Materials Transactions Online

Materials Transactions, Vol.58 No.03 (2017) pp.499-504
© 2017 The Japan Institute of Metals and Materials

A “Mold Filling” Model from Viscosity Measurements in a Strengthened Injection-Molded Reduced Glass Fiber Length Polyester Bulk Molding Compound

Michael C. Faudree1, Yoshitake Nishi1, Takashi Asaka2 and Michael Gruskiewicz3

1Department of Materials Science, School of Engineering, Tokai University, Hiratsuka 259-1292, Japan
2Graduate School of Applied Chemistry of Tokai University, Hiratsuka 259-1292, Japan
3Citadel Plastics, Conneaut, Ohio, 44030, USA

Experimental viscosity measurements (50 to 100 Pas at mold walls, T = 273 to 373 K) of an injection-molded highly-filled glass fiber reinforced polyester bulk molding compound (GFRP-BMC) whose fiber length (lfiber = 0.44 mm) was optimized for tensile mechanical strength agreed well with that previously calculated by Navier-Stokes equation from fiber orientation mapping. The mapping was from 0.44 mm fiber formulation molded sample exhibiting ~60, ~40 and 20% higher tensile strength, strain, and modulus, respectively than commercially used (lfiber = 6.4 mm). Based on the viscosity measurements a new “mold filling” model is constructed with physical meaning to predict needed injection molding parameters pressure (dP), shot time (ts) and shot weight (ms) for various size dog-bone specimens varying length (Ltot), gauge length (LB), width (w) and thickness (th) for the optimized formulation. Moreover, the Mooney-Rabinowitsch calculation is found to be a decent predictor for shear rates across specimen thickness and at mold walls measured from the mapping. This was without buying new equipment, using the existing injection molding machine to save cost.


(Received 2016/09/29; Accepted 2016/12/22; Published 2017/02/25)

Keywords: glass fiber reinforced polymer (GFRP), polyester, glass fibers, bulk molding compound, injection molding, viscosity

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