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Study Polymer Science And Processing

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  • 1. Why Study Polymer Science and Processing?
    • Employment Opportunities:
      • 135,000,000 tons of plastics alone are produced annually
      • an estimated one in three research dollars in North America is invested in polymer science.
    • Scientific Interest:
      • structure-property relationships of polymers and polymer compounds
      • chemical modification of polymers for advanced applications
      • polymer blending and compatiblization techniques
    • Engineering Design Challenges:
      • life-cycle analyses
      • polymer compound development
      • design/optimization of polymer processing methodologies
      • polymer synthesis
  • 2. U.S. Polymer Production (billions of pounds) 1993 1992 PLASTICS Thermosetting Resins Phenol resins 3.08 2.92 Urea resins 1.74 1.55 Polyesters (unsaturated) 1.26 1.18 Epoxies 0.51 0.46 Melamine resins 0.27 0.23 Thermoplastic Resins Low-density polyethylene 12.04 11.92 PVC and copolymers 10.26 9.99 High-density polyethylene 9.91 9.81 Polystyrene 5.37 5.10 Polypropylene 8.61 8.42 Total 53.06 51.57 Chemical and Engineering News, April 11, 1994. 1993 1992 FIBERS Cellulosics Rayon 0.28 0.28 Acetate 0.23 0.22 Noncellulosics Polyester 3.56 3.58 Nylon 2.66 2.56 Olefin 2.14 2.00 Acrylic 0.43 0.44 Total 9.30 9.07 SYNTHETIC RUBBER Styrene-butadiene rubber 1.89 1.92 Polybutadiene 1.03 1.02 Ethylene-propylene rubber 0.58 0.58 Nitrile rubber (NBR) 0.14 0.13 Other 1.37 1.42 Total 5.00 5.07 TOTAL PRODUCTION 67.35 65.71
  • 3. Polymer Science and Processing Technology
    • Successful product design requires a knowledge of:
      • the requirements of the final product
      • the behaviour of polymeric materials
      • commercial polymer processing technology
      • relevant cost and market factors.
    • At the heart of polymer science and
    • technology is molecular structure. It
    • dictates not only final product properties,
    • but polymer synthesis and processing
    • methods.
  • 4. Classification of Polymer Applications
    • 1. Elastomers
      • static uses: gaskets, hoses
      • dynamic uses: tires, sports equipment
    • 2. Adhesives
      • structural: epoxy resins
      • non-structural: pressure-sensitive tapes, hot-melt adhesives
    • 3. Coatings
      • lacquers, paints
    • 4. Plastics
      • semi-crystalline: automobile exterior
      • amorphous: packaging films, plexi-glass
    • 5. Fibres
      • natural/modified: cotton, rayon
      • synthetic: carpeting, apparel
  • 5. Emphasis of Course Material (Weeks 1-6)
    • Each of the five applications will be examined from the following perspectives:
      • Industrial requirements for end-use and processing
      • Basic testing methods
      • Polymer compound formulations
        • essential polymer properties
        • compound additives
      • Relevant engineering science
        • Elastomers: origin of elasticity, crosslinking, reinforcement
        • Adhesives: surface energy
        • Coatings: viscosity
        • Plastics: mechanical properties, polymer composites
        • Fibres: crystallization
  • 6. Emphasis of Course Material (Weeks 7-12)
    • Each of the five applications will be examined from the following perspectives:
      • Industrial polymer processing techniques
        • extrusion
        • injection molding
        • fibre spinning
        • compression molding
        • polymer/additive blending
      • Key processing variables
        • polymer compound rheology
        • fluid mechanics
      • Assessment of processing variables
  • 7. Design Project
    • Develop a polymer compound and processing method for a component of your choice.
    • 1. Define engineering and aesthetic qualities.
    • 2. Propose a compounding recipe that will satisfy these
    • requirements.
    • 3. Recommend appropriate processing techniques for
    • manufacturing the product.
    • Examples?
    • Contact lens, medical catheter, biodegradable packaging,
    • artificial joint, high-performance tire tread...
  • 8. Basics of Polymer Structure
    • What distinguishes polymers from other organic compounds is molecular weight and dimension.
    • Differences in composition, architecture and molecular weight
    • give rise to differences in mechanical properties (strength, elasticity, toughness) and chemical properties (solubility, aging).
  • 9. Polymer Classification: Terminology
    • While we have chosen an applications perspective on polymer classification, many alternate schemes are widely used.
    • These are usually composition/property specific, as opposed to applications oriented.
  • 10. Polymer Classification: Thermoplastic/Thermoset
    • One of the most practical and useful classification of polymer compounds is based on their ability to be refabricated.
    • Thermoplastic: polymers that can be heat-softened in order to
    • process into a desired form.
      • Polystyrene, polyethylene
      • recyclable food containers
    • Thermoset: polymers whose individual chains have been
    • chemically crosslinked by covalent bonds and therefore
    • resist heat softening, creep and solvent attack.
      • Phenol-formaldehyde resins, melamine paints
      • permanent adhesives, coatings
  • 11. Polymer Classification: Chain Architecture
    • Linear: A linear polymer chain is one without branches. Its actual conformation may not be “line-like”, but varies with chain stiffness, crystallinity and applied stresses.
    • Branched: Chains with an appreciable number of side-chains are classified as branched. These side chains may differ in composition from the polymer backbone.
    • Crosslinked: A continuous
    • network of polymer chains is
    • a crosslinked condition. In effect,
    • there is just one polymer chain
    • of infinite molecular weight.
    • Chain architecture has a dramatic
    • effect on properties such as
    • viscosity, elasticity and temperature
    • stability.
  • 12. Polymer Classification: Chemical Microstructure
    • Homopolymers: polymers derived from a single monomer (can be
    • linear, branched or crosslinked).
      • poly(ethylene), poly(butadiene).
    • Random copolymers: two monomers randomly distributed in chain.
      • AABAAABBABAABBA
      • poly(acrylonitrile- ran -butadiene)
    • Alternating copolymers: two monomers incorporated sequentially
      • ABABABABABABABAB
      • poly(styrene- alt -maleic anhydride)
    • Block copolymers: linear arrangement of blocks of high mol weight
      • AAAAAAAAAAABBBBBBBBBBBBBBBAAAAAAAA
      • polystyrene- block -polybutadiene- block -polystyrene or poly(styrene- b -butadiene- b -styrene)
    • Graft copolymers: differing backbone and side-chain monomers
      • poly(isobutylene- graft -butadiene)
  • 13. Polymer Classification: Chemical Class
    • A popular classification scheme amongst chemists is based on polymer functionality.
    • Polyesters:
      • poly(ethylene terephthalate) - Dacron
    • Polyamides:
      • poly(caprolactam) - nylon 6
    • Urethanes:
      • carbamate linkages through reaction
      • of diisocyanates and diols.
    • Another (!) classification scheme, again favoured by chemists is based on differences between the polymer and constituent monomer(s).
      • Condensation polymers: synthesis involves elimination of some small molecule (H 2 O in the preparation of nylon)
      • Addition polymer: formed without loss of a small molecule i.e. ethylene polymerization to generate poly(ethylene)
  • 14. Additive Classification: Terminology
    • It is relatively rare for an article to be made from polymer alone. Most are polymer compounds , consisting of a mixture of polymer and various additives. These include:
    • Fillers: solid additives used to modify physical properties.
      • Dilution - talc
      • Reinforcing - carbon black in tires
      • Toughening - rubber in ABS plastic
    • Plasticizers: non-volatile solvents added to improve flexibility
      • Dialkyl phthalates in poly(vinylchloride)
    • Colourants: additives used to change product aesthetics
      • Pigments - soluble colourants
      • Dyestuffs - insoluble additives
    • Antioxidants: compounds that reduce polymer degradation through
    • intervention in free radical reactions
  • 15. Chain-A linear polymer formed by covalent linking of monomeric units. Backbone-Used in graft copolymer nomenclature to describe the chain onto which the graft is formed. Side chain-The grafted chain in a graft copolymer. Cross-link-A structure bonding two or more chains together. Network-A three-dimensional polymer structure, where (ideally) all of the chains are connected through cross-links. Multicomponent polymer, multipolymer, and multicomponent molecule-General terms describing intimate solutions, blends, or bonded combinations of two or more polymers. Copolymer-Polymers that are derived from more than one species of monomer. Block-A portion of a polymer molecule in which the monomeric units have at least one constitutional or configurational feature absent from the adjacent portions. Block copolymer-A combination of two or more chains of constitutionally or configurationally different features linked in a linear fashion. Graft copolymer-A combination of two or more chains of constitutionally or configurationally different features, one of which serves as a backbone main chain, and at least one of which is bonded at some point(s) along the backbone and constitutes a side chain. Polymer blend-An intimate combination of two or more polymer chains of constitutionally or configurationally different features which are not bonded to each other. Interpenetrating polymer network-An intimate combination of two polymers both in network form, at least one of which is synthesized and/or cross-linked in the immediate presence of the other. Semi-interpenetrating polymer network -A combination of two polymers, one crosslinked and one linear, at least one of which was synthesized and/or cross-linked in the immediate presence of the other. Star polymer-Three or more chains linked at one end through a central moiety. Star block copolymer-Three or more chains of different constitutional or configurational features linked at one end through a central moiety.