Technical Briefs

Flake Orientation in Injection Molding of Pigmented Thermoplastics

[+] Author and Article Information
Jang Min Park

Department of Mechanical Engineering,  POSTECH, Pohang, Gyeongbuk 790-784, Korea

Seok Jae Jeong

CMF Group, HA Common Technology R&D Sil, HA Division,  LG Electronics, Changwon, Gyeongnam 642-711, Korea

Seong Jin Park1

Department of Mechanical Engineering, POSTECH, Pohang, Gyeongbuk 790-784, Korea; Division of Advanced Nuclear Engineering,  POSTECH, Pohang, Gyeongbuk 790-784, Koreasjpark87@postech.ac.kr


Corresponding author.

J. Manuf. Sci. Eng 134(1), 014501 (Jan 11, 2012) (4 pages) doi:10.1115/1.4005309 History: Received April 03, 2011; Revised September 30, 2011; Published January 11, 2012; Online January 11, 2012

In the present work, experimental studies are carried out to understand orientation kinematics of pigment flakes during the injection molding process. The injection molding experiments are carried out using ABS resin compounded with aluminum flakes. Thin specimens are sliced off from the injection molded sample, and then the orientation distribution is observed using transmitted microscopy. Generally, the microscopic result shows a sandwich structure where the orientation state near the mid-plane differs significantly from that around the surface. Particularly at the weldline region, locally different orientation is observed near the part surface, which is the result of fountain flow at the melt front. Also the effect of mold temperature on the flake orientation is presented.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Fiber and disk in simple shear flow

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Figure 2

Particle orientation vector evolution for fiber and disk

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Figure 3

Test geometry having holes and ribs

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Figure 4

Real image of injection molded test geometry

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Figure 5

Three locations where specimens are sliced off for microscopic observations

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Figure 6

Transmitted microscopic images for specimens from (a) location A and (b) location B

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Figure 7

Schematic representations of (a) disk orientation kinematics and (b) sandwich structure in injection molding

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Figure 8

Transmitted microscopic image of location C for three different mold temperature conditions of top surface: (a) room temperature, (b) 120 °C, and (c) 220 °C

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Figure 9

Schematic representations of (a) flow and orientation kinematics at the weldline and (b) core layer shift



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