Synthesis, Characterization and applications of cellulosic products with high water absorbing capacity

Abstract

In this thesis , Synthesis, Characterization and applications of cellulosic products with high water absorbing capacity will be discussed. This work wasdivided into threeparts :

First Part :

Synthesis and characterization of Superabsorbent hydrogels based on carboxymethyl cellulose In current work, trials are made to introduce carboxymethyl groups into the molecular structure of cellulose and the CMC, so formed will act as a backbone into the hydrogel for keeping its appearance when it absorbs large amounts of water. Moreover, CMC was used as hydrophilic filler in the hydrogel network to increase the absorption of water. Silver nitrate (AgNO3) was incorporated in thehydrogel with a view of inducing antimicrobial activity to the CMC based superabsorbent hydrogel. The structure and properties of the superabsorbent materials are evaluated, that is,the intermolecular interaction and morphological change of the hydrogels are characterized using Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscope (SEM).

Given below are the main conclusions arrived at with this part : 1.1.1. Synthesis of Carboxymethyl Cellulose (CMC)

Cotton fibers were pretreated with sodium hydroxide solution. Active alkali cellulose was reacted with monochloro acetic acid solution. The primary treatment of pure cellulose fiber with variable weight percentage of NaOH in static solution and cotton fiber was conducted. The amount of adsorbed NaOH for the Cotton fiber was 39% higher than that in the static solution. The results revealed that the amount of adsorbed NaOH was proportional to concentration of NaOH solution as shown in figure 1 & eqn.3. The range of DS obtained was from 0.7 to 2.173 as shown in Table 1. 1.1.2. Preparation of CMC hydrogels and Silver CMC hydrogel

The 3 wt% CMC solution was prepared as follows: 3 g was dispersed into 97 g of 6 wt% NaOH/4 wt% urea/90 wt% water mixture with stirring for 5 min followed by storing in the refrigeration (-20 °C) for 12 h. The frozen solid was thawed and stirred extensively at room temperature to obtain a transparent CMC solution having a 3 wt% polymer concentration. The CMC solution was mixed with AgNO3solution(0,1, 2 ml)(0.1mmol). ECH (98%) was added to the mixture as crosslinker, stirred at 30 °C for 2 h to obtain a homogeneous solution. The latter was kept at 60 °C for different duration(3, 6, 10, 12 h) whereby gels could be achieved. Gels were washed with water to obtain hydrogels.

II. Characterization of CMC hydrogels and Silver CMC hydrogel The CMC hydrogels and Silver CMC hydrogel were analyzed using FTIR-spectra, Differential scanning calorimetry( DSC) and Thermogravimetric Analysis (TGA). The CMC hydrogels and Silver CMC hydrogel were confirmed by Scanning Electron Microscope (SEM). The silver particles formation is characterized by measuring the Energy Dispersative X-Ray Analysis.

III. Factor affecting on Swelling properties of the hydrogels 1. Effect of time on CMC hydrogel formation 2. Effect of AgNo3 Solution on CMC hydrogel 3. Effect of ECH as crossliner on CMC hydrogel

Second Part : Novel Superabsorbent Hydrogels Using CarboxymethylCellulose/ Hydroxyethyl Cellulose/Citric Acid Aqueous System

In the present work, citric acid (CA) is used in preparation of hydrogels based on CMCNa /HEC mixture. Citric acid is used in hydrogel preparation for the first time. This together with its nontoxicity advocate preparation and characterization along with the properties of the hydrogels in queotion. The work in future extended to include Ag in the hydrogel using AgNO3 .State of the art tools are used for detailed investigation of the hydrogel.