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Evaluation of the Mechanical Resistance of a Powder‐powder Coating by Modulated Dry Feed Particle Size Analysis
Author(s) -
Vilela Ana,
Concepcion Lucia,
Accart Philippe,
Chamayou Alain,
Baron Michel,
Dodds John A.
Publication year - 2006
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.200601020
Subject(s) - magnesium stearate , coating , materials science , particle size , environmental scanning electron microscope , particle (ecology) , scanning electron microscope , composite material , powder coating , chemical engineering , chemistry , chromatography , dosage form , oceanography , engineering , geology
Dry powder coating is a powerful method for modifying the surface properties of particles whilst retaining their essential bulk properties. The coating of a host powder by guest particles can be achieved via different means ranging from simple stirring together of the two components, to high energy impact coating in devices such as a Nara Hybridizer or Turbula Mixer. The quality of the powder coating resulting from such methods is an important parameter, which depends both on the force of the mechanical action used, and also the physico‐chemical interactions between the host and guest particles. Here, a method for evaluating the strength of host‐guest interactions based on particle size analysis using a standard Malvern Mastersizer with dry powder feed is presented. Basically, the liberation of small guest particles from host particles can be achieved by increasing the air pressure, and the presence of liberated fine particles mixed with guest particles can be detected from differences in volume and number distributions. Complementary examination is undertaken using an environmental scanning electron microscope (ESEM). This technique has been used to evaluate the interaction strength of a coating of hydrophobic magnesium stearate on a herbal extract (Harpagophytum). It is shown that effective coating can be achieved by three different means: simple stirring, a Turbula Mixer and by using a Nara Hybridizer. The respective strength of the coatings is greater with increasing mechanical force used for the process. The method is proposed as a simple means of evaluating powder‐powder coating processes.