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Dental material based on poly(methyl methacrylate) with magnesium-aluminum layered double hydroxide (MgAl-LDH) on bio-silica particles
No full textThe MgAl-LDH@SiO2 particles are prepared by the coprecipitation of LDH on silica originating from plants.Particles are of submicron size and are well dispersed in the matrix. Composites consisting of PMMA reinforcedwith MgAl-LDH@SiO2 particles have improved hardness and resistance to viscoelastic deformation, as tested bymicrohardness measurements
Morphology of the Polyurethane Networks Based on Polycaprolactone
No full textPolyurethane networks (PUNs) are versatile materials that have a wide range of
applications. Their structure is often segmented which means that it is built from thermodynamically
incompatible flexible soft (SS) and rigid hard segments (HS) leading
to the formation of microphase separation in the PUNs. With the careful design
and selection of SS and HS it’s possible to control PUNs structure, morphology,
solvent resistance, etc. Here, polycaprolactone (PCL) was used as SS to prepare segmented
PUNs, due to its attractive features, such as low glass transition temperature (around
-60 °C), biocompatibility, biodegradability, hydrophobicity, good solubility in various solvents,
high permeability to many gasses, etc., in order to prepare PUNs with desired surface
properties for their application as coatings [1,2].
In this study, a series of PUNs was synthesized by a two-step polymerization process, according
to the procedure described elsewhere [1,3]. The synthesized PUNs are based on Boltorn®
hydroxy-functional aliphatic hyperbranched polyester of the second pseudo generation (BH-20,
Mn = 1340 g mol-1), isophorone diisocyanate (IPDI) and polycaprolactone diol (PCL, Mn = 2000
g mol-1). Five samples with diferent SS content (from 10 to 50 wt.% SS content) and constant
–NCO/−OH molar ratio of 1.05 were synthesized. Stannous octoate (Sn(Oct)2) was used as a
catalyst, while a mixture of N,N-dimethylacetamide (DMAc) and tetrahydrofuran (THF) was
used as a solvents during the synthesis of PUNs. PUN samples were labeled as PUN-XX, where
XX represents the SS content (from 10 to 50). Surface morphology and the surface roughness
of the PUNs were investigated by atomic force microscopy (AFM). AFM examination of
PUNs was performed by applying NTEGRA Prima atomic force microscope (NT-MDT, Moscow,
Russia). Measurements were done using NT-MDT NSGO1 silicon cantilevers (N-type,
antimony doped with Au reflective coating). The nominal force constant of the cantilevers was
5.1 N m-1, whereas the cantilever driving frequency was around 150 kHz. Intermittent-contact
AFM mode was applied and data related with topography and phase were collected. AFM
images were created and analyzed with Image Analysis 2.2.0 (NT-MDT) and Gwyddion 2.61
(Free and Open Source software, Czech Metrology Institute) software. The scan area of the
PUNs surface was 20 × 20 μm2.
AFM analysis was carried out to explore the surface topography, homogeneity and the
impact of the SS content on microstructural features of the synthesized PUNs, such as nanometer scale structures and roughness. The recorded 3D height and 2D phase pictures (scan size 20
× 20 μm2) and obtained roughness values are presented in Figure 1 and Table 1, respectively.
According to the captured 3D height pictures it can be seen that surface topography of PUNs
strongly depends on the SS content. That is reflected in the fact that samples with smaller SS
content have more flat and smoother relief structures, without any larger domains, opposite
to the samples with the higher SS content. Furthermore, according to the presented 2D phase
pictures it can be observed that prepared PUNs have heterogeneous surface morphology, due to
the existence of more pronounced and more noticeable interface borders between phases. This
behavior is more prevalent in PUN samples with higher SS content [3]. The examined roughness
of the PUNs shows that samples with SS content of 30 and 40 wt.% (PUN-30 and PUN-40
samples) have the highest roughness values (Rq and Ra, Table 1). The reason for this may lie in
the fact that these samples have optimal ratio between HS and SS, allowing easier organization
of SS [4].
A series of PUNs based on BH-20, IPDI and PCL was successfully synthesized. AFM
analysis showed that the content of SS has a significant impact on the surface properties of
these PUNs. Moreover, PUNs have two phase morphology that originates from the presence of
HS and SS, and it was more pronounced in the samples with higher SS content [5]
Investigation of morphology of the polyurethane/TiO2 composites
No full textTwo series of polyurethane (PU) composites based on poly(ε-caprolactone), aliphatic
hyperbranched polyester, isophorone diisocyanate and different content (0.5, 1 and 2 wt.%) of
unmodified or surface-modified TiO2 nanoparticles were prepared. For the surface modification
of TiO2 nanoparticles lauryl gallate was applied. Neat PU and composites were prepared by a
two-step solution polymerization method, using sonification in an ultrasonic bath for composite
fabrication in order to achieve homogenous distribution of nanoparticles, added in the first step of
polymerization reaction. Morphology of prepared neat PU and its composites were investigated
by utilizing scanning electron microscopy (SEM) and atomic force microscopy (AFM).
According to the obtained SEM micrographs, neat PU has compact and uniform cross-sectional
morphology, while in the structure of its composites small voids and certain micro-structures,
such as clusters or aggregates, can be observed. Furthermore, SEM-EDS measurements
confirmed the presence of Ti atoms in composites, originating from the incorporated nanoparticles. AFM analysis showed the existence of microphase separated morphology on the
surface of PU and its composites. Moreover, the surface of both series of composites became
rougher with the addition of nanoparticles, and its roughness increases with increasing amount of
TiO2 nanoparticles. Prepared PU composites may have potential application as coatings
Morphology of the polyurethane composites based on TiO2 nanoparticles
No full textPolyurethane composites based on polycaprolactone (PCL), Boltorn® aliphatic hyperbranched
polyester of the second pseudo generation (BH-20) and isophorone diisocyanate (IPDI) and
unmodified and surface modified TiO2 nanoparticles, were successfully prepared. The surface
modification of TiO2 nanoparticles was performed with lauryl gallate (LG). The impact of added
TiO2 nanoparticles and their content on the morphology of the polyurethane network (PU) were
examined. The obtained results show that the addition of both, unmodified and modified TiO2
nanoparticles, has significant impact on the cross-sectional and surface morphology of PU
Green and sustainable recovery of polyphenols, flavonoids, alkaloids, and pigments from green tea leaves: Comparative analysis of Soxhlet, accelerated solvent, and supercritical fluid extraction techniques
No full textThe growing interest in green tea extracts for their applications in pharmaceutical, food, and cosmetic industries underscores the need for environmentally sustainable extraction methods. This study presents optimized strategies for the green recovery of bioactive compounds from Gun powder green tea leaves using Soxhlet extraction, accelerated solvent extraction, and supercritical fluid extraction techniques. By varying extraction solvents (supercritical CO2, ethanol, water, and their combinations) and temperatures (from 35 to 140 °C), high yields of polyphenols, flavonoids, alkaloids, and pigments were achieved. Key bioactive compounds extracted in significant quantities included caffeine (23.8 mass%), chlorophyll A (8.1 mg/g), chlorophyll B (0.7 mg/g), carotenoids (0.4 mg/g), epicatechin (7.7 mass%), catechin gallate (4.6 mass%), and epigallocatechin-3-gallate (30.2 mass%). The extract obtained in optimized processes demonstrated potent antioxidant activity (IC50 up to 88 μg/mL), strong antimicrobial activity (including methicillin-resistant Staphylococcus aureus- MRSA) with MIC up to 0.06 mg/mL, and selective anticancer activity against colon cancer cells. The presented findings provide a theoretical basis and technical guidance for enhancing the sustainable concentration of natural bioactive compounds, promoting their use in various industrial applications
Synthesis of Titanium-Based Powders from Titanium Oxy-Sulfate Using Ultrasonic Spray Pyrolysis Method
No full textSubmicron and nanosized powders have gained significant attention in recent decades due to their broad applicability in various fields. This work focuses on ultrasonic spray pyroly- sis, an efficient and flexible method that employs an aerosol process to synthesize titanium-based nanoparticles by transforming titanium oxy-sulfate. Various parameters are monitored to better optimize the process and obtain better results. Taking that into account, the influence of temperature on the transformation of titanium oxy-sulfate was monitored between 700 and 1000 ◦C. In addition to the temperature, the concentration of the starting solution was also changed, and the flow of hydrogen and argon was studied. The obtained titanium-based powders had spherical morphology with different particle sizes, from nanometer to submicron, depending on the influence of reaction parameters. The control of the oxygen content during synthesis is significant in determining the structure of the final powder
Eco-friendly solution for water treatment: Chitosan hydrogels as color catchers
No full textZagađenje vode izazvano bojama iz veš mašina predstavlja važan ekološki problem zbog čega se poslednjih godina stavlja akcenat na istraživanja o sorbentima na bazi prirodnih polimera, kao što je hitozan. Jedan od rešenja ovog problema je priprema hidrogel-kuglica pomoću hitozana modifikovanog različitim jedinjenjima. Dobijeni sorbenti su testirani prema protokolu Međunarodne asocijacije za sapune, detergente i proizvode za održavanje (A.I.S.E.). Efikasnost pripremljenih sorbenata ispitana je korišćenjem pamučnih tkanina različitih boja i pomoću C.I. Acid Orange 7 kao model boje. Rezultati ukazuju da sintetisani sorbenti imaju potencijal da deluju kao hvatači boje za pranje veša. Ovo istraživanje otvara prostor za jednostavno i ekološki prihvatljivo rešenje za problem otpadnih voda iz veš mašine.The dye pollution from washing machines presents a significant environmental concern, therefore research about natural-based polymer sorbents, such as chitosan, is performed. One of the solutions to this problem is the preparation of hydrogel beads using chitosan modified with various compounds. The obtained sorbents were tested according to the protocol of the International Association for Soaps, Detergents, and Maintenance Products. The efficiency of prepared sorbents was evaluated using differently colored cotton fabrics and C.I. Acid Orange 7 as a dye model. The results indicate the potential of the synthetized sorbents to act as a color catcher for laundry machine-washing. Overall, this research highlights a practical and eco-friendly solution to address dye pollution in wastewater from washing machines, contributing to the broader efforts in environmental sustainability
“Green” chemistry approach for preparation of hydrogels used for controlled drug delivery
No full textThermosensitive hydrogels based on N-isopropyl acrylamide (NIPAM) were synthetized using
bio-based initiator and the controlled release of encapsulated water soluble and insoluble active
compounds was studied.1 An effect of the concentration of either cross-linker, initiator and
temperature of surrounding on the hydrogels swelling and controlled delivery of active compounds
was investigated. With an increase in the amount of the cross-linker the degree of swelling declines
resulting in lower quantities of the released drug. The increase in the initiator concentration slightly
decreases the swelling degree and thus, the amount of released drug. Rise in the temperature of
surrounding leads to lower swelling degrees of NIPAM hydrogels. Poorly water-soluble drug was
released in higher amounts than the water-soluble one
Surface roughness of ultrafine-grained Ti-13Nb-13Zr alloy induced using anodic oxidation
No full textNanotechnology can be used to form nanostructured implant surfaces, which show non-specific protein adsorption and can increase the biocompatibility of the material in the human body. One of the ways to produce a nanostructured implant surface is formation of an oxide layer composed of nanotubes, using different methods of surface modification. One of those methods is anodic oxidation, which is used in the case of a large number of metal materials, but it can also be applied to titanium-based materials in order to obtain a nanostructured surface. The nanotubes formed in this way are specifically structured nanoparticles of defined geometries with a nanometer wall thickness, a large length-to-diameter ratio and a certain chemical composition that can lead to changes in surface properties. In the present study, nanostructured oxide layer on the ultrafine-grained Ti-13Nb-13Zr (UFG TNZ) alloy was formed by anodic oxidation (electrochemical anodisation) in the solution of 1M H3PO4 acid with F- ions, during 30 and 120 min. The scanning electron microscopy (SEM) was used to analyse the oxide layer morphology and showed that nanoporous oxide layer and nanotubular oxide layer were formed by anodic oxidation, depending on anodising time. In order to characterise the surface topography of all tested materials, the atomic force microscopy (AFM) was used. Results showed that the surface roughness is higher after anodic oxidation compared to bare surface of the ultrafine-grained tita-nium alloy. It was also shown that increase of anodising time induces increase of the surface roughness and induces obtaining of highly ordered nanotubular oxide layer
Which regional zeolitic tuff is the best? Comparison of the impact of particle size on adsorption process
No full textZeolite is a porous aluminosilicate mineral that shows effective adsorption of heavy metal ions.
Natural zeolite is a cost-effective adsorbent suitable for water purification processes after milling
and simple preparation. In this work, zeolitic tuff from three different deposits was used: Slanci
and Vranjska Banja (Serbia), and Novakovići (Bosnia and Herzegovina). The adsorption
properties of zeolites towards copper and zinc ions were examined depending on the particle
size. Four fractions of zeolite were used: less than 63, 63-125, 125-180 and 180-250 μm.
Additionally, the effect of pretreating each zeolite fraction with a NaCl solution was
investigated. The obtained results showed that the zeolite fraction with particles smaller than
63 μm showed the best adsorption properties for all three zeolitic tuffs. Zeolite from the
Novakovići deposit showed superior zinc adsorption, while the zeolite from the Slanci deposit
showed the highest copper binding capacity. Na-modification of zeolite, resulting in Na+
as the
only non-structural cation in the zeolite lattice, significantly increased adsorption. The
Na-modified zeolite achieved over 95% removal efficiency for all three zeolitic tuffs regardless
of particle size. This shows that the presence of a single type of exchangeable cation in the
structure of natural zeolite has a dominant influence on heavy metal adsorptio