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- 저자 : Dorneles (검색결과 3 건)
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Bruno Dorneles de Castro,Kláudia Maria Machado Neves Silva,Rômulo Maziero,Paulo Eustáquio de Faria,Priscila Pereira Silva-Caldeira,Juan Carlos Campos Rubio 한국섬유공학회 2020 Fibers and polymers Vol.21 No.8
The use of treatments in natural fibers is largely used, because it can improve the interfacial adhesion of polymercomposites. However, the choice of the most appropriate treatment should take into account environmental factors, due to theneed of new materials to meet requirements related to the concept of sustainability. This article investigated the influence ofthe mercerization, acetylation and gamma radiation treatments on the mechanical properties of sisal fibers, to use incomposite materials. Experimental conditions were defined with different concentrations of reagents and radiation doses inorder to understand the impact of these reactions on the tensile properties of sisal fibers. Thermal gravimetric analysis (TGA)and Fourier Transform Infrared (FTIR) spectroscopy were used to investigate the fiber degradation process and the chemicalmodifications after the treatments. The use of mercerization (0.1 M and 1.0 M NaOH concentrations) combined withacetylation increased the hydrophobic character of the sisal fiber, which may improve its interaction with polymeric matrices. In addition, mercerized sisal fiber at 0.5 M NaOH concentration, exposed to 25 kGy gamma radiation dose, showed physicaland chemical structural changes that positively influence the fiber-matrix adhesion in polymer composite materials. Alltreatments made can reduce the natural tensile properties of the sisal fibers, because they can remove fundamentalcomponents to the structure and the stiffening of these fibers. Considering changes in the mechanical behavior, the use ofgamma radiation presented similar results of the traditional chemical treatments, being less aggressive to the fibers and notcausing the same negative impact on the environment.
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Catalytic Properties of Lipases Immobilized onto Ultrasound-treated Chitosan Supports
Matheus Dorneles de Mello,Deborah Cordeiro,Lilian Terezinha Costa,Cristian Follmer 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.6
Ultrasound sonication has been utilized toproduce fragmentation of chitosan polymer and hence increasethe chitosan surface area, making it more accessible tointeractions with proteins. In this context, we haveinvestigated the catalytic properties of lipases from differentsources immobilized onto ultrasound-treated chitosan (ChiS)pre-activated with glutaraldehyde (ChiS-G). Atomic forcemicroscopy indicated that ChiS-G displays a more cohesiveframe without the presence of sheared/fragmented structureswhen compared with ChiS, which might be attributed tothe cross-linking of the polysaccharide chains. Theimmobilization efficiency onto ChiS-G and ChiS wereremarkably higher than using conventional beads. Incomparison with the free enzymes, lipases immobilizedonto ChiS show a slight increase of apparent Km anddecrease of apparent Vmax. On the other hand, immobilizationonto ChiS-G resulted in an increase of Vmax, even though aslight increase of Km was also observed. These datasuggest that the activation of chitosan with glutaraldehydehas beneficial effects on the activity of the immobilizedlipases. In addition, the immobilization of the lipases ontoChiS-G displayed the best reusability results: enzymesretained more than 50% of its initial activity after fourreuses, which might be attributed to the covalent attachmentof enzyme to activated chitosan. Overall, our findingsdemonstrate that the immobilization of lipases ontoultrasound-treated chitosan supports is an effective andlow-cost procedure for the generation of active immobilizedlipase systems, being an interesting alternative to conventionalchitosan beads.
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Continuous ZIF-8/reduced graphene oxide nanocoating for ultrafast oil/water separation
Kim, Dae Woo,Eum, Kiwon,Kim, Hanim,Kim, Daeok,Mello, Matheus Dorneles de,Park, Kangho,Tsapatsis, Michael Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.372 No.-
<P><B>Abstract</B></P> <P>Continuous ZIF-8/reduced graphene oxide (RGO) nanocoating is fabricated by growing ZIF-8 on RGO-coated polyurethane (PU) foam. Surface modification of PU foam can be easily achieved by immersing the PU foam in GO solution, followed by mild thermal treatment to turn the GO layer into RGO layer. Adhesion between polymer foam and ZIF-8 layer was enhanced by the inserted RGO layer because oxygen-containing groups of RGO could interact with Zn<SUP>2+</SUP> precursor of ZIF-8 localizing the layer growth preferentially on the surface of RGO. The synergetic hydrophobic/oleophilic properties of RGO and ZIF-8 enable selective oil absorption of PU foam with an absorption capacity of 15–35 g/g depending on the viscosity of organic solvents. Most of all, the ZIF-8/RGO coated PU foam can filter organic solvent selectively <I>via</I> vacuum filtration, showing ultrafast hexane flux up to 800,000 Lm<SUP>−2</SUP> h<SUP>−1</SUP> and no water flux.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A method to fabricate continuous hydrophobic/oleophilic RGO/ZIF-8 nanocoating on polymeric foam. </LI> <LI> Selective oil absorption with an absorption capacity of 15–35 g/g depending on the viscosity of organic solvents. </LI> <LI> Ultrafast hexane flux up to 800,000 Lm<SUP>−2</SUP> h<SUP>−1</SUP> and no water flux during vacuum filtration. </LI> <LI> Universal method to fabricate metal-organic frameworks on polymeric foam. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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