Abstract
In this paper, new scientific insights in relation to the re-compaction of microcrystalline cellulose (MCC; Avicel®® PH-101) under specific compaction conditions are reported. MCC was subjected to multiple compaction cycles (1st, 2nd, and 3rd) under high compaction pressures, up to 20,000 kPa, using a roller compactor of 100 kg/h capacity. Initially, granules from the 1st and 2nd compaction cycles produced tablets with lower crushing strength compared to those made from the original non-compacted MCC. Tablet weakness was found to be correlated to the generation of a higher intra-granular pore size (diameter) and hence higher tablet porosity compared to that of the original MCC particles. Using Kawakita and Heckel compression analyses, it is suggested that such behavior is attributed to the formation of harder granules of re-compressed powder with a larger diameter than non-compacted MCC particles. Moreover, these granules resulted in a reduction in powder bed volume after the powders were subjected to the 1st and 2nd compaction cycles. Surprisingly, granules resulting from the 3rd compaction cycle produced tablets displaying a higher crushing force than non-compacted MCC. Results from compression analysis indicated a reduction in both the intra-granular pore size (diameter) and in tablet porosity of Avicel PH-101-3rd compaction cycle compared to that of the original non-compacted MCC. It is concluded that intense compression causes shedding of one or more layer from MCC fibers exposing new surfaces with strong binding ability. The foregoing results infer that intensified roller compaction can be employed to improve MCC powder compactibility without any deleterious effects on compact strength.
Highlights
Cellulose is a linear polymer which consists of hundreds to thousands of linked D-glucose units having β-(1-4)-glycosidic bonds with a general formula (C6 H10 O5 )n
These units are inter-connected through hydrogen bonding and van der Waals forces to form fibrils [1]. This polysaccharide is found in cells of all plants, in addition to hemicellulose, lignin, and other comparably small amounts of extractives
Cellulose exists in plant cells in the form of fibers with a high axial stiffness and which can be separated into nanocellulose fibers (NCF)
Summary
Cellulose is a linear polymer which consists of hundreds to thousands of linked D-glucose units having β-(1-4)-glycosidic bonds with a general formula (C6 H10 O5 )n. These units are inter-connected through hydrogen bonding and van der Waals forces to form fibrils [1]. Cellulose exists in plant cells in the form of fibers with a high axial stiffness and which can be separated into nanocellulose fibers (NCF). This transformation can be carried out either by chemical or mechanical treatments; the former use enzymes or chemicals such as mineral acids.
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