Basic HTML Version
1. Rockwell Hardness
A common method of testing a plastic(s) material for resistance to
indentation in which a diamond or steel ball, under pressure, is used
to pierce the test specimen. The load used is expressed in kilograms
and a 10-kg weight is first applied and the degree of penetration
noted. The so-called major load (60—150 kgs) is next applied and a
second reading obtained. The hardness is then calculated as the
difference between the two loads and expressed with nine different
prefix letters to denote the type of penetrator used and the weight
applied as the major load.
2. Viscosity
The resistance to fluid flow (strictly speaking the resistance to shear-
ing). It is defined as the ratio of shear stress (Tangential Force/Area)
to shear rate (velocity/gap). The viscosity of a polymer decreases as
the shear rate increases. This property is referred to as pseudoplastic
behavior or shear thinning. The viscosity of a polymer at (near) zero
shear for a polymer like PE might be 5000 to 10,000 Pa s, while
during flow in an extrusion channel it could be much lower (i.e. 500
Pa s or less). Melt flow index corresponds to just one point on a
viscosity curve (actually inverse). High viscosity implies low melt
index and high molecular weight. Viscosity is measured in units of
Pa s or poise. 1 Pa s = 10 poise. The viscosity of water is 10
-3
Pa s (1
centipoise) and for a typical polymer melt at least one million times
larger (i.e., over 1000 Pa s or 10,000 poise).
3. Zero Shear Viscosity
The asymptotic viscosity value at zero shear rate (i.e., the maximum
value). As the shear rate increases, the viscosity decreases because
of alignments of molecular chains in the direction of flow and
molecular chain disentanglements. The zero shear viscosity is
proportional to the weight average molecular weight raised to the
3.4 power (i.e.
η
0 = constant * M
w
3.4
for most common polymers).
This means that if we increase the molecular weight of a polymer
from 1000,000 to 200,000, the viscosity will increase by 2
3.4
=
10.55 times. Obviously, it is extremely difficult to extrude polymers
having very high molecular weight.
R
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ET enables recapitulating few definitions
and technical terms with respect to
extruders and compounds
EXCERPTS
Here’re few excerpts from the book
“Built to Last” by J C Collins and
J I Porras
• We worked furiously [to realize our goals]. Because we didn’t have fear,
We could do something.
- Masuaru Ibuka, Founder, Sony Coporation.
• Big hairy audacious goals Far better to dare mighty things, to win glorious
triumphs, even though checkered by failure, than to take rank with those
poor spirits who neither enjoy much nor suffer much, because they
live in the gray twilight that knows not victory, nor defeat.
- Theodore Roosewelt, 1899
• Paul Galvin urged us to keep moving forward, to be in motion for motion’s
sake. . . He urged continuous renewal . . . Change unto itself is essential.
But, taken alone: it is limited. Yes, renewal is change. It calls for “do
differently.” It is willing to replace and redo. But it also cherishes the
proven basics.
- Robert W Galvin, Former CEO, Motorola 1991
• Clock building, not time telling. Above all, there was the ability to build
and build and build---never stopping, never looking back, never
finishing---the institution . . . In the last analysis, Walt Disney’s greatest
creation was Walt Disney [the company]
- Richard Schickfl, The Disney
Version
Understanding and Knowing
• Knowledgeable fool is the king among fools. To know and not to act
on what you know is equal to not knowing.
• Knowledge does not give you understanding. Knowing gives you
understanding. Knowing involves being open. Knowledge is often
closed to knowing. It relies on what it has known. Knowing should
be a continuous process.
• If it does not happen, then there would be misunderstanding. Misun-
derstanding can make a beautiful incident ugly and unhappy.
• A husband writes to his wife a letter from New York, ‘Wish you were
here’. Wife feels miserable for she read it as ‘Wish you were her’ Life
is beautiful, but mind filled with misunderstanding is ugly and hence
one experiences life as ugly.
• Make your mind beautiful and it will then see life as an expression of
the divine. Life is divine, make the mind pure, then misunderstanding
will disappear and appear as a mantra.
MARCH-APRIL 2006
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VOL .01 / ISSUE-02
C A T A L Y S T
Through this column ET will cover briefly
relevant information on key components that
goes into an extruder
Single Row Tooth Mixing Element
This Single Row Tooth mixing Element is used for distributing
strands in the melt. It was originally introduced as the last element
in front of the die for equalising pressure. The tooth formation has
varied from supplier to supplier. WP follows a symmetric tooth
formation with different angles for the flight.
Bi-lobed Multi Channel Screw Mixing Element
with Short Lead
This Bi-lobed Single Channel Screw Mixing Element With Short Lead
has a higher clearance due to reduction in Outer Diameter. The
higher clearances allow for more back mixing and better distributive
mixing.
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