This document discusses the key steps and properties involved in transforming polymer pellets into finished products. It outlines the process from pellet to product, including polymerization, extrusion, processing, fabrication, and the resulting properties. The document emphasizes the importance of thermal and rheological analysis for understanding the flow properties and thermal characteristics needed for processing. It describes techniques like differential scanning calorimetry and thermogravimetric analysis for thermal analysis, and defines concepts like viscosity, viscoelastic behavior, and storage and loss modulus for rheological analysis. The document argues that thermal analysis combined with rheological analysis provides an advantage for process and product design.

1. DR. R. K. KHANDAL
SHRIRAM INSTITUTE FOR INDUSTRIAL RESEARCH
19, UNIVERSITY ROAD, DELHI-110 007
Email : sridlhi@vsnl.com Website : www.shriraminstitute.org
POLYMER WORKFLOW – FROM PELLET TO
PRODUCT
RELEVANCE OF THERMAL & RHEOLOGICAL
ANALYSIS
Keynote Address by

2. Outline
 From Pellet to Product : Steps, Process &
Properties
 Thermal Analysis by DSC & TGA
 Rheological Properties
 Importance of Rheology
 Visco-Elastic Behaviour

3. Monomer
Pellet
From Pellet to Product: Steps
Product
Type CharacteristicsNature Chemistry
IonicFunctionality
Unsaturation Non-ionic
Esters
Amides
Urethanes
Olefinics
Vinylics
Ketones
Sulfones
Carbohy-
drate
Viscosity
Polarity
Stability
Physico-mechanical
Physico-chemical
Thermal
Electrical
Optical
Magnetic
Homopolymer
Copolymer
Cross-linked
Thermoplastic
Thermoplastic
Thermoset
Melting
Plastic
Mol. Wt.
Mol. Wt. distribution
Crystallinity
Flow
Alcohols
Acids
Unsaturation
Application-
driven
Shape-
driven
 Thermo-plastic behaviour: Key feature for designing polymeric product
 Flow properties & thermal characteristics need to be understood for processing
Polymerization
Extrusion
Processing
Fabrication
Thermoplastic
ThermosetPolymer

4. Granules
Melt
Pellet
Flow
From Pellet to Product: Steps
Product
Flakes Powders
Fluid
Block
Die
Mold
Films LensFiber

5. Heat sink
PRESSUREHEAT
From Pellet to Product: Process
Melt
Absorbed Released
Heat outflow
Crystallization
Deformation
Flow
Phase change
 Key process parameters: Heat & Pressure
 Behaviour under heat & pressure: Thermal & Rheological analysis
Flow

6. Melting PointPellet
Processing
From Pellet to Product : Properties
Product
Mol. Weight
Uniformity
Stability Flow
Wear & tear
Stability Compatibility
Mol. Wt. Distribution
Compatibility
Thermal Rheological
Temp./ Time dependent
Shear stress/ strain
Consistency
 Thermal analysis combined with rheological analysis is an
added advantage for process/ product design
Stability
Interparticle interactions
Processibility

7. Differential Scanning Calorimetry (DSC)
 Glass transition temperature
 Provides qualitative & quantitative information
 Analysis as a function of temperature & time
 Melting/ boiling points
Heats of fusion & reaction
Percent crystallinity
 Crystallization time and temperature
 Specific heat
Oxidative stability
Rate/ degree of cure
Reaction kinetics
 Purity
Measures temperature & heat flow associated with transitions

8. Thermogravimetric Analyzer (TGA)
 Provides quantitative weight change information
 Analysis as a function of temperature
 Moisture & Volatile content
 Composition of multi-component systems
 Thermal stability
 Oxidative stability
 Shelf-life studies using kinetic analysis
Decomposition kinetics
Effect of reactive atmosphere
Measures weight changes as temperature is increased

9. Glass Transition - DSC
 Step in thermogram
 Transition from solid to
liquid
 Transformation of a
glass-forming liquid into a
glass
 Tg, glass transition
temperature Temperature, K
DSC thermogram
dH/dt,mJ/s
Glass transition
Tg

10. Crystallization
 Sharp exothermic peak
 Disordered to ordered
transition
 Material can crystallize
 Observed in glassy solids,
e.g., polymers
 Tc, crystallization
temperature
Temperature, K
DSC thermogram
dH/dt,mJ/s
Crystallization
Tc

11. Melting
 Endothermic peak
 Ordered to disordered
transition
 Tm, melting temperature
 Tm > Tg
Temperature,
K
DSC thermogram
dH/dt,mJ/s
Melting
Tm

12.  dqp/dt = heat flow
 dT/dt = heating rate
 (dqp/dt) / (dT/dt) = dqp/dT = cp
Heat Capacity
 Specific heat capacity is the measure of heat energy
required to raise the temperature of a unit amount
of the substance by 1°C

13. Importance Of Rheology
Material
Spraying
Transporting
Extending
Extruding
Molding
Heating
Swallowing
Storing
Molding
RubbingCoatingMixing
Chewing Cooling
 Rheology ; one of the most important quality parameter
Ageing

14. Newtonian
Example :Oil,Water
Shear rate γ•
[1/ S]
Shearstressτ[Pa]
Viscosity is independent of shear rate
 Shear rate ∝ shear stress

15. Non-Newtonian: Dilatant
Shear-thickening or Dilatant
Shear rate[1/S]
Shearstressτ[Pa]
Viscosity  with  in shear rate
Example: ceramic suspension, plastisol pastes, starch
dispersions

16. Non-Newtonian: Pseudoplastic
Shear rate[1/ γ•
S]
Shear thinning: Example: Polymer melts, paints, glues.
Viscosity  as shear rate 
Material shows plasticity only after yield point
 Above yield point Plasticity,below yield point elasticity
Shearstressτ[Pa]

17. THIXOTROPY & RHEOPEXY
Time(t)
For Thixotropic
materials, viscosity 
as time , at a constant
shear rate.
Example: Paraffin
oil,Pastes,cream,gels
For Rheopectic fluid ,
viscosity as time 
at a constant shear
rate
Thixotropic
Rheopectic
Shearstressτ[Pa]

18. Rheological Properties
Ideal Solid Ideal Fluid
Steel Water
Strong Structure Weak Structure
Rigidity Fluidity
Deformation Flow
Retains / recovers form Looses form
Stores Energy Dissipates Energy
Purely Elastic Purely Viscous
V
I
S
C
O
E
L
A
S
T
I
C
Elasticity Viscosity
Polymer melts & solutions exhibit a combination of
viscous & elastic response: Viscoelastic

19. Single phase: Gas Liquid Solid
Interparticle interactions are independent of time but
depend on temperature
Viscosity or elasticity




Multiphase : Suspension/ Emulsion / Suspoemulsion
Interactions depend on concentration, time & temperature
Visco-Elastic
Macromolecules: Polymeric/ Oligomeric
Interactions depend upon time & temperature
Visco-Elastic
Visco-Elastic Behaviour

20. Solute - Solvent Interactions
Polysaccharide Hydrated Polysaccharide
The molecules do not see each
other. Interparticle distance > the
total of hydrodynamic radii
Soft interactions : Interactions
occur at the hydrodynamic radii
Hard interactions : Interactions
occur at the level of the polymeric
chains entangling with each other
< 0.05 %
Conc.
> 0.05 %
> 0.6 %

21. Loss Factor or damping factor
Tan = Sin δ / Cos δ = G” / G’
Lost Energy
Stored Energy
Viscous
Elastic
=
0 ≤ tanδ ≤ tan ∞ 0° ≤ δ ≤ 90 °;
δ = 0, tan δ = 0: G’ >>> G”
δ = 90 ° , tan δ = ∞ : G’ <<< G”
δ = 45 ° , tan δ = 1 : G’ = G”
Visco-Elastic Behaviour

22. Sol Gel

Tan δ = 1: G’ = G’’ Transition point : Gel point holds
 The transitions can be evaluated by the visco-elastic behaviour
 Visco-elastic measurements are the best way to monitor such
transitions
Tan δ > 1: G” > G’ Sol state : Liquid state
Tan δ < 1: G’ > G” Gel state : Solid state
Visco-Elastic Behaviour

23. Visco-Elastic Behaviour
Tack behavior Stickiness=
Tan δ = Medium range = Stickiness
Tack can be produced to be  or 
Water Stone
Tan δ = 0
Flows off
No tack
Tan δ = ∞
Brittle
No tack
 Designing Adhesives; Lubricants; Gels; Sols
Tackiness

24. T
Tg
lg G’
Tan 
lg G”
Molecular chains are chemically
unlinked; no regular structure
Below Tg : G’ > G”  Polymer
shows consistency of rigid &
brittle solid
Above Tg : G” > G’  Polymer
behaves as viscoelastic liquid
Storage & Loss Modulus

25. Molecular chains are chemically
unlinked; partial regular
structure
Below Tg : G’ > G”  Polymer
shows consistency of rigid &
brittle solid
Between Tg & Tm : Higher is
crystallinity, higher is the
value of G’  Polymer is in
rubber-elastic state Ig G’
Tan 
Ig G”
Tg TTm
Above Tm : Crystalline polymer
also melts, G” > G’  Polymer
behaves as viscoelastic liquid
Storage & Loss Modulus

26. Storage & Loss Modulus
Tan 
Tg
lg G’
lg G”
T
Molecular chains are chemically
connected
Below Tg : G’ > G”  Polymer
shows consistency of rigid &
brittle solid
Above Tg : G’ > G” 
Polymer does not melt
completely due to rigid
network

27. THANK YOU