The plastics which get deformed easily on heating are known as:
Thermo Plastics
Understanding Plastics: Thermoplastics vs. Thermosetting Plastics
Plastics are a broad range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Based on how they behave when heated, plastics are primarily classified into two main types: Thermoplastics and Thermosetting Plastics.
The question asks about plastics that get deformed easily on heating. Let's examine the characteristics of the two main types:
What are Thermoplastics?
Thermoplastics are polymers that become soft and pliable when heated and solidify when cooled. This process of softening and solidifying can be repeated multiple times without significant degradation of the material. This property allows thermoplastics to be easily moulded, extruded, or thermoformed into various shapes. Because they can be repeatedly melted and reshaped, thermoplastics are generally recyclable.
- They soften upon heating.
- They solidify upon cooling.
- The heating/cooling process is reversible.
- They can be easily remoulded.
- Examples include Polyethylene (PE), Polypropylene (PP), Polyvinyl Chloride (PVC), Polystyrene (PS), and Polyethylene Terephthalate (PET).
What are Thermosetting Plastics?
Thermosetting plastics, also known as thermosets, are polymers that undergo an irreversible chemical change (curing) when heated during their initial moulding process. Once cured, they become rigid and cannot be softened or remoulded by heating. Heating them further typically leads to degradation or charring rather than softening.
- They undergo irreversible curing upon heating.
- They become rigid and retain their shape once cured.
- They do not soften upon subsequent heating.
- Examples include Bakelite, Epoxy Resins, Melamine, and Polyester Resins.
Comparison of Thermoplastics and Thermosetting Plastics
Here's a comparison to highlight the difference in their behavior upon heating:
| Property | Thermoplastics | Thermosetting Plastics |
|---|---|---|
| Behavior on Heating | Soften and deform easily | Do not soften; become hard and brittle (char on excessive heating) |
| Structure | Linear or branched polymer chains with weak intermolecular forces | Heavily cross-linked 3D network structure |
| Remoulding | Can be remoulded repeatedly | Cannot be remoulded after initial curing |
| Recyclability | Generally recyclable | Generally not recyclable in the same way as thermoplastics |
| Strength & Rigidity | Lower strength and rigidity compared to thermosets | Higher strength and rigidity; more brittle |
Based on this comparison, the plastics which get deformed easily on heating are clearly Thermoplastics. This property is a defining characteristic that distinguishes them from thermosetting plastics.
Revision Table: Key Concepts
| Term | Definition / Property |
|---|---|
| Thermoplastics | Soften and deform easily upon heating; can be remoulded. |
| Thermosetting Plastics | Do not soften upon heating after initial curing; cannot be remoulded. |
| Polymer | Large molecule made of repeating subunits. |
Additional Information: Applications and Properties of Thermoplastics
The ease with which thermoplastics deform on heating makes them suitable for numerous applications where shaping and recycling are important. Their properties vary widely depending on the specific polymer:
- Polyethylene (PE): Used in plastic bags, films, bottles (like milk jugs), containers. Properties vary with density (LDPE, HDPE).
- Polypropylene (PP): Used in containers, fibers, car parts, laboratory equipment. Known for its strength and chemical resistance.
- Polyvinyl Chloride (PVC): Used in pipes, window frames, flooring, cables. Can be rigid or flexible depending on additives.
- Polystyrene (PS): Used in disposable cutlery, foam packaging (Styrofoam), CD cases.
- Polyethylene Terephthalate (PET): Used in beverage bottles, synthetic fibers (polyester). Known for its clarity and strength.
The ability of thermoplastics to deform upon heating is directly related to their molecular structure, which consists of long, linear or branched chains that can slide past each other when energy (heat) is applied. Thermosets, with their cross-linked network, prevent such movement, making them resistant to deformation by heat.
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