Development Of Innovative Gas- Assisted Foam Injection .
Development of Innovative GasAssisted Foam Injection MoldingTechnologyByPeter Ungyeong JungA thesis submitted in conformity with the requirementsfor the degree of Doctor of PhilosophyDepartment of Mechanical and Industrial EngineeringUniversity of Toronto Copyright by Peter Ungyeong Jung 2013
Development of Innovative Gas-Assisted FoamInjection Molding TechnologyPeter Ungyeong JungDegree of Doctor of Philosophy, 2013Department of Mechanical and Industrial EngineeringUniversity of TorontoABSTRACTInjection molding technology is utilized for a wide range of applications frommobile phone covers to bumper fascia of automotive vehicles. Foam injection molding(FIM) is a branched manufacturing process of conventional injection molding, but it wasdesigned to take advantage of existing foaming technology, including material costsaving and weight reduction, and to provide additional benefits such as improvement indimensional stability, faster cycle time, and so on. Gas-assisted injection molding (GAIM)is another supplemental technology of injection molding and offers several advantages aswell. This thesis study takes the next step and develops innovative gas-assisted foaminjection molding (GAFIM) technology, which is the result of a synergistic combinationof two existing manufacturing technologies, FIM and GAIM, in order to produce aunique thermoplastic foam structure with proficient acoustic properties. The foamstructure manufactured by GAFIM consists of a solid skin layer, a foam layer, and ahollow core; and its 6.4-mm thick sample outperformed the conventional 22-mm thickpolyurethane foam in terms of the acoustic absorption coefficient. With respect toii
foaming technology, GAFIM was able to achieve a highly uniform foam morphology bycompletely decoupling the filling and foaming phases. Moreover, the additional shear andextensional energies from GAFIM promoted a more cell nucleation-dominant foamingbehavior, which resulted in higher cell density and smaller cell sizes with both CO2 andN2 as physical blowing agents. Lastly, it provided more direct control of the degree offoaming because the pressure drop and pressure drop rate was controlled by a singleparameter, that being the gas injection pressure. In summary, innovative, gas-assistedfoam injection molding technology offers not only a new strategy to produce acousticallyfunctioning thermoplastic foam products, but also technological advantages over theconventional foam injection molding process. Gas-assisted foam injection molding canbecome the bedrock for more innovative future applications.iii
ACKNOWLEDGEMENTFirst of all, I would like to thank God the Father for presenting this opportunity tome six years ago and giving me courage to accept this challenging task. I truly believethat He walked this long journey with me and I could not have finished it without Hislove, guidance, and blessings.I cannot say enough how grateful I am for my supervisor, Prof. Chul B. Park, forhis excellent guidance and the valuable life lessons that I learned from him. He has beenvery supportive and patient throughout my program and presented numerousopportunities for me to mature as a researcher and a person. I also would like to thankProf. Hani E. Naguib for being my Ph.D. thesis committee member and alwaysencouraging me as one of his own students. I am also very appreciative to Prof. Chandrafor his time and effort as my Ph.D. thesis committee member and his very valuabletechnical advice. I am grateful for Prof. Ashgriz and Prof. Turng for becoming my examcommittee members in such a short notice and for their valuable feedback.I am indebted to my colleagues at the Microcellular Plastics Manufacturing Labfor sharing my ups and downs on daily basis, which is not an easy task. I sincerely thankmy previous and current colleagues, Dr. Anson Wong, Reza Nofar, Kamlesh Majithiya,Nemat Hossieny, Hassan Mahmood, Dr. Amir Ameli, Davoud Jahani, Dr. Saleh Amani,Konstantin Kovalski, Medhi Saniei, Dr. Jing Wang, Dr. Sunny Leung, Dr. MohamedHassan, Dr. Yanting Guo, Lun Howe Mark, Mo Xu, Ali Rizvi, Alireza Naeini, VahidShaayegan, Weidan Ding, Anna Zhao, Sai Wang, Dr. Reza Bazegari, Dr. AdhikaryKamal. I am also grateful to the many undergraduate students who have assisted me iniv
my research throughout the years, especially, Hyunwoo Lee, Taewon Park, and ChenkunLi.There are two of my colleagues with whom I have shared a lot of struggles andfrustrations; together, we were able to overcome obstacles, and they have supported meincredibly throughout the years. Thus, my special thanks go to Raymond Chu and Dr.Changwei Zhu.I was very fortunate to get to know so many hyungs and establish valuablefriendships with them throughout the years. They helped me to get through difficult timesof my life, and shared their personal experiences and wisdoms with me. I would like tothank Dr. Kevin Y.H. Lee, Dr. Richard Eungkee Lee, Dr. Ryan S.G. Kim, Dr. YongarkMoon, Dr. Myungjae Lee, Dr. Kyungmin Lee, Dr. John W.S. Lee, Dr. Taekyun Lee, andDr. Patrick Lee. I was also privileged to share special friendships with Esther Lee, Prof.Dongwoo Cho, Prof. Bosung Shin, Dr. Youngseok Kim, and Prof. Simon Park.Last, but definitely not the least, I would like to thank very special people in mylife. I owe a big thank to Donna Lee for being a huge part of my life and inspiring mewith her caring support, positive energy, and love. I cannot thank enough my belovedfamily, my dad, mom, and sister, Maria, for their unconditional love, endless support,having faith in me when I was doubting myself, encouraging me when I was struggling,and motivating me every day to try my best at everything I do to become a better person.I really am indebted to my mom, especially, for packing my lunch (and dinner sometimes)every weekday for the last six years, which have been fuel to my engine. I thankeveryone else who helped me to get through this tall, challenging task.v
TABLE OF CONTENTSABSTRACT . . IIACKNOWLEDGEMENT . IVTABLE OF CONTENTS . VILIST OF TABLES . . XIILIST OF FIGURES . . XIIILIST OF SYMBOLS. . XIXNOMENCLATURE .XXICHAPTER 1INTRODUCTION . 11.1Thermoplastic Foams . 11.2Open-Cell and Closed-Cell Foams . 11.3Thermoplastic Foam Processing . 11.4Injection Molding . 21.5Foam Injection Molding. 41.6Acoustic Thermoplastic Foams . 5vi
1.7Research Motivation . 61.8Thesis Objectives and Scope of Research . 71.9Organization of Thesis . 8CHAPTER 2LITERATURE REVIEW AND THEORETICAL BACKGROUND . .112.1Thermoplastic Foam Processing . 112.1.1Fundamentals of Blowing Agents . 112.1.2Formation of Polymer/Gas Solution . 142.1.3Theoretical Principles of Cell Nucleation and Growth Mechanisms . 172.2Manufacturing of Open-Celled Foam Structures . 212.2.1Open-Celled Structures with Foam Extrusion Technology . 212.2.2Porous Structures by using Sacrificial Fillers . 222.32.3.1Foam Injection Molding Technologies . 23Conventional Foam Injection Molding and Microcellular InjectionMolding Technologies . 232.3.2Low Pressure and High Pressure Foam Injection Molding Technologies .252.3.3Investigation of Foaming Behaviors in Foam Injection Molding UsingMold Pressure Profile . 272.3.4Effect of Gas Counter Pressure on Foam Injection Molding Behavior 29vii
2.4Gas-Assisted Injection Molding . 302.4.1Conventional Gas-Assisted Injection Molding Technology . 302.4.2Effect of Gas Channel . 322.4.3Computer Simulation Analysis . 332.4.4Effect of GAIM on Polymer Crystalline Morphology . 352.5Acoustic Absorption and Insulation . 372.5.1Principles of Acoustic Absorption . 372.5.2Principles of Acoustic Insulation . 382.5.3Thermoplastic Foams for Acoustic Applications. 40CHAPTER 3PROPOSED DESIGN OF GAS-ASSISTED FOAM INJECTIONMOLDING TECHNOLOGY. 573.1Motivation . 573.1.1Advantages of Gas-Assisted Injection Molding . 573.1.2Advantages of Foam injection molding . 583.1.3Synergistic Effects of the Proposed Gas-Assisted Foam InjectionMolding Technology . 583.23.2.1Fundamental Foaming Principles of the Proposed Technology . 62Coupled Nature of Conventional Foam Injection Molding Technology .623.2.23.3Decoupling of the Filling and Foaming Mechanism. 64System Implementation of the Proposed Technology . 68viii
3.3.1Schematic of the Proposed Technology . 683.3.2Required Equipment for the Proposed Technology . 69CHAPTER 4EXPERIMENTALSTUDIESOFGAS-ASSISTEDFOAMINJECTION MOLDING TECHNOLOGY . 764.1Introduction . 764.2Experimental Materials . 764.3Experimental Set-up . 774.3.1Advanced Structural Foam Molding System . 774.3.2Arburg Injection Molding Machine with MuCell System . 774.3.3Gas-Assisted Injection Molding System . 784.3.4Moldflow Simulation Study . 814.4Experimental Procedure. 814.4.1Manufacturing of Foams . 814.4.2Foam Structure Characterization. 814.4.3Acoustic Characterization . 824.5Effects of Processing Parameters of Gas-Assisted InjectionMolding Technology. 834.5.1Effect of Delay Time . 834.5.2Effect of Gas Injection Pressure Profile . 854.5.3Simulation Study Using MoldFlow . 87ix
4.6Low Cavity Pressure Case of the Proposed Technology . 894.6.1Experiment with CO2 . 904.6.2Experiment with N2 . 924.6.3Foaming Mechanism Analysis . 934.7Highly Pressurized Case of the Proposed Technology. 954.7.1Experiment with Low Gas Injection Pressure. 964.7.2Experiment with High Gas Injection Pressure . 994.7.3Foaming Mechanism Analysis . 1024.8CHAPTER 5Summary . 108ACOUSTIC PROPERTY CHARACTERIZATION OF THEMANUFACTURED FOAMS. 1475.1Introduction . 1475.2Strategies to Improve Acoustic Properties of Injection FoamMolded Samples . 1485.2.1Perforation . 1485.2.2Implementation of Mold Opening Technology . 1535.2.3Utilization of Gas-Assisted Foam Injection Molding Technology . 1575.3Relationships between Cellular Morphologies and AcousticProperties . 1595.4Summary . 161x
CHAPTER 6CONCLUSIONS AND RECOMMENDATIONS FOR FUTURERESEARCH . 1786.1Summary of Major Contributions. 1786.2Recommendations for Future Research . 182REFERENCES . 185xi
LIST OF TABLESTable 2.1 DSC parameters of different zones of G6.7 and G11.6 samples [165] . 45Table 4.1 Physical properties of Pellethane 2355-75A. 110Table 4.2 Common fixed processing conditions of injection molding process for GAIMexperiments . 110Table 4.3 GAIM processing conditions for the delay time study . 111Table 4.4 GAIM processing conditions for the gas injection pressure study . 111Table 4.5 GAIM processing conditions for the gas injection pressure profile . 112Table 4.6 Fixed processing parameters for Moldflow . 112Table 4.7 GAIM processing parameters for CO2 experiment. 113Table 4.8 Common processing parameters for the pressurized case . 113Table 4.9 GAIM processing conditions for the pressurized case . 114Table 5.1 Fixed processing conditions for the mold-opening experimental study . 164Table 5.2 Processing conditions of FIM process for the perforation study . 164Table 5.3 Variable processing parameters for the perforation roller study . 164xii
LIST OF FIGURESFigure 1.1 Schematics of closed-cell and open-cell foam structures . 10Figure 2.1 Gas bubble shape changes with different contact angles on a planar surface[135] . 46Figure 2.2 Conical cavity for bubble nucleation [135] . 46Figure 2.3 Schematic for creating porous structure with using sacrificial fillers . 47Figure 2.4 SEM picture of foamed porous structure by leaching of NaCl particulates [36]. 47Figure 2.5 Measurement of cavity pressure profile [127]. 48Figure 2.6 Pressure profiles in foam extrusion and FIM [127]. 49Figure 2.7 Comparison of estimated cell density from foam extrusion and actual celldensity from FIM of (a) HDPE, (b) PP, and (c) TPO [127] . 50Figure 2.8 Schematic of conventional gas-assisted injection molding technology . 51Figure 2.9 Fingering effect of GAIM TPU . 52Figure 2.10 Req values of semi-circular and rectangular gas channels on thin plates [154]. 52Figure 2.11 SEM pictures of etched GAIM PP at (a) skin layer and (b) near inner core[164] . 53Figure 2.12 Acoustic functional mechanisms of a porous medium [167] . 53Figure 2.13 Transmission loss values of ABS and ABS/carbon-black composites withvarious carbon-black contents [173] . 54Figure 2.14 Acoustic absorption behavior of PP/PE blend foams with various thicknessesxiii
[91] . 54Figure 2.15 Acoustic absorption coefficients of PP/PE blend foams with differentperforation density [91]. 55Figure 2.16 Acoustic absorption behaviors of various types of 3 mm-thick PLLAcomposites [176] . 55Figure 2.17 Acoustic absorption of 6.5-mm PP samples with different sizes of voids [31]. 56Figure 3.1 Technological innovations for the proposed GAFIM . 71Figure 3.2 Foaming mechanisms of conventional foam injection molding. 72Figure 3.3 Effect of injection flow rate on the final cell structure [127] . 72Figure 3.4 Effect of void fraction setting on the final cell structure [127] . 73Figure 3.5 Schematic of the proposed gas-assisted foam injection molding technology . 74Figure 3.6 Effect of additional shear on cell density [178]. 74Figure 3.7 Effect of extensional strains on cell density [179] . 75Figure 4.1 Schematic of advanced structural foam molding machine [75] . 115Figure 4.2 Arburg ALLROUNDER 270C [187] . 115Figure 4.3 Schematic of MuCell system setup . 116Figure 4.4 Original cavity drawing . 116Figure 4.5 Modified cavity with gas channels and measurement locations . 117Figure 4.6 Engineering drawing of cavity with gas channels . 118Figure 4.7 Picture of actual cavity insert with gas channels . 119Figure 4.8 Drawing of sample part with gas channels . 120Figure 4.9 Spring-loaded check valve . 121xiv
Figure 4.10 Schematic of ‘through nozzle’ gas injection system . 121Figure 4.11 Effect of gas injection delay time . 121Figure 4.12 Cavity pressure profile when GAIM was applied . 122Figure 4.13 Effect of gas injection pressure . 122Figure 4.14 Cavity pressure profile of Exp. 4.6 . 123Figure 4.15 Cavity pressure profile of Exp. 4.7 . 124Figure 4.16 Filled polymer volumes by gas injection pressure changes based onMoldflow . 124Figure 4.17 Voids created by GAIM based on Moldflow . 125Figure 4.18 Gas voids from different GAIM pressure profiles . 125Figure 4.19 The effects of shot sizes on the degree of filling of GAIM samples . 126Figure 4.20 The effects of melt temperature on the degree of filling of GAIM samples 126Figure 4.21 SEM pictures of FIM and GAFIM samples with 35 vol% of void fractionsetting . 127Figure 4.22 Cell density values of both FIM and GAFIM samples. 128Figure 4.23 Cellular morphologies of FIM and GAFIM samples with N2 as PBA . 129Figure 4.24 Cell density values of FIM and GAFIM at three different locations . 130Figure 4.25 Cavity pressure profiles of (a) FIM and (b) GAFIM for 35 vol% void fractionsetting and N2 as PBA . 130Figure 4.26 Measurement locations of non-gas injection and gas injection regions in afoamed sample . 131Figure 4.27 Cavity pressure profiles of medium GAIM pressure experiment . 132Figure 4.28 SEM images of gas injection (GI) and non-gas injection (NGI) regions ofxv
GAFIM sample . 133Figure 4.29 SEM pictures of FIM and GAFIM samples at gas injection (GI) regions . 134Figure 4.30 SEM pictures of both FIM and GAFIM (6.89 MPa of gas injection pressure)samples at gas injection regions . 134Figure 4.31 Magnified SEM images of both FIM and GAFIM samples at non-gasinjection regions . 135Figure 4.32 Cell density changes at both gas injection (GI) and non-gas injection (NGI)regions due to the implementation of GAFIM . 136Figure 4.33 Average cell diameters at both gas injection (GI) and non-gas injection (NGI)regions of FIM and GAFIM samples . 137Figure 4.34 Average foam density values at gas injection (GI) and non-gas injection (NGI)regions of FIM and GAFIM samples . 138Figure 4.35 Cavity pressure profile of highly pressurized cavity case with 13.79 MPa ofgas injection pressure . 139Figure 4.36 SEM pictures of gas injection (GI) regions for FIM and two GAFIM cases. 140Figure 4.37 Magnified SEM pictures of gas injection (GI) regions for FIM and twoGAFIM cases . 141Figure 4.38 SEM images of non-gas injection regions (NIG) for FIM and two GAFIMcases . 142Figure 4.39 Magnified SEM images of non-gas injection (NGI) regions for FIM and bothGAFIM cases . 143Figure 4.40 Cell density changes of gas injection (GI) and non-gas injection (NGI) areasxvi
due to the increase of gas injection pressure of GAFIM . 144Figure 4.41 Average cell diameter values of gas injection (GI) and non-gas injection(NGI) regions for FIM and two GAFIM cases . 145Figure 4.42 Average foam density values at gas injection (GI) and non-gas injection (NGI)regions of FIM and two GAFIM cases . 146Figure 4.43 Images from the visualization batch foaming system with respect to time . 146Figure 5.1 Impedance tube testing setups for acoustic absorption of (a) high frequencyrange with 30 mm diameter tube and (b) low frequency range with 100 mm diameter tube. 165Figure 5.2 Impedance tube testing set-ups for acoustic transmission loss of (a) 30 mmdiameter tube and (b) 100 mm diameter tube . 165Figure 5.3 Acoustic absorption coefficients with different open area ratios of rigid coverplate (a) 0.4, (b) 0.1, (c) 0.025, and (d) 0.005 . 166Figure 5.4 Manually perforated samples with different hole sizes . 166Figure 5.5 Acoustic absorption coefficients of polyurethane foam with the manuallyperforated samples . 167Figure 5.6 Acoustic absorption behaviors of perforated samples . 167Figure 5.7 Acoustic absorption coefficients of perforated samples followed by regularfoamed samples. 168Figure 5.8 Effects of perforation on the acoustic absorption coefficients for (a) Exp. 1, (b)Exp. 2, and (c) Exp. 3 . 169Figure 5.9 Acoustic absorption coefficients of mold opening samples . 170Figure 5.10 Foam samples with various degrees of mold opening. 170xvii
Figure 5.11 Transmission losses of different mold opening samples . 171Figure 5.12 Acoustic absorption behaviors of two different injection flow rate settings171Figure 5.13 Cellular morphologies of (a) high injection flow rate samples and (b) lowinjection flow rate samples . 172Figure 5.14 Transmission loss values for two different injection flow rate settings . 173Figure 5.15 Acoustic absorption coefficients of two injection flow rate settings at higherfrequency range . 173Figure 5.16 Acoustic insulation behaviors of two injection flow rate settings . 174Figure 5.17 Acoustic absorption coefficients of FIM and GAFIM samples . 174Figure 5.18 Transmission loss behaviors of FIM and GAFIM samples . 175Figure 5.19 Acoustic absorption coefficients of GAFIM samples with two gas injectionpressures, 13.79 and 6.89 MPa . 176Figure 5.20 Transmission loss values of GAFIM samples with two different gas injectionpressures, 13.79 and 6.89 MPa . 177xviii
LIST OF SYMBOLSA area of the micrograph, m2Ab surface area of bubble, m2Co concentration of gas molecules, mol/m3Do diffusivity coefficient constant, m2/sD diffusivity, m2/sE elastic modulus of polymer, Pafo frequency factor of gas molecules joining the nucleus, dimensionlessF(θc) shape factork Boltzmann constant, m2kg/s2-KM magnification factors of the micrograph, dimensionless nucleation rate of homogenous nucleation ( Jhom), #/m3-sn number of bubbles in the micrograph, dimensionlessr cell radius, mRg universal gas constant, J/K-molTsys system temperature, KVb volume of bubble
Injection molding technology is utilized for a wide range of applications from mobile phone covers to bumper fascia of automotive vehicles. Foam injection molding (FIM) is a branched manufacturing process of conventional injection molding, but it was . 4.3.2 Arburg Injection
etc. Some hybrid machining processes, such as ultrasonic vibration-assisted [2], induction-assisted [3], LASER-assisted [4], gas-assisted [5] and minimum quantity lubrication (MQL)-assisted [6,7] machining are used to improve the machinability of those alloys. Ultrasonic-assisted machining uses ultrasonic vibration to the cutting zone [2]. The
assisted liposuction, vaser-assisted liposuction, external ultrasound-assisted liposuction, laser-assisted liposuction, power-assisted liposuction, vibro liposuction (lipomatic), waterjet assisted and J-plasma liposuction. This standard sets out the requirements for the provision of Liposuction service. Liposuction
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VDSS Division of Family Services Assisted Living Facility Assessment Manual Assisted Living Facility (ALF) Any public or private assisted living facility that is required to be licensed as an assisted living facility by the Department of Social Services under Chapter 17 (§63.2-1700 et seq.) of Title .
Futhermore, we have recently studied gas-assisted and laser-gas(XeF 2)-assisted He etching and have realized both reduced swelling as well as enhanced etch rates for titanium thin films. We will overview the processing parameters and the ion/photon/reactive gas fluxes that lead to both damage mitigation as well as laser- and gas-assisted etching.
The gas lift application supports both Plunger Assisted Gas Lift (PAGL) and Gas Assisted Plunger Lift (GAPL) modes. The gas lift program can be used in an independent way, or it can coordinate with the plunger program to inject gas at certain parts of the plunger cycle. The
to the carrier-gas assisted HKP could be of support for mass-production in early stage. The present paper is a summary of a part of this process, to be more precise, the discharging part. For the carrier-gas assisted discharging (CAD), a special device (TGD20a) had been designed, produced and tested which is content of this paper.
Abstract: Natural gas compressibility factor (Z) is key factor in gas industry for natural gas production and transportation. This research presents a new natural gas compressibility factor correlation for Niger Delta gas fields. First, gas properties databank was developed from twenty-two (22) laboratory Gas PVT Reports from Niger Delta gas .
