Elastomers and Composites Vol. 52, No. 2, pp. 99~104 (June 2017) Print ISSN 2092-9676/Online ISSN 2288-7725 DOI: https://doi.org/10.7473/ec.2017.52.2.99 FDM 3D Printing of Environmental Friendly and High Strength Bio-based PC Filaments for Baby Toys Seong Je Park *,**, Ji Eun Lee *,**, Jean Ho Park *, Min-Young Lyu **, Keun Park **, Myung Sool Koo ***, Sun Chul Jin ***, Ki Yong Kim ***, and Yong Son *, * Micro/Nano Scale Manufacturing R&D Group, Korea Institute of Industrial Technology, 143 Hanggaulro, Sangnok-gu, Gyeonggi-do 15588, South Korea ** Department of Mechanical System Design Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, South Korea *** Chemincal Research Center, Samyang Co., Hwoam-dong, Yuseong-gu, Daejeon 34055, South Korea (Received April 18, 2017, Revised April 27, 2017, Accepted May 8, 2017) Abstract: Due to the depletion of fossil oil and the increasing oil price, bio-plastic is currently topical. Bio-based plastics are synthesized from plant resources, unlike conventional petroleum-based counterparts. Therefore, the former minimizes global warming and reduces carbon dioxide emission. Fossil polycarbonate (PC)has good mechanical and optical properties, but its synthesis requires bisphenol-a and phosgene gas, which are toxic to humans. To address these problems, the fused deposition 3D printing process (hereafter, FDM) is studied using environmentally-friendly and high-strength bio-based PC. A comparisonof the environmental impact and tensile strength of fossil PC versus bio-based PC is presented herein, demonstrating that bio-based PC is more environmentally-friendly with higher tensile strength than fossil PC. The advantages of bio-based PC are applied in the FDM process for the fabrication of environmentally-friendly baby toys. Keywords: bio-based PC, isosorbide, fused deposition modeling (FDM), 3D printing, baby toys, Environmental friendliness Introduction 현재플라스틱의생산량은철강의생산량보다많으며고분자시대라불릴만큼우리주변에서흔히플라스틱제품을볼수있다. 1,2 그러나석유산업기반의플라스틱사용으로현재지구상의심각한환경오염및석유자원고갈의문제가야기되고있다. 따라서최근이를해결하기위한바이오플라스틱 (bio-plastic) 개발에관한연구가크게각광받고있다. 3,4 바이오플라스틱을대표하는플라스틱으로는자연에서분해될수있는생분해성플라스틱과식물에서원료를추출한식물기반플라스틱등이있다. 5 폴리카보네이트 (Polycarbonate, PC) 는석유에서추출한비스페놀 A(Bisphenol-A, BPA) 와포스겐가스 (Phosgene gas) 로합성되며 fossil PC 혹은 bisphenol-a PC라불린다. PC는기계적물성및광학적물성이매우뛰어나자동차부품, 렌즈그리고방탄헬멧등과같이산업전반에서많이사용되고있다. 6,7 하지만비스페놀 A와포스겐가스는인체에매우유해하기때문에영유아용품등친환경성이요구되는제품에는 Corresponding author E-mail: sonyong@kitech.re.kr 사용이제한된다. 8-10 이와같은문제로최근일본의 Mitsubishi chemical사는옥수수전분에서 isosorbide를추출하여인체에무해한친환경 bio-based PC를개발하였다. 11 이를활용하여본연구에서는기존유해성분이검출되던기존 PC필라멘트를 bio-based PC 필라멘트로대체하고그에맞는 FDM 3D 프린팅공정을개발함으로써친환경제품및부품제작으로활용할수있도록하였다. 3D 프린팅공정은절삭가공에비하여버려지는재료의양이매우적고형상제작의한계가없다는큰장점으로현재활발히연구되고있는플라스틱가공방법이다. 12 대표적으로 FDM 방식 3D 프린팅은 Figure 1과같이필라멘트상태의소재를모터로히팅블록에공급하고높은열로용융시켜노즐을통해압출하여베드위에서한층씩적층하는방식이다. 13-15 일반적으로 FDM 방식 3D 프린팅에서사용되는재료는 PLA (Poly Lactic Acid), ABS (Acrylonitrile Butadiene Styrene), PA (Poly Amide) 그리고 PC (Poly Carbonate) 등이있다. PLA의경우식물기반친환경바이오플라스틱이며변형이거의없어 FDM 방식 3D 프린팅재료로가장많이활용된다. ABS 의경우 Acrylonitrile, Butadiene 그리고 Styrene의합성비율에따라매우다양한물성의구현이가능하다. 15 따라서사용
100 Seong Je Park et al. / Elastomers and Composites Vol. 52, No. 2, pp. 99-104 (June 2017) Figure 2. Molecular structure of (a) fossil PC and (b) bio-based PC. Figure 1. Schematic of FDM type 3D Printer. 하고자하는용도에맞게재료를선택할수있는폭이넓다. PA 와 PC는엔지니어링플라스틱으로높은기계적물성을나타내기때문에보편적인 FDM 방식 3D 프린팅에서가장높은기계적물성을구현할수있는재료이다. 이와같이다양한재료를바탕으로 3D 프린팅을통한제품제작은재료가갖는장점과 3D 프린팅가공방법의장점을모두표현할수있기때문에 3D 프린팅을활용한재료의어플리케이션에대한연구가반드시필요하다. 본연구에서는 bio-based PC로필라멘트를제작하고 FDM 3D 프린팅을이용하여친환경성유아용장난감을제작하였다. Fossil PC와 bio-based PC의친환경성을정량적으로비교분석하여 bio-based PC의친환경성을증명하였으며, FDM 방식 3D 프린팅으로제작한시편의인장강도를측정하여 biobased PC의우수한기계적물성을확인하였다. 이러한 biobased PC의친환경성및우수한강도물성의장점을바탕으로 FDM 방식 3D 프린팅공정의활용성을확대하고자한다. Experimental Figure 3. Photos for filament of (a) fossil PC and (b) bio-based PC. 족고분자로이루어져있으며강성이매우뛰어난특성을지니고있다. 따라서본연구에서는위와같은 bio-based PC 원재료를 FDM 방식 3D 프린팅에적용하기위하여지름 1.75 mm의필라멘트로제작하였다. Figure 3와같이상용 fossil PC 와개발된 bio-based PC의필라멘트를나타내었다. 2. 실험장비 본연구에서사용한 FDM 방식 3D 프린터는한국생산기술 1. 실험재료 본연구에서사용한상용 fossil PC는 PC-10(Stratasys) 이며 bio-based PC는 DURABIO D7340IR (Mitsubishi Chemical) 을활용하여필라멘트로제작하여사용하였다. Figure 2(a), (b) 에는 fossil PC와 bio-based PC의분자구조를도시하였다. Figure 2(a) 와같이기존 fossil PC의경우비스페놀 A와포스겐가스로합성되어유해물질이발생할수있다. 하지만 Figure 2(b) 의 bio-based PC는옥수수전분에서추출한 isosorbide 구조를포함하고있어유해성분이없다. 또한 isosorbide는지방 Figure 4. FDM 3D printer developed by KITECH.
FDM 3D Printing of Environmental Friendly and High Strength Bio-based PC Filaments for Baby Toys 101 연구원에서자체제작한프린터를사용하였으며 Figure 4에도시하였다. 최대사용가능한노즐온도는 270 o C이며베드온도는 120 o C이므로엔지니어링플라스틱의출력이가능하다. FDM 방식 3D 프린팅으로제작한시편의인장강도측정을위해 EZ20(Instrument) 의인장시험기를사용하였다. 3. 실험방법 Fossil PC와 bio-based PC의친환경성을파악하기위하여가장많이사용되고있는상용 fossil PC인 PC-10과 bio-based PC인 DURABIO D7340IR을 ASTM D6866-12 Method B의규격에의거하여친환경성을비교하였다. 또한, Bio-based PC의우수한기계적물성을증명하기위하여 FDM 방식 3D 프린팅으로인장시편을제작하였고규격은 ASTM D638 type 1을사용하였다. 인장시편제작조건은 Table 1에도시하였으며 Figure 5와같이 2가지 toolpath로시편을제작하였다. Figure 5(a) 와같이 longitudinal은원소재와가장비슷한강도를나타내며 FDM 방식 3D 프린팅에서가장높은강도를보이는방향이다. FDM 방식 3D 프린팅의특징은한층씩적층하는방식이므로소재간접착력에의해강도가좌우된다. 따라서 Figure 5(b) 와같이소재간접착의연속형태로시편을제작하였다. Toolpath G-code는 x, y, z축좌표와필라멘트피딩량을조절하기위하여직접코딩하였다. 인장시험시사용한인장시험속도는 5 mm/min으로진행하였다. Table 1. Experimental Conditions of FDM Type 3D Printing. Item Value Nozzle temperature ( o C) 270 Bed temperature ( o C) 120 Layer height (mm) 0.2 Nozzle moving speed (mm/s) 80 Volume flow rate (mm 3 /s) 6.3812 Nozzle diameter 0.4 Results and Discussion 1. 친환경성평가친환경정도를파악하기위하여 BETA 연구소 (U.S.A) 에친환경성분석을의뢰하여플라스틱소재내의바이오물질함량을분석하였다. 바이오물질함량을분석할수있는방법에는용해선별법과탄소동위원소질량분석법등이있다. 16 본연구에서는탄소동위원소질량분석법을이용하여 fossil PC와 bio-based PC의친환경성을비교분석하였다. 탄소동위원소질량분석법은플라스틱소재의총탄소함량대비식물유래탄소 (Biomass carbon) 의함량으로친환경성을정량적으로파악하는방법이다. 17 친환경성평가결과를 Figure 6 에도시하였다. fossil PC의경우 100% 석유유래탄소 (Fossil carbon) 가검출되었으며 bio-based PC의경우 44% 의석유유래탄소와 56% 의식물유래탄소가검출되었다. 이를통하여 bio-based PC의친환경성이 fossil PC보다월등히높다는것을파악하였다. 2. 적층시편의인장강도 Fossil PC와 bio-based PC을이용하여 Figure 5와같이 longitudinal 방향과 transverse 방향으로시편을제작하고인장시험을진행하였다. Figure 7에는 longitudinal 시편의응력 -변형율그래프를도시하였으며 Figure 8에는파단시편을도시하였다. Table 2에 longitudinal 방향의탄성계수와인장강도를비교하였으며탄성계수와인장강도모두 Bio-based PC가우수하였다. Figure 9와 10에는 transverse 시편의응력-변형율그래프와파단시편을각각도시하였다. Table 3에 transverse 방향시편의탄성계수와인장강도를도시하였으며 longitudinal 방향과마찬가지로탄성계수와인장강도모두 bio-based PC가우 Figure 5. Generated toolpaths of tensile specimens for (a) longitudinal and (b) transverse directions. Figure 6. Comparison of biomass carbon about fossil PC and bio-based PC.
102 Seong Je Park et al. / Elastomers and Composites Vol. 52, No. 2, pp. 99-104 (June 2017) Table 3. Experimental result for tensile strength of transverse direction. Material Young s Modulus (MPa) Tensile Strength (MPa) Fossil PC 1192.36 24.28 Bio-based PC 1646.19 40.78 Figure 7. Stress-strain curve for longitudinal direction specimens. Table 2. Experimental result for tensile strength of longitudinal direction. Material Young s Modulus (MPa) Tensile Strength (MPa) Fossil PC 1292.62 49.62 Bio-based PC 1733.44 61.15 Figure 10. Fracture specimen for transverse direction. (a) Fossil PC and (b) Bio-based PC. Figure 8. Fracture specimen for longitudinal direction. (a) Fossil PC and (b) Bio-based PC. Figure 11. Experimental results of tensile test. Figure 9. Stress-strain curve for transverse direction specimens. 수하였다. Figure 11에는 fossil PC와 bio-based PC의 longitudinal과 transverse 시편의최대응력을비교한그래프를도시하였다. Longitudinal 방향에서 bio-based PC는 fossil PC 대비 23.24% 높은인장강도를보였다. 이는 Figure 2에서볼수있듯이 biobased PC는뛰어난강성을나타내는 isosorbide를포함하고있기때문이다. 18,19 따라서 longitudinal 방향에서높은인장강도를보인것으로사료된다. Transverse 방향의경우 bio-based PC는 fossil PC 대비 67.96% 높은인장강도를보였다. 이를통하여 bio-based PC는 FDM 방식 3D 프린팅에서소재간접착이매우유리하다고판단되었다. 이또한분자구조에서찾을수있다. Isosorbide를형성하고있는지방족고분자는 fossil PC를이루고있는방향족고분자보다열적특성이낮기때문이다. 20 Fossil PC 보다열적특성이낮은 bio-based PC 는높은노즐온도로인하여 road간접합되는 neck radius가증가되어접촉면적이넓어졌다고사료된다. 15,21,22 이로인하여 bio-based PC는친환경고강도소재로 FDM 방식 3D 프린팅공정에매우적합한소재로파악되었다.
FDM 3D Printing of Environmental Friendly and High Strength Bio-based PC Filaments for Baby Toys 103 3. 유아용장난감어플리케이션 Bio-based PC는친환경고강도소재이며 FDM 방식 3D 프린팅에매우적합한소재이다. 또한 FDM 방식 3D 프린팅은형상의제약이없어 3차원모델링데이터를바탕으로단시간에제품의제작이가능하다. 따라서본연구에서는 FDM 방식 3D 프린팅을이용하여 bio-based PC 소재로형상에따라조립이가능한유아용장난감을제작하였다. Figure 12(a), (b), (c) 와같이간단한형상인세모, 네모, 동그라미그리고 Figure 12(d) 와같이복잡한격자구조알형상을제작하였다. Figure 13과같이블록형상과같은기둥형상에만조립이가능하도록설계함으로써유아의인지능력향상에도움이되도록제작하였다. Figure 14에전체조립형상을도시하였다. 그림과같이장난감의조립및 Figure 14. Overall assembly shape for baby toy. 분리가용이하여유아들이사용함에있어불편함이없도록제작하였다. Conclusion 본연구에서는새로이개발된 bio-based PC의활용성을검토하기위하여기존상용화된 fossil PC와친환경성및인장강도를비교분석하였다. Fossil PC는 0% 의친환경성을보이는반면 bio-based PC 56% 의친환경성을보였다. 또한 FDM 방식 3D 프린팅을이용하여상용 fossil PC와 bio-based PC를 longitudinal과 transverse 방향으로인장시편을제작하고인장시험을진행하였다. Longitudinal, transverse 방향모두 fossil PC보다 bio-based PC에서우수한인장강도를보였다. 이를통하여 bio-based PC는친환경고강도소재임을증명하였다. 이러한소재의장점을바탕으로다양한형상의유아용장난감을제작하여그 FDM 방식 3D 프린팅공정의다양한활용성을검토하였다. Acknowledgments Figure 12. Block of baby toy using bio-based PC and FDM type 3D Printing. (a) Triangle, (b) Rectangle, (c) Circle and (d) Mesh type egg. 본논문은산업통상자원부산업핵심기술개발사업으로지원된연구결과입니다 (10051680, 3D 프린팅용친환경고강도고분자소재개발 ). References Figure 13. Pillar structure of baby toy using bio-based PC and FDM type 3D Printing. 1. M.-Y. Lyu and H. Y. Kim, Introduction to polymer shaping processes and their principles, Polymer Science and Technology, 20, 157 (2009). 2. D. H. Cho and H. J. Kim, Naturally cyclable biocomposites, Elastomers and Composites, 44, 13 (2009). 3. H. Storz and K.-D. Vorlop, Bio-based plastics: Status, challenges and trends. Landbauforschung Applied Agricultural and Forestry Research, 63, 321 (2013). 4. S. Khoramnejadian, J. J. Zavareh, and S. Khoramnejadian, Bio-based plastic a way for reduce municipal solid waste,
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