gel fraction
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2022 ◽  
Vol 30 ◽  
pp. 096739112110632
Author(s):  
SI Radwan Torab ◽  
MM Shehata ◽  
HH Saleh ◽  
ZI Ali

Poly (vinyl alcohol) is blended with ethylene glycol by casting method to form PVA-EG blend films. These films were irradiated by both N2 ion beam extracted from dc ion source at different ion fluences and γ-rays with various irradiation doses. The effects of ion beam and γ-rays irradiation on the thermal, micro-hardness, and gel fraction properties of PVA-EG blend films were investigated. The gel fraction % and micro-hardness increase with increasing the γ-rays doses up to 150 kGy and then decreased, where they increased at all fluences of ion beam irradiation. The improvement in the gel fraction percentage and micro-hardness suggest that PVA-EG blend films exhibited a crosslink density. The thermal behavior was examined by thermogravimetric analysis and it shows different thermal patterns depending on the type and dose of radiation. The thermal stability parameters of γ-rays- and ion beam-irradiated PVA-EG samples were evaluated using the Ti, Ts, T0.5, Tf temperatures, and activation energy (Ea) values. The thermal stability parameters were dependent on both the type and extent of irradiation dose and fluence. Finally, there is a good agreement between the obtained results from different measurement techniques.


Author(s):  
Bagus Sediadi Bandol Utomo ◽  
Dina Fransiska ◽  
La Ode Sumarlin ◽  
Ihya Sulthonuddin

Eucheuma seaweed from tropical waters habitat mainly contains carrageenan, a type of hydrocolloid potential for hydrogel production. This study aims to determine the characteristics of hydrogel formulated from composite i- and k-carrageenan combined with polyvinyl alcohol (PVA) which, could be used further for wound dressing application. The concentrations of composite i/k-carrageenan used were 1.0%, 1.5%, 2.0%, 2.5% and 3.0% w/w, and the PVA concentration was 12.5% w/w. Composite i/k-carrageenan in a proportion of 6:4 by weight. The hydrogel was irradiated using 60Co g-rays with the irradiation dose of 25 and 2 kGy.h-1. The concentration of composite i- and k-carrageenan influenced the gel fraction, water holding capacity, tensile strength, elongation, and surface morphology of the hydrogel. The optimum formula of irradiated composite hydrogel was obtained from 3.0% w/w of composite i/k-carrageenan. The formula had a gel fraction of 61.67%, water holding capacity of  1067.12%, tensile strength of  32.37 x 10-3 MPa, and elongation of  251.67%. Interestingly, the product with the optimum formula had a porous surface morphology and transparency, which are applicable for wound dressing purposes.


2021 ◽  
Vol 22 (21) ◽  
pp. 12022
Author(s):  
Katarzyna Bialik-Wąs ◽  
Klaudia Pluta ◽  
Dagmara Malina ◽  
Mateusz Barczewski ◽  
Katarzyna Malarz ◽  
...  

The impact of different amounts of glycerin, which was used in the system of sodium alginate/poly(vinyl alcohol) (SA/PVA) hydrogel materials on the properties, such as gel fraction, swelling ability, degradation in simulated body fluids, morphological analysis, and elongation tests were presented. The study shows a significant decrease in the gel fraction from 80.5 ± 2.1% to 45.0 ± 1.2% with the increase of glycerin content. The T5 values of the tested hydrogels were varied and range from 88.7 °C to 161.5 °C. The presence of glycerin in the matrices significantly decreased the thermal resistance, which was especially visible by T10 changes (273.9 to 163.5 °C). The degradation tests indicate that most of the tested materials do not degrade throughout the incubation period and maintain a constant ion level after 7-day incubation. The swelling abilities in distilled water and phosphate buffer solution are approximately 200–300%. However, we noticed that these values decrease with the increase in glycerin content. All tested matrices are characterized by the maximum elongation rate at break in a range of 37.6–69.5%. The FT-IR analysis exhibits glycerin changes in hydrogel structures, which is associated with the cross-linking reaction. Additionally, cytotoxicity results indicate good adhesion properties and no toxicity towards normal human dermal fibroblasts.


2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Ngoc Linh Nguyen ◽  
Thi My Linh Dang ◽  
Tuan Anh Nguyen ◽  
Hoang Thu Ha ◽  
Thien Vuong Nguyen

This study is aimed at exploring the effects of SiO2 nanoparticles on the crosslinking and mechanical and thermal properties of UV curing acrylic epoxy coating. The curing polymerization process and thermal and mechanical properties of UV-curable acrylate epoxy system have been evaluated with or without the presence of SiO2 nanoparticles. To fabricate the UV curing acrylic epoxy/SiO2 nanocomposite coating, nano-SiO2 particles (0.5–5 wt.% by weight of resin) were added in the photo-curable system using sonication for 3 h. Various techniques for characterization have been used, such as FESEM (field emission scanning electron microscope), FTIR (Fourier-transform infrared spectroscopy), TGA (thermogravimetry analysis), gel fraction, and swelling degree analyses. FESEM data indicated that at the content of 2.5 wt.%, nanosilica was homogeneously dispersed in the coating procedure. However, once added 5 wt.%, large aggregation portions were found inside the coating matrices. Surprisingly, nano-SiO2 could play dual roles, as both UV absorbers and nanoreinforcers, in this nanocomposite coating. Besides, data from FTIR, gel fraction, and swelling degree analyses confirmed the role of SiO2 nanoparticles as UV absorbers that reduced the conversion performance of acrylate double bonds, thus increased slightly the swelling degree of coating. In addition, incorporation of SiO2 nanoparticles (as nanofillers, at content of 2.5 wt.%) in the polymer matrix enhanced significantly the abrasion resistance and thermal stability of the coating, by 60% (from 98.3 to 158.4 lite/mil) and 9°C (from 348°C to 357°C), respectively.


2021 ◽  
Author(s):  
Parvaneh Mohamadinia ◽  
Navideh Anarjan

Abstract Hydrogels are specific groups of polymers that are highly swellable in aqueous solutions, despite their water-in-soluble structures. Thus, they are promising drug delivery systems attributable to their unique characteristics such as high hydrophilicity, high controllability, facile production routines and, good biocompatibility. The aim of this research was the preparation of sodium alginate/acrylic acid composite hydrogels conjugated to silver nanoparticles to deliver the cephalexin as a model antibiotic compound. The reduction of silver ions into silver nanoparticles as well as the stabilization of created nanoparticles ensued simultaneously with hydrogel backbone formulation during microwave irradiation and monomer cross-linking processes. The impact of acrylic acid and silver ions concentrations and also the radiation time of microwave were then investigated on the main characteristics of hydrogels, namely, swelling ratio, gel fraction, cephalexin load and, antibacterial activity. The results indicated that the hydrogels’ characteristics could be significantly predicted by studied all independent parameters, through various second-order polynomial models. The multiple optimization analysis suggested that the prepared hydrogels using 7.8 g acrylic acid and 1.5 g silver nitrate and 1 min microwave radiation could give the best hydrogels with the highest swelling degree, gel fraction, cephalexin absorption and, antibacterial activity. The morphology and either absorption or release kinetics of cephalexin by/from the optimum prepared hydrogels were also investigated. No significant differences between the experimental and predicted data was confirmed the suitability of the suggested models.


2021 ◽  
Vol 55 (3-4) ◽  
pp. 375-383
Author(s):  
NEDA PAVANDI ◽  
ELHAM TAGHAVI ◽  
NAVIDEH ANARJAN

"The preparation of carboxymethyl cellulose and polyvinyl alcohol (CMC/PVA) composites is proposed in the present work. The CMC/PVA hydrogels were prepared using freeze−thaw processes. The effects of freezing time and of the number of freeze−thaw cycles on the swelling ratio and gel fraction of achieved hydrogels were evaluated using response surface methodology. The multiple regression analysis suggested second order polynomial equations as models for predicting changes of the studied hydrogel characteristics by selected process variables, with relatively high coefficients of determination (R2 > 0.82). The numerical optimization suggested that freezing the polymer solutions for 5 h and repeating the freeze−thaw process for 5 times would give the most desirable hydrogels with highest either swelling ratio or gel fraction. Remarkably, the ion adsorption studies showed that the adsorption of Cu2+ and Zn2+ ions by the hydrogels obeys zero order kinetics and the high capability of the produced optimum hydrogels to adsorb selected ions from synthetic waste was confirmed."


2021 ◽  
Vol 63 (3) ◽  
pp. 6-11
Author(s):  
Bao Ngoc Pham ◽  
◽  
Giang Nguyen ◽  
Van Toan Le ◽  
Xuan Cuong Le ◽  
...  

Copolymer hydrogel (PVA-g-AA) having varied PVA (Polyvinyl alcohol) and AA (Acrylic acid) content is prepared by gamma induced radiation polymerization. The parameters affecting the gel fraction yield have been studied. The gel fraction and the swelling property are found to be 92.39 and 905% respectively at an absorbed dose of 20 kGy. Structural and property characteristics were determined by Fourier Transform Infrared (FTIR) spectrometer and Differential Scanning Calorimetry (DSC). The surface morphology of PVA and copolymer has been studied with Scanning Electron Microscope (SEM). The factors affecting the metal uptake such as pH, time, and initial feed metal concentration were investigated. It is found that at pH 5 and after 240 minutes the maximum adsorption amount are 178, 161, 117, and 110 mg/g for Pb2+, Zn2+, Co2+, and Ni2+ respectively.


Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 747
Author(s):  
Marguerite Meeremans ◽  
Lana Van Damme ◽  
Ward De Spiegelaere ◽  
Sandra Van Vlierberghe ◽  
Catharina De Schauwer

(1) Background: Tendinopathy is a common injury in both human and equine athletes. Representative in vitro models are mandatory to facilitate translation of fundamental research into successful clinical treatments. Natural biomaterials like gelatin provide favorable cell binding characteristics and are easily modifiable. In this study, methacrylated gelatin (gel-MA) and norbornene-functionalized gelatin (gel-NB), crosslinked with 1,4-dithiotreitol (DTT) or thiolated gelatin (gel-SH) were compared. (2) Methods: The physicochemical properties (1H-NMR spectroscopy, gel fraction, swelling ratio, and storage modulus) and equine tenocyte characteristics (proliferation, viability, and morphology) of four different hydrogels (gel-MA, gel-NB85/DTT, gel-NB55/DTT, and gel-NB85/SH75) were evaluated. Cellular functionality was analyzed using fluorescence microscopy (viability assay and focal adhesion staining). (3) Results: The thiol-ene based hydrogels showed a significantly lower gel fraction/storage modulus and a higher swelling ratio compared to gel-MA. Significantly less tenocytes were observed on gel-MA discs at 14 days compared to gel-NB85/DTT, gel-NB55/DTT and gel-NB85/SH75. At 7 and 14 days, the characteristic elongated morphology of tenocytes was significantly more pronounced on gel-NB85/DTT and gel-NB55/DTT in contrast to TCP and gel-MA. (4) Conclusions: Thiol-ene crosslinked gelatins exploiting DTT as a crosslinker are the preferred biomaterials to support the culture of tenocytes. Follow-up experiments will evaluate these biomaterials in more complex models.


Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 596
Author(s):  
Chang Liu ◽  
Amit K. Tripathi ◽  
Wei Gao ◽  
John G. Tsavalas

Waterborne latex is often called a product-of-process. Here, the effect of semi-batch monomer feed rate on the kinetics and gel formation in seeded emulsion polymerization was investigated for the copolymerization of n-butyl methacrylate (n-BMA) and ethylene glycol dimethacrylate (EGDMA). Strikingly, the gel fraction was observed to be significantly influenced by monomer feed rate, even while most of the experiments were performed under so-called starve-fed conditions. More flooded conditions from faster monomer feed rates, including seeded batch reactions, counterintuitively resulted in significantly higher gel fraction. Chain transfer to polymer was intentionally suppressed here via monomer selection so as to focus mechanistic insights to relate only to the influence of a divinyl monomer, as opposed to being clouded by contributions to topology from long chain branching. Simulations revealed that the dominant influence on this phenomenon was the sensitivity of primary intramolecular cyclization to the instantaneous unreacted monomer concentration, which is directly impacted by monomer feed rate. The rate constant for cyclization for these conditions was determined to be first order and 4000 s−1, approximately 4 times that typically observed for backbiting in acrylates. This concept has been explored previously for bulk and solution polymerizations, but not for emulsified reaction environments and especially for the very low mole fraction divinyl monomer. In addition, while gel fraction could be dramatically manipulated by variations in linear monomer feed rates, it could be markedly enhanced by leveraging non-linear feed profiles built from combination sequences of flooded and starved conditions. For a 2 h total feed time, a fully linear profile resulted in 30% gel while a corresponding non-linear profile with an early fast-feed segment resulted in 80% gel.


Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 919
Author(s):  
Yin Ran ◽  
Ling-Ji Zheng ◽  
Jian-Bing Zeng

Epoxy vitrimers with reprocessability, recyclability, and a self-healing performance have attracted increasingly attention, but are usually fabricated through static curing procedures with a low production efficiency. Herein, we report a new approach to fabricate an epoxy vitrimer by dynamic crosslinking in a torque rheometer, using diglycidyl ether of bisphenol A and sebacic acid as the epoxy resin and curing agent, respectively, in the presence of zinc acetylacetonate as the transesterification catalyst. The optimal condition for fabricating the epoxy vitrimer (EVD) was dynamic crosslinking at 180 °C for ~11 min. A control epoxy vitrimer (EVS) was prepared by static curing at 180 °C for ~11 min. The structure, properties, and stress relaxation of the EVD and EVS were comparatively investigated in detail. The EVS did not cure completely during static curing, as evidenced by the continuously increasing gel fraction when subjected to compression molding. The gel fraction of the EVD did not change with compression molding at the same condition. The physical, mechanical, and stress relaxation properties of the EVD prepared by dynamic crosslinking were comparable to those of the EVS fabricated by static curing, despite small differences in the specific property parameters. This study demonstrated that dynamic crosslinking provides a new technique to efficiently fabricate an epoxy vitrimer.


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