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

THANK YOU ANY QUESTION?