Download - Polymers and its Viscoelastic Nature
Polymer Materials and
their Viscoelastic Nature
University of Engineering and Technology, PeshawarMaterials 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-polymerConsist 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 unitare distributed randomly e.g.
Alternating copolymer They are made of alternating sequencesof the different monomers e.g.
Block copolymer Long sequences of a monomer are followed by long sequences of another monomer e.g.
Graft copolymerOne type of monomers with branches ofanother 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
CharacterizationCharacterization 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
VISCOELASTICITY
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 – Temperature Relaxation
Modulus
• Relaxation modulus as a function of time
Er (t) = σ(t)/ϵ0RelaxationModels Contd..
• Isothermal stress relaxation
RelaxationModels 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
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