• Advanced Composite Materials
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• 제16권4호
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• pp.361-376
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• 2007

Disposing of conventional fiber-reinforced polymers (FRPs) poses an environmentally challenging problem. Disposal of FRPs by combustion discharges carbon dioxide in the air because the resin of FRPs is made of fossil fuel. When they are disposed of in the ground, FRPs remain semipermanently without decomposing. In response to these problems, green composites are now being developed and are extensively studied as a material that produces a lower environmental burden. In this paper, green composites using kenaf fiber yarn bundles and PLA (poly(lactic acid)) are fabricated and their tensile properties are evaluated in the experiment. The tensile Young's modulus of all of the laminations is larger than that of PLA alone and the tensile strength of some laminations is larger than that of PLA alone. In particular, the value of UD composite of $0^{\circ$ shows double the tensile strength of PLA alone. Furthermore, the molding conditions for fabricating with a hot press are investigated and the heat resistant tensile properties of green composites are also reported.

• Journal of the Korean Wood Science and Technology
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• 제37권5호
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• pp.426-433
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• 2009

This study investigates the tensile and morphological properties of nanocomposites prepared from poly(lactic acid) (PLA), wood flour (WF) and montmorillonite (MMT) by melt compounding with a twin screw extruder. In order to enhance the mechanical properties of PLA/WF composites, maleic anhydride grafted PLA (MAPLA) is synthesized as a compatibilizer. MAPLA prepared in the laboratory is characterized using FT-IR (Fourier transformed infrared spectroscopy). From the results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis for nanocomposites, we confirmed that silicate layers of MMT are intercalated and partially exfoliated. When 2 wt% MAPLA is added, the tensile strength and modulus of PLA/WF/MAPLA composites were higher than those of the PLA/WF composite. The addition of MMT increases the tensile modulus of PLA/WF/MAPLA composites but decreases the tensile strength.

• Composites Research
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• 제35권6호
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• pp.419-424
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• 2022

Using non-biodegradable polymers is a severe environmental problem as they are not recyclable and generate a large amount of waste. Biopolymers, such as starch-based composites, have been considered one of the most promising replacement materials. These eco-friendly materials have the advantage of being low-cost, biodegradable, and obtained from renewable sources. However, as starch tends to be brittle and hydrophilic, it can make these materials unusable when exposed to water and limit its processability for further applications. In this work, a biobased modified starch was grafted using two bioderived materials, lauryl methacrylate (LMA) and tetrahydrofurfuryl methacrylate (THFMA), by radical polymerization. A polylactic acid (PLA) composite based on the modified starch (m-St) was fabricated to enhance its toughness. These samples were characterized by Fourier transform infrared, ¹H NMR and ¹³C NMR analysis, optical and scanning electron microscopy. The starch was successfully grafted, thus improving the compatibility with the PLA matrix. The mechanical properties of these films were also studied. Results from mechanical tests showed a slight enhancement of the mechanical performance of these composites when m-St was added to the PLA matrix. Such behavior is related to the improved dispersion of m-St 1:2 on PLA, confirmed by SEM images showing enhanced compatibility between modified starch and PLA matrix. This indicated excellent properties of the produced composite film for further eco-friendly applications.

• 한국콘텐츠학회논문지
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• 제21권3호
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• pp.609-615
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• 2021

본 연구는 PLA에 β-TCP를 첨가한 복합체의 생체활성도와 기계적 성질을 평가하고자 한다. 클로로프롬 용액에 24 시간 교반기를 이용해서 PLA와 β-TCP를 무게별로 0, 10, 30, 50 wt% 용해한 후 에탄올 용액에서 PLA/β-TCP 복합체를 추출 후 사출성형을 통해 다양한 기계적 평가를 위한 시편을 제작하였다. SBF 인체 유사 체액에 1, 7, 30, 90 일 동안 침전하여 생체활성도를 평가하였다. 본 연구 결과 PLA/β-TCP 10-30 wt% 첨가한 실험군에서는 유의하게 강도가 증가하였으나 50 wt% 첨가한 실험군에서는 감소하였다. 결론적으로 β-TCP 30 wt% 이상 첨가하는 것은 사출성형 고분자 복합체의 기계적 특성이 개선되지 않는다. 표면 생체활성도는 90일 침전 후 표면 전체에 아파타이트 결정을 형성하였다. β-TCP는 표면특성과 기계적 성질 개선효과가 있음을 입증하였다. 향후 PLA/β-TCP 첨가량에 따른 효율성과 폭 넓은 물성 연구가 필요할 것으로 사료된다.

• Journal of the Korean Wood Science and Technology
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• 제41권2호
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• pp.134-140
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• 2013

UV curing was introduced via a chemical treatment by adding small amounts of a hexafunctional acrylic monomer and a photoinitiator to improve the mechanical properties of PLA. This study also employed a semi-interpenetrated structured polymer network through the process of UV-curing. The UV curing behaviors were investigated using FTIR-ATR spectroscopy and gel fraction determination. Also, the tensile strength was investigated with different hexafunctional acrylic monomer contents and UV doses. The results showed that the crosslinking of UV-induced chemically treated PLA started at a low content of hexafunctional acrylic monomer, resulting in a significant improvement of the mechanical properties compared to those of neat PLA due to crosslinking.

• 한국포장학회지
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• 제29권1호
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• pp.51-57
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• 2023

이 연구에서는 고압 균질기를 통해 제작된 CNF 수 분산액을 PLA에 적용시키는데 있어 비용과 생산 효율성을 고려하여 동결 건조 방식이 아닌 오븐 건조를 통해 수분을 제거한 ODCNF를 제조하였다. 건조 후 고형화된 CNF 분말을 생분해성 고분자인 PLA에 접목시켜 압출, 사출 공정에서 발생하는 전단응력으로 재분산을 유도하였고, 성공적으로 시편이 만들어졌다. 제작된 시편에 대하여 진행된 전계방사 전자현미경 측정을 통해 셀룰로오스 입자가 PLA 매트릭스 내에 함침되어 있는 것을 확인하였다. 또한 시차주사열량계 측정에서 ODCNF가 PLA에 적용되었을 때 결정화도 상승과 냉 결정화 온도가 앞당겨지는 것을 확인하였다. 그리고 냉각 과정에서 결정이 생성되는 것을 통해 실제 생산 공정에 적용할 경우, 친환경 핵제로써 역할을 수행할 수 있을 것으로 판단하였다. 추가적으로 유변물성 측정기를 통해 첨가된 ODCNF가 PLA의 점도를 과도하게 증가시키지 않아 기존 공정 조건에 그대로 적용할 수 있음을 확인하였고, 이는 제작된 시편을 통해서도 알 수 있었다. 동적 점탄성 특성에서는 첨가된 ODCNF 입자의 필러 효과와 향상된 결정화도로 인해 유리상과 고무상에서 모두 저장 탄성율의 비율이 PLA에 비해 높게 유지되는 것으로 밝혀졌다. 이러한 연구결과를 바탕으로 대량 생산이 가능하고, 생산단가를 낮춘 ODCNF를 이용하여 CNF/PLA 기반의 100% 생분해성 복합재 개발이 가능할 것으로 기대된다.

• Journal of the Korean Wood Science and Technology
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• 제37권5호
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• pp.434-439
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• 2009

This study investigates the thermal properties of nanocomposites prepared from poly(lactic acid) (PLA), wood flour (WF) and montmorillonite (MMT) by melt compounding with a twin screw extruder. In order to enhance the mechanical properties of PLA/WF composites, maleic anhydride grafted PLA (MAPLA) is synthesized as a compatibilizer. MAPLA prepared in the laboratory is characterized using FR-IR. From SEM microphotographs, the presence of MAPLA has a positive effect on the mechanical properties of WF-reinforced PLA composites. The addition of WF/MAPLA into neat PLA increased the glass transition temperature ($T_g$). The addition of 1 to 5 wt% MMT into PLA/WF/MAPLA composite decreases the $T_g$. The cold crystallization temperature ($T_{cc}$) was decreased by the addition of MMT. The MMT could act as effective nucleating sites of PLA crystallization. The thermal stability evaluated by thermogravimetric analysis (TGA) is improved with the contents of MMT up to 3 wt%.

• Composites Research
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• 제24권3호
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• pp.1-5
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• 2011

환경 문제가 대두 됨에 따라 세계 각국에서는 환경규제를 통해서 산업계에 친환경 제품의 개발을 독려하고 있어 생분해성 재료에 대한 산업계의 관심이 높아지고 있다. 생분해성 재료인 Polylactic acid(PLA)는 강성과 내화학성이 뛰어나지만 내열성과 내충격성이 낮아서 자동차용 재료로서 요구되는 성능을 만족시킬 수 없다. 이에 본 연구에서는 천연섬유(황마)를 강화재로 사용하여 PLA의 내열성과 내충격성을 향상 시키기 위한 실험을 수행하였다. 특히 PLA와 황마 계면 간의 결합력을 증가시키기 위해 다양한 표면처리를 수행하였고 내충격성이 향상됨을 확인하였다. 또, 어닐링 처리를 통해서 PLA의 내열성이 크게 증가함을 보였다.

• 폴리머
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• 제38권4호
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• pp.464-470
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• 2014

A chemo-mechanical method was used to prepare lignin-containing cellulose nanofibrils(L-CNF) from unbleached woodpulps dispersed uniformly in an organic solvent. L-CNF/PLA composites were obtained by solvent casting method. The effects of L-CNF concentration on the composite performances were characterized by tensile test machine, contact angle machine, scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). The tensile test results indicated that the tensile strength and elongation-at-break increased by 50.6% and 31.8% compared with pure PLA. The contact angle of PLA composites decreased from $79.3^{\circ}$ to $68.9^{\circ}$. The FTIR analysis successfully showed that L-CNF had formed intermolecular hydrogen bonding with PLA matrix.

• Elastomers and Composites
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• 제52권3호
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• pp.201-210
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• 2017

We studied the antibacterial effect and mechanical properties of PLA composites with in organic porous zeolite-type bacteriocides. The specimens were prepared by an intermeshing co-rotating twin screw extruder using different contents of inorganic bacteriocide. The degree of dispersion of the in organic bacteriocide in the PLA composite was confirmed by FE-SEM. The contents of Ag and Zn in the composite were also investigated by energy dispersive spectroscopy at different concentrations of the inorganic bacteriocide. The antibacterial effects were analyzed by turbidity analysis, shaking culture, and drop-test. The mechanical properties, such as the tensile and flexural properties, impact strength, and physical properties, were also investigated. As the content of inorganic bacteriocide increased, the antibacterial activity was increased, especially against Staphylococcus aureus. Mechanical properties, namely, tensile strength, elongation, flexural strength, and impact strength, tended to decrease with an increase in inorganic bacteriocide content, but the tensile and flexural modulus increased.