An Investigation on the Influence of a Vinyl Pyrrolidone/Vinyl Acetate Copolymer on the Moisture Permeation, Mechanical and Adhesive Properties of Aqueous-Based Hydroxypropyl Methylcellulose Film Coatings

Abstract

Film coating of tablets is commonly used to protect the integrity of the core material against environmental factors, for taste masking or providing a tough and better quality finish to minimize possible damage from mechanical handling during high speed packing.1) In view of environmental health and safety issues, as well as the higher costs associated with organic solvents, aqueous film coating is currently the method of choice in the pharmaceutical industry. One of the most widely used polymers for aqueous film coating of tablets is hydroxypropyl methylcellulose (HPMC).2) Generally, to minimize coating time and maximize production efficiency, the lowest possible viscosity grade of the polymer is the preferred choice as a high solid content in the coating solution is possible and, thus less water needed to be removed. The sprayable solution viscosity for aqueous film coating should be in the range of 150 to 400 mPa s. The apparent viscosity of aqueous HPMC solution is related to the molecular weight of the HPMC polymer and lowering of the molecular weight reduces the physical properties of the film coat.3) The advantage of using low viscosity grade polymer is limited if film quality, such as vapour permeabililty and tensile strength, is compromised.Due to the brittleness of plain HPMC films, plasticizers are often included in HPMC coating formulations. The functions of a plasticizer include softening films, reducing brittleness, increasing flexibility and ductility. Plasticization can increase the segmental mobility of HPMC, resulting in depression of the glass transition temperature. 4) As plasticizers lower both the mechanical properties and glass transition temperature, their compatibility and concentration are very important in coating formulations. Over-plasticization can lead to increased diffusivity, 5) making the film coat a poor protector of its core. In high humidity environments, adsorbed water itself has a plasticizing effect. Another additive, polyvinyl alcohol (PVA), had been reported to interact with HPMC resulting in decreased diffusivity. 5)Mechanical properties, such as tensile strength or maximum tensile stress, elastic modulus indicating stiffness and rigidity, 6) tensile strain at breakage or elongation (%) and work of failure (energy) are often used to gauge the performance of the film. An ideal film coat should be hard and tough with a high tensile strength and elastic modulus, 7) as well as a large work of failure and moderate elongation before break.Film coating on a tablet should be in intimate and continuous contact with the substrate surface.1) Strong film-tablet adhesion is also essential for good quality coated tablets as poor adhesion not only indicates visible film-coating defects but also affects the stability of moisture sensitive drugs and compromises the level of mechanical protection the film coat confers to the core. Evaluation of the adhesion characteristics provides useful information on the internal stress in films and film coating defects.8) The adhesiveness of film coa...

Preparation of Deproteinized Natural Rubber Latex and Properties of Films Formed by Itself and Several Adhesive Polymer Blends

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Characterization of physical and viscoelastic properties of polymer films for coating applications under different temperature of drying and storage

“…HPMC 603 and HPMC 615 were smooth, clear and colourless (Kwok et al, 2004). However HPMC 615 was harder and stiffer owing to its higher viscosity grade (higher molecular weight).…”

Isolation and characterization of natural and modified seed gum

“…Traditionally fenugreek seed are used in the treatment of diabetes (Dutta et al, 2005, Garg et al, 2018. Application of fenugreek seed gum have been reported as oral drug release retardant (Gowthamrajan et al, 2002, Ikoni et al, 2014, Kwok et al, 2004, binder (Nitalikar et al, 2013;Nayak et al, 2013;Nitalikar et al, 2013), mucoadhesive (Nokhodchi et al, 2008;Olga et al, 2016), emulsifiers (Rhodes et al, 1998;Rhodes et al, 2016;Rhodes et al, 2017), suspending agent (Senthil et al, 2011), gelling agent and formulation of nanoparticles Shanmuganathan et al, 2016).…”