Proposed Cross-Linking Model for Carboxymethyl Cellulose /Starch Superabsorbent Polymer Blend

Abstract

Superabsorbent polymer (SAP) blend has been synthesized from Carboxymethyl Cellulose (CMC) , starch, and aluminum sulfate octadecahydrate cross-linker. Water Absorption Capacity (WAC), FTIR, SEM, DSC, CHO, Flame Photometer and ignition tests are carried out to determine the used CMC formula, investigate the cross-linking process, and suggest a cross-linking model. Flame Photometer results showed there are two sodium acetate groups in the CMC molecule. This result confirmed by theoretical calculations and CHO test . To investigate which of Al 3+ and SO 4 2-ions causes the crosslinking : the extraction of the cross-linked CMC/starch tested with BaCl 2 solution(showed dense white precipitate ; sulfate group not share for blend formation), NaOH solution( showed white precipitate of aluminum hydroxide; Al 3+ ion present (i.e. Al 3+ ion share in the blend structure). These results confirmed by flame test for sodium ion, which showed high Na emission energy (5.75); there is an exchange between Al and Na ions. To check that aluminum is a part of the structure, sample of the cross-linked CMC ignited. A white precipitate appear for aluminum oxide ,which confirms the presence of Al. Based on that there are three CMC molecules connected to each Al atom, theoretical calculations about the amount of Al in the cross-linked CMC molecule showed a good agreement with the CHO results (5.613% Vs. 5.739 % respectively). FTIR spectrum of the cross-linked CMC/starch blend showed that there is a reaction between CMC and starch molecules; i.e. the new repeating unit contains three starch molecules. This conclusion confirmed by theoretical calculations and results of EDX, CHO, and ignition tests. Al% in the new mer appeared a good agreement between theoretical calculations (4.32%) and CHO results (4.512%). Ignition test calculations confirmed that the new mer contains three Al atoms. Evidences of the occurrence of the cross-linking process were obtained from FTIR, morphology, DSC and absorbency results. Absence of the primary hydroxyl alcohol band in the CMC/starch blend spectrum, indicates that this site is active and the reaction between starch and CMC molecules occurs through it. Morphologies studies showed that the sample after crosslinking is more compact than before as well as show one piece for after cross-linking comparing with different pieces before cross-linking.Optimum cross-linking ratio appeared to be 2wt% corresponded to WAC equal to 58 g/g.in distilled water and DSC results indicates that CMC/starch is a miscible blend.

Preparation and Characterization of Superabsorbent Polymers (SAPs) Based on PUL-g- AM/AA by Microwave Irradiation

“…According to equation 6, the porosity % increased with an increase in the pore volume of the hydrogel. The percentage of increment in the pore volume was 263.78 % after adding 3 mM SDBS to the PUL-g-AM /AA; the results of pore volume (nm 3 ) and porosity % of SAPs are shown in Table 2. The pore volume of the hydrogel increased with SDBS compared to the pore volume of the hydrogel that did not contain SDBS [41].…”

“…These polymers have 3D networks that can absorb large amounts of water up to 300 times or more of their initial mass [2]. SAPs may be natural or synthetic depending on where they came from [3,4].…”

Use of mechanically ground lignocellulosic native fines (LF) in the all-cellulosic composite filaments: fines properties and plasticizers

“…to Al 3? ) (Braihi et al 2014). Spinning was carried out with a constant flow rate of 5 ml/min by utilising converging nozzles with diameters of 0.28 mm and 0.41 mm (plastic…”

Synthesis of Biodegradable Superabsorbent Polymers from Carboxymethyl Cellulose/Humic Acid

“…Recently interest in developing superabsorbent from biopolymer such as starch [1], cellulose and its derivates [2], and chitosan [3] has been increased due to their exceptional properties compared to petroleum-based polymers that is sustainable, biocompatible, biodegradable, renewable and nontoxic [4]. Owing to their three-dimensional polymeric networks that can absorb and retain large volumes of water, superabsorbents are widely used in many fields, such as hygienic products, drugdelivery systems, agriculture and horticulture [5].…”

“…Superabsorbent prepared through electrostatic complexing can be used for example crosslinking of CMC/HEC [2] and CMC/starch [1] with aluminium sulphate as cross-linking agents. Aluminium sulphate, with its cationic species in effective form of Al 3+ , Al(OH) 2+ and oligomeric species in aqueous solution when pH< 5, provides multivalent positive charges and abundant sites for crosslinking with anionic groups [6] such us NaCMC that containing -COO groups to form hydrogel structures.…”