Studies on the interaction of water with ethylcellulose: Effect of polymer particle size

Abstract

The purpose of this research was to investigate the interaction of water with ethylcellulose samples and assess the effect of particle size on the interaction. The distribution of water within coarse particle ethylcellulose (CPEC; average particle size 310 micro m) and fine particle ethylcellulose (FPEC; average particle size 9.7 micro m) of 7 cps viscosity grade was assessed by differential scanning calorimetry (DSC) and dynamic vapor sorption analysis. The amounts of nonfreezing and freezing water in hydrated samples were determined from melting endotherms obtained by DSC. An increase in water content resulted in an increase in the enthalpy of fusion of water for the two particle size fractions of EC. The amount of nonfreezable water was not affected by the change in particle size at low water contents. Exposure of ethylcellulose to water for 30 minutes is sufficient to achieve equilibration within the hydrated polymer at 47% wt/wt water content. The moisture sorption profiles were analyzed according to the Guggenheim-Anderson-de Boer (GAB) and Young and Nelson equations, which can help to distinguish moisture distribution in different physical forms. The amount of externally adsorbed moisture was greater in the case of FPEC. Internally absorbed moisture was evident only with the CPEC. In light of these results, an explanation is offered for the success of FPEC in wet-granulation methods where CPEC was not successful.

Influence of Some Formulation Variables on the Optimization of pH-dependent, Colon-targeted, Sustained-release Mesalamine Microspheres

“…EC is a water-insoluble polymer; it has been widely used in microencapsulation in order to retard the release of many drugs (33)(34)(35)(36). Being hydrophobic in nature (37), EC is expected to prolong the release of 5-ASA from ES100-based microspheres at pHs higher than the threshold of ES100 ionization (pH 7).…”

Hydrophilic excipients modulate the time lag of time-controlled disintegrating press-coated tablets

“…18 Furthermore, the particle size of EC powder and the porosity in compact EC are the major factors that influence the uptake of water and the dissolution of drug from the compacted form. [19][20] Recently, the unique suitability of EC powders to act as an outer shell has also been explored to directly prepare the press-coated tablet with a special time-controlled rupturing function. 21 This function can be further and effectively controlled by modifying the compression force applied to the outer shell, the amount of outer shell used, and the excipients added to the inner core tablet.…”

Composition dependent changes in the swelling and mechanical properties of nanocomposite hydrogels

“…5 displays the effect of Na-m. on the DSC curves of the most hydrophobic poly(NIPAAm)-based composites. Following the method of Agarwal et al, we also recorded the DSC curve of distilled water for reference [29]. The heat of evaporation of distilled water was determined as 41.74 kJ/mol.…”

“…Differential scanning calorimetry (DSC) has been employed to study the states of water in a number of polymer stabilised hydrogel systems [26][27][28][29][30]. The interaction of water with such polymers and its distribution within the gel are critical to the physicochemical behaviour of the gel.…”

“…The peak in the DSC associated with a phase transition of loosely bound water is generally observed as a shoulder on the free water melting endotherm peak, and not as a discrete endotherm. The bound water content depends on the chemical and higherorder structure of the polymer [29].…”