Stearic acid crystals stabilization in aqueous polymeric dispersions

Abstract

In wet granulation processes, coatings or binders generally consist of mixtures of various raw materials that confer or enhance specific properties to the final product. Typically, a coating solution is composed of water, film forming polymer (such as hydroxypropylmethylcellulose, HPMC) and filler (such as stearic acid, SA). One of the important issues in wet granulation processes is the stability of the aqueous coating (or binder) dispersion. An unstable dispersion results in the agglomeration of the colloidal particles, thereby affecting the film coating properties and eventually the coating process. In this study, we use dissipative particle dynamics (DPD) to elucidate the structure of aqueous colloidal formulations. DPD is a coarse-grained molecular dynamics simulation method where the materials are described as a set of soft beads interacting according to the Flory-Huggins (1942) model. The DPD simulation results are compared to experimental results obtained by Cryogenic-SEM and particle size distribution analysis. It is shown from the DPD simulation results that the HPMC polymer is able to form a layer that covers SA particles and thus produces stable colloids. Microcrystalline cellulose (MCC) also covers SA agglomerate but it is not able to diffuse inside its inner core. The agglomerate structure is characterized via the density distribution and the polymer chain end-to-end distance. Experimental results show similar trends; particle size distribution analysis shows that in the presence of HPMC, the majority of SA particles are below 1 m in diameter, also MCC is able to prevent the formation of big SA agglomerates and may be a better stabilizing agent than HPMC. SEM images reveal that HPMC surrounds SA agglomerates with a hatching textured film and anchors on their surface.

A new HPF specimen carrier adapter for the use of high‐pressure freezing with cryoscanning electron microscope: two applications: stearic acid organization in a hydroxypropyl methylcellulose matrix and mice myocardium

“…When HPMC is mixed with SA, white crystals appear. Those crystals have been previously described as SA crystals (Jarray, , ) and never occur in ‘pure HPMC‐water’ (Fig. ).…”

Lipid nanoparticles with fats or oils containing β-carotene: Storage stability and in vitro digestibility kinetics

“…On the other hand, cocoa butter LNPs presented a bimodal particle size distribution, with a main intensity peak around 10 µm and a minor intensity peak around 100 nm. The main large peak might be attributed to the formation of crystalline structures from the released free fatty acids after digestion, since FFA from the digestion were not efficiently incorporated in the micelle fraction (section 3.5) and stearic acid, which is the main fatty acid from cocoa butter, is highly insoluble in water (Jarray, Gerbaud, & Hemati, 2016). In this regard, thin crystals were visualized with the microscopy analysis of the cocoa butter LNPs after small intestinal conditions (Figure 4), even at the temperature at which the microscopy analysis was conducted (37 °C).…”

Hydrophobicity and Macroscale Tribology Behavior of Stearic Acid/Hydroxypropyl Methylcellulose Dual-Layer Composite

“…However, because of the increase in volume and weight, precipitation is prone to occur, which prevents the SA molecules from being uniformly distributed in the aqueous solution. The results from a simulation study on the distribution of SA and HPMC molecules in HPMC aqueous solutions of different concentrations based on dissipative particle dynamics were compared to the experimental particle size distribution of SA micelles [13]. It was deduced that when the number of HPMC molecules (i.e., concentration) is greater than or equal to that of the SA molecules, the long-chained HPMC molecules trap the SA molecules and restrict their free motion, preventing the contact of SA molecules with the water molecules.…”