Mixing characteristics and rheological properties of two polymer binder systems for the injection molding of silicon nitride powders were investigated. Based on the thermal analyses and the flow behavior of the melt. polypropylene and poly(vinyl butyral)/poly(buty1 methacrylate) were used as two binders. The binder system was then prepared by mixing polymeric binder with additives such as stearic acid and paraffin wax. Each binder system was mixed with submicron silicon nitride powders in a twin-screw Brabender mixer. Mixtures of silicon nitride and polymer binder systems, containing ceramic powders of 50% ,55% and 60% by volume, were pelletized. Their rheological properties were determined by using a capillary rheometer and the injection shear rate of 1500 s^-1, depending on the ceramics content. Spiral flow lengths for the mixtures were 10∼15 cm, which suggests the above-mentioned mixtures could be injection-molded using the appropriate apparatus.

질화규소 분말의 사출성형에 필수적인 고분자 결합제 시스템을 연구하였다. 평균 입자 크기가 0.5 μm인 질화규소의 사출성형을 위하여, polypropylene과 poly(vinyl butyral)/poly(butyl me-thacrylate)의 두 종류의 고분자에 wax, stearic acid 등을 첨가하여 결합제 시스템을 만들었다. 부피분율로 0.5, 0.55 및 0.6의 질화규소 분말을 두 종류의 결합제 시스템과 Brabender 혼합기 내에서 혼합한 뒤 펠렛화하였다. 혼합물의 유동학적 성질을 capillary rheometer로 측정하였고. 사출성형기에 부착된 spiral flow mold를 이용하여 성형성을 측정하였다. Capillary rheometer측정 결과 전단속도가 1500s^-1 일때 혼합물의 겉보기 점도는 80∼700Pa·s 정도였다. Spiral flow length는 사출성형 조건에 따라 차이는 있지만, 10∼15cm 정도로 나타났다.