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Processing Additives
Published in Mohamed N. Rahaman, Ceramic Processing, 2017
Because of its solubility in water, methyl cellulose finds considerable use in forming methods such as extrusion, die pressing, and tape casting. Ethyl cellulose is soluble in ethanol, and provides an effective binder when an aqueous solvent cannot be used. Both binders provide high strength to the green article. Methyl cellulose demonstrates the property of thermal gelation, in which the polymer can form a high-viscosity gel on heating [10]. The reversible gelation process can be used to control the rheology of ceramic slurries and pastes. It is particularly useful as a binder in forming ceramic green articles by extrusion (Chapter 10). Figure 8.13 shows the thermal gelation profile of Methocel A100, a methyl cellulose-based polymer.
Cellulose-Based NanoBioMaterials
Published in Bhupinder Singh, Om Prakash Katare, Eliana B. Souto, NanoAgroceuticals & NanoPhytoChemicals, 2018
Michael Ioelovich, Sumant Saini, Teenu Sharma, Bhupinder Singh
Methyl cellulose is synthesized using a reaction between alkali-cellulose and chloromethane. The initial cellulose is cut into small pieces, which are mixed with a 20-fold of amount of 40% NaOH for 1 h. The swollen cellulose is pressed to obtain alkali to cellulose ratio of 3, crushed and kept in air-atmosphere at 35°C for 1 h to reduce DP. The alkali-cellulose is placed into the autoclave, which is purged with nitrogen. After adding of a 3-fold amount of chloromethane to cellulose weight, the autoclave is closed and heated to 70°C for 5 h. The obtained product is isolated from liquid phase, washed, and dried.
Naturally Occurring Polymers—Plants
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Methylcellulose is formed from basic cellulose and its reaction with chloromethane. Cellulose−OH,NaOH+CH3Cl→Cellulose−O−CH3Methylcellulose
Flurbiprofen-loaded interpenetrating polymer network beads based on alginate, polyvinyl alcohol and methylcellulose: design, characterization and in-vitro evaluation
Published in Journal of Biomaterials Science, Polymer Edition, 2020
In vitro release studies of FBP from beads was carried out in pH 1.2 HCl solution for the initial 2 h, then in pH 7.4 phosphate buffer solution for 4 h. Figures 7 and 8 display the cumulative FBP release of beads in different NaAlg/PVA/MC ratios (with 1/2 and 1/4, FBP/polymer ratios and exposure time to GA of 30 min). As shown in Figure 7 (for the FBP/polymer ratio of 1/2, exposure time to GA of 30 min) and in Figure 8 (for the FBP/polymer ratio of 1/4, exposure time to GA of 30 min) release rate of FBP increased with increment of NaAlg amount in the bead formulations. Among NaAlg/PVA/MC formulations (A1, A2, B1 and B2), the highest release rate was obtained from B2 formulation with cumulative FBP release of ∼100% in 6 h, while the lowest release rate was obtained from A1 formulation with cumulative release 84.8% at the end of the 6 h. Methylcellulose is a natural water-soluble polymer and contains methyl groups as well as a lesser number of residual –OH groups. PVA is virtually a linear polymer with –OH groups. On the other hand, alginate, a natural water-soluble polymer, contains hydroxyl and carboxyl groups, which impart hydrophilicity to the molecule. Therefore, penetration of liquid molecules through blend beads and then diffusion of FBP to external medium increases as the amount of NaAlg in the formulations increases. Similar observations have been observed in some studies [20,43]. Güncüm et al. [43] prepared amoxicillin–loaded poly(vinyl alcohol)/sodium alginate (PVA/NaAlg) nanoparticles as a polymer-based controlled release system and reported that as the amount of the NaAlg in the formulations increases, the drug release rate increases. The equilibrium swelling degrees were performed in buffer solution of different pH values (pH: 1.2 and 7.4) for various empty bead formulations and are displayed in Table 2.