1 Introduction

ME332 재료가공(Materials Processing)

Polymer Processing Technology

Tai Hun Kwon

DEPARTMENT OF MECHANICAL ENGINEERING POHANG UNIVERSITY OF SCIENCE & TECHNOLOGY

 2003 by T. H. Kwon

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Why Polymer Processing? Advances in Various plastic materials Plastic based composites

Merits of using plastic components: Strength to weight ratio is high Good formability

reduce weight

Versatile complicated parts

Good for Mass production

Replace metallic components with plastic components

Conventional Applications: 1. Electric appliances, Automobile components, etc. 2. Precision optical products such as CD, DVD, Lenses

Futuristic Applications Microstructures, Microfluidics, Nanotechnology, etc.

Multidisciplinary research for the futuristic goal is in need and thus asks us to understand macromolecular behavior in more detail.

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Examples of Futuristic Applications

1. Chaotic mixing in screw extrusion

(a)

(b)

(c)

(d)

(e)

Fig. 0.1 Chaos screw proposed by Kim and Kwon(1995): (a) schematic of chaos screw, mixing experimental results at zones (b) without and (c) with barrier,

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2. Chaotic Micromixers (Barrier embedded Micromixer, BEM)

Barrier 240µm 60µm 9µm

Slanted grooves

30µm 40µm 100µm

(a) Barrier

Hyperbolic point

Elliptic point

Elliptic points

(b) At the zone with barrier on slanted grooves

(c) At the zone with only slanted grooves

Fig.0.2 Barrier Embedded Micromixer: (a) schematic view, (b) and (c) corresponding cross-sectional velocity fields. Slanted grooves cause the crosssectional velocity field of (c) and the velocity

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Experimental observation Phenolphthalein Flow

NaOH

Interface

(a) (b) (c)

Fig. 0.3 Mixing experimental results of: (a) T-channel, (b) only slanted grooves and (c) BEM at the indicated positions at Q = 10.0µl/min (Re ≈ 0.457). Only the phenolphthalein portion at the interface between phenolphthalein and NaOH streams shows red color.

Numerical simulations by Finite Element Method

At the entrance

7th cycle

1st cycle

2nd cycle

5th cycle

10th cycle

13th cycle

15th cycle

Fig. 0.4 Cross sectional view of mixing patterns after several cycles in BEB

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3. Microlens arrays

(a)

(b)

(c) Fig. 0.5 Proposed fabrication process and result: (a) Step 1, X-ray irradiation, (b) Step 2, thermal treatment, and (c) fabricated microlenses by a modified LIGA process.

Fig. 0.6 Relaxation of free volume: relation between temperature and specific volume of polymer.

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(a) TH = 105°C (b) TH = 115°C Fig. 0.7 Predicted microlens shapes (nominal diameter of 1500µm) in comparison with experimental ones (solid) at two different heating temperatures of (a) 105°C (b) 115°C: predictions without considering the relaxation process (dotted), and with considering the relaxation process (broken).

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Microlenses

2 Seed layer deposition

3 Ni electroplating

4 Mold insert

(a) (b) Fig. 0.8 Fabrication of the microlens mold insert for the hot embossing: (a) sequence of steps and (b) photographs of Ni-electroplated mold insert.

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Fig. 0.9 Surface profiles of the injection molded φ 500µm micro-lenses (PC) with mold insert.

(a) f200 µm microlens array mold insert

(c) f300 µm microlens mold insert

(b) f200 µm microlens array embossed PMMA

(d) f300 µm microlens embossed PC

Fig. 0.10 SEM images of the mold insert and replicated polymers

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PART I. POLYMER PROCESSING TECHNOLOGIES Extrusion Process Single Screw Extruders Twin Screw Extruders Injection Molding Process Compression Molding Process Transfer Molding Process Blow Molding Process Thermoforming Process

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1.1 Screw extrusion process

Fig. 1.1 A single screw extruder

Fig. 1.2 A conventional single screw

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Fig. 1.3 Corotating twin screw elements

Fig. 1.4 Counter-rotating twin screw elements

Fig. 1.5 Static mixers

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1.2 Injection molding process

Fig. 1.6 An injection molding machine

Fig. 1.7 Reciprocating screw injection molding

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1.3 Compression molding, Transfer molding

Fig. 1.8 Schematic view of the compression molding process

Fig. 1.9 Two stages of the injection/Compression molding process

Fig. 1.10 Schematic view of the transfer molding process

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1.4 Blow molding process

Fig. 1.11 Schematic view of the blow molding process

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1.5 Thermoforming process

Fig. 1.12 Schematic view of the thermoforming process (a) Vacuum forming, (b) Plug-assisted vacuum forming