Pick up the non-inflammable plastic from the following:
🔬 Understanding Flammability in Plastics
Most plastics are organic polymers, primarily composed of carbon and hydrogen, which makes them inherently combustible. However, some plastics have a chemical composition that gives them natural fire-retardant properties. "Non-inflammable" in this context usually means the plastic is difficult to ignite and will stop burning once the external flame source is removed (self-extinguishing).
⚖️ Detailed Analysis of the Options
Let's examine the chemical nature of each plastic to determine its flammability.
(b) Polyvinyl chloride plastics (PVC)
Why it's correct: PVC has a high content of chlorine in its molecular structure. When PVC is exposed to fire, it releases hydrogen chloride (HCl) gas. This gas is non-combustible and heavier than air, so it displaces oxygen from the surface of the plastic, effectively smothering the flame. This gives PVC excellent, inherent fire resistance and makes it self-extinguishing. It is widely used for applications where fire safety is a concern, such as electrical wire insulation and conduit.
(a) Cellulose acetate plastics
Why it's incorrect: This plastic is derived from cellulose (wood pulp). While it is less flammable than its predecessor, celluloid, it is still an organic material that will sustain a flame and burn. It is not considered non-inflammable.
(c) Phenol formaldehyde plastics (Bakelite)
Why it's incorrect: As a thermosetting plastic, Bakelite has excellent heat resistance and will not melt. However, at high temperatures, it will char and eventually burn. It is not self-extinguishing in the way PVC is.
(d) Urea formaldehyde plastic
Why it's incorrect: Similar to Bakelite, this is a thermosetting plastic with good heat resistance. It is often used in electrical fittings. While it has better fire resistance than many thermoplastics, it will still char and combust under intense heat and is not considered non-inflammable.
💡 Study Tips for Plastic Properties
- Chlorine Cools the Fire: The key to PVC's fire resistance is its chlorine content. Associate the "Chloride" in Polyvinyl Chloride with its ability to choke out a flame.
- Thermosets Resist Heat, but Still Burn: Remember that thermosets like Bakelite don't melt, which gives them good heat resistance, but they are not truly non-flammable and will decompose and burn in a fire.
- Cellulose = Wood Origin: Plastics based on cellulose (like acetate) are derived from plant matter, which is naturally flammable.