Preparation and Characterization of Carboxymethylcellulose Hydrogel Fibers

Preparation and Characterization of CarboxymethylCellulose Hydrogel Fibers Jie Liu1, Chuanjie Zhang2, Dagang Miao1, Shuying Sui1, Fenglin Deng2, Chaohong Dong1, Lin Zhang1, Ping Zhu, PhD1 1College of Textiles and Clothing, Qingdao University, Qingdao, Shandong Province CHINA 2College of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan CHINA Correspondence to: Ping Zhu email: [email protected] ABSTRACT Carboxymethyl cellulose (CMC) hydrogel fibers sensitivity. It is used in various biomedical were prepared via a solution spinning method with applications primarily due to its easy availability, aluminum sulfate as the crosslinking agent. The high viscosity, good water solubility, nontoxicity, low preparation process of the CMC hydrogel fibers was price, biocompatibility, biodegradability, and good optimized via orthogonal experiments. FTIR, POM, film-forming ability [7-12]. SEM and TGA were used to characterize the structure and properties of the hydrogel fibers. The mechanical Hydrogels prepared via CMC crosslinking are highly properties and absorption ability of the hydrogel absorbent and have excellent physical properties and fibers were also investigated. The results indicated dynamic viscoelasticities [13]. Due to its unique that an even structure was formed in the hydrogel. properties, the CMC hydrogel is a potential candidate The mechanical properties of the hydrogel fibers for wound dressings [14]. CMC hydrogel fibers have were improved with increasing CMC degree of similar properties as CMC hydrogels. Moreover, they substitution. The hydrogel fibers had excellent can be further processed into other forms of moisture absorption performance, and are well-suited biomedical materials. Thus, the hydrogel fiber has for biomedical applications such as wound dressings. attracted increasing attention in many fields [15-16]. Keywords: Carboxymethyl cellulose hydrogel, fibers, Aluminum sulfate, with its cationic species in the preparation, characterization, moisture absorption effective forms of Al3+, provides multivalent positive charges and abundant sites for cross-linking with INTRODUCTION anionic groups. Aluminum sulfate has been widely Hydrophilic polymer networks containing a large used as a cross-linking agent in the preparation of amount of water or other biological fluids are known biomaterials; it exhibits excellent performance and as hydrogels. They can simulate the function of low toxicity [17]. In the present study, a novel natural gels in living organism including swelling, electrostatic complexing method is proposed for the but they do not dissolve in water [1]. The swelling preparation of CMC/HEC hydrogels with aluminum capability of a hydrogel depends on the skeleton and ions as a cross-linker [18]. crosslinking density of its network [2-3]. There is a strong interest in hydrogels because these polymeric In this study, we propose to use aluminum ions as a materials can trap large amounts of water and solutes, cross-linking agent to prepare CMC hydrogel fibers and form a solid-like gel structure [4-5]. In particular, via a solution spinning method. The optimum the relatively high water content and soft, rubbery preparation process of CMC hydrogel fibers was consistency gives hydrogels a strong resemblance to investigated. The CMC hydrogel fibers were many soft living tissues [6]. characterized with various instrumental techniques. CMC is an ether derivative of cellulose in which the EXPERIMENTAL H atoms of the hydroxyl groups are replaced by Materials carboxymethyl groups (-CH2COOH). It is often used Carboxymethyl cellulose (CMC) with the same as its sodium salt, Na-CMC, and exhibits pH molecular weight but different degrees of substitution Journal of Engineered Fibers and Fabrics 6 http://www.jeffjournal.org Volume 13, Issue 3 – 2018 (0.47, 0.59, 0.77 and 0.94) was prepared with cotton Measurements of Properties pulp as the raw materials according to Ramli et al. Mechanical Properties [19]. Analytical grade Al2(SO4)3, glycerol and KBr After air-drying, the tensile strength and elongation at were purchased from China National Pharmaceutical break of the CMC hydrogel fibers were measured on Group (Beijing, China). All reagents were used as a Textechno fiber electron tensile tester at constant obtained without further purification. temperature and humidity. The gauge length was 100 mm, and the crosshead speed was 100 mm/min. Ten Preparation of CMC Hydrogel Fibers individual fiber samples were tested from each group CMC was dissolved in distilled water under constant and the measurements were reported as the mean± stirring to obtain final CMC concentration of 3, 3.5, 4 standard deviation. and 4.5 wt%. The well-mixed CMC solution was then transferred to a centrifuge tube that was then Water-absorption Values (WAVs) and Water-retention centrifuged in a refrigerated centrifuge at 5000 rad/s, Values (WRVs) 20°C for 3 min. The resulting clear CMC solution was used as a spinning solution and was extruded WAVs and WRVs were calculated using the into Al2(SO4)3 solution via a needle tube at 25°C. The following Eq. (1) and Eq. (2), respectively. as-spun fibers were washed in distilled water at 25°C after 2–8 s and then air-dried to afford white fibers. WAV = (W1 – W0)/W0 × 100% (1) Characterization FTIR Study WRV = (W2 − W0)/W0 × 100% (2) 1 mg dry sample was ground, mixed well with 100 mg KBr power, and compressed into a transparent Here, W0 denotes the original weight of fiber that was disk. The FTIR spectra of the fibers and raw dried at 70°C until a constant weight was achieved; materials were recorded on a Bruker Tensor 27 W1 is the weight of the fiber after 30 min immersion −1 spectrometer in the range of 4000–400 cm using an in distilled water; W2 is the weight of the fully −1 average of 32 scans with a resolution of 1 cm . swollen fiber after being centrifuged at 2500 rmp for 5 min. All experiments were done at least in Polarizing Microscope Photographs triplicate. Dry CMC hydrogel fibers were immersed into distilled water. After 30 min, the fibers were removed Moisture Absorption Kinetics and the surface was dried with a filter paper. The dried fibers were immersed into distilled water Afterwards, the dry and wet CMC hydrogel fibers or 0.9 wt% NaCl aqueous solution or “A Solution” were put onto glass slides separately. Images were (mimic blood containing 142 mmol/L Na+ and 2.5 collected with a digital camera and evaluated with a mmol/L Ca+) at room temperature (~25°C). The polarizing microscope. samples were removed from aqueous solution at regular time intervals and weighed after the surface Scanning Electron Microscopy was dried with a filter paper. The micro morphological structure of the CMC hydrogel fibers was studied with Phenom-World BV RESULTS AND DISCUSSION SEM. Prior to examination, the fiber samples were The Crosslinking Mechanism fractured in liquid nitrogen, the fiber sections were CMC is a white, powdery or flocculent polymer coated with gold, and the sample was then observed material [20]. The free segments of CMC entangle and photographed. with each other after the CMC powder is dissolved into water with increasing CMC content. The Thermogravimetric Analysis viscosity increases and the flow index decreases. The Thermogravimetric analyses were conducted on a CMC hydrogel mold samples formed after the CMC Netzsch TG 209 thermal gravimetric analyzer. The solution was dried in glass dishes. A thin layer of the sample was heated from 50 to 800°C at 10°C/min CMC hydrogel surface was dissolved when under a nitrogen flow of 50 mL/min. immersed into a coagulation bath containing Al2(SO4)3. The crosslinking mechanism of CMC Journal of Engineered Fibers and Fabrics 7 http://www.jeffjournal.org Volume 13, Issue 3 – 2018 hydrogel is shown in Figure 1. The carboxymethyl TABLE I. Factors and levels of the orthogonal experiments. groups of CMC were ionized and were negatively charged. Thus, a thin reticular film was formed on the (X1) (X2) (X3) (X4) surface of the CMC hydrogel samples via a CMC Al (SO ) Level 2 4 3 coagulation DS of CMC concentration concentration combination of chemical bonds of carboxymethyl time (s) groups of CMC and aluminum ions. The crosslinking (wt% ) (wt% ) films could keep CMC from dissolving in water and 1 0.4 3 0.2 2 lock the free water inside the samples to form 2 0.6 3.5 0.3 4 hydrogel. Thus, the crosslinking thickness of the 3 0.8 4 0.4 6 4 0.9 4.5 0.5 8 hydrogel surface could be controlled via the soaking time of the coagulation bath. At the beginning, crosslinking occurred on the surface layer while the The orthogonal experiment was designed to obtain CMC inside the samples could still be dissolved. The the optimal preparation process for CMC hydrogel hydrogel rapidly absorbed water with a large swelling fibers using water-absorption values (WAVs) and ratio when the dried hydrogel was immersed into water-retention values (WRVs) as an index. The water again. results in Table II show that the order of impact of the four factors on WAV follows the sequence: DS of CMC > coagulation time > Al2(SO4)3 concentration > CMC concentration. The preparation process was optimized as follows: the DS of CMC was 0.94, the CMC concentration was 4 wt%, Al2(SO4)3 concentration was 0.4 wt%, and the coagulation time was 4 s. The WRV impact was as follows: DS of CMC > Al2(SO4)3 concentration > coagulation time > CMC concentration. The preparation process was optimized as follows: the DS of CMC was 0.94, the CMC concentration was 3 wt%, Al2(SO4)3 concentration was 0.4 wt%, and the coagulation time was 4 s. The optimal levels obtained via the WAV FIGURE 1. CMC hydrogel crosslinking mechanism. index remained consistent with that of the WRV index, except for the CMC concentration that has the least influence on WAV and WRV of the fibers.

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