Surface Treatment Effects of the Knitted Cotton Textile Pre-Forms in All-Cellulose Composites

Review Article

Adv Res Text Eng. 2024; 9(1): 1093.

Surface Treatment Effects of the Knitted Cotton Textile Pre-Forms in All-Cellulose Composites

Grozdanov Anita1,2*; Avella Maurizio2

¹Faculty of Technology and Metallurgy - Univeristy Ss Cyril and Methodius in Skopje, R. North Macedonia

²Institute for Polymers, Composites and Biomaterials (IPCB)-CNR, Italy

*Corresponding author: Grozdanov Anita Faculty of Technology and Metallurgy - Univeristy Ss Cyril and Methodius in Skopje, Rugjer Boskovic 16, 1000 Skopje, R. North Macedonia. Email: anita@tmf.ukim.edu.mk

Received: December 11, 2023 Accepted: January 23, 2024 Published: January 29, 2024

Abstract

The aim of this paper is to report the surface treatment effects of the knitted cotton textile preforms on the behavior of all-cellulose cotton composites. Surface modified knitted cotton pre-forms were used for preparation of so called all-cellulose bio-composites by using a fiber surface dissolution method in lithium chloride dissolved in N,N-dimethylacetamide (LiCl/DMAc). The main advantages of the obtained all-cellulose composites are the facts that being fully bio-based and biodegradable, they meet the needs of green transformation and are at the same time fully bio based, easily recyclable and biodegradable.

Cotton fiber surface was modified with two different methods: (i) alkaline scouring with bleaching and (ii) enzymatic scouring with acid and alkaline pectinases followed with bleaching. The mechanical properties of the obtained all-cellulose cotton based bio-composites were characterized through tensile test measurements. The composite morphology was observed by using scanning electron microscopy. Better effects and higher mechanical strength was measured for the all-cellulose composites based on enzymatic scoured and subsequently bleached knitted cotton fabrics.

Keywords: All-cellulose composites; Kknits; Cotton pre-forms

Introduction

Last decades, due to the enlarged efforts for sustainable development, the interest for eco-composites reinforced with natural fibers remarkably was increased [1-4]. Compared to the conventional technical fibers usually used as an reinforcements of the composite materials, Natural Fibers (NF) have demonstrate several advantages such as very good price/performance ratio, low density, non-toxicity, recyclability, renewability and biodegradability. It was shown that natural fiber reinforcements can be divided into three main groups: vegetables (based on cellulose), animals (based on proteins such as wool and silk) and mineral fibers (mainly based on silica sand) [4]. Furthermore, vegetable fibers were classified by the part from they were formed such as bast fibers (jute, flax, hemp), leaf fibers (sisal, manila hemp) and seed and fruit fibers (seed-hairs and flosses cotton). Application of natural fibers in polymer eco-composites is growing continuously every day [5]. One of the biggest sector is their application in the automobile industry where natural fiber reinforced eco-composites are incorporated in door panels, trunk trims and many other interior parts [6,7]. Usually NF was combined with both polymer matrices, thermoplastic and thermosets. One of the types of the developed eco-composites are so called All-Cellulose Composites (ACCs). Primary, the concept of “All-Cellulose Composites” was promoted by Nishino and his co-workers [8]. They applied the natural fibers in the concept of “All-Polymer Composites” and designed new eco-composite based on mono-cellulose component with both functions, as the incorporated fiber reinforcement and the matrix [8,9]. In fact, all-cellulose composites were designed using the original concept of self-reinforced composites, developed for thermoplastic high density polyethylene and polypropylene “all-fiber composites” [9]. Ligno-cellulosic fibers were selected to be a single-constructive element of the all-cellulose composites since they belong to the group of renewable and biodegradable biopolymer resources with concurrent mechanical properties [4,5,8]. Among them, cotton fibers were representative material which contains all cellulose components (cellulose, hemi-cellulose, lignin, pectin) as well and non-cellulose components, waxes. It is known that cellulose is a polydisperse linear homopolymer, consisting of β-1,4-glycosidic linked D-glucopyranose units (so-called anhydro-glucose units). The cellulose polymer chain contains free hydroxyl groups (OH) at the C-2, C-3, and C-6 atoms. Based on the OH groups and the oxygen atoms of both the pyranose and the glycoside bond, ordered hydrogen bond networks form various types of supramolecular semi-crystalline structures. So, from the composite structural point of view, the reinforcing component was played by the spirally oriented cellulose fibrils, while the matrix was a soft hemi-cellulose and non-cellulosic components. In order to create the matrix phase, it was necessary to dissolve the cellulose and again to regenerate it because the cellulose does not exhibit a melting point. Physical structure of the natural cellulose fibers consists of several layers where the surface layer of the fibers can be partially dissolved and transformed into the composite matrix phase. On this way, composite structural phases, the fiber and matrix one, are of the same, chemically identical composition.

Literature review has shown that up to today, several methods were developed, but mainly, two methods (2-steps and 1step methods) were applied for ACCs processing [9,10,11]. In two-steps method, first step covered the part of cellulose dissolved in a solvent which is then, in the second step, regenerated in the presence of undissolved cellulose. In the one-step method, partial dissolution of the surface of cellulosic fibres proceeds and then regenerated in situ to form a matrix around the undissolved portion. Several types of solvent systems were used for dissolution, usually solvent mixtures: Lithium Chloride/N,N-dimethylacetamide (LiCl/DMAc), Dimethyl Sulfoxide (DMSO)/Tetrabutyl-ammonium fluoride, NH3/NH4SCN, NaOH/urea, ionic liquids, PEG/NaOH, etc [8,9,10,11].

Nishino et al. prepared the all-cellulose composites from pure cellulose and ramie fibers in LiCl/DMAc system [8]. The obtained ACCs, created by their method exhibited high mechanical properties due to the fact that this method overpassed the overheating of the fibers during the thermal processing. Gindl and Keckes worked on a special type of optically transparent all-cellulose composite from Microcrystalline Cellulose (MCC) using the method of partial dissolution of cellulose surface with the same solvent system of LiCl/DMAc [12]. These researchers designed also all-cellulose composite based on cellulose and Rice Husk by using ionic liquid, 1-N-butyl-3-methylimidazo-lithium chloride ([C4mim]/Cl-)) as processing medium [13]. The obtained results clearly confirmed that silica was evenly distributed, and silica content in ACCs increased with the Rice Husk loading. In addition, higher crystallinity and better mechanical properties were registered for this type of ACCs. Duchemin et al. analyzed the effect of processing parameters such as dissolution time and cellulose concentration on the crystallography of precipitated cellulose, in Microcrystalline Cellulose (MCC) based composites [14]. The obtained results of their work contributed to further understanding of the phase transformations that occurred during the formation of all-cellulose composites by partial dissolution. Shibata et al. have compared ACCs based on cotton fabric with hinoki lumber – all wood composites [15]. They have used 1-butyl-3-methylimidazolium chloride (BMIMCl) for impregnation of cotton fabric and hinoki lumber.

Cotton fibers usually contain various natural non-cellulose impurities on its cuticle and primary wall that can provoke bad interface in ACCs. Because of that, in order to improve the surface absorbency, all of these natural impurities such as waxes, pectin’s, proteins and other, should be removed. Generally, the common industrial method used for removing the non-cellulosic impurities was performed by the alkaline treatment of the cotton yarn. Cotton fibers were treated by sodium hydroxide solution in the presence of chelating agents and surfactants at a boiling temperature for one/or two hours. These working conditions contribute the waxes and fats to be saponify or emulsify, and to turn pectin into soluble sodium pectat, proteins into soluble sodium salts of different amino acids, solubilize the ash and dissolve hemicelluloses with low DP. The scoured cotton exhibited improved wettability, and almost completely removed cuticle and non-cellulosic components. On this way, applying various fiber surface pretreatments (alkaline or enzymatic), the fiber surface sorption capacity of the cotton fabrics was tailored to result in better mechanical and structural properties of the all-cellulose composites. For this purpose, an attempt was made to replace the conventional alkaline with enzymatic scouring. Also, several enzyme classes (cellulases, pectinases, lipases, proteases, and their mixtures) were tested. Research investigations confirmed that the best results were obtained with pectinases [16-18]. Mechanism of enzyme treatment was based on pectinases penetration on the cuticle through cracks or micro-pores digesting the pectin. In the same time the enzyme facilitated the partial removal of the cuticle components [19].

Useful results obtained for the all-cellulose composites based on cotton woven textile fabrics have encourage us to design and tested all-cellulose composites based on cotton knitted fabrics, also [20]. So, this paper reports the results of the analysis of the all-cellulose composites produced from 2D – cotton knitted textile preforms using the method of partial fiber surface dissolution in the solvent mixture of N.N-dimethylacetamide and Lithium chloride (LiCl/DMAc). In the same time, the effects of the various fiber-surface treatments, enzyme and alkaline scouring, on the composite structural performances were followed.

Experimental

Knitted textile preforms based on cotton fibers were used for preparation of all-cellulose composites using the method of a fiber surface dissolution in solvent system of Lithium Chloride and N,N-dimethylacetamide (LiCl/DMAc). Knitted cotton textile preforms of two-layers were mounted on the metal frame and bonded on the angles to avoid fabric deformation. Then the knitted preform was activated in acetone (2h) and then (with 3 wt/v cellulose concentrations) were immersed in 8 % wt/v LiCl/DMAc for the immersion time of 24 h in order to provide good impregnation of cotton textile pre-forms. After 24 h, the knitted cotton fabrics were washed with distilled water and hot-pressed between two Teflon sheets at 130oC for 20 min and allowed to cool down at room temperature alone.

Characteristic parameters of the cotton knitted fabrics used in this research are presented in Table 1.