Electrostatic powder coating: Principles and pharmaceutical applications

pH-Responsive, Thermoset Polymer Coatings for Active Protection against Aluminum Corrosion

This paper describes the synthesis and use of multifunctional methacrylic monomers, which contain basic (amine) functional groups, including an example in which an acid-labile tert-butylcarbamate-protected glycine is used to form a novel methacrylic monomer. The "protected" amino acid-derived functional monomer (BOC-Gly-MA) is copolymerized with an epoxide functional methacrylic monomer (GMA), to deliver novel multifunctional polymers, which are processed into powder coatings and used to study filiform corrosion at the surface of an aluminum substrate. The BOC-Gly-MA-containing copolymers were shown to improve a coating's anticorrosion performance, presenting the lowest average filiform corrosion (FFC) track length, total FFC number, and total corroded surface area (CSA) of the coatings investigated. Further to this, a mode of action for the role of BOC-Gly functional polymers in corrosion protection is proposed, supported by both solution and polymer-aluminum interface studies, delivering new insights into the mode of action of pH-responsive polymer coatings.

A novel approach of external lubrication in a rotary tablet press using electrostatics

PURPOSE

In powder compaction on rotary tablet presses, the addition of a lubricant is normally mandatory. However, the typical internal lubrication method tends toward overlubrication, resulting in an alteration of the critical quality attributes of the product. In this study, the feasibility of an external lubrication system only using electrostatics for the application was investigated.

METHODS

Three well-established lubricants were analyzed regarding their ability to accumulate and retain charge. In subsequent tableting experiments, the impact of different lubrication methods on critical quality attributes and process parameters was investigated.

RESULTS

Due to material characteristics, the charge on magnesium stearate particles was most stable over time. The application of this lubricant on the punches via external lubrication with electrostatic forces resulted in a significant reduction of the ejection forces. Furthermore, the tensile strength of the tablets produced in these trials was significantly higher compared to tablets that were produced with internal lubrication.

CONCLUSION

The external lubrication method with an electrostatically charged lubricant is a promising method for reducing both the necessary amount of lubricant and the impact of the lubricant on the product.

Evaluation of electrostatic powder coating method to prolong the shelf life of cheese slices

Electrostatic coating is being developed as an attractive alternative to overcome the problems encountered during conventional coating which includes non-uniform coating, dust generation, high energy and time consuming, equipment cleaning, and operating expenses. In this method, powder particles are charged by passing through an ion-rich region, which repel each other to produce an evenly distributed coating. This results in a uniform distribution of powder on target surface. In this study, the electrostatic coating of black pepper powder was applied by varying the applied voltage (0-20 kV), at a conveyor belt speed of 10 m/s and compared with manually coated cheese slices. The values of transfer efficiency (52.7%-87.0%), dust reduction (76.2%-85.8%), and adhesion (20.8%-85.3%) were higher for electrostatic coatings. The weight losses were lower (0.19%) at 15 kV as compared to 20 kV (0.67%). The total plate count of cheese slice coated at 20 kV was significantly higher (p < 0.05), whereas at 15 kV it was lower than all other treatments. The shelf life of coated cheese slices at 15 kV lasted up to 1 month due to better coating compared to other treatments. From the results, it can be concluded that electrostatic coating of cheese slice with black pepper is best at 15 kV along with higher transfer efficiency and dust reduction. PRACTICAL APPLICATION: Electrostatic powder coating of cheese resulted in higher transfer efficiency and reduction in dust production. later one has reduce the coating material requirement, thereby, reducing the processing cost. Moreover, dust reduction will reduce the burden of cleaning cost of environment and enhance worker health.

Recent advances of oral film as platform for drug delivery

Orally drug delivery film has received extensive interest duo to a distinct set of its advantageous properties compared to the traditional orally administered dosages, including faster rate of drug absorption, higher bioavailability and better patient compliance for children and elders with swallowing deficiencies. In particular, its potential capacity of delivering proteins and peptides has further attracted great attention. Lately, tremendous advances have been made in designing and developing both novel mucoadhesive films and orodispersible films to fulfill specific accomplishments of drug delivery. This review aims to summarize those newly developed oral films, discussing their formulation strategies, manufacturing methods as well as advantages and limitations thereof. Conclusions and future perspectives are also provided in brief.

A Comprehensive Review on Pharmaceutical Film Coating: Past, Present, and Future

Pharmaceutical film coating is considered a key part in the production of solid pharmaceutical dosage forms since it gives superior organoleptic properties products. In addition, it can improve the physical and chemical stability of dosage forms, and modify the release characteristics of the drug. Several troubleshooting problems such as twinning mottling, chipping, etc., may arise during or after or even during the shelf life of the film coated dosage forms. These troubleshooting problems may be due to tablet core faults, coating formulation faults and/or coating process faults. These problems must be overcome to avoid unnecessary product problems. Film coating as well as other parts of the pharmaceutical technology is subjecting to continuous innovation. The innovation may be at different levels including pharmaceutical excipients, processes, software, guidelines and equipment. In fact, of particular note is the growing interest in process analytical technology, quality by design, continuous coating processing and the inclusion of new ready for use coating formulations. In this review, we tried to explore and discuss the status of pharmaceutical film coating, the challenges that face this manufacturing process and the latest technological advances in this important manufacturing process.

Self-Limiting Electrospray Deposition for the Surface Modification of Additively Manufactured Parts

Electrospray deposition (ESD) is a spray coating process that utilizes a high voltage to atomize a flowing solution into charged microdroplets. These self-repulsive droplets evaporate as they travel to a target substrate, depositing the solution solids. Our previous research investigated the conditions necessary to minimize charge dissipation and deposit a thickness-limited film that grows in area over time through self-limiting electrospray deposition. Such sprays possess the ability to conformally coat complex three-dimensional (3D) objects without changing the location of the spray needle or orientation of the object. This makes them ideally suited for the postprocessing of materials fabricated through additive manufacturing (AM), opening a paradigm of independent bulk and surface functionality. Having demonstrated 3D coating with film thickness in the range of 1-50 μm on a variety of conductive objects, in this study, we employed model substrates to quantitatively study the technique's limits with regard to geometry and scale. Specifically, we examined the effectiveness of thickness-limited ESD for coating recessed features with gaps ranging from 50 μm to 1 cm, as well as the ability to coat surfaces hidden from the line-of-sight of the spray needle. This was then extended to the coating of hydrogel structures printed by AM, demonstrating that coating could be conducted even into the body of the structures as a means to create hydrophobic surfaces without affecting the absorption-driven humidity response. Further, these coatings were robust enough to create superhydrophobicity in the entire structure, causing it to resist immersion in water.

An Update of Moisture Barrier Coating for Drug Delivery

Drug hydrolytic degradation, caused by atmospheric and inherent humidity, significantly reduces the therapeutic effect of pharmaceutical solid dosages. Moisture barrier film coating is one of the most appropriate and effective approaches to protect the active pharmaceutical ingredients (API) from hydrolytic degradation during the manufacturing process and storage. Coating formulation design and process control are the two most commonly used strategies to reduce water vapor permeability to achieve the moisture barrier function. The principles of formulation development include designing a coating formulation with non-hygroscopic/low water activity excipients, and formulating the film-forming polymers with the least amount of inherent moisture. The coating process involves spraying organic or aqueous coating solutions made of natural or synthetic polymers onto the surface of the dosage cores in a drum or a fluid bed coater. However, the aqueous coating process needs to be carefully controlled to prevent hydrolytic degradation of the drug due to the presence of water during the coating process. Recently, different strategies have been designed and developed to effectively decrease water vapor permeability and improve the moisture barrier function of the film. Those strategies include newly designed coating formulations containing polymers with optimized functionality of moisture barrier, and newly developed dry coating processes that eliminate the usage of organic solvent and water, and could potentially replace the current solvent and aqueous coatings. This review aims to summarize the recent advances and updates in moisture barrier coatings.

Photoinduced Degradation of Polymer Films Using Polyglyoxylate-Polyester Blends and Copolymers

Polymeric coatings are commonly employed to alter surface properties. While some coatings are designed to remain stable over a prolonged period, in applications such as pharmaceuticals or fertilizers, the coating is designed to erode and reveal or release the underlying material. Self-immolative polymers (SIPs) undergo depolymerization following the cleavage of stimuli-responsive end-caps from their termini, enabling controlled depolymerization in the solid state and in solution. Poly(ethyl glyoxylate) (PEtG) is a promising SIP because of its depolymerization to benign products, but its amorphous structure and low glass-transition temperature make it unsuitable alone for coating applications. This study explored the blending of PEtG with polyesters including polycaprolactone (PCL), poly(l-lactic acid), and poly(R-3-hydroxybutyrate). Block copolymers of PEtG with PCL were also synthesized and studied. It was found that the phase separation behavior and consequently the thermal and mechanical properties of the materials could be tuned according to the composition of the blend, while the stimuli-responsive degradation of PEtG was retained in the blends. This work therefore provides a framework for the application of PEtG-based coatings in applications ranging from pharmaceuticals to agricultural products.