Chapter 3 L07 Flashcards
Name the definition of plastics
Plastics are macromolecular materials whose essential components are organic, which are synthetically or naturally formed
List 3 fields where plastics are used. Give one example for each.
Medicine: Rubber Gloves
Data Storage: DVD
Electronics: Insulator for cables
What is vulcanization?
It is proccess to enhance the mechanical properties of rubber by creating new cross-links. Two things are needed:
- Curatives: Sulfur normally
- Heat
Name 5 important features of plastics. Tell some difference between plastics and metals&ceramics
Density is the main difference between plastics and metals&ceramics. 5 important features:
- Wide range of mechanical properties
- Low processing temperatures
- Thermal and electrical insulators
- Chemical resistance
- Recycable
Order this elements form lower to higher density:
Plastics, titanium, iron, ceramics, aluminium
Plastics < Aluminum < Ceramics < Titanium < Iron
Describe the structure of plastics
- Plastics are macromolecular structures consisting of individual molecules called monomeres
- The union formed by monomeres is called polymer.
- They main chain consists of Carbon atoms
Name the 3 Polymer Synthesis (production of polymers) and describe one in detail.
- Polymerization (double bonds)
- Polycondesation (reactive functional groups)
- Polyaddition (Rearangement of H of 2 different monomers)
List all plastic groups and one characteristic from them
- Thermoplastics: Can be melted as often as desired
Amorphous: Transparent and brittle at room T
Semi-crystalline: Viscoplastic material behavior - Elastomers: Cannot be melted after vulcanization.
Used as force transmitters, not for construction - Thermosets: Cannot be melted after vulcanization. Constant material properties up to thermal failure
What are the main forces responsible for the bonding of polymeres?
- Inside the monomere, covalent bonds
- In between monomeres, weaker forces like Hydrogen bonds
Difference between thermoplastics and thermosets based on the polymer structure
“Notes”
What is a copolymer?
A polymer consisting of two or more monomers
Explain the influence of temperature in plastics
Temperature affects plastics in 2 ways:
-Glass transition temperature: Above this temperature, plastics go from a brittle state into a rubbery state
-Changes the Shear Modulus (G, resistance to deformation under shear forces): At higher temperatures G is lower for all plastics
Name one advantage and one disadvantage of plastics compared to metals
- Advantage: Plastics have a higher toughness than metals (elongation to failure)
- Disadvantage: The thermal resistance of plastics is significantly lower than the ones of metals
Explain why is it important to consider different material properties for the design of plastic components.
A new plastic-metal component can be created
Difference between recycling of virgin and mixed thermoplastics
Mixed thermoplastics are harder to recycle than virgin plastics. The steps for recycling plastics are: Shredding (trituracion), Washing, Drying and Melting. For mixed thermoplastics the melting point is harder to reach as there are incompatibilities between the plastics
