POLYMER Flashcards
Polymers
High molecular weight compounds formed by the repeated union of simple molecules called monomers.
Origin of the word Polymer
Derived from Greek words “poly” (many) - “mer” (unit or part).
Definition of Polymer
A macromolecule made up of repeating structural units linked by covalent bonds.
Process of Polymerization
The formation of polymers from monomers through chemical reactions.
Natural Polymers
Found in plants and animals - e.g. rubber - silk - cellulose - and proteins.
Synthetic Polymers
Man-made polymers created through chemical reactions - usually derived from fossil fuels.
Semi-Synthetic Polymers
Chemically modified natural polymers - e.g. cellulose acetate - vulcanized rubber.
Elastomers
Rubber-like polymers with weak intermolecular forces - e.g. Natural Rubber (polyisoprene) - Styrene-Butadiene Rubber (SBR) - Nitrile Rubber (NBR).
Fibers
Strong - thread-like polymers used in textiles and construction - e.g. Nylon - Polyester.
Liquid Resins
Low-viscosity polymers used in coatings and adhesives.
Plastics
Synthetic polymers that can be molded into different shapes.
Thermoplastics
Soften when heated and harden when cooled; process is reversible.
Thermosetting Plastics
Undergo irreversible chemical changes when heated - forming a rigid structure.
Definition of Thermoplastics
Polymers that soften when heated and harden when cooled (fully reversible process).
Intermolecular Forces in Thermoplastics
Moderate forces like van der Waals interactions and some hydrogen bonding.
Advantages of Thermoplastics
Versatile - durable - impact-resistant - recyclable - easy to reshape - chemically resistant - good electrical insulation.
Common Thermoplastics
Polyethylene (PE) - Polypropylene (PP) - Polyvinyl Chloride (PVC) - Polystyrene (PS) - Polytetrafluoroethylene (PTFE).
Resin Identification Code
A number system developed by the Society of the Plastics Industry (SPI) to classify plastic types.
Polyethylene Terephthalate (PET or PETE)
Formed by polymerizing ethylene glycol and terephthalic acid.
Uses of PET
Used in packaging - textiles - and plastic bottles.
Properties of PET
Strong - stiff - lightweight - resistant to chemicals and moisture.
High-Density Polyethylene (HDPE)
A petroleum-based thermoplastic that resists chemicals and has high durability.
Uses of HDPE
Plastic bottles - pipes - containers - and outdoor furniture.
Polyvinyl Chloride (PVC)
One of the most widely used synthetic polymers.
Uses of PVC
Pipes - flooring - medical tubing - window frames.
Properties of PVC
Durable - resistant to chemicals - flame-retardant.
Low-Density Polyethylene (LDPE)
A flexible and corrosion-resistant polymer.
Uses of LDPE
Plastic bags - squeeze bottles - food packaging.
Limitations of LDPE
Not suited for applications requiring structural strength or heat resistance.
Polypropylene (PP)
A polyolefin slightly harder than polyethylene.
Uses of PP
Food containers - car parts - textiles - ropes - medical applications.
Properties of PP
Heat-resistant - flexible - chemical-resistant - lightweight.
Polystyrene (PS)
A widely used plastic known for affordability and insulation properties.
Uses of PS
Disposable cups - insulation - food containers - electrical insulation.
Definition of Thermosets
Polymers that undergo irreversible chemical changes when heated or cured with catalysts.
Cross-Linking in Thermosets
Prevents molecular movement after curing - making them heat-resistant.
Examples of Thermosets
Phenolics (PF) - Amino Plastics (UF and MF) - Polyester Thermosets (TS) - Epoxies (EP) - Polyimides (PI).
Phenolics (PF)
Machinable thermoset plastics with strong physical and chemical properties.
Uses of Phenolics
Electrical insulation - automotive parts - construction materials.
Properties of Phenolics
Thermally stable - electrically insulating - chemical-resistant.
Amino Plastics (UF and MF)
Made from aldehydes and amino compounds.
Uses of Urea-Formaldehyde (UF)
Adhesives - coatings - plywood laminates.
Uses of Melamine-Formaldehyde (MF)
Heat-resistant materials like countertops - tableware - and electrical components.
Polyester Thermosets (TS)
Low-cost materials with high strength-to-weight ratio.
Uses of Polyester Thermosets
Automotive parts - HVAC components - electrical applications.
Polyimides (PI)
High-performance plastics resistant to heat and chemicals.
Uses of Polyimides
Electronics - medical tubing - adhesives - gears - valve seats.
Properties of Polyimides
Low creep - high tensile strength - flame-resistant.
Epoxies (EP)
A widely used thermoset resin with strong adhesion and mechanical properties.
Uses of Epoxies
Coatings - adhesives - composites - electrical applications.
Properties of Epoxies
Resistant to moisture - heat - and chemicals.
