Directional bonding in compacted microcrystalline cellulose

The mechanical properties of compacts of microcrystalline cellulose (MCC) a nd silicified microcrystalline cellulose (SMCC) were evaluated by tensile t esting, diametric compression testing, and compression testing. For tensile and compression testing, cubic specimens were carefully machined from MCC and SMCC compacts, and the tensile and compression strengths were evaluated both normal and parallel to the compaction direction. The cubic tensile st rengths were compared to values obtained from the diametric compression tes t. The results obtained using the diametric compression test suggested comp acts of SMCC exhibit greater strength than those of MCC. In addition, the c ubes machined fi-om compacts of MCC and SMCC exhibited directional strength : the direction normal to the compaction direction displayed the greater te nsile strength; and the parallel direction had greater compression strength . The diametric compression test afforded strength values with reduced spre ad compared to the values collected from the cubic tensile test, suggesting that the errors involved in collecting diametric compression test data of compacts are less than those for the cubic tensile test. Analysis of the cu bes using X-ray diffraction (XRD) suggested that they display directional s tructural anisotropy, with the direction normal to the compaction direction being more crystalline than the parallel direction. However, it is not cle ar whether the difference in the directional strength is solely a consequen ce of the increased crystallinity or a culmination of crystallographic and mechanical keying effects.