PPT POLYMERS

• POLYMERS

  • can be found everywhere
  • large molecules created by chemically joining a number of constituent pieces
• A polymer is a molecular compound that is distinguished by a high molar mass, ranging into thousands and even millions of mass and they are made up of many repeating units
• Synthetic (man-made) polymers developed in the early 20th century, revolutionized the world by offering ideal properties for various material production applications.
• Monomers

  • mono means “one” ; meros means “unit”
  • The small molecules that are used for synthesizing polymers, and each monomer is analogous to a link in a chain.
• Polymers

  • poly means “many”
  • Created from one monomer or a combination of two or more different monomers.
• Homopolymers

  • A polymer that is made up of only one type of monomer

  Polyethtlene

  Poly Vinyly Chloride (PVC)

  Teflon
• A copolymer is a polymer that is made up of two or more monomer species.
• Crude Oil

  • Synthetic polymers are typically produced from various raw materials, including crude oil. 
  • Crude oil is the starting material for many plastics, pharmaceuticals, fabrics, and other carbon - based products.
• Polymers, also known as macromolecules, are massive molecules composed of carbon-chain polymers with a string of carbon atoms at their backbone, bound together by covalent interatomic bonds
• The hydrocarbon ethylene (C2H4) is a gas at ambient temperature and pressure which has the following molecular structure:
• Under suitable conditions, ethylene gas transforms into polyethylene (PE), a solid polymeric material, by forming an active center through a reaction between an initiator or catalyst species (R·) and the ethylene monomer.
• The polymer chain forms by adding monomer units sequentially to an actively growing chain molecule, represented schematically as follows:
• The polyethylene molecule is formed by adding numerous ethylene monomer units, as depicted in Figure 1. The polyethylene chain structure is shown below:

   
• For polyethylene, (a) a schematic representation of repeat unit and chain structures, and (b) a perspective of the molecule, indicating the zigzag backbone structure (Callister & Rethwisch, 2014).
• Other chemistry of polymer structure such as tetrafluoroethylene monomer to form polytetrafluoroethylene (PTFE) is shown below:
• Teflon, also known as polytetrafluoroethylene, belongs to the fluorocarbon family of polymers. Its vinyl chloride monomer (CH2=CHCl) is a variant of ethylene, replacing one of its four H atoms with a Cl atom. Its polymerization is represented as:
• Repeat unit and chain structures for (a) polytetrafluoroethylene, (b) poly (vinyl chloride), and (c) polypropylene (Callister & Rethwisch, 2014).
• The physical characteristics of a polymer are not solely determined by its molecular weight and shape; they also involve variations in the structure of its molecular chains.

  Note that polymers may have more than one distinctive structural type, for example, a linear polymer may have limited branching and crosslinking.
• • Linear polymers consist of repeat units joined in single chains, with each circle representing a unit.
  • These flexible chains may have extensive van der Waals and hydrogen bonding.
• Linear

  • Common linear polymers include polyethylene, poly (vinyl chloride), polystyrene, poly (methyl methacrylate), nylon, and fluorocarbons.
• Branched

  • Side branch formation leads to a decrease in chain packing efficiency, lowering polymer density. 
  • High-density polyethylene (HDPE) is linear, while low-density polyethylene (LDPE) has short-chain branches.
• Crosslinked

  • Crosslinking is a process where adjacent linear chains are joined by covalent bonds.
  • This is often achieved during synthesis or through a nonreversible chemical reaction.
• Crosslinked

  • This process is often achieved by additive atoms or molecules covalently bonded to the chains.
  • Many of the rubber elastic materials are crosslinked. 
• • Network polymers are multifunctional monomers with active covalent bonds, forming three-dimensional networks.
  • A polymer that is highly crosslinked may also be classified as a network polymer.
• Network

  These materials have distinctive mechanical and thermal properties; the epoxies, polyurethanes, and phenol-formaldehyde belong to this group.
• Polyethylene (LDPE)

  • Translucent if not pigmented.
  • Soft and flexible.
  • Unreactive to acids and bases.
  • Strong and tough
  • It is used for bags, films, sheets, bubble wrap, toys, and wire insulation. 

   

  
• Polyethylene (HDPE)

  • Similar to LDPE
  • More rigid, tougher, slightly more dense.
  • Used for opaque milk, juice, detergents, & shampoo bottles. 
  • It is also applied in the production of buckets, crates, and fencing.

  
• Polyvinyl Chloride (PVC or V)

  • Variable. Rigid if not softened with a plasticizer. 
  • Clear and shiny, but often pigmented. 
  • Resistant to most chemicals, including oils, acids, and bases
  • Rigid PVC is often used in plumbing pipes, house siding, charge cards, hotel room keys.
  • Meanwhile, softened PVC is utilized in garden hoses, waterproof boots, shower curtains, IV tubing.

  
• Polystyrene

  • Variable. crystal forms transparent, sparkling, somewhat brittle. 
  • Expandable form lightweight foam.
  • Both forms are rigid and degraded in many organic solvents.
  • In its crystal form, polystyrene is used in food wrap, CD cases, and transparent cups.
  • In its expandable form, foam cups, insulated containers, food packaging trays, egg cartons, packaging peanuts.

  
• Polypropylene

  • Opaque, very tough, good weatherability. High melting point. 
  • Resistant to oils. 
  • It is utilized in bottle caps, yogurt, cream, and margarine containers.
  • It is also used in carpeting, casual furniture, luggage.

  
• Polyethylene terephthalate

  • Transparent, strong, shatter resistant. 
  • Impervious to acids and atmospheric gases.
  • Most costly of the six.

  
• Polyethylene terephthalate

  • It is used in soft-drink bottles, clear food containers, beverage glasses, fleece fabrics, carpet yarns, fiber-fill insulation. 
• Molecular Weight

  • Molecular weight, M: Mass of a mole of chains.
  • During polymerization, chains of monomers grow at different lengths. As a result, there is a distribution of molecular weights.
• Molecular weight determines the physical properties of the polymer
• mpact of Molecular Weight on Polymer Properties

  • Low molecular weight (<100 g/mol): Polymers are liquids at room temperature, as the chains are too short to solidify.
  • Medium molecular weight (<1000 g/mol): Polymers may be soft, waxy solids, like paraffin wax.
• Impact of Molecular Weight on Polymer Properties

  • High molecular weight (<100,000 g/mol): Polymers with long chains are tough, solid, and have higher melting points.
  • Very high molecular weight (<millions g/mol): Polymers exhibit exceptional mechanical properties, such as high tensile strength and toughness.
• Average Molecular Weights

  • It's impractical to measure the molecular weight of every individual chain in a polymer sample. Instead, it’s more useful to compute an average molecular weight, to describe the entire polymer batch. 
  • These averages help predict the polymer’s properties and performance, making them useful for materials science and engineering applications. 
• Number-Average Molecular Weight (Mn) 

  • based on the number fraction of polymer chains
• Weight-Average Molecular Weight (Mw)

  • based on the weight fraction of polymer chains
• Number-Average Molecular Weight (Mn)