Characterization of Polyolefin – Alumina compounded mix for FDC processing

Bhat, V.V.
Geetha, K.
Das, R.N.
Gurumoorthy, B.
Umarji, A.M.
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Fused deposition of ceramics (FDC) uses thermoplastic binder and ceramic blend as feed material. The geometry of the fused deposition machine restricts the workability of the FDC feed material, which is in the form of a filament. The feasibility of the usage of these filaments is mainly based on the viscosity at the working temperature and the compressive modulus of the feed material at near room temperature. The polymers based on Polyethylene (PE), having two molecular weights 3,000 (LDWAX) and 341,000 (LDPE) were mixed in various weight proportions by solvent method using toluene as solvent, to develop a binder system for Fused Deposition Modeling of alumina. Variation of viscosity as a function of composition, temperature and solid loading was measured using spindle viscometer and capillary rheometer. Dilatometric thermal expansion of 50 Vol% alumina compounded binders is measured up to 120°C. The pronounced softening of the compounded mixture is observed beyond 70°C, when the volume % of LDWAX is in excess of 50% total binder content. The compression strength decreases from 720 N to 310 N for pellet having 1.2cm diameter and 1.5 aspect ratio, when the percentage of LDWAX varies from 40 to 70% in the binder composition. The suitability of the compounded mix of LDWAX and LDPE binder with 40 Vol. % alumina for FDC is being evaluated in a StratasysTM1600 machine.