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S18 Processos Mecânico-Metalúrgicos |
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Title:
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INFLUENCE OF ADITIVES IN VISCOSITY OF A METAL INJECTION MOLDING MIXTURE
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Summary :
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POWDER INJECTION MOLDING (PIM) IS AN ALTERNATIVE ROUTE TO PRODUCE PARTS FROM POWDER. THIS HAS RECEIVED A SUBSTANTIAL GROWTH IN THE LAST YEARS. THIS PROCESS EMPLOYS A MIXTURE OF POWDER (AROUND 90% IN MASS) TO A BINDER, WHICH YIELDS LOW VISCOSITY WHEN HEATED UP. THE BINDER, BESIDES PROVIDING LOW VISCOSITY WITH HIGH VOLUME FRACTION OF POWDER, INHIBITS THE SEGREGATION AND THE GATHERING OF THE POWDER PARTICLES DURING THE INJECTION. TYPICAL COMPOSITIONS OF BINDERS PRESENT A MAJOR COMPONENT THAT WILL INFLUENCE DECISIVELY IN THE RHEOLOGICAL CHARACTERISTIC OF THE MIXTURE (POLYMER OF HIGH MOLECULAR WEIGHT). TO THIS MAJOR COMPONENT OTHER ADDICTIVES ARE ADDED, SEEKING TO IMPROVE WETTABILITY CHARACTERISTICS, FURTHERMORE THE VISCOSITY AND MELTING TEMPERATURE DECREASE. IN THE PRESENT WORK, THE INFLUENCE OF COMPOSITION IN THE RHEOLOGICAL PROPERTIES OF A POLYPROPYLENE AND IRON POWDER MIXTURE WAS EVALUATED. DIFFERENT AMOUNTS OF PARAFFIN WAX, EVA AND STEARIC ACID WERE EXPLORED. FOR ALL CASES THE VOLUMETRIC FRACTION OF POWDER WAS KEPT CONSTANT AND EQUAL TO 55%. FOR EXPLORING THE RELATIONSHIP BETWEEN VISCOSITY AND SHEAR RATE, A CAPILLARY RHEOMETERS WAS EMPLOYED. THE TORQUE MEASUREMENTS OFFERED A GOOD QUALITATIVE INDICATOR OF THE VISCOSITY OF THE MIXTURES. BINDERS SYSTEMS USING PARAFFIN PRESENTED WITH SMALLER VISCOSITY VALUES, WHEN COMPARED WITH SYSTEMS WHERE STEARIC ACID WAS USED.
KEY-WORDS: RHEOLOGY, POWDER INJECTION MOLDING, BINDERS SYSTEMS
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Author :
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Böhmer, Carlos Henrique
Klein, Aloísio Nelmo
Prata, Álvaro Toubes
Resende, Luis Mauricio
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Paper View :
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