1. Mechanical Behaviour
1.1. Stress and Strain
1.1.1. Brittle
1.1.2. Plastic
1.1.3. Totally Elastic
1.1.4. Properties
1.1.4.1. Highly Flexible
1.1.4.2. Low Densities
1.1.4.3. Corrosion Resistant
1.1.5. Characteristics
1.1.5.1. Sensitive to Temperature
1.2. Macroscopic Deformation
1.2.1. Small neck forms
1.2.2. Chains orientated parallel to elongation
1.2.3. Localised Strengthening
1.2.4. Propagation of necking region
1.2.5. Subsequent deformation confined to the neck
1.3. Viscoelastic Deformation
1.3.1. Mechanical Behaviour
1.3.1.1. Glass at low temperature
1.3.1.2. Robbery solid at intermediate temperature
1.3.1.3. Vicious liquid as the temperature
1.3.2. Relaxation Modulus
1.3.2.1. Time-dependent modulus of elasticity
1.3.2.2. Sensitive to temperature
1.3.2.3. Depends on molecular configuration
1.3.3. Viscoelastic Creep
1.3.3.1. Constant Stress Level
1.3.3.2. Significant at room temperature
1.4. Fracture of polymers
1.4.1. Low fracture strengths
1.4.2. Ductile and brittle mode of fracture possible
1.4.3. Thermoplastic materials
1.4.3.1. Ductile to brittle transformations
1.4.3.2. Crazes may cause crack formation
1.5. Mechanical Characteristics
1.5.1. Impact Strength
1.5.1.1. Degree of resistance to impact loading
1.5.2. Fatigue
1.5.2.1. Structural failure when subjected to a cyclic load
1.5.3. Tear strength
1.5.4. Hartdness
2. Mechanisms of deformation and for strengthening polymers
2.1. Deformation of Semicrystalline Polymers
2.1.1. Elastic Deformation
2.1.1.1. Low stress Levels
2.1.1.2. Elongation of chain molecules in amorphous regions
2.1.2. Plastic Deformation
2.1.2.1. Lamellae slide phase one another
2.1.2.2. Segments separate from the lamellae
2.1.2.3. Tie chains and chain folded block segments align with the tensile axis
2.1.3. Spherulites experience shape changes for moderate elongation
2.1.4. Large elongation results in complete destruction of the spherulites
2.2. Factors that influence the mechanical properties
2.2.1. Molecular weight
2.2.1.1. Tensile strength increases with increasing molecular weight
2.2.1.2. Tensile modulus not directly related
2.2.2. Degree of Crystallinity
2.2.2.1. Tensile strength and modulus increase with increasing percent crystallinity
2.2.3. Pre-deformation by drawing
2.2.3.1. Permanent deformation increases mechanical strength and tensile modulus
2.2.4. Heat Treating
2.2.4.1. Increase in tensile modulus
2.2.4.2. Increase in yield strength
2.2.4.3. Decrease in ductility
2.3. Deformation of Elastomers
2.3.1. Rubber-like elasticity
2.3.1.1. Large elastic extensions are possible
2.3.2. Unlinking and uncoiling of chains causes deformation
2.3.3. Vulcanization
2.3.3.1. Crosslinking process
2.3.3.2. Increased crosslinking leads to <-
2.3.3.2.1. Increased modulus of elasticity
2.3.3.2.2. Increased tensile strength
3. Phenomena in Polymers
3.1. Crystallization
3.1.1. Transform into chain-folded layered crystallization
3.1.2. Tangled and random molecules become ordered
3.2. Melting
3.2.1. Transformation from solid to viscous liquid
3.2.1.1. Solid - ordered structure with aligned molecular chains
3.2.1.2. Liquid - Highly random structure
3.3. Glass Transition
3.3.1. Occurs in amorphous regions
3.3.2. Transformation from liquid to rubbery material and finally into a rigid solid
3.3.3. Overall reduction in motion of large segments of molecular chains with decreasing temperature
3.4. Melting and Glass Transition Temperatures
3.4.1. Define the upper and lower temperature limits
3.4.2. Determined from plot of specific volume vs temperature
3.5. Factors that influence Melting and Glass Transition Temperatures
3.5.1. Stiffer chains are susceptible to double chain bonds
3.5.2. Increasing chain stiffness increases melting and glass transition temperatures
4. Polymer Types
4.1. Plastics
4.1.1. Some structural rigidity
4.1.2. Most common
4.1.3. Flexible
4.2. Elastomers
4.2.1. Highly resistant to degradation
4.2.2. Flexible
4.3. Fibres
4.3.1. Capable of being drawn into long filaments
4.3.2. High tensile strength
4.3.3. Almost non-flammable
4.4. Applications
4.4.1. Coatings
4.4.1.1. Protect the item from the environment
4.4.1.2. Improve the items appearance
4.4.1.3. Provide electrical insulation
4.4.2. Adhesives
4.4.2.1. Bond together the surfaces of two solid materials
4.4.2.2. Bond depends on:
4.4.2.2.1. Materials to be bonded
4.4.2.2.2. Required adhesive properties
4.4.2.2.3. Max/Min exposure temperatures
4.4.2.2.4. Processing conditions
4.4.3. Foams
4.4.3.1. High volume percentage of small pores and trapped bubbles
4.4.3.2. Solid upon cooling
4.5. Advanced Polymeric Materials
4.5.1. Ultra-high-molecular-weight polyethylene
4.5.1.1. High impact resistance
4.5.1.2. Wear and abrasion resistant
4.5.1.3. Low coefficient of friction
4.5.1.4. Self-lubricating
4.5.1.5. Chemically resistant to solvents
4.5.1.6. Great low temperature properties
4.5.1.7. Electrically insulated
4.5.2. Liquid crystal Polymers
4.5.2.1. Neither Crystalline nor liquid
4.5.2.2. Thermal stability
4.5.2.3. High impact strengths
4.5.2.4. Chemical inertness
4.5.2.5. Inherent flame resistant
4.5.3. Thermoplastic Ectomeres
4.5.3.1. Exhibits elastomeric behavior at ambient temperatures
4.5.3.2. Physical Crosslinks
4.5.3.3. Melt at high temperature
5. Synthesis and Processing of Polymers
5.1. Polymerization
5.1.1. Synthesis of large molecules
5.1.2. Two types of synthesis
5.1.2.1. Addition polymerization
5.1.2.1.1. Monomer units attached one at a time in a chain like manner to form a linear macromolecule
5.1.2.2. Condensation polymerization
5.1.2.2.1. Stepwise intermolecular chemical reactions that may involve more than one manometer spieces
5.2. Polymer Additives
5.2.1. Fillers
5.2.1.1. Improve strength
5.2.1.2. Abrasion resistance
5.2.1.3. Toughness
5.2.1.4. Dimensional and thermal stability
5.2.2. Plasticizers
5.2.2.1. Enhances flexibility
5.2.2.2. Ductility
5.2.2.3. Toughness
5.2.3. Stabalizers
5.2.3.1. Counteracts deterioration from light and gasses in the atmosphere
5.2.4. Colourants
5.2.4.1. Used to impart a specific colour to a polymer
5.2.5. Flame Retardants
5.2.5.1. Enhances the flammability resistance of the polymer
5.3. Forming Techniques for Plastic
5.3.1. Methods depend on factors
5.3.1.1. Thermoplastic or Thermosetting
5.3.1.2. If thermoplastic, the temperature rises where it softens
5.3.1.3. Atmospheric stability
5.3.1.4. Physical geometry and size of the finished product
5.3.2. Compresson molding
5.3.2.1. A mixed polymer and additives are placed between a male and female mold
5.3.2.2. Mold is heated and pressure is applied
5.3.2.3. Plastic becomes viscous and flows to conform the mold shape
5.3.3. Transfer molding
5.3.3.1. Solids are first heated and injected into mold chamber
5.3.3.2. Used for complex geometries
5.3.4. Injection Molding
5.3.4.1. Material is heated in a spreader
5.3.4.2. Viscous molten plastic is impelled into a mold
5.3.4.3. Pressure is maintained until mold has solidified
5.3.5. Extrusion
5.3.5.1. Molding under pressure through an open ended die
5.3.5.2. Molten mass is forced through a die orifice
5.3.6. Blow molding
5.3.6.1. A hollow piece formed by blowing air or steam under pressure into the parson
5.3.6.2. Tube walls are forced to conform to the contours of the mold
5.3.7. Casting
5.3.7.1. Molten plastic material is poured into a mold and allowed to solidify
5.4. Fabrication of Elastomers
5.4.1. Essentially the same as for plastics
5.4.2. Most rubber materials are vulcanized
5.4.3. Some reinforcement with carbon black
5.5. Fabrication of Fibres and Films
5.5.1. Fibres
5.5.1.1. most fibres are spun from the molten state - molten spinning
5.5.1.2. Dry spinning - polymer is dissolved in a volatile solvent
5.5.1.3. Wet spinning - formed by passing a polymer-solvent through a spinneret directly into a second solvent, polymer fibre comes out of the sun
5.5.2. Films
5.5.2.1. Extruded through a thin die slit
5.5.2.2. Blown through an annular die
5.5.2.3. Co-extrusion multilayers of more than one polymer are extruded simultaneously