Precise deposition of complex particles for structured functional products

Lead Research Organisation: Newcastle University
Department Name: Sch of Engineering

Abstract

In the pharmaceutical industry, coatings have a very important place in manufacturing and product development. Solid dosage forms like tablets, pellets, granules etc. are typically coated in order to control the drug release within the body, and also to protect against external factors like moisture or attrition. This is often achieved through dry coating with fine powders, since this provides reduced environmental concerns (no volatile organic solvents emitted) and lower energy consumption (no subsequent drying or evaporation operations required). However, the dry coating process is wasteful in terms of coating powder used and energy input, since when the coating uniformity does not meet the requirement, the entire batch is disposed of. To mitigate this, an excess of coating powder is often used, with excessive energy input to ensure all solids are sufficiently coated. We aim to address these problems by determining for a given combination of substrates and powder coatings: (i) How is coating of a single powder layer influenced by particle properties? (ii) How should a mixer operate to provide uniform coating across the entire batch? (iii) What is the minimum energy input to ensure uniform product coating?

In this research we will determine how coating is achieved on the fundamental, particle level, by controlling and manipulating the distribution of particle physical (size, shape) and surface (roughness, interface energy) properties and characterising the resulting coating quality. Coating powders are typically extremely fine and cohesive, and hence are prone to agglomerating to form large clusters. Industrial powder coating requires these coating powder agglomerates to be consistently broken down to single particles and precisely delivered to the host. We will establish how the process can be tailored to enhance the ability of the system to achieve this for any powder. By determining the underlying principles of powder coating, and the influences of material properties and process parameters, we will create a regime map for dry powder coating, which will enable industry to tune coating operations to minimise powder and energy use.

Planned Impact

The proposed research will achieve impacts in terms of knowledge, economy and people. In terms of knowledge, we will determine how coating is achieved on the fundamental, particle level, in order to optimise mixer design and operation; creating a regime map for dry powder coating. The developed framework will establish the fundamental science behind powder structuring in response to mechanical application. This knowledge will in itself be transformative, by allowing precise control of a single powder layer to be achieved. This also has far-reaching implications for industrial processes, such as dry powder spray-coating (e.g. of automotive and aviation vehicles), and additive manufacturing. Knowledge of the optimal combination of material properties to deliver dense, even coatings, will enable new coating materials, application methods and operational conditions to be developed.

In terms of economy, the improved understanding of coating mechanisms and optimisation of mixing processes developed in this research will lead to increased efficiency in pharmaceutical dry coating processes, through improved powder utilisation, reduction in waste batches and reduction in energy use. This will provide significant savings in resources (material and energy) and processing time. In the short term this will provide the greatest benefit to the UK pharmaceutical industry, a flagship of the UK manufacturing sector. The natural extension of this research to powder spray-coating and additive manufacturing will provide economical advantage to the UK automotive and aviation industries.

In terms of people, this research will train researchers to become highly skilled experts on powder structuring, mixing and surface interactions of powders. There is a distinct lack of this knowledge within the pharmaceutical sector, and so the trained researchers will be of great value to the UK workforce. The training of these researchers will be enhanced by (i) exposure to the UK and international research community through active conference attendance and participation (ii) in-coming and out-going visits between university and industry (iii) co-supervision of PhD and Masters Student research projects with the PI/Co-I in areas related to the project (iv) access to a wide range of training courses at the University of Surrey/Imperial College to boost their skills and develop their career, including public engagement training.
 
Description The influence of material properties (size ratio, density ratio and surface energy) and process operating conditions (blade rotational speed, filling level, guest particle concentration, initial guest particle location and blade geometry) on coating efficiency was assessed. Increasing the size ratio and surface energy tends to provide good coating performance, however, for very high surface energies coating efficiency is reduced. Increasing the density ratio reduces the coating efficiency. High blade rotational speeds, low filling level and initially placing the guest particles just above the rotating blades give more uniformly distributed coatings. Furthermore, increasing the number of blades mobilises a greater volume of the powder bed, thus improving the coating performance.

A regime map for the dry powder coating process in a blade-driven mixer was developed based on the granular bond number and mixing energy by considering the influence of the aforementioned material properties and process conditions on coating performance. A critical granular bond number exists above and below which good and poor coating occur, respectively. This regime map identifies combination of material properties and process conditions which provide optimal coating performance.

Dry powder coating was shown to reduce the surface energy of the coated host powder compared to the uncoated host, which leads to a more free-flowing and less cohesive powder. For coating processes in which 2 guest powders are to be coated onto the host powder (tertiary system), the order of addition of the guests influences their surface coverage on the hosts. The material which is added first achieves a greater surface coverage than the one added second, however the surface energy is closer to that of the material added last.
Exploitation Route The developed regime map can be applied to industrial dry coating processes to identify optimum operating conditions to achieve good coating performance, thus reducing energy and material costs. Furthermore, the methodology used to develop the regime map in this work can be replicated to create regime maps for specific dry coating systems. The developed regime map can be further developed to incorporate the influence of other material properties such as particle shape and roughness.
Sectors Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

 
Description Business engagement fund
Amount £1,500 (GBP)
Funding ID BEF#192 
Organisation Newcastle University 
Sector Academic/University
Country United Kingdom
Start 03/2023 
End 07/2023
 
Description EPSRC Imperial College London UKRI Impact Acceleration Account
Amount £77,837 (GBP)
Funding ID EP/X52556X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2023 
End 11/2023
 
Description Impact Acceleration Account - EPSRC IAA: Development of a pilot scale coating regime map
Amount £12,500 (GBP)
Funding ID NU-014628 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2023 
End 06/2023
 
Description APCChE - VK 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Vikram Karde from Imperial College London presented his work 'A quick and contactless analysis of powder mixing conditions using a shear-sensitive coloured tracer' in 19th Asian Pacific Confederation of Chemical Engineering (APCChE) Congress, 2022
Year(s) Of Engagement Activity 2022
URL http://apcche2022.org/#:~:text=APCChE%202022%20will%20be%20a,benefit%20of%20the%20chemical%20enginee...
 
Description CHoPS - CH 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Colin Hare presented the work of Marv Khala on "A regime map for dry powder coating" at the 10th International Conference on Conveying and Handling of Particulate Solids (CHoPS).
Year(s) Of Engagement Activity 2022
URL https://ifpri.net/events/10th-international-conference-conveying-and-handling-particulate-solids-cho...
 
Description CHoPS 2022 - VK 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Vikram Karde from Imperial College London presented his work 'Investigating particle properties and process parameters for generating efficient dry particle coated system' in 10th International Conference on Conveying and Handling of Particulate Solids (CHoPS).
Year(s) Of Engagement Activity 2022
URL https://ifpri.net/events/10th-international-conference-conveying-and-handling-particulate-solids-cho...
 
Description ChemEngDay UK 2022. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Virkam Karde presented the work about the 'Estimating mixing efficiency in guest-hosts particulate system using coloured nano-tracer'
Year(s) Of Engagement Activity 2022
URL https://www.ucl.ac.uk/chemical-engineering/sites/chemical_engineering/files/chemengdayuk2022programm...
 
Description Northumbria seminar 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Colin Hare presented the work of Marv Khala on dry powder coating in a seminar at Northumbria University.
Year(s) Of Engagement Activity 2022
 
Description P&G Seminar 2022 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Colin Hare gave a presentation on the work of Marv Khala and Vikram Karde on dry powder coating to R&D groups at Cincinnati (USA) and Newcastle (UK) over Teams.
Year(s) Of Engagement Activity 2022
 
Description WCPT 9 - CH 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Colin Hare presented the work of Marv Khala on "Assessing the influence of surface energy heterogeneity on dry powder coating performance in DEM" at the 9th World Congress on Particle Technology.
Year(s) Of Engagement Activity 2022
URL https://wcpt9.org/wp-content/uploads/WCPT9-Scientific-Program_Madrid-2022.pdf
 
Description WCPT 9 - VK 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr. Vikram Karde presented his work about 'Tracking the order of mixing effects in ternary adhesive mixtures using a coloured tracer'. In the 9th World Congress on Particle Technology (WCPT9), 2022, Madrid, Spain.
Year(s) Of Engagement Activity 2022
URL https://wcpt9.org/wp-content/uploads/WCPT9-Scientific-Program_Madrid-2022.pdf