SOME PROPERTIES OF ELASTIC PRESS COMPONENTS
IN POWDER MATERIAL QUASIISOSTATIC PRESSING
M. I. Timokhova
Translated from Novye Ogneupory, No. 6, pp. 19 – 21, June, 2009.
Original article submitted December 25, 2008.
A polyurethane elastomer of grade SKU-7l is the best material for press buffers in quasiisostatic pressing.
Methods are given for making and processing these buffers. Basic specifications for the material are formu
lated for use in buffers for quasiisostatic pressing.
Keywords: quasiisostatic pressing theory, kinetics, press buffer, elastomer, polyurethane, plunger, pressing.
An elastic press buffer is a basic element in quasiisostatic
pressing, so a major aspect of developing such pressing is to
choose a suitable constructional material for the elastic
pressing elements to provide the necessary conditions for
consolidating a powder and providing reliable operation of
the pressing mold in the industrial production of pressed
items [1, 2].
Various elastomers have been tested: gelatin, some res-
ins, technical rubber, and natural and synthetic rubbers. The
gelatin pressing elements were made by pressing a specially
prepared solution in metal molds of appropriate configura-
tion. However, the low hardness made it undesirable. Buffers
have also been made of technical rubber with medium hard
ness, which is usually supplied as sheets of thickness
30 – 60 mm, and which was used by cementing together pre
viously cut blanks and then processing with a cutter or abra
sive wheel. The preparation labor and inhomogeneity of
some compound press buffers has forced one to seek other
materials. Some polyurethane elastomers have been tested in
molds for pressing ceramic materials based on Al
have been found to be promising [3, 4]. Table 1 gives the ba
sic physicomechanical characteristics of polyurethane elasto
These tests showed that the best material is SKU-7l ma
terial prepared by casting. This elastomer if prepared by
other technologies such as pressing shows a deterioration in
the parameters of the pressed components.
The SKU-7l material provides components equally dense
throughout the volume, and with more even and less rough
surfaces than when other elastomers are used. The SKU-7l
has exceptionally high wear resistance and capacity to work
at pressures exceeding 1000 MPa. Its strength is 6 – 8 times
higher than that of rubber, and the wear resistance exceeds
that of St3 steel by a factor 3, and of epoxide resin by a fac
Most ordinary elastomers lose their properties on attain-
ing a Shore hardness of A85. Out of all known elastomers,
only polyurethane ones preserve their elasticity in a wide
range of Shore hardnesses (³A95). The unique combination
of physicomechanical properties means that they can be used
for pressing powders. They as constructional materials not
only replace metals but also are better than the latter as re-
gards working properties.
Press buffers were made of SKU-7l polyurethane by
firms that specialized in making polyurethane components
by pouring a solution into aluminum molds we supplied and
subsequent heat treatment. The resulting buffers did not re
quire mechanical processing, but with that technology it was
difficult to provide tools for the pouring, so it was decided to
be economically justified to make buffers of appropriate
shape by the mechanical processing of polyurethane blanks
provided by the specialized firms. Much of the research was
directed to methods and modes of mechanical processing.
In the mechanical treatment it must be remembered that
polyurethane is an elastic material that has a tendency to de
flect away from the cutting tool, so the latter should be very
sharp. The elasticity means that the clamps holding an item
for treatment should not distort it too much. It is found that in
any mechanical treatment operations one needs a high speed
for the cutting tool and a slow feed for the workpiece to
Water-soluble oils and emulsions can be used in cutting
to prevent excessive heating and are usually recommended
for the softer polyurethanes. Satisfactory results have been
obtained with the following parameters: cutting tool speed
Refractories and Industrial Ceramics Vol. 50, No. 3, 2009
1083-4877/09/5003-0189 © 2009 Springer Science+Business Media, Inc.