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Relationship between processing, surface energy and bulk properties of ultrafine silk particles

journal contribution
posted on 01.01.2015, 00:00 authored by Rangam RajkhowaRangam Rajkhowa, A Kafi, Q T Zhou, A Kondor, David MortonDavid Morton, Xungai WangXungai Wang
Silk particles of different sizes and shapes were produced by milling and interactions with a series of polar and non-polar gaseous probes were investigated using an inverse gas chromatography technique. The surface energy of all silk materials is mostly determined by long range dispersive interactions such as van der Waals forces. The surface energy increases and surface energy heterogeneity widens after milling. All samples have amphoteric surfaces and the concentration of acidic groups increases after milling while the surfaces remain predominantly basic. We also examined powder compression and flow behaviours using a rheometer. Increase in surface energy, surface area, and static charges in sub-micron air jet milled particles contributed to their aggregation and therefore improved flowability. However they collapse under large pressures and form highly cohesive powder. Alkaline hydrolysis resulted in more crystalline fibres which on milling produced particles with higher density, lower surface energy and improved flowability. The compressibility, bulk density and cohesion of the powders depend on the surface energy as well as on particle size, surface area, aggregation state and the testing conditions, notably the consolidated and unconsolidated states. The study has helped in understanding how surface energy and flowability of particles can be changed via different fabrication approaches.

History

Journal

Powder technology

Volume

270

Pagination

112 - 120

Publisher

Elsevier

Location

Amsterdam, The Netherlands

ISSN

0032-5910

eISSN

1873-328X

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2015, Elsevier