EBB 427. Technology and Application of Engineering Polymers. EBB 427. Course Synopsis : This course covers topics on technology and applications of various polymers in engineering applications.
Technology and Application of Engineering Polymers
Contribution of Assessment :
Final Examination : 70%
Coursework : 30%
What is the difference between
polymers, plastics and resins???
Think of how spaghetti noodles look on a plate - Amorphous organization.
Linear chain molecules - Thermoplastics
Branched chain molecules - Thermoplastics
Weakly cross-linked chain molecules - Elastomers
Highly cross-linked molecules - Thermosets
Thermoplastic - meaning that once the polymer is formed it can be heated and reformed over and over again (facilitates recycling)
. Thermosets & Elastomers - can not be remelted.
Characteristics of plastics when compared to Metals and Ceramics
Shear stress, ζ = Shear force/Area of the shear face
= F/A Nm-2
Shear strain,γ = Amount of shear displacement, S/Distance between shearing surfaces (D)
= Tan θ
Viscosity, η = Shear stress/Rate of shear strain
= ζ / (d γ/dt) = ζ / γ
1 mPa·s = 1 cP.
Shear rate is a measure of the rate
Rheogram for Newtonian liquids.
A - high viscosity, B - low viscosity.
with yield value
Newtonian and non-Newtonian bahavior
Variation of apparent viscosity with shear rate
Thixotropic substance at different shear rates.
ηo – viscosity at a very low shear
Rate, which behave like
ηa – is the slope of the secant line
from the origin to the shear stress
at the given value of shear rate
ηc – the slope of the line at the
chosen value of Rate of shear
The ηa is greater than ηc
Schematic diagram of a cone and plate viscometer.
Schematic diagram of a rotational viscometer
How to relate MFI with molecular
1. The external heat supplied-i.e. by heater on the barrel of extruder, etc
2. Heat generated when a highly viscous fluid being sheared at high shear rate