Preparation and properties of amphiphilic copolymers based on polyaspartamide derivatives

( Bach Quang Vu ),문종록,김지흥 한국공업화학회 2006 한국공업화학회 연구논문 초록집 Vol.2006 No.1

Improvement of Mechanical Properties and Blood Compatibility of PLLA Nanocomposites by Incorporation of Polyhedral Oligomeric Silsesquioxane

Quang Vu Bach,한동근,최지연,정윤기,박방주 한국고분자학회 2012 Macromolecular Research Vol.20 No.9

A series of hybrid nanocomposites containing poly(L-lactide) (PLLA) and polyhedral oligomeric silsesquioxane (POSS) was prepared by solvent casting method for the enhancement of the mechanical properties of PLLA. One of them was mixed by only a physical blending between PLLA and POSS to form PLLA/POSS nanocomposite that did not show considerable improvement. In the other hand, two types of PLLA-POSS additives were synthesized via the ring-opening polymerization of L-lactide in the presence of POSS in different content. On these additives, POSS played as not only an initiator for the ring-opening polymerization reaction due to its hydroxyl functional groups on the surface but also a type of hybrid filler for PLLA/PLLA-POSS nanocomposite after mixing with PLLA matrix. PLLA/PLLA-POSS composite showed significant improvement in mechanical properties because of covalent bonding between PLLA and POSS. In particular, the tensile modulus has been apparently increased in PLLA/5PLLA-5POSS nanocomposites (1,449 MPa) with respect to PLLA control (498 MPa). SEM and XRD data indicated that the dispersion of PLLA-modified POSS was better than that of POSS in PLLA matrix. Although the contact angle was not significantly different, the protein adsorption and platelet adhesion are reduced slightly in PLLA/PLLA-POSS nanocomposite as compared to those of PLLA control and PLLA/POSS. Therefore,it is expected that biodegradable POSS nanocomposite may be helpful to be utilized in biomedical devices such as drug-eluting stents and artificial implants

A new hybrid sewage treatment system combining a rolled pipe system and membrane bioreactor to improve the biological nitrogen removal efficiency: A pilot study

Bach, Quang-Vu,Le, Van Tam,Yoon, Yong Soo,Bui, Xuan Thanh,Chung, Woojin,Chang, Soon Woong,Ngo, Huu Hao,Guo, Wenshan,Nguyen, Dinh Duc Elsevier 2018 Journal of Cleaner Production Vol.178 No.-

<P><B>Abstract</B></P> <P>A new hybrid pilot plant configuration based on a modularized rolled pipe system (RPS) combined with a submerged flat sheet membrane bioreactor (MBR) was investigated to enhance the sewage treatment and membrane performance. The system was operated under actual conditions for more than four months, that is, at a constant flow rate of 30 m³/d and with two internal recycling ratios. The results indicate that the hybrid system produces an excellent effluent quality and considerably mitigated membrane fouling. The average concentrations of SS, COD, TN, NH<SUB>4</SUB> <SUP>+</SUP>-N, NO<SUB>3</SUB> <SUP>−</SUP>-N, and PO<SUB>4</SUB> <SUP>3-</SUP>-P remained below 2.81, 8.29, 8.77, 0.15, 8.17, and 1.49 mg/L, respectively. It was estimated that the periodic chemical cleaning of the membrane could be extended to approximately six months. The MBR and RPS can virtually complete nitrification and denitrification, respectively. The highest average denitrification rate of the RPS is 116.95 mg NO<SUB>3</SUB>-N/(g MLVSS d), with a hydraulic retention time of 1.05 h. Therefore, the RPS–MBR hybrid system has potential to improve the sewage treatability. The emerging RPS technique can obtain high rates of denitrification coupled with a compact design, ease of installation, and small footprint.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new hybrid sewage treatment system was explored. </LI> <LI> Excellent denitrification is achieved with the novel rolled pipe system. </LI> <LI> High rates of simultaneous nitrification and denitrification are obtained. </LI> <LI> The hybrid system performs well in removing organic and nitrogen compounds. </LI> <LI> The membrane fouling rate of the hybrid system is significantly low. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Lower critical solution temperature behavior of amphiphilic copolymers based on polyaspartamide derivatives

Bach, Quang Vu,Moon, Jong-Rok,Lee, Doo Sung,Kim, Ji-Heung Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of applied polymer science Vol.107 No.1

<P>Novel copolymers consisting of poly(N-isopropylaminoethyl-co-6-hydroxyhexyl aspartamide) and poly (N-isopropylaminoethyl-co-hexyl aspartamide) were prepared from polysuccinimide, which was the thermal polycondensation product of L-aspartic acid, via a ring-opening reaction with 6-amino-L-hexanol (AH) or hexylamine (HA) and N-isopropylethylenediamine at different ratios. The copolymers, containing 75–90 mol % of AH and 35–45 mol % of HA, produced thermoresponsive polymers through their lower critical solution temperatures (LCSTs) in aqueous solution. We could control the LCST could be controlled by modifying the hydrophobic–hydrophilic balance by changing the content of AH or HA. The pH dependencies of the LCST were opposite in these two different copolymer systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008</P>

Process modeling and optimization for torrefaction of forest residues

Bach, Quang-Vu,Skreiberg, Øyvind,Lee, Chul-Jin Elsevier 2017 ENERGY Vol.138 No.-

<P><B>Abstract</B></P> <P>This work aims to build a comprehensive biomass torrefaction model, which can provide a wide range of information essential for industrialization and commercialization of the process. Norwegian forest residue (birch branches) was chosen as feedstock. The model is capable of presenting detailed distributions of main and by-products from the torrefaction process. In addition, important fuel properties (ultimate analysis and heating value) of the main solid product after torrefaction can be predicted. The model is validated and simulation results show good agreement with available experimental data in the literature. Reduction in mass and energy yields as well as improvement in heating value of torrefied biomass with increasing torrefaction temperature are observed. Trends for carbon, oxygen and hydrogen contents are also consistent with other experimental works. Moreover, overall energy consumption and process energy efficiency can be estimated from the model. It reveals that drying accounts for 76–80% of the total heat demand. Furthermore, the process energy efficiency reduces with increasing temperature, thus torrefaction at high temperatures is not advisable. More importantly, process optimization shows that optimal conditions for torrefaction of birch branches are 30 min holding time and a temperature between 275 and 278 °C.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Completed torrefaction model has been built in the Aspen Plus and validated by experimental data. </LI> <LI> The model is capable of providing the distributions of both the torrefied biomass and by-products. </LI> <LI> The model reveals that drying accounts for 76–80% of the total heat demand. </LI> <LI> A temperature within 275–278 °C is optimal for a torrefaction time of 30 min for birch branches. </LI> </UL> </P>

Carbon-Fiber-Reinforced Epoxy Resin with Sustainable Additives from Silk and Rice Husks for Improved Mode-I and Mode-II Interlaminar Fracture Toughness

Cuong Manh Vu,Quang-Vu Bach,Huong Thi Vu,Dinh Duc Nguyen,Bui Xuan Kien,장순웅 한국고분자학회 2020 Macromolecular Research Vol.28 No.1

This paper presents an effective method for enhancing both the mode I (GIC) and mode II (GIIC) interlaminar fracture toughness of carbon fiber reinforced epoxy resin (CFRE). For precursor materials, silk fibroin nanofibers (nSF) and rice husk silica were prepared from sustainable resources. Nanocomposite samples were prepared using various loading ratios of the silica and nSF in epoxy resin (EP). Mechanical stirring and sonication techniques were used to prepare homogenous mixtures of silica and nSF in epoxy resin. Non-isothermal differential scanning calorimetry and the Kissinger equation were used to examine and calculate the cure kinetics and activation energy (Ea) of EP and the composite samples. The CFRE sample with hybrid fillers of nSF and silica at the ratio 0.2/20 (wt%/wt%) exhibited the highest GIC, and improved upon the mode-I and mode-II toughness of the pure-resin sample by 36.08% and 30.06%, respectively. Study of the fracture surfaces indicated that adding nSF and silica as fillers increases the energy required to fracture the CFRE.

Effects of DOPO-Grafted Epoxidized Soybean Oil on Fracture Toughness and Flame Retardant of Epoxy Resin/Rice Husk Silica Hybrid

Cuong Manh Vu,Quang-Vu Bach 한국고분자학회 2020 Macromolecular Research Vol.28 No.9

In this work, the effects of 9,10-dihydro-9-oxa-10-phosphaphenanthrene- 10-oxide (DOPO) grafted epoxidized soybean oil (ESO-G-DOPO) on mechanical properties and flame retardant of rice husk silica filled epoxy based composite were investigated detail. The silica was extracted from rice husk before using as reinforcement for epoxy resin. While the epoxidized soybean oil (ESO) was synthesized from soybean oil via epoxidation processing prior to react with 9,10-dihydro-9-oxa- 10-phosphaphenanthrene-10-oxide (DOPO) to form ESO-G-DOPO. The Fourier transform infrared spectroscopy and nuclear magnetic resonance were used to confirm the chemical structure of silica, ESO and ESO-G-DOPO. The content of rice husk silica was also kept at constant of 20 wt.% while the content of ESO-G-DOPO was varying in range from 0 to 15 wt.% according to epoxy weight. The experimental results indicated that the presence of ESO-G-DOPO help to enhance the fracture energy, tensile strength, flexural strength up to 111.36, 67.26, and 87.79 %, respectively in comparison with virgin sample. Especially, the results of cone calorimeter testing, limiting oxygen index indicated that the flammability of epoxy resin was extremely reduced with presence of ESO-G-DOPO. A mechanism of flame retardant was also proposed to answer for the question how ESO-G-DOPO acted in a flame.

Crack prevention of biodegradable polymer coating on metal facilitated by a nano-coupled interlayer

Cho, Youngjin,Vu, Bach Quang,Bedair, Tarek M,Park, Bang Ju,Joung, Yoon Ki,Han, Dong Keun Technomic Pub. Co 2014 Journal of bioactive and compatible polymers Vol.29 No.5

<P>Crack prevention of biodegradable polymer coatings on drug-eluting stents was investigated by introducing a nano-coupled layer at the interface between the metal surface and the polymer coating layer using surface-initiated ring-opening polymerization of ε-caprolactone. Poly(<SMALL>d</SMALL>,<SMALL>l</SMALL>-lactide-co-glycolide) coating on cobalt-chromium control and ricinoleic acid-poly(caprolactone)–grafted cobalt-chromium was carried out using electrospraying. The cracking of the biodegradable polymer coating on drug-eluting stents during ballooning was addressed by introducing a nano-coupled interlayer on the cobalt-chromium surface. The ricinoleic acid-poly(caprolactone) nano-coupled interlayer and poly(<SMALL>d</SMALL>,<SMALL>l</SMALL>-lactide-co-glycolide)-coated top layer were characterized using attenuated total reflection Fourier transform infrared, contact angle, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy. Based on scratch tests, the nano-coupled samples had stronger interfacial adhesion compared to the control sample without the nano-coupled layer. Scanning electron microscope images indicated that the cracking on the poly(<SMALL>d</SMALL>,<SMALL>l</SMALL>-lactide-co-glycolide) coating was addressed. Introducing a nano-coupling interlayer may be an important strategy to preventing polymer coating cracking on drug-eluting stents.</P>

Jasminum albicalyx Kobuski (Oleaceae): a new record from Vietnam

Bui Hong Quang,Ritesh Kumar Choudhary,Tran The Bach,Vu Tien Chinh,Nguyen Sinh Khang,이창영,이중구 한국식물분류학회 2014 식물 분류학회지 Vol.44 No.3

We report a new record of Jasminum albicalyx Kobuski in Vietnam. The plant differs from J. pedunculatum Gagnep., a closely related taxon, by foliar and floral characters such as less number of lateral veins, presence of domatia at vein axils on the abaxial surface of leaf, smaller bracts, white calyx having more number of lobes and less number of lobes in corolla. Morphological description, line drawing and color photographs are provided in addition to the species key of allied species of Jasminum albicalyx in Vietnam.

Synthesis of Cr-doped Al₂O₃ by Pechini sol-gel method and its application for reversible thermochromic sensors

Nguyen, Duy Khiem,Bach, Quang-Vu,Kim, Buyoung,Lee, Heesoo,Kang, Choonghyun,Kim, In-Tae Elsevier 2019 Materials chemistry and physics Vol.223 No.-

<P><B>Abstract</B></P> <P>Aluminum oxide doped with a small amount of chromium is known as “ruby” or “ruby solution” and can be used as a thermochromic material. The Pechini sol-gel process is applied to synthesize this advanced material. The crystal structure, chemical composition, and morphology of the synthesized materials are analyzed using X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, and Fourier transform infrared (FT-IR) spectroscopy. The color performance of the synthesized material is analyzed using UV-VIS spectrometry. Finally, the thermochromism exhibited by the pigment powders at high temperatures is investigated. The pigment exhibits exceptional thermochromic properties, transitioning from pink to gray in a temperature range of 25–600 °C. The change in color is reversible and is dependent on the temperature and chromium concentration; however, it is independent of the exposure time. This novel property of Cr-doped Al<SUB>2</SUB>O<SUB>3</SUB> can be potentially employed in reversible thermochromic sensors that could be used not only for warning users of damage due to overheating when the environmental temperature exceeds certain limits, but also for detecting and monitoring the temperature of various devices, such as aeronautical engine components, hotplates, and furnaces.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cr-doped Al<SUB>2</SUB>O<SUB>3</SUB> powders were prepared by Pechini sol-gel method. </LI> <LI> The Cr<SUP>3+</SUP> contents influence slightly the phase transition temperature but control the brightness of the powders. </LI> <LI> The powder exhibits reversible thermochromic properties in a temperature range of 25–600 °C. </LI> <LI> The color change is dependent on the temperature but independent of the exposure time. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>