Influence of Hydroxyapatite Content on Physical and Rheological Properties of Chitosan-based Scaffold

Chitosan-based scaffolds offer significant potential in tissue engineering and regenerative medicine. Whilst exhibiting great bio-regenerative and biocompatible properties, their mechanical properties remain quite poor. The presented research is focused on the modification of macroporous chitosan scaffolds with various amounts of bioactive ceramics (hydroxyapatite) and its influence on the physical and rheological properties of the composite scaffold. Chitosan/hydroxyapatite composite scaffolds with a highly porous microstructure have been prepared by suspending hydroxyapatite (HAp) particles into the chitosan matrix. According to SEM imaging, homogeneous dispersion of the inorganic phase in a chemically-crosslinked chitosan matrix had been achieved. The obtained composite scaffolds exhibited lower swelling capacity with respect to pure chitosan after 24 h of incubation in Hanks’ balanced salt solution. Rheological measurements show an increase in storage and loss modulus indicating an improvement in mechanical properties under shear stress. Furthermore, no significant change in loss factor (tanδ) was observed indicating no change in composite viscoelastic properties with an increase in HAp content

Nanofluids as Heat Transfer Media

U posljednjih 20 godina nanofluidi su privukli pažnju znanstvene zajednice te se broj radova na temu nanofluida tijekom godina znatno povećao. Povećana toplinska vodljivost fluida uslijed dodatka nanočestica osnovno je svojstvo koje je potaknulo intenzivno istraživanje nanofluida. S obzirom na to da u industriji uvijek postoji težnja poboljšanju učinkovitosti proizvodnih procesa, pa tako i procesa hlađenja procesnih struja, povećana toplinska vodljivost rashladnih fluida otvara mogućnosti za postizanje navedenog cilja. U ovom radu dan je pregled metoda priprave nanofluida te opis parametara koji utječu na njihovu toplinsku vodljivost. Dan je i osvrt na modele kojima se opisuje toplinska vodljivost nanofluida te pregled mogućih mehanizama koji doprinose povećanju njihove toplinske vodljivosti. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.Nanofluids have attracted the attention of the scientific community during last twenty years and the number of papers on nanofluids has increased significantly as a result. The increased thermal conductivity of the fluid due to the addition of nanoparticles is a basic feature that has raised intensive research on nanofluids. Considering a permanent urge in the industry to improve efficiency of production processes, including the cooling streams of processes, the increased thermal conductivity of cooling fluids opens the possibility of achieving that goal. This paper provides an overview of nanofluid preparation methods and a description of parameters that affect the thermal conductivity of nanofluids. Also, the overviews of few models that describe the thermal conductivity of nanofluids as well as of possible mechanisms that contribute to the increase in thermal conductivity of nanofluids are given. This work is licensed under a Creative Commons Attribution 4.0 International License

Preparation and Characterization of Poly(methyl methacrylate) Composites with Nanocellulose

Provedenim istraživanjem priređeni su kompozitni materijali na osnovi poli(metil-metakrilata) i poli(metil-metakrilat-ko-dimetilaminoetil-metakrilata) s nanocelulozom u udjelu 1, 2,5 i 5 mas. %. Metodom ex situ iz otopine dobivena je homogena raspodjela nanopunila u polimernoj matrici. Kromatografijom isključenja po veličini ustanovljeno je da jaka smična sila primijenjena pri homogenizaciji uzrokuje pucanje najvećih molekula polimera i time blago smanjenje prosjeka molekulskih masa polimerne matrice. Veća staklišta kompozita u odnosu na čiste polimerne matrice i porast staklišta s povećanjem udjela punila potvrđuju homogenost raspodjele i kompatiblnost nanoceluloze s istraživanim metakrilatnim matricama. Dodavanjem nanoceluloze povećava se hidrofilnost materijala, što olakšava tisak i može pogodovati njihovoj primjeni kao ambalažnih materijala. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.The composite materials based on poly(methyl methacrylate) and poly(methyl methacrylate-co-dimethylaminoethyl methacrylate) with nanocellulose in the proportion of 1, 2.5, and 5 wt% were prepared. The homogeneous distribution of nanofillers in the polymer matrix was obtained from the solution by the ex situ method. Exclusion size chromatography showed that the strong shear force applied during homogenization caused the largest polymer molecules to crack and thus slightly reduce the average molecular weight of the polymer matrix. Higher glass transition temperatures of composites compared to pure polymer matrices and their increase with increasing filler content, confirm the homogeneity of distribution and compatibility of nanocellulose with the investigated methacrylate matrices. The addition of nanocellulose increases the hydrophilicity of materials, which facilitates printing and may favor their use as packaging materials. This work is licensed under a Creative Commons Attribution 4.0 International License

Ružička days : International conference 16th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2)

Plan upravljanja istraživačkim podacima

Razrađen plan upravljanja istraživačkim podacima na projektu Hrvatske zaklade za znanost "Razvoj funkcionalnih biogoriva i (bio)aditiva te ispitivanje primjenskih svojstava mješavina s mineralnim gorivima"

Plan upravljanja istraživačkim podacima

Razrađen plan upravljanja istraživačkim podacima na projektu Hrvatske zaklade za znanost "Razvoj funkcionalnih biogoriva i (bio)aditiva te ispitivanje primjenskih svojstava mješavina s mineralnim gorivima"

Biodiesel Produced from Propanol and Longer Chain Alcohols—Synthesis and Properties

Biodiesel has established itself as a renewable fuel that is used in transportation worldwide and is partially or in some cases completely replacing conventional fuels. Chemically, biodiesel is a fatty acid monoalkyl ester (FAAE). Generally, the term biodiesel refers to the fatty acid methyl or ethyl esters (FAME or FAEE). Herein, an overview of the research on the synthesis of FAAE in which the alkyl moiety is a C3+ alkyl chain (branched/unbranched) is given. In addition, a comparison of the properties of the aforementioned FAAE with each other, with FAME and FAEE, and with fuel standards is given. The length of the alkyl chain has a major influence on viscosity, while pour point temperatures are generally lower when branched alcohols are used, but the fatty acid part of the molecule also has a major influence. The development of new pathways for the synthesis of higher alcohols from biomass opens a future perspective for the production of long chain FAAE as biofuels, fuel additives, or biolubricants. Due to their properties, FAAEs produced from C3–C5 alcohols have the potential to be used as fuels, while all C3+ FAAEs can be used as valuable bioadditives, and C8+ FAAEs can be used as biolubricants and viscosity improvers

Correlation Method for Conversion Determination of Biodiesel Obtained from Different Alcohols by ¹H NMR Spectroscopy

This work presents a correlation method that uses ¹H NMR spectra for determining the conversion during transesterification of vegetable oil with 10 alcohols: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, 1-pentanol, isopentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-decanol, 1-dodecanol, and benzyl alcohol. Conversions ranging from 70 to 99%, depending on primary alcohol used, are obtained using organic catalyst <i>N</i>,<i>N</i>′,<i>N</i>″-tris­(3-(dimethylamino)­propyl)­guanidine. Catalysts, alcohols, and intermediate products can cause signal overlapping, debilitating the use of the conventional ¹H NMR method. Thus, our method uses the correlation between the triplet signal of α-carbonylmethylene and two signals of unsaturated parts of the fatty acid chain, where signal overlapping does not occur, hence, adding robustness and flexibility to the method. The method is applicable for unsaturated oils and is not affected by the amounts of residual alcohol, catalyst, or intermediate products, making it ideal for conversion determination and <i>in situ</i> monitoring of complex mixtures. In addition, we present a systematic analysis of the ¹H NMR spectra of biodiesels produced with the mentioned alcohols