07 Plastics

Historical examples of plastics (2)

• Goodyear (1839) and the rubbern (vulcanized caoutchouc)

• Celluloid

Def: plastics

• Materials whose components consist of such macromolecular organic compounds that are formed synthetically or by transformation of natural products

• Plastically moldable under heat and pressure conditions

Name the fields of application of Plastics (8)

• Packaging

• Electrical and electronics

• Communication technology

• Automotive

• Data storage

• Mobility

• Renewable energies

• Medicine

What aspects are related to Plastics Technology? (3)

• Material

• Processing

• Design

What does Plastic Processing depend on? (5 + Ex)

• Design requirements

• Material properties

• Quantity

• Reinforcements?

• Tool mold or production options

• Ex: Vessels

  • It is not the same a HP vessel made to withstand up to 700 bar

  • than a tupper (also a vessel) to store food

What is comprised within Plastic Design? (5 + Ex)

• Processing

• Material

• Function

• Service requirements (mechanical, chemical and physical reqs.)

• Installation space

• Ex: Vessels

  • Pressure vessel carbon winding with different winding methods (polar, helical, hoop)

  • Injection molding rule (draft angles for demolding)

Organize following materials as a function of their density: Al, Fe, Ceramics, Plastics, Ti

• Plastics (0.8 - 2.2 g cm^-3) < Al < Ti < Fe < Ceramics

Characterize Plastics (10)

• Adjustable spectrum of mechanical properties

• Economic

• Low processing temperatures

• Good thermal insulation

• Good electrical insulation

• Variety of colors

• High chemical resistance

• Permeable

• Recyclable

• Lightweight

What is retardation when talking about polymers?

• Analogous to the creep for solid materials

How is visco-elastic behavior described?

• Mathematically through Maxwell’s spring-damper model for e.g. polymer melt

• Through Kelvin’s mode

What are the main mechanisms of Polymer Synthesis? (3)

• Polymerization

• Polycondensation

• Polyaddition

What is Polymerization? (2 + Ex)

• Formation of polymers by linking monomers

• Can be radiacal, ionic or coordinative

• Ex:

  • Polyehtylene (PE)

  • Polypropylene (PP)

  • Polystyrene (PS)

What is Polycondensation? (1 + Ex)

• Reaction of monomers + release of small molecules

• Ex:

  • Polyamide

  • Polyester (Polyethylene Terephthalate = PET)

  • PBT

  • Bakelite

What is Polyaddition? (1 + Ex)

• Monomer combination without by-product

• Ex:

  • Polyurethane (PUR)

  • Epoxy resins

In which groups are plastics divided?

• Thermoplastics: Amorphous and Semi-Crystalline

• Elastomers

• Thermosets

What are thermoplastics? (4)

• Plastics with linear ore branched molecules, with almost no crosslinking

• Amorphous: generally transparent

• Semicrystalline: more visco-plastic

• Can be melted as oft as desired

What are elastomers? (4)

• Syn: rubber

• Low degree of crosslinking

• Cannot be melted without undergoing breakdown processes

• Usually vulcanized

What are thermosets? (4)

• Cured plasticas

• Cannot be melted without undergoing breakdown processes

• Syn: duromers

• Constant material properties up to breakdown

Order the plastic types as a function of the degree of crosslinking of their molecules

• Thermoplastics < Elastomers < Thermosets

Which kind of intermolecular forces are present in plastics? (3)

• Keesom-Forces (dipole-dipole force between permanent dipoles)

• Debye-Forces (permanent dipole to induced dipole)

• Van-der-Waals-Forces (induced dipole to induced dipole (between non-polar molecules))

• Hydrogen bonds (stronger than Van-der-Waals)

What defines a meltable substance?

• Intramolecular forces > Intermolecular forces (able to change state before decomposing in its constituent elements)

What is copolymerization?

• Polymers with more than one kind of monomers

What are the types of copolymerization (4)

• Alternating Copolymer

• Statistical Copolymer

• Block Copolymer

• Graft Copolymer

What are alternating copolymer?

• Two monomers alternately lined up in the chain

What are statistical copolymer?

• Random arrangement of monomers

What are block copolymer?

• Monomers arranged in blocks of same monomers

What are Graft copolymers?

• 2-dimensional arrangement of monomers in blocks

What is the difference of miscible and immiscible blends?

• Miscible blends: homogeneous, single-phase, similar thermal properties

• immiscible blends: heterogeneous, multi-phase, different thermal properties

What are polymer blends used for?

• To tailor polymers by enhancing desired properties depending on the application

What is T_G? (3)

• Glass transition temperature (syn: softening temperature)

• Polymer changes form flexible to glassy/brittle state

• Border between rubbery and glassy

Mechanical Behavior of Plastics as a fct of Temperature (4)

• Elastomers: stable after certain point

• Thermosets: relatively stable

• Amorphous thermoplastics: abrupt drop after certain temperature

• Semicrystalline thermoplastics: two quick decrease points

Mechanical Properties of Plastics (E-Modulus) (2)

• Wide range of E-modulus

• Tailorability

Mechanical Properties of Plastics (Stress-Strain-Diagram) (2)

• Plastics are (in gneeral) extremely ductile

• Amorphous Thermoplastics: brittle behavior due to random chain arrangement

Thermal Properties of Plastics (2)

• Poor thermal resistance (relative low service temperatures)

• Very high thermal expansion

Thermal Properties of Plastics: Effects (1)

• Formation of huge residual stresses due to high thermal expansion

Electrical Properties of Plastics

• Extremely low electrical conductivity → very good electrical insulator (e.g. good for lighting strinke protection)

How can plastics originate? (2)

• Fossil-based

• Bio-based

What are recycling methods suitable for plastics? (2)

• Mechanical recycling (PCR) (Thermoplastic)

• Depolymerization (Thermoplastic)

• Pyrolisis (Thermoplasztic and Thermosets)

What End-of-Life options are there for plastics? (3)

• Composting

• Energy recovery (burning)

• Landfill disposal

What is necessary for plastic recycling?

• Sorting, at least in thermoplastics and thermosets

What are the steps of Mechanical Recycling? (4)

• Shredding

• Washing

• Drying

• Part Production

What is PIR? (3)

• Post Industrial Recyclate

• Made from rejected parts/offcuts

• Low influence of quality

What is PCR? (4)

• Post Consumer Recyclate

• Polymer sorting

• Different fabrication sources

• High influence quality

What are the steps for Solvolysis/Depolymerization? (6)

• Shredding

• Solve

• Filter

• Precipitation

• Drying

• Monomer

For which kind of plastics is Solvolysis normally used?

• Polycondensation plastics

What are the steps for Pyrolisis? (4)

• Shredding

• Pyrolisis

• Condensation

• Fractioning

  • Gas

  • Naphtha

  • Wax

What is Pyrolisis?

• Heating up plastic past breakdown temperature in absence of oxygen to get shorter hydrocarbon chains

Order plastics according to their degree of complexity (3)

• Vrigin Thermoplastics

• Mixed Thermoplastics

• FRP

Order recycling processes according to their degree of Utilization and Sustainability (3)

• Energy Recovery (not classified as recycling bc it needs high tech filters for the exhaust gases)

• Chemical Recycling and Pyrolisis

• Mechanical Recycling

SQ: Name the definition of plastics

• Materials whose components are macromolecular organic compounds

• Formed synthetically or by transformation of natural products

• Plastically moldable during processing under certain heat and pressure conditions

SQ: List three field of applications for plastics and give one explicit example in each case

• Packaging

• Automotive: vibration damping, car interior, insulation

• Mobility: FRP, leightweight construction, vibration damping

• Renewable energies: connections, organic solar cells, heat exchangers

• Medicine: everyday devices like contact lenses, disposable syringes, dressing materials, artifical blood vessels…

• Data storage: CD, etc

• Communication technology: plastic sheating for message transmision

• Electrical and electronics: insulator or sheting materials for cables, organic electronics

SQ: Name five important features of plastics

• Leightweight (low density)

• Adjustable spectrum of mechanical properties

• Economically machined

• Good thermal insulator

• Good electrical insulator

• High chemical resistance

SQ: Name all three types of polymer synthesis and explain one in detail

• Polymerization: covalent, ionic or coordination bonding between monomers e.g. Polyehtelene

• Polycondensation: reaction of monomers, releasing small molecules like water e.g. Polyamide or Polyester

• Polyaddition: monomer combination without by-products e.g. Epoxy Resins

SQ: List all Plastic groups and name one distinctive characteristic of each

• Thermosplastics: linear or branched with very low degree of interlocking. Can be melted as oft as desired

  • Amorphous

  • Semicrystalline

• Elastomers: rubber-elastic materials formed through vulcanization. Low degree of crosslinking. Breakdown before melting

• Thermosets: temperature stable up to thermal breakdown, need curing, cannot be melt after curing

SQ: Distinguish Thermoplastics of Thermosets bases on polymer structure

• Thermoplastics: consist of linear or branched molecules that are not covalently bonded to each other via crosslinking reactions. This allows them to melt repeatedly

• Thermosets: molecular threads that are closely crosslinked. This chemical reaction during curing makes them unable to be melted afterwards

SQ: Name on major advantage and disadvantages of plastics compared to metals

• Advantage: Plastics have a considerably higher elongation at break compared to metals like steel or copper

• Disadvantage: lower thermal resistance, with continuous usage temperatures ending where metals do not yet show temperature-dependent properties.

SQ: Explain the influence of temperature on plastics

• Transition between brittle glassy state to viscous state at glass transition temperature T_G

• Thermal unstable properties (in general)

• Extremely high thermal expansion coefficient

SQ: Explain why it is important to consider different material properties for the design of plastic components

• Plastic processing and design depend on specific requirements and material properties, meaning different applications demand specific manufacturing processes.

• Design considerations for plastics must focus on processing, material properties, and functionality, including mechanical, chemical, and physical requirements.

• Understanding material properties like thermal expansion is crucial, especially when combining plastics with other materials (e.g., metals), to prevent issues like residual stresses and deformation.

SQ: Explain the difference between recycling of virgin and mixed thermoplastics

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