ethyl-cellulose and diethyl-phthalate

Plasticizers play a crucial role in various process of microencapsulation. In this study, the effect of incorporation of plasticizer in process of emulsion solvent evaporation was investigated on properties of ethyl cellulose (EC) microcapsules containing propranolol hydrochloride. The effect of plasticizer type and concentration were investigated on characteristics of microcapsules prepared from different viscosity grades of EC. Product yield, encapsulation efficiency, mean particle size, shape, surface characteristics, solid state of drug, and drug release profiles were evaluated. Product yield and encapsulation efficiency were not dependent on plasticizer type and concentration. However, encapsulation efficiency decreased with increase in EC viscosity grade in the most of the cases. The mean particle size was in the range of 724-797 μm and was not dependent on plasticizer type. Microcapsules formed in the presence of PEG had a very smooth surface with few pores. XRD and DSC studies revealed a reduction of drug crystallinity after microencapsulation especially in presence of PEG. The results showed that the presence of TEC and DEP with different concentrations had no marked effect on drug release from microcapsules containing different viscosity grades of EC. This was not the case when PEG was used, and despite its water solubility it reduced the drug release rate noticeably. The reduction in the drug release in the presence of PEG was concentration-dependent. The use of PEG as a plasticizer in process of emulsion solvent evaporation highly improved the EC microcapsule structure and retarded the drug release rate and therefore is recommended.

Topics: Capsules; Cellulose; Citrates; Drug Compounding; Emulsions; Particle Size; Phthalic Acids; Plasticizers; Polyethylene Glycols; Propranolol; Solubility; Solvents; Viscosity

The effects of plasticizer, physical aging, and film-forming temperature on the mechanical and transport properties of films formed from aqueous dispersions of ethylcellulose latex were investigated. The water vapor permeability of latex films was found to decrease with diethyl phthalate to a minimum value and then to increase with diethyl phthalate at higher concentrations. Because of the decrease in free volume and the further coalescence of particles of latex polymer films in the physical aging range, the creep compliance of latex films decreased with physical aging time. Within 60 to 100 degrees C, the film-forming temperature was found to have no effect on the mechanical and transport properties of Aquacoat films. However, since many pinholes formed in the latex films when the film-forming temperature was above 100 degrees C, the water vapor permeability of latex films was higher than that of latex films formed between 60 and 100 degrees C. The formation of films from aqueous latex dispersions is suggested to proceed gradually from the top to the bottom of the latex dispersion in this study.

Topics: Cellulose; Latex; Membranes, Artificial; Permeability; Phthalic Acids; Plasticizers; Sucrose; Temperature; Water