• Composites Research
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• v.26 no.4
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• pp.230-234
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• 2013

The continuous glass fiber reinforced poly-lactic acid (PLA) composite was manufactured by direct melt impregnation. The mechanical and thermal properties of continuous glass fiber reinforced PLA composite were observed. Measured properties were compared with the reference values of neat PLA and the injection molded glass fiber/ PLA composite. The continuous glass fiber reinforced PLA composite having a fiber volume fraction of 27.7% shows enhanced tensile strength of 331.1 MPa, flexural strength of 528.6 MPa, and flexural modulus of 24.0 GPa. The enhanced heat deflection temperature (HDT) and the increased cystallinity were also observed. The degree of impregnation as a function of pulling speed was also assessed. The degree of impregnation at the pulling speed of 5 m/min was over 90% in this research.

• Composites Research
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• v.27 no.3
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• pp.96-102
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• 2014

In this study, we fabricated jute fiber reinforced polylactic acid (PLA) composite in the form of sandwich panel structure which includes core foam of chopped jute fiber reinforced PLA and outer skin layer of continuous glass fiber reinforced PLA. Flexural properties of the composite were assessed for different jute fiber weight fractions. Density of the core foam ranged from 0.31 to 0.67 $g/cm^3$ and void content fraction 0.51 to 0.71. The maximum flexural strength was 92.7 MPa at 12.5 wt.% of jute fiber content, and the maximum flexural modulus was 7.58 GPa at 30.0 wt.%. Cost analysis was also conducted. The cost to enhance the flexural strength of the applied structure was estimated to be $0.010USD/m^3/MPa$ for 12.5 wt.% fiber content.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1671-1676
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• 2015

A unique crystallization behavior of poly(L-lactide)(PLLA)/poly(D-lactide)(PDLA) stereocomplex(SC) was observed when a PLLA/PDLA blend was subjected to the specific melting conditions. Therefore, we tried to blend PLLA and PDLA at overall composition to form PLA stereocomplexes. Moreover, impact modifier and reinforcement materials such as talc and glass fiber added to enhance the mechanical and thermal properties such as impact strength and heat distortion temperature(HDT). As a result, we got one representative result, one composite recipe with HDT $115^{\circ}C$. For more economic technology, we tried to blend PLLA and Polypropylene at overall composition and we got another representative result which could be applied to current PP/talc composites and ABS materials. The core technology of this might be the well dispersion of glass fibers into the matrix resin such as PP, PLLA and impact strength modifier.

• Polymer Science and Technology
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• v.22 no.2
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• pp.166-172
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• 2011

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.03a
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• pp.108-108
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• 2011

PLA 즉 폴리유산섬유는 옥수수를 발효하여 글루코오스(포도당)상태를 만든 후 젖산(유산, Lactic acid)으로 만들고 이것을 탈수, 축합반응시켜 polylactic acid로 만든 것이다. 생분해성이 있으므로 저탄소, 녹색성장의 모토를 대변하는 소재라는 이점이 있다. 구조는 에스테르기의 반복단위를 가지는 소수성 섬유로 벤젠환은 없으나 그 외 구조는 폴리에스테르와 비슷하며, 에스테르기가 존재하므로 분산염료와 수소결합하여 염착된다. 그러나 PLA는 융점이 $170^{\circ}C$, Tg $57^{\circ}C$로 내열성이 낮아서 염색온도, 열처리온도, 다림질에 제약이 있으며, 알칼리에 약한 단점이 있다. 따라서 PLA섬유는 낮은 염착량, 내알칼리성, 염착온도 때문에 염색 및 후가공 단계에 많은 사전 실험을 통한 조건 설정이 필요한 까다로운 섬유이다. 본 연구에서는 (주)휴비스의 PLA원사로 제직한 직물(경사:DTY 75/72SD, 위사:DTY 100/72SD, 조직:DOBBY) 생지에 대하여 열처리 시 장력의 유무, 온도, 시간에 따른 폭의 변화를 측정하여 수축률을 알아보았다. 또한, PLA직물을 온도별로 정련한 후 열처리하여 인열강도 측정을 통해 최적 전처리 조건을 조사하였다. 실험결과, PLA생지를 무장력 상태에서 열처리 시 수축이 심하게 일어나고, 장력이 주어져도 열처리 온도에 따라 수축의 정도에 차이가 나타났다. 열처리 시간은 30, 60, 90, 120초로 주었으나 큰 편차는 없었고, 경사가 위사보다 수축 정도가 더 컸으며, $130^{\circ}C$에서는 전체적으로 수축이 심하였다. 생지의 정련에는 인산에스테르계 정련제와 약알칼리인 탄산나트륨으로 조액하여 60, 70, 80, $90^{\circ}C$에서 10분간 처리한 후, Lab. tenter(Mathis, LTE)를 이용하여 110, 120, $130^{\circ}C$에서 30, 60, 90, 120초간 열처리한 다음, KS K 0535 펜듈럼법에 의거하여 인열강도를 측정하였다. 그 결과, 상기 정련온도에서는 인열강도에 영향을 주지 않았으나, 열처리 온도가 $130^{\circ}C$일 때 현저한 강도의 저하를 나타내었다. 실험조건 하에서 가장 적절한 열처리 조건은 $110^{\circ}C$, 60초로 사료된다. 따라서 PLA의 약한 내열성과 내알칼리성 실험결과, 강도나 수축 등 물성변화가 일어나지 않도록 열처리 온도의 제어에 주의가 필요함을 확인할 수 있었다. 실제 섬유가공 작업현장에서는 일반적으로 열처리기가 $180^{\circ}C$이상의 고온으로 고정된 경우가 많은데, 작업자들에게 PLA소재에 대한 사전주의 및 공정변경에 대한 주지가 요구된다.

• Journal of Life Science
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• v.28 no.5
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• pp.547-554
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• 2018

Flaxseed (Linum usitatissimum L.), also called linseed and one of the raw materials for making linen, is rich in omega-3 fatty acids, vegetable estrogen, ${\alpha}$-linolenic acid, and dietary fiber. Studies on flaxseed have reported various additional effects, such as the inhibition of cholesterol, blood clotting, and tumor growth. In this study, we investigated the functional components of flaxseed fermented with lactic-acid bacteria. Lactic-acid bacteria was inoculated into heat-treated (roasted) flaxseed and fermented at $37^{\circ}C$ for 72 hr. The fermented flaxseed was extracted with 70% ethanol and the antioxidant effect of the fermented extracts according to the lactic-acid bacteria was analyzed. It was confirmed that the total polyphenol contents had expanded by about 1.5-8 times, and the total flavonoid contents had increased around 1.2 times in the case of fermented flaxseed with lactic-acid bacteria compared to non-fermented flaxseed (NFFS). DPPH radical scavenging and superoxide dismutase-like activities had increased around 5.6 and 2.3 times, respectively, in the fermented flaxseed compared to the NFFS at 100 ppm concentration. The study concluded that fermentation of flaxseed with lactic-acid bacteria is possible and that it is effective to increase the antioxidant effects of flaxseed. These results can be applied to the development of improved foods and cosmetic materials.

• Journal of the Korean Society of Clothing and Textiles
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• v.37 no.7
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• pp.952-961
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• 2013

This study optimizes a suitable dyeing method for polylactic acid (PLA) fabrics using disperse dyes. For this, disperse red 60 (DR 60), disperse blue 56 (DB 56), and disperse yellow 54 (DY 54) were used and dyed on PLA fabrics dependent of dyeing temperature and time. The fastness of PLA fabrics dyed with three disperse dyes were evaluated; in addition, dye exhaustion, color strength (K/S value), and colorimetric properties of PLA fabrics were compared with PET fabrics. The experiments indicated optimum dyeability of PLA fabrics with disperse dyes. The dyeing temperature was $90^{\circ}C$ for every dye and the dyeing time were 20 min, 60 min, and 40 min for DR 60, DB 56, DY 54, respectively. PLA fabrics had good color fastness to washing, dry cleaning fastness, hot pressing fastness, rub fastness, and perspiration fastness by DR 60, DB 56, and DY 54. The dye exhaustion of PLA fabrics were lower than PET fabrics; however, K/S values were higher than PET fabrics.