Alkaline Hydrolysis of Polyester Fabric and Dyeing with Natural Colorants Extracted from Henna Leaves

Research Article

Adv Res Text Eng. 2023; 8(1): 1080.

Alkaline Hydrolysis of Polyester Fabric and Dyeing with Natural Colorants Extracted from Henna Leaves

Bayeleyegn Mekonnen Aragie; Asaye Dessie Wolela*

Department of Textile Engineering, Kombolcha Institute of Technology, Wollo University; Kombolcha, Ethiopia

*Corresponding author: Asaye Dessie Department of Textile Engineering, Kombolcha Institute of Technology, Wollo University, Ethiopia. Email: ase25dessie@gmail.com

Received: May 08, 2023 Accepted: June 06, 2023 Published: June 13, 2023

Abstract

The aim of this study was to dye polyester fabric with natural colorant obtained from henna leaves. Due to the hydrophobic nature of polyester, it makes the dyeing process difficult at low temperature and also prevents dye molecules from diffusing into the fiber interior during dyeing. To solve such dyeability problems of polyester, the fabric were treated with alkali to convert the hydrophobic nature into hydrophilic. This alkaline hydrolysis of polyester improved its chemical properties and made dyeing of polyester with natural colorant can be possible. The coloration of hydrolyzed polyester was carried out with the extracted aqueous natural dye. In this study optimizations of surface treatment conditions of polyester were investigated and the effects of hydrolysis on the fabric properties were also studied. Dyeing conditions like MLR, time, temperature and pH were optimized based on their dyeing properties results. Modifications of the fiber surface were confirmed by wettability test and FTIR study. The alkaline hydrolysis of polyester showed weight loss but achieved weight loss has no significant effect on the fabric’s strength. Beside this, characterization of the dyeing properties like color strength, dyeing evenness and color fastness were carried out for lawsone (primary colorant in henna leaves) dyed polyester. It was observed from the study that as the dyeing temperature and time increases, the K/S value increases until dye exhaustion attains equilibrium and then there is decrease. Higher color strength was obtained at basic pH conditions. Color fastness to washing and rubbing result obtained showed good to excellent grades.

Keywords: Polyester; Hydrolysis; Henna dye; Dyeing

Introduction

Natural dyes can provide not only a rich and varied source of dyestuff, but also an income through sustainable harvest and selling of these plants in many developing countries such as Ethiopia, Nigeria, Uganda, India, and Iran [1]. Natural dyes or colorants may be derived from several different parts of the plant kingdom, including leaves, fruits, wood, heartwood, roots, bulbs, seeds, and barks. Ethiopia is home to a plethora of plant species that produce dye [2]. Natural dyes are in high demand around the world these days, thanks to a growing understanding of their therapeutic properties [3].

Polyethylene Terephthalate (PET) is an aliphatic–aromatic polymer composed of Terephthalic Acid (TPA) and Ethylene Glycol (EG) that is the most commercially important and long- established polyester fiber material [4,5]. Polyethylene terephthalate macromolecules have large molecules and an inflexible structure, resulting in a compact and highly crystalline molecular arrangement in polyester fiber, which is correlated with a high melting point and glass transition temperature, as well as insensitivity to moisture and various chemicals [6].

Polyester fiber is hydrophobic in nature [7] due to its strongly crystalline structure and lack of polarity, which prevents water molecules from entering the polymer system and limits swelling in water. As a result, the hydrophobicity of polyester fibers prevents dye molecules from diffusing into the fiber interior during dyeing [8], making the dyeing process extremely difficult at low temperatures. Because of its small particle size and non-ionic nature, synthetic colorants such as disperse dye are used to dye polyester fiber at high temperatures and pressures [5].

However, due to rising global awareness and environmental concerns, there has been a renewed interest in natural dyes from various natural resources such as onion, madder, saffron, kola nut, dolu, and curcumin, which has led to several studies focusing on coloration of polyester fibers with natural dyes from various natural resources such as onion, madder, saffron, kola nut, dolu, and curcumin [1,9,10]. Several researches used the conventional exhaust approach to dye polyester fibers with natural dyes like henna [5]. However, no systematic study of henna dye application on alkali-treated polyester fabric has been published. As a result, the aim of this study was to see how Henna dyeing of alkali surface modified polyester with different metallic mordants like copper sulphate, aluminum sulphate, and iron sulphate, as well as bio mordants like lemon, affected the results. It is anticipated that mordanting with lemon would result in the introduction of tannins [11], which will develop binding properties that will improve the dyeing of polyester fabric.

The majority of textile factories use disperses dyes for polyester coloration, which are extremely polluting to the atmosphere. As a result, this study was conducted in order to ensure the commercial use of henna leaves and to introduce an environmentally sustainable dyeing method for polyester fabric [2].

This means that textiles can be treated to achieve hydrophilization or hydrophobization; additionally, the surface chemistry and topography can be affected to enhance adhesion and repellence properties, as well as the confinement of functional groups to the surface. The hydrophobic polyester was converted to the hydrophilic polyester in this study by treating it with alkali. Aqueous sodium hydroxide hydrolyzes polyester, which undergoes nucleophilic substitution. Polyester's alkaline hydrolysis offers hydrophilicity, wettability, and increased moisture resorption, among other benefits.

Polyethylene Terephthalate (PET) fibers have excellent chemical, physical, and mechanical properties, but their inherent hydrophobic and inert nature has some disadvantages. Low moisture regain and wettability cause a number of issues during manufacturing (static electricity build-up) and during consumers use (clinging to the body, accumulation of fluff and soil). Alkaline hydrolysis of polyester, which turns hydrophobic PET into hydrophilic due to fibre surface modification [12], can solve these problems.

Lawsonia inarmis produces “lawsone,” also known as hennotannic acid, a red orange dye molecule. This molecule has been used to dye skin, fingernails, hair, leather, silk, and wool because of its affinity for protein bonding [13,14]. Henna (L. inermis) is a plant that grows wild in abandoned areas. Henna is commonly used as a dyeing agent in the cosmetic industry, and it is used to color hair, skin, and nails [14].

Lawsone is the primary colorant in henna leaves, and its chemical formula is 2-hydroxy-1, 4-napthoquinone, as shown in Figure 1. Natural orange 6 (CI 75480) is a substantive keratin dye that imparts an orange color due to the inclusion of a –OH (auxochrome) group in the naphthoquinone structure [15].