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Polymers and its Viscoelastic Nature

Polymers and its Viscoelastic Nature






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    Polymers and its Viscoelastic Nature Polymers and its Viscoelastic Nature Presentation Transcript

    • University of Engineering and Technology, Peshawar Materials Engineering Department Presented BY: Mohsin Ali Marwat & Adil Jan Presented To: Dr. Afzal Khan
    • Contents  Introduction  Types of Polymers  Fabrication Techniques  Mechanical Behavior  Characterization Techniques  Applications  Latest Research Polymer Materials
    • Monomer: It is the smaller molecule(s) that are used to prepare a polymer Oligomer:  A molecule having a reaction of several repeating units.  Not large enough to be consider a polymer  (dimer , trimer, tetramer) Polymer:  A large molecule consisting of a number of repeating units  Its molecular weight is typically several thousand or higher Definitions Introduction
    •  Low Density  Good corrosion resistance  Good moldability  Excellent surface finish can be obtained  Economical  Low coefficient of friction  Lower to higher mechanical properties  Chain Length  Branching  Side groups  Crosslinking)  Can be produced transparent or in different colours  Poor tensile strength and temperature resistance Characteristics Introduction CHARACTERISTICS OF POLYMERS
    • Classification on the basis of Origin  Natural/Bio polymers  Proteins  Polypeptides  Polynucleotide  Polysaccharides  Natural rubber  Synthetic organic polymers  Semi-synthetic polymers  Inorganic polymers  Siloxanes  Silanes  phosphazenes) Classification Classification of Polymers
    • Classification by Monomer Composition Homo-polymer Copolymer Block Graft Alternating Statistical Homo-polymer Consist of only one type of constitutional repeating unit (A) e.g. A-A-A-A-A-A-A-A-A Copolymer Consists of two or more constitutional repeating units (A.B ) Classification Classification of Polymers
    • Random copolymer two or more different repeating unit are distributed randomly e.g. Alternating copolymer They are made of alternating sequences of the different monomers e.g. Block copolymer Long sequences of a monomer are followed by long sequences of another monomer e.g. Graft copolymer One type of monomers with branches of another type Classification on the basis of Chain Structure Classification Classification of Polymers
    • Classification by polymerization Classification Condensation Polymerization: A type of polymerization in which monomers combine together in such a way that they eliminate small molecules like H2O. Addition Polymerization: A type of polymerization that involves the rearrangement of bonds within the monomer in such a way that the monomers link up directly with each other. Classification of Polymers
    • Classification on the basis recyclability/temperature Response Classification Classification of Polymers
    • Elastomers: Materials with very low modulus of elasticity and high extensibility Plastics: Polymers in which, when a sufficiently intense force is applied, they irreversibly deform Fibers: Present a high modulus of elasticity and low extensibility Coatings: Polymers that are used to modify the surface of a material Adhesives: Polymers that are used to adhere/join other materials Types on the basis of Applications Classification Classification of Polymers
    • Fabrication Methods  Compression Molding Methods Fabrication  Injection Molding
    •  Blow Molding Methods Fabrication  Extrusion
    • Mechanical Behavior of Polymers Figure: The effect of temperature on the stress-rupture behavior of high- density polyethylene.
    • Techniques Characterization Characterization Techniques Morphology Testing:  SEM  TEM  AFM Thermal Analysis:  DSC  TGA Molecular Structure Testing:  Infrared spectroscopy  Raman spectroscopy  NMR spectroscopy Mechanical Analysis:  Tensile Testing  Dynamic mechanical analysis  Shore Hardness
    • Applications
    • 1. The Self-Healing Polymers 2. High melting temperature Polymers 3. Electrical conductive polymers Research Latest Research:
    • Adil Jan
    • Introduction Viscoelasticity:  the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation.  It was examined in the late twentieth century. Introduction
    • Properties of viscoelastics  Hysteresis is seen in the stress–strain curve.  Stress relaxation occurs:  step constant strain causes decreasing stress  Creep occurs:  step constant stress causes increasing strain Properties
    • Types of viscoelasticity • Linear viscoelasticity • Non-linear viscoelasticity Types
    • Models of viscoelasticity • Maxwell model • Kelvin-Voigt model • Standard linear solid model Models
    • Viscoelasticity in terms of Polymers • At low temperature, it is elastic • At high temperature, it is liquid or viscous. • Combined mechanical characteristics are termed as viscoelasticity. In terms of Polymers
    • VISCOELASTIC RELAXATION MODULUS • Viscoelastic behavior depends upon – Time – TemperatureRelaxation Modulus
    • • Relaxation modulus as a function of time Er (t) = σ(t)/ϵ0Relaxation Models Contd..
    • • Isothermal stress relaxation Relaxation Models Contd..
    • Viscoelastic Creep • Polymeric materials are susceptible to time dependent deformation when the stress level is maintained constant; such deformation is termed viscoelastic creep. Ec (t) = σ0 / ϵ(t) Creep
    • Measuring viscoelasticity • Resonant Ultrasound Spectroscopy (RUS) • Broadband Viscoelastic Spectroscopy (BVS) Characterization