Elsevier

Carbohydrate Polymers

Volume 150, 5 October 2016, Pages 232-240
Carbohydrate Polymers

Effect of epichlorohydrin on the wet spinning of carrageenan fibers under optimal parameter conditions

https://doi.org/10.1016/j.carbpol.2016.05.032Get rights and content

Highlights

  • The optimum spinning parameters of carrageenan were obtained through orthogonal experiment method.

  • The crosslinked carrageenan fibers were prepared under the optimal conditions using a custom-made wet spinning device.

  • Structure and performance of carrageenan fibers were analyzed after processing by epoxy chloropropane.

  • The stability, necking phenomenon and strength property of modified fibers were studied.

Abstract

Motivated by the extensive application of carrageenans, this work prepared carrageenan fibers via wet spinning. The optimum spinning parameters were explored by means of an orthogonal test. According to the results of tensile test, dope concentration, draw ratio, coagulation bath temperature, and coagulation bath concentration set to 9%, 1.2, 15 °C and 5%, respectively, were the optimum spinning conditions. These parameters were then applied to fabricate fibers treated with epichlorohydrin in a stretch bath. The result of tensile testing demonstrated a positive improvement in the intensity, and SEM showed obvious necking phenomenon of the crosslinked carrageenan fibers. The structures and special groups were characterized with X-ray diffraction and FTIR, and the results indicated the regularity of the net structure and the increase in ether bond and methylene. In some, crosslinking reactions in optimum parameter conditions yield excellent fibers and thus present promising applications.

Introduction

The inner tissues of seaweeds, such as Chondrus, Eucheuma, Gigartina, and Hypnea, comprise extensive carrageenans called algal polysaccharides. These carrageenans are wildly used as gelling, thickening, and stabilizing agents in industrial applications, as well as in food, personal care, and pharmaceutical products (Abad, Aranilla, Relleve, & Dela Rosa, 2014; Azevedo, Torres, Sousa-Pinto, & Hilliou, 2015). The modification of carrageenan fibers has attracted significant attention from academia and the industry. Carrageenans, the raw material of these fibers, are sulfated galactans that are widely used as anionic polysaccharides (Azevedo et al., 2015). The linear polymer comprises alternating disaccharide repeating units of 3-linked β-d-galactopyranose (G units) and 4-linked α-d-galactopyranose (D units) or 4-linked 3, 6-anhydro-α-d-galactopyranose (DA units) (Das, Sharma, Mondal, & Prasad, 2016; Perez Recalde et al., 2016). Three main types of carrageenan have been identified according to the number and position of sulfate groups: kappa (κ), iota (ι), and lambda (λ) carrageenans (Van De Velde, Peppelman, Rollema, & Hans Tromp, 2001). Meanwhile, these types of carrageen comprise abundant hydroxide radicals, which are capable of inducting crosslinking reactions with some crosslinking reagents.

The physical or chemical characteristics of carrageenans are relevant to their structures and functional groups. A particular feature is a sequential layout with hexatomic rings, sulfate groups, and hydroxide radicals included in every repeat unit. They have an important effect on molecular weight, appearance, solubility, viscosity, and gelation of carrageenans (Farahnaky, Azizi, Majzoobi, Mesbahi, & Maftoonazad, 2013). Chemically, sulfate groups and hydroxide radicals play dominant roles in reactivity and mechanisms, such as strong anionic properties and crosslinking reactions. These characteristics are considered to produce additional agents to improve the quality of food, cosmetic, and pharmaceutical products (Liu, Zhan, Wan, Wang, & Wang, 2015; Selvakumaran & Muhamad, 2015; Selvakumaran, Muhamad, & Abd Razak, 2016; Wang, Chen, Huynh, & Chang, 2015).

The crosslinking method is widely used because the crosslinking agent and matrix can form a three-dimensional reticular structure, which plays an important role in the change of the performance of a crosslinked product (Rodrigues, da Costa, & Grenha, 2012). For example, the crosslinking reaction significantly affects the rheological and viscoelastic behavior of products, as well as their swelling and kinetic properties are also changed along with the structure (El-Aassar, El Fawal, Kamoun, & Fouda, 2015; Keppeler, Ellis, & Jacquier, 2009). A feasible approach has been adopted to reduce the degradation of molecular mass through the interaction between crosslinking agents and matrixes (Aminlashgari et al., 2015). Moreover, the control of release delivery systems by preparing them as beads is an innovative application of the crosslinking approach (Keppeler et al., 2009). Hence, crosslinked polymers are expected to become hot research topics in the near future.

The emerging applications of radiation-modified carrageenans, whose molecular structure backbones are changed by radiation, show immense potential in the areas of healthcare and environment. These materials are used as antioxidants, radiation dose indicators, wound dressings, superwater absorbent materials, and plant growth promoters (Abad et al., 2014). Owing to carrageenans bear sulfate group, they can be mixed with chitosan according to different proportions taking part in anti-thrombogenic and anti-calcification mechanisms. Thus they show great promise as stent coating (Campelo et al., 2016). The anionic groups of carrageenans demonstrate strong interactions with cation groups, similar to negatively charged sulfate groups and positively charged groups (such as amino groups in gelatin). This condition leads to significant transformations in coagulation kinetics and gelation abilities (Derkach, Ilyin, Maklakova, Kulichikhin, & Malkin, 2015). Recent studies have attempted to replace the gelatin with dually modified sogo starch through the addition of an appropriate amount of carrageenan. Moreover, carrageenan mechanism in rheology has been widely described in several studies (Fakharian, Tamimi, Abbaspour, Mohammadi Nafchi, & Karim, 2015). As another advanced exploration, carboxymethyl κ-carrageenan collagen peptides can generate new epithelium when smeared on wounded skin (Fan et al., 2015). Therefore, the biological activities of carrageenan macromolecules will continue to serve as an important research area.

These peculiarities are closely related to the spinnability of carrageenan solutions when prepared in the appropriate concentrations. The spinning of carrageenan fiber involves at least two prerequisites: (i) a carrageenan spinning dope with a high concentration to achieve enough viscosity for spinning and (ii) an effective spinning process which is capable of commercializing and yielding lustrous carrageenan fibers with a uniform diameter, circular profile, and tensile properties that are similar to or better than those of natural fibers. The wet spinning process is successfully applied to natural extracts (Kong & Ziegler, 2013), organic composite materials (Lai, Wei, Zou, Xu, & Lu, 2015), and blended materials (He et al., 2012).

In many reports, ethanol has been used as coagulant for the wet spinning of carrageenan fibers (Kong & Ziegler, 2013). However, the coagulant does not produce usable fibers, probably because ethanol induces excessively rapid conformation transition from a random coil/helix structure to a double helix structure that prevents adequate molecular chain adjustment. Calciumions (Ca2+) favor the gelation of ι-carrageenans, whereas potassium ions (K+) favor the gelation of κ-carrageenans (Morris and Chilvers, 1983, Tako and Nakamura, 1986; Tako, Nakamura, & Kohda, 1987). Therefore, we can use these inorganic salt solutions as coagulation bath. After the traditional extrusion of synthetic polymers or cellulosics, post-drawing to improve molecular orientation and packing is important to the mechanical properties of fibers (Hufenus, Reifler, Fernández-Ronco, & Heuberger, 2015). In this paper, we use barium chloride solution (BaCl2) as coagulation bath to further explore the fiber state under crosslinking conditions. A custom-made simplified industrial wet spinning device is also applied for continuous mechanical post-drawing. In this work, we detailedly describe the combined effects of spinning dope concentration, coagulant concentration, coagulant temperature, and draw ratio on the morphology and tensile properties of the resultant carrageenan fibers. Hence, we perform an orthogonal test to clarify the joint effects (Table 1).

The purpose of this work is to explore the new applications of carrageenans by preparing carrageenan fibers. The performance of these fibers is studied to fill the gap of knowledge about the influencing factors of fiber properties. When the solution temperature is below 65 °C, gelation is an adverse condition for the wet spinning of carrageenan solutions. The aqueous alkali NaOH can prevent spinning solutions from gelling at room temperature and thus makes spinning feasible. Adding metal ions to coagulation bath can facilitate gelation for alkaline carrageenan solutions upon extrusion from the spinneret. In the process of cooling, carrageenans indeed form thermoreversible gels in aqueous solutions or in the presence of several cations. Thermoreversible gelation involves a coil-to-double helix conformational change, then forming the aggregation of ordered molecules in an infinite network (Fig. 2) (Patel, Campanella, & Janaswamy, 2013). On the basis of this process, we employed the fibers treated with special methods (i.e. crosslinking formation) in various performance tests so as to determine the optimum spinning conditions.

Section snippets

Materials

Carrageenans (κ-) were purchased from Shishi Universal Joan Glue Industrial co., Ltd. (Quanzhou, China) and were used without further purification. If there were no special instruction, we all used kappa carrageenan as raw materials. Epoxy chloropropane, ethanol, barium chloride, and sodium hydroxide were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China), and these reagents were all analytical grade and all commercially available and used as received.

Wet spinning of carrageenan fibers and orthogonal test

Carrageenan fibers were

Parameters for wet spinning of carrageenans

Several types of solvent were used to dissolve carrageenans in the past study. For example, deionized water and sodium hydroxide solution were widely studied among these solvents. Carrageenans dissolved by sodium hydroxide solution demonstrated the lower gel temperature and suitable viscosity. Thus, sodium hydroxide solution is widely used as the solvent to prepare carrageenan solutions for artificial spinning. The optimum concentration of sodium hydroxide aqueous solution is 2 mol/L.

Generally,

Conclusion

Products with carrageenans as a raw material show valuable potential in various applications in the food and textile industry, as well as in the environment (Datta, Mody, Gopalsamy, & Jha, 2011). This study aimed to achieve a high-performance fiber treated with epoxy chloropropane through a crosslinking reaction. The crosslinking reaction formed a complex network structure with the continuous combination of hydroxide radicals and epoxy chloropropane. The stability and tenacity of the

Acknowledgments

This work is supported by the National Natural Science Foundation of China (50803030), the Postdoctoral Science Special Foundation of China (201104581) and the Postdoctoral Science Foundation of China (20100471495). The authors are also thankful to the International Cooperation Program for Excellent Lectures of 2012 by Shandong Provincial Education Department of China.

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