Thermoplastic or thermosetting plastics are the two major classifications of plastics or polymers that are mainly differentiated on the basis of their response when exposed to heat. The difference between thermoplastic and thermosetting plastic is that a thermoplastic when exposed to heat becomes soft thus is capable of getting remolded again and again by reheating. As against, thermosetting plastic is a type of plastic that gets hard on heating and does not support remolding.
More simply, thermoplastics offer reshaping with multiple heating whereas in thermosetting after initial heating, the plastic gets strengthened and takes an appropriate shape, and cannot be remolded.
Majorly the reason behind showcasing different behavior on the application of heat is related to their formation and the type of forces existing between them.
What is Plastic?
Plastic is a special type of polymer. Polymers are basically composed of small or uniform molecules whereas plastics are composed of long-chain polymers. Monomers (i.e., a combination of various small identical molecules) form polymers. In general use, the word plastic is used in place of polymers and the reason is plastics are composed of polymers.
Condensation and addition polymerization reactions give rise to plastics. The two major categories in which plastics are categorized are thermoplastic and thermosetting plastics and here we will discuss how the two are differentiated on the basis of various factors.
Content: Thermoplastic Vs Thermosetting Plastic
Comparison chart
| Basis for Comparison | Thermoplastic | Thermosetting Plastic |
|---|---|---|
| Formation/ Synthesization | By addition polymerization reaction. | By condensation polymerization reaction. |
| Initial existing form | Solid | Soft solid or viscous liquid |
| Nature possessed | Weak and less brittle. | Comparatively hard and more brittle. |
| Molecular weight | Less | More |
| Remolding | Possible | Not possible |
| Type | Linear polymer | Cross linked polymer |
| Solubility | Soluble in organic solvent | Insoluble in organic solvent. |
| Melting point | Low | Comparatively high |
| Force existing | Van der Waal | Covalent bond |
| Branching | Long chain orientation with slight branching. | Heavy branches with linked structure. |
| Tensile strength | Low | High |
| Bending | Easy | Not easy |
| Cost | Expensive | Inexpensive |
| Example | PVC, Teflon, Polythene, Nylon, etc. | Epoxy, Silicone, Bakelite, Urea formaldehyde resin, etc. |
Definition of Thermoplastic
Thermoplastics are defined as the class of polymers that are showing less resistance towards heat and thus can be easily reshaped with continuous application of heat. Basically, the monomers whose combination constitutes the thermoplastics are bonded together by Van der Waals forces that exhibit weak attractive forces. Due to this weak force of attraction, the application of heat easily softens the plastic. This permits molding the plastic into various shapes by softening.
The thermoplastics possess a low melting point thereby offering easy melting thus do not suit high-temperature applications.
Polyethylene is considered to be one of the best examples of thermoplastics and is generally finds use in covering rigid bodies like electrical equipment. Also, adhesives like acrylates, epoxy are also thermoplastic polymers.
Definition of Thermosetting Plastic
Thermosetting plastic exists in soft solid or liquid form but is strengthened and solidified on heating. By the application of heat, such chemical reaction takes place because of which cross-linking between polymer chains increases. Due to this reason, once after getting hardened, it is not possible to remold it by the application of further heat.
These possess three-dimensional structures and are irreversibly rigid. One of the crucial behaviors that thermosets exhibit is that they permanently deform when encounters with excessive load and also show a more brittle nature in comparison to thermoplastics.
The various examples of thermosets include polyester resin, bakelite, melamine, polyurethane, etc.
Key Differences Between Thermoplastic and Thermosetting Plastic
- The key factor of differentiation between thermoplastic and thermosetting plastic is that thermoplastic exists in a solid-state at room temperature but when heated or reheated it becomes soft and is remolded into the desired shape multiple times. As against, thermosets or thermosetting plastics exists in solid or viscous liquid form but once heated they get strengthened and after getting molded into a specific shape they cannot remold even after providing additional heating.
- The thermoplastics are synthesized by performing an addition polymerization reaction whereas thermosets are formed when condensation polymerization reaction takes place.
- Thermoplastics are generally weak in nature and exhibit a less brittle nature, whereas, thermosetting plastics are hard and possess a more brittle nature.
- We have already discussed that polymers are formed when various monomers are combined. In order to combine multiple monomers, the molecular force of attraction existing in the case of thermoplastics is Van der Waal forces whereas, in the case of thermosets, a strong hydrogen bond combines the molecules.
- The orientation of thermoplastic is such that the molecules are arranged in long-chain with slight branching whereas thermosetting plastics offer a cross-linked structure which is the result of complex branching.
- As we have already discussed that thermoplastics get easily remolded with the application of heating thus they possess a small value of melting point. On the contrary, thermosetting plastics hold the ability to withstand high temperatures as these do not change their shape obtained after initial heating even on applying further heating hence the thermosets exhibit a high melting point.
- Thermoplastics offer recycling ability as heating the plastic makes it soft and then it can be reused easily according to the requirement. While thermosets do not offer to recycle as they resist deformation after getting shaped once thus in not reusable.
- Thermosetting plastics are considered to be more cost-effective in comparison to thermoplastics.
- The tensile strength possessed by thermoplastics is low and this allows them to get bent easily whereas thermosets have high tensile strength and due to this reason they are not easy to bend and forcible bending may lead to cause breaking.
- Thermoplastics show high solubility when dissolved in organic solvents whereas this is not the case with thermosetting plastics as they are insoluble in organic solvents.
Conclusion
Thus, we can conclude that thermosets offer high dimensional stability than thermoplastics and the reason for the same is that thermosets are more chemical and heat resistant than the thermoplastics.