ester formed from the chemical reaction of these 2 starting materials.
PET is highly flexible and semi-crystalline. It can, however, be made rigid or semi-rigid, based on the mode of production adopted.
The melting point of PET is estimated to be approximately 260 degrees centigrade and its thermal conductivity occurs within the range of 0.15-0.30W/mK.
All the plastic above are flammable even when they differ in properties from each other. A PVC plastic might burn slowly compared to PET plastic. However, they are all still flammable.
Therefore, it is better to stay away from fire and fire-causing agents, especially when you have an important appliance/property/device to protect.
Sit down! Have a critical review of what you want and what you have before choosing your choice of plastic and where to keep them.