Principles of Polymeric Materials

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Principles of Polymeric Materials

• Engineering Materials
• Chapter 4

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Chapter 4 Goals

• How polymers are used s engineering materials
• Understand the chemical makeup of polymeric
  materials
• Understand strengthening techniques for polymers

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Chapter 4 Purpose

• Illustrate where plastics came from
• Understand how they form
• Recognize
• What holds them together
• What makes them stronger
• How they are similar or not

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Chapter 4 Introduction

• Natural polymers
• Cellulose and lignin
• Synthetic
• Cellulose nitrate
• Phenolics
• WWII saw many more!
• Polymer v. plastic
• ASTM D883 definition of a polymer
• Polymer refers to chemical formation
• Plastic polymers in finished form

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4.1 Polymerization Reactions (Fig 4-2)

• Addition (free-radical)
• Condensation
• Crosslinking
• Role of the catalyst
• Polymerization technique can control length of
  polymer chains
• Determine molecular weight (MW) chemical
  structure (CS)
• Intrinsic viscosity - MW
• FTIRS - CS
• Melt flow index MW

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4.1 Polymerization Reactions

• Copolymerization
• Stereospecificity
• Isotactic, Syndiotactic, Atactic
• Most new thermoplastics are alloys or blends
• Terpolymers (will see some in ch. 5)
• Summary
• The process of making long-chain polymer
  molecules, is achieved by causing identical
  monomers to add on to each other or by a
  condensation reaction that involves combining a
  number of chemicals to form a polymer.

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4.2 Basic Types of Polymers (Fig 4-4)

• Thermoplastic (TP) v. thermoset (TS)
• Linear or branched v. 3-D network
• The glass transition temperature (Tg)
• Fabrication costs of TPs and TSs
• Families
• Olefins, vinyls, styrenes (more in ch. 5)
• Engineering plastics
• TSs

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4.3 Altering Polymer Properties

• Molecular weight changes
• Copolymerization
• Alloys or blends of polymers
• Linear v. branching
• Intra- and inter- bonding in polymers
• Amorphous v. semicrystalline
• Crosslinking
• Chain stiffening
• Adding large group to polymer chain (steric
  hindrance)
• Fig 4-20

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4.3 Altering Polymer Properties

• Structural Melting Characteristics
• Amorphous v. semicrystalline
• Linear v. branched
• Viscosity (Fig 4-11, 4-12)
• Specific volume
• Free volume
• Properties above and below Tm crystalline part
• Fig 4-13 4-18
• Properties above and below Tg amorphous part
• Fig 4-14 4-18
• Summaries
• Amorphous
• Semicrystalline

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4.3 Altering Polymer Properties

• Additives
• Method of delivery
• Fully compounded v. masterbatch resins
• Fillers fibers
• Impact modifiers
• Plasticizers
• Stabilizers antioxidants
• Nanoparticles
• Blending Alloying
• Miscible v. immiscible
• IPNs
• Crosslinked

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Summary Critical Concepts

• Families based on structures
• Repeat units make up chains
• TP v. TS
• Polymerization processes
• Alloys Blends
• Fillers

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Case History

• Use of PP PE in sterilization pouch
• PP with corrosion inhibitor pouch
• PE pillow
• Lower Tm than PP