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Questions and Answers
Polycondensation involves the creation of water as a byproduct.
Polycondensation involves the creation of water as a byproduct.
True
Thermosets can be melted and reshaped after hardening.
Thermosets can be melted and reshaped after hardening.
False
Amorphous plastics are disordered and brittle.
Amorphous plastics are disordered and brittle.
True
Thermoplastics have strong covalent bonds that remain intact at high temperatures.
Thermoplastics have strong covalent bonds that remain intact at high temperatures.
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Polyaddition requires a catalyst and high pressure or temperature to proceed.
Polyaddition requires a catalyst and high pressure or temperature to proceed.
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Elastomers are rigid and do not change shape upon temperature increase.
Elastomers are rigid and do not change shape upon temperature increase.
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Semi-crystalline plastics are partially ordered and often have better thermal resistance than amorphous plastics.
Semi-crystalline plastics are partially ordered and often have better thermal resistance than amorphous plastics.
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Polymerization reactions include only polycondensation.
Polymerization reactions include only polycondensation.
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Study Notes
Plastics Composition
- Plastics are composed of carbon-hydrogen bonds.
- Monomers form polymers.
- Two main polymerization reactions exist: polycondensation and polyaddition.
Polycondensation
- Combines two or more different or identical substances.
- Creates water as a byproduct, which must be managed.
- Examples include polyester, polyether, and polyamide.
Polyaddition
- Combines two identical or different substances.
- Rearranges the atoms of the monomers.
- Requires a catalyst and high pressure/temperature.
- Produces no byproducts.
Types of Plastics
- Plastics are categorized into thermoplastics, elastomers, and thermosets.
Thermoplastics
- Melt when heated.
- Covalent bonds are strong and resistant to temperature.
- Also have intermolecular forces (e.g., hydrogen bonds), which can weaken with increasing temperature.
- Can be linearly plastically and deformable.
- Amorphous thermoplastics are disordered (glassy, transparent, brittle).
- Semicrystalline thermoplastics are partially ordered with crystallites (ductile loops, opaque, better thermal resistance).
- Examples include: PP (Polypropylene), PE-HD (high-density polyethylene), PE-LD (low-density polyethylene), PE-LLD.
Elastomers
- Soften at room temperature.
- 2D or 3D network with large meshes and connections between chains.
- Have rubber-elastic properties, allowing them to spring back.
- Examples include EPDM (ethylene-propylene-diene-monomer).
Thermosets
- Have a 3D network structure with strong connections between chains.
- Rigid structure.
- Harden chemically, not through melting.
- Resistant to high temperatures.
- Can't be melted again without decomposing.
- Examples include Bakelite, Melamine formaldehyde.
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Description
Explore the fascinating world of plastics, focusing on their composition, polymerization reactions like polycondensation and polyaddition, and the various types of plastics such as thermoplastics, elastomers, and thermosets. Test your knowledge on key concepts that define the behavior and applications of different plastics.
