• 한국포장학회지
• /
• 제28권3호
• /
• pp.157-163
• /
• 2022

본 연구에서는 전자레인지 조리 시 발생하는 포장 내부의 수증기를 스스로 방출할 수 있는 PLA 기반 스마트 복합 필름을 제조하였다. 제조된 복합필름의 전자레인지 조리가 가능한 HMR 제품의 포장재로써 적용가능성을 평가하기 위해 DSC, UTM, GTR 및 전자레인지 모의 적용 평가를 통해 열적 특성, 기계적 특성, 온도 구간별 기체 투과도 및 전자레인지 적용성을 평가하였다. 복합필름의 열적 특성을 확인한 결과, PLA와 PEG의 강한 화학적 상호작용을 확인하였고 본 연구에서 기대한 전자레인지 조리 온도 내에서 PEG가 용융되는 것을 확인하였다. 또한, 제조된 복합필름은 PEG의 첨가로 인해 인장강도는 감소하였지만 연신율이 증가하였고, nanoclay의 함량이 증가함에 따라 감소된 인장강도가 일부 회복한 것을 확인하였다. 또한, 기체투과도의 경우 PEG의 T_m1 이상인 65℃ 부터 PEG가 용융되면서 투과도가 비약적으로 증가한 것을 확인하였다. 전자레인지 모의 적용 평가를 통해 pure PLA는 내부 수증기를 방출하지 못하고 그 압력을 버티지 못해 폭발한 것에 비해, 복합필름의 경우 전자레인지 수증기 발생 온도에서 그 형태를 유지하며 효과적으로 내부 수증기를 자가방출한 것을 확인하였다. 이러한 결과를 바탕으로 본 연구에서 제조한 스마트 복합필름은 포장재로써 향후 전자레인지 조리 HMR식품 포장재로써 적용될 수 있다.

• Journal of Periodontal and Implant Science
• /
• 제33권4호
• /
• pp.599-613
• /
• 2003

The goal of periodontal treatment is regeneration of the periodontium. Bone graft and absorbable PLA/PGA membrane have been used for this purpose. In this study, 4${\times}$4mm 1-wall intrabony defects were surgically created bilaterally in the mandible of five male beagles. The control group went through a conventional flap operation, while the experimental group I was treated with absorbable PLA/PGA membranes only, group II was treated with absorbable membrane and calcium phosphate. The results are the following : 1. The defect height was 4.82${\pm}$0.45mm in the control group, 4.93${\pm}$0.79mm in the experimental I group, and 4.92${\pm}$0.62mm in the experimental II group. There was no statistically significant difference among 3 groups(P <0.05). 2. The amount of junctional epithelium migration was 30.90${\pm}$9.92% of the defect height in the control group, 39.16${\pm}$7.51% in the experimental I group, and 38.68${\pm}$12.22% in the experimental II group. There was no statistically significant difference among 3 groups(P <0.05). 3. The amount of connective tissue adhesion was 36.38${\pm}$9.03% in the control group, 14.73${\pm}$3.93% in experimental I group, and 27.87${\pm}$9.70% experimental II group. Experimental group I was a statistically significantly different from control group(P <0.05). 4. The amount of new cementum regeneration was 32.92${\pm}$10.51%, 50.04${\pm}$7.61%, and 39.62${\pm}$12.14% for the control, experimental I, and experimental II group respectively. Experimental group I was a statistically significantly different from control group(P<0.05). 5. The amount of new alveolar bone regeneration was 27.24${\pm}$7.49%, 40.75${\pm}$8.03%, and 36.47${\pm}$15.11% for the control, experimental I, and experimental II group respectively. Experimental group I was a statistically significantly different from control group(P <0.05). The results suggest that the use of PLA/PGA membrane in 1-wall intrabony defect of beagle dogs may promote periodontal regeneration. Further studies are required to determine their regeneration effects.

• 한국산학기술학회논문지
• /
• 제16권3호
• /
• pp.1671-1676
• /
• 2015

폴리-L-유산 (PLLA)/폴리-D-유산(PDLA)의 스테레오컴플렉스(SC) 특유의 결정 거동은 PLLA/PDLA의 블렌드의 특정한 용융 조건에서 나타난다. 이를 적용하여 PLA 스테레오컴플렉스를 제조하기 위해 전반적인 조성에서 PLLA와 PDLA를 블렌드 하였다. 또한 충격 강도와 열변형온도 같은 기계적 물성 및 열적 특성을 향상시키기 위해 충격보강제, 탈크와 유리섬유(GF) 등의 보강제를 첨가하였다. 그 결과로 열변형 온도가 $115^{\circ}C$ 에서 관찰 되는 조성의 복합재를 제조하였다. 더 경제적인 방법으로, PLLA와 상용화된 폴리프로필렌(PP)을 전반적인 조성에서 블렌드 하였다. 그 결과, 특정 조성에서 상용화된 PP/탈크 복합재와 ABS에 적용시킬 수 있는 물성을 나타내었다. 이러한 결과는 PP와 PLLA같은 매트릭스 수지에 유리섬유 및 충격보강제를 잘 분산시키는 것에서 기인하는 것으로 판단된다.

• Composites Research
• /
• 제33권4호
• /
• pp.198-204
• /
• 2020

본 연구에서는 탄소나노튜브 다발을 포함하는 나노복합재료의 열-기계적 특성을 정량적으로 예측하기 위하여 분자동역학 전산모사와 유한요소 기반 균질화 기법을 적용하였다. 응집된 탄소나노튜브의 수가 증가함에 따라 동일한 탄소나노튜브의 체적분율에도 불구하고, 면내 영률 및 면내 전단계수는 감소하였고, 면내 열팽창계수는 증가함을 확인할 수 있었다. 계면의 두께를 조사하기 위하여 밀도의 반경 방향 분포(Radial density distribution)을 조사하였으며, 계면의 두께는 탄소나노튜브의 수와는 거의 무관함을 확인할 수 있었다. 기지와 계면은 등방성 재료로 가정하였으며, 예측한 계면의 열-기계적 특성에 따르면, 응집된 탄소나노튜브의 수가 증가함에 따라 계면의 영률 및 전단계수는 감소하였으며, 열팽창계수는 반대로 증가하였다. 이를 토대로, 탄소나노튜브 다발을 포함하는 PLA 나노복합재료의 열-기계적 특성 예측을 위한 멀티스케일 균질화 모델을 개발하였다.

• 한국의류산업학회지
• /
• 제23권4호
• /
• pp.527-535
• /
• 2021

In this study, electroconductive textiles were developed by screen-printing technology using a complex solution of PEDOT:PSS/AgNW on a polylactic acid nanofiber web. A performance evaluation was then conducted to utilize this electroconductive textile as a signal transmission line. To obtain highly conductive electroconductive textiles, this study sought to determine the optimal mixing ratio of PEDOT:PSS/AgNW. Sheet resistance was measured to evaluate the electrical properties of electroconductive textiles, Finite element-scanning electron microscopy images were then used to examine surface properties, and Fourier transform-infrared analysis was performed to evaluate chemical properties. The signal waveform characteristics of the electroconductive textile were observed using a signal generator and an oscilloscope. Radio-frequency characteristics were then evaluated to confirm frequency range, and bending tests were conducted to evaluate durability. The signal transmission lines produced in this study had a sheet resistance value of 3.30 ?/sq, and signal transmission performance was evaluated to observe that the input value of the voltage was nearly identical to the output value. In addition, S21 analysis confirmed that it was available in the frequency domain up to 35 MHz. The performances of the transmission lines were maintained after 100, 200, 500, and 1,000 repeated bending tests, and sufficient durability was confirmed.

• 한국환경보건학회지
• /
• 제44권6호
• /
• pp.524-538
• /
• 2018

Objective: This study aimed to identify the size distributions of particulate matter emitted during 3D printing according to operational conditions and estimate particle inhalation exposure doses at each respiratory region. Methods: Four types of printing filaments were selected: acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA), Laywood, and nylon. A fused deposition modeling (FDM) 3D printer was used for printing. Airborne particles between 10 nm and $10{\mu}m$ were measured before, during, and after printing using real-time monitors under extruder temperatures from 215 to $290^{\circ}C$. Inhalation exposures, including inhaled and deposited doses at the respiratory regions, were estimated using a mathematical model. Results: Nanoparticles dominated among the particles emitted during printing, and more particles were emitted with higher temperatures for all materials. Under all temperature conditions, the Laywood emitted the highest particle concentration, followed by ABS, PLA, and nylon. The particle concentration peaked for the initial 10 to 20 minutes after starting operations and gradually decreased with elapsed time. Nanoparticles accounted for a large proportion of the total inhaled particles in terms of number, and about a half of the inhaled nanoparticles were estimated to be deposited in the alveolar region. In the case of the mass of inhaled and deposited dose, particles between 0.1 and $1.0{\mu}m$ made up a large proportion. Conclusion: The number of consumers using 3D printers is expected to expand, but hazardous emissions such as thermal byproducts from 3D printing are still unclear. Further studies should be conducted and appropriate control strategies considered in order to minimize human exposure.

• 한국산업보건학회지
• /
• 제32권2호
• /
• pp.153-162
• /
• 2022

Objectives: Fused deposition modeling (FDM) 3D printer which is one of the material extrusion (MEX) technologies is an additive manufacturing (AM) process. 3D printers have been distributed widely in Korea, particularly in school and office, even at home. Several studies have shown that nanoparticles and volatile organic compounds (VOCs) were emitted from an FDM 3D printing process. The objective of this study was to identify types of chemicals possibly emitted from FDM 3D printing materials such as PLA (polylactic acid), ABS (acrylonitrile butadiene styrene), nylon, PETG (polyethylene terephthalate glycol), PVA (polyvinyl alcohol), PC (polycarbonate) filaments. Methods: 19 FDM 3D printing filaments which have been distributed in Korea were selected and analyzed VOCs emitted of 3D printing materials by headspace gas chromatography mass spectrometry (headspace GC-MS). Subsamples were put into a vial and heated up to 200℃ (500 rpm) during 20 minutes before analyzing FDM 3D printing filaments. Results: In the case of PLA filament, lactide and methyl methacrylate, the monomer components of one, were detected, and the volume ratio ranged 27~93%, 0.5~37% respectively. In the case of ABS filaments, styrene (50.5~59.1%), the monomer components of one, was detected. Several VOCs among acetaldehyde, toluene, ethylbenzene, xylene, etc were detected from each FDM 3D printing filaments. Conclusions: Several VOCs, semi-VOCs were emitted from FDM 3D printing filaments in this study and previous studies. Users were possibly exposed to ones so that we strongly believe that we recommend to install the ventilation system such as a local exhaust ventilation (LEV) when they operate the FDM 3D printers in a workplace.

• 한국의학물리학회지:의학물리
• /
• 제30권4호
• /
• pp.155-159
• /
• 2019

Radiological properties of newly introduced and existing 3-dimensional (3D) printing materials were evaluated by measuring their Hounsfield units (HUs) at varying infill densities. The six materials for 3D printing which consisted of acrylonitrile butadiene styrene (ABS), a unique ABS plastic blend manufactured by Zortrax (ULTRAT), high impact polystyrene (HIPS), polyethylene terephthalate glycol (PETG), polylactic acid (PLA), and a thermoplastic polyester elastomer manufactured by Zortrax (FLEX) were used. We used computed tomography (CT) imaging to determine the HU values of each material, and thus assess its suitability for various applications in radiation oncology. We found that several material and infill density combinations resembled the HU values of fat, soft tissues, and lungs; however, none of the tested materials exhibited HU values similar to that of bone. These results will help researchers and clinicians develop more appropriate instruments for improving the quality of radiation therapy. Using optimized infill densities will help improve the quality of radiation therapy by producing customized instruments for each field of radiation therapy.

• Elastomers and Composites
• /
• 제55권1호
• /
• pp.46-50
• /
• 2020

Material extrusion (ME)-type 3D printing is the most popular among the 3D printing processes. In this study, the cross-section morphologies of ME-type 3D printing manufactured specimens were observed with respect to the thermal properties of the material. The cross-section morphology of a specimen is related to the deposition strength, and the outside profile of the cross-section is related to the surface roughness. The filaments used in this study, with different thermal conductivities, were the acrylonitrile-butadiene-styrene (ABS), the high impact polystyrene (HIPS), the glycol-modified polyethylene terephthalate (PETG), and the polylactic acid (PLA). The cross-sections and the surfaces of the 3D manufactured specimens were examined. In ME-type 3D printing, the filaments are extruded through a nozzle and they form a layer. These layers rapidly solidify and as a result, they become a product. The thermal conductivity of the material influences the cooling and solidification of the layers, and subsequently the cross-section morphology and the surface roughness.

• 대한방사선기술학회지:방사선기술과학
• /
• 제41권1호
• /
• pp.53-60
• /
• 2018

The purpose of this study was investigating the effect of 3D printing technology that changes the speed of sound (SOS) and the broadband ultrasound attenuation (BUA) by controlling the density of the media phantom. We used 3D printers which called additive manufacturing (AM) by using material with polylactic acid (PLA). The inside of the medium phantom was filled crossly with 100%, 90%, 80%, 70%, 60%, and 50% of the material. The ultrasonic instrument measured the SOS and the BUA using a 0.55 MHz ultrasound output in opposing mode with a pair of transducers. As a result, the density of the medium phantoms with the SOS showed very high correlation (r = 0.944), but the SOS showed very low correlation (r = 0.500). It is expecting that the manufacturing and measurement method of the medium phantom using 3D printing technology will be used as basic data for ultrasonic bone mineral density.