Browsing by Author "Ondaral S."

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Chitosan adsorption on nanofibrillated cellulose with different aldehyde content and interaction with phosphate buffered saline
(2018-04-15) Ondaral S.; Çelik E.; Kurtuluş O.; Aşıkuzun E.; Yakın İ.
The chitosan adsorption on films prepared using nanofibrillated cellulose (NFC) with different content of aldehyde group was studied by means of Quartz Crystal Microbalance with Dissipation (QCM-D). Results showed that frequency change (Δf) was higher when the chitosan adsorbed on NFC film consisting more aldehyde group indicating the higher adsorption. The (Δf) and dissipation (ΔD) factors completely changed during adsorption of chitosan pre-treated with acetic acid: Δf increased and ΔD decreased, oppositely to un-treated chitosan adsorption. After acid treatment, molecular weight and crystallinity index of chitosan decreased addition to change in chemical structure. It was found that more phosphate buffered saline (PBS), as a model liquid for wound exudate, adsorbed to acid treated chitosan-NFC film, especially to film having more aldehyde groups. Comparing with bare NFC film, chitosan-NFC films adsorbed less PBS because chitosan crosslinked the NFC network and blocked the functional groups of NFC and thus, preventing swelling film.
Different amount of carboxyl-aldehyde fractionated nanofibril cellulose and main characteristics of chitosan, gelatin, alginate added composites
(2023-07-01) Kurtuluş O.Ç.; Ondaral S.; Emin N.; Aşıkuzun E.
In this research, two different types of nanofibrillated celluloses (NFCs) having different amounts of aldehyde and carboxyl groups were mixed with chitosan (CH), gelatin (GL), and alginate (AL) with different mixing ratios to produce biocomposite aerogels. There was no related study in the literature about producing aerogels with the addition of NC and mentioning biopolymers in addition to the effect of carboxyl and aldehyde fraction of the main matrix NC on composite properties. For this purpose, the main aim of this study was to investigate how carboxyl and aldehyde groups affect the basic characteristics of NFC-biopolymer based materials addition to efficiency of biopolymer amount in main matrix. Even after preparing homogenous NC-biopolymer compositions at 1 % concentration with varied proportions (75 %–25 %, 50 %–50 %, 25 %–75 %, 100 %), aerogels were still made using the fundamentally easy lyophilization procedure. Porosity values for NC-Chitosan (NC/CH) based aerogels range from 97.85 to 99.84 %, whereas those made from NC-Gelatin (NC/GL) and NC-Alginate (NC-AL) have values of 99.2–99.8 % and 98.47 to 99.7 %, respectively. In addition, densities were determined in the range of 0.01 g/cm3 for both NC-CH and NC-GL composites, but higher values were obtained in ranged between 0.01 and 0.03 g/cm3 for NC-AL samples. The crystallinity index values showed a decreasing trend with the addition of biopolymers into NC composition. SEM images showed that all materials have a porous micro structure with different size pores and homogenous surface topography. As a result of the specified tests, these materials can be used in many different industrial applications, such as dust collectors, liquid adsorbers, specific material for packaging and medical materials.
The adsorption of phosphate-buffered saline to model films composed of nanofibrillated cellulose and gelatin
(2019-01-01) Ondaral S.; Çelik E.; Kurtuluş O.Ç.
Phosphate-buffered saline (PBS) adsorption on model films composed of gelatin and nanofibrillated celluloses (NFCs) with different aldehyde and carboxyl contents was studied by means of the quartz crystal microbalance with dissipation (QCM-D) technique in this study. The results showed that frequency shift (Δf) due to PBS adsorption increased with increasing gelatin content to 50% in NFC-containing films. The dissipation shift and adsorption rate of PBS followed the same trend. Model films with NFC-1 having 1.22 mmol/g aldehyde and 0.6 mmol/g carboxyl groups adsorbed more PBS than those consisting of NFC-2 with 0.25 mmol/g aldehyde and 1.15 mmol/g carboxyl groups except for film composed of 50% gelatin. However, adsorption rate of PBS was found to be slower for NFC-1 containing film because the acetal and amidol bonds formed by functional groups in the network of cellulose and gelatin needed more time to let PBS migrate into the films.