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AbstractThe effects of holding pressure (PIII) and holding time
(tIII) on the properties of injection molding parts were
investigated. Besides, gate pressure and cavity pressure were
monitored by pressure sensors positioned in front of and inside
of the gate. Three polymeric additives, paraffin wax,
polypropylene, stearic acid, and alumina feedstocks with former
polymeric additives, in a solid loading containing 56.6 vol%,
were studied by thermogravimetric analysis in air. In addition,
weight loss, pore size distribution and dilatometry of test bars
were measured during solvent debinding.Increasing holding
pressure from 5% to 95% and holding time up to 75 sec, the
pressure-time traces showed different tendency in the mold.
Maximum pressure occurred at the end of pressure build-up.
Increasing the holding pressure (PIII), 5% to 95%, raised the
gate pressure and cavity pressure. Because of resistance through
the gate, the cavity pressure was slightly smaller than the gate
pressure. The mass, dimensions and flatness of injection molded
were measured, and would increased as holding pressure. A high
holding pressure(≧50%) would also decrease the sink of
specimens, and prolonged the packing time by increasing holding
time. Green bulk density, fired density and four-point bending
fracture strength were obtained. The results showed that there
was not apparent dependence of green bulk density, fired density
and fracture strength on the injection pressure(PIII) .N-heptane
was used to leach soluble polymers in solvent debinding. The
weight of sample measurements decreased with time was measured
by two methods, either interruption and in-situ time methods.
The temperature effects of n-heptane tested from 40oC to 60oC,
the result showed that the case of 60oC exhibited a fast
leaching rate and a maximum swelling ratio measured by a laser
dilatometer. Pore size of debinding specimens were measured by a
mercury porosimeter, and showed a bimodal distribution, but
increased the pore volume as the debinding time proceeded.TGA at
a heating rate from 2 oC/min to 20 oC/min of polymeric additives
and alumina greens were conducted up to 550 oC in purged air
50ml/min. The TGA curves of polymeric additives and feedstocks
shifted to low temperature as the heating rate decreased. Then,
the activated energy and reaction order were analyzed using
Ozawa and Friedman, methods. The activated energy was in range
90?0 kJ/mol, but the reaction order of alumina green parts
changed from 0 to 3.2 in the later stage of the thermal
debinding of alumina feedstocks. Keywords：alumina, injection
molding, pressure, solvent debinding, reaction order, thermal
debinding.
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