| |
|
|
GROUND
MICA POWDER (MUSCOVITE)
<<
Pages [1] [2]
[3] >>
MICRONISED
MICA
It
is produced in a special type of dry grinding machine that has
no moving parts but depends on jets of high-pressure superheated
steam which is capable of reducing the mica to ultrafine particles
size ranging between 5 to 45 microns. This machine consists
of a shallow circular grinding chamber into which minus 6mesh
mica is fed continuously. High-pressure steam issued from orifices
around the periphery of the chamber and set at an angle of the
wall, keeps the mica rotating at a high speed. Grinding is accomplished
by the innumerable collisions of the mica particles whirling
at high speed. The steam is withdrawn at the center of the grinding
chamber. As the mica particles become finer, centrifugal force
no longer keeps them near the walls of the grinding chamber.
The fine mica gravitates towards the center and drops into the
chamber below through a conical bottom and discharged for bagging
for marketing. Undoubtedly, it is the finest grade of ground
mica, as well as, competitively cheaper as compared to wet ground
mica. It is suitably used as a filler in paints and plastics.
a)
MICRONISED MICA FOR PAINTS & COATINGS
Micronised
Muscovite Mica is extensively used as a pigment extender in
various paints and coatings. It is a tough, flexible and transparent
mineral that can be ground to less than a micron sieve mesh.
|
|
|
|
b)
MICRONISED MICA FOR RUBBER APPLICATION
It is used as an inert filler in rubber products. The use of mica
helps to increase the hardness, tensile strength and tear resistance
of rubber products. It improves the resilence and appearance of
rubber articles. When used as a lubricant, mica particles form
a continuous uniform film which effectively prevents undesirable
adhesion of the rubber compounds to itself or the moulding surface.
As a rubber compounding agent mica prevents massing and reduces
gas penetration.
It
is used as a base in the moulding and tumbling of latex, synthetic
foam and hose-pipes. The use of mica in the said applications
is to eliminate the tendency to shrink. At the same time it helps
to improve resistance in the sponge rubber goods. The use of mica
permits expansion of the rubber in the mould during blowing without
sticking.
It
is further used as a high temperature lubricant and flame-proof
insulation for the manufacture and coating of PVC flexible insulating
wires and cables. It is suitably used for both natural and specially
coloured rubber articles, such as, bathing caps, costumes, toys,
balloons, etc. The mica particles provide an attractive glossy-finish,
as well as, a bright and sparkling appearance to rubber articles.
|
|
|
|
c)
MICA FOR COMPOSITE PLASTIC SYSTEMS
High-aspect-ratio muscovite mica is widely used as a reinforcing
filler and extender in composite plastic systems because of its
functional, morphological and surface characteristics. The addition
of mica in plastic polymer compounds improves its material properties
significantly, such as, higher heat deflaction temperature, increase
tensile and flexural strengths, reduce isotropic shrinkage and
permeability, enhance the dielectric, heat resisting and insulating
properties, better surface properties, etc. In fact, mica is an
unique mineral which offers the multiple advantage of high-respect
ratio, high thermal stability and multi-directional lateral reinforcement
to composite plastic systems. Besides, mica also offers plastic
compounders a potential substitute for more expensive fiberglass
reinforcements. No other products provide such functional enhancement
to a wide range of plastic polymer compounds as superior quality
and excellent dimentional stability than mica.
|
|
|
WET
GROUND MICA
It
is produced in mills of the chaser types. It consists of a cylinderical
steel tank with a diameter of 6 to 10 feet and height of 3 to
5 feet. The bottom is lined with wooden blocks laid with the
end grain up. Four wooden rollers of 2 to 3 feet in diameter
and 1 to 3 feet across the faces revolve round a central shaft,
at 13 to 30 r.p.m. These rollers are so fitted that they can
be raised or lowered according to the height of the charge in
the wall. Cleaned and washed mica scrap is fed into the mills,
water is added and the rollers revolve at low speed and churn
tha mass until the grinding is complete. After about 36 hours
the water is siphoned from the settling tanks, the sludge is
dewatered and dried either in steam-jacketed kettles or in a
steam-heated drier. The dried product is sieved on multiple-deck
vibrating screens, usually in 160 and 325 mesh, and finally
bagged for marketing. Wet ground mica have a high metallic lustre
or silvery sheen and is free from grit. However, it is a slow
and costly process, and therefore, the product is relatively
expensive. It is especially used as a pigment extender in paints,
particularly in zinc-oxide paint and as a mould lubricant and
dusting agent in pneumatic tyres as well as wall paper.
|
|
|
COLOURED
MICA
They
are special-effects high-aspect ratio non-dispersing pigmentand
fillers derived from natural mica in carefully controlled process
and designed to impart granite-like appearances in most decorative
coatings and thermoplastic and thermoset resins. They are not
a coated material. They can be easily incorporated into plastic
compounds, colour concentrates, liquid color dispensions and
dry color blends. They are resistant to chemicals, high-heat
and natural elements and endures consistency even when the most
aggressive production processes whose needs are not being met
by current glitter, metallic and coloured-filler compounds.
|
|
|
|
|
|
|