| dc.description.abstract | The compression and compaction properties of hydroxypropyl methylcellulose (HPMC) and ethylcellulose (EC) are affected by particle size, moisture content, compression force, compression speed, viscosity grade and substitution type. A decrease in particle size generally causes an increase in the tensile strengths of HPMCs or EC matrices. The tensile strengths of HPMC 2208 and EC tablets decreased as the viscosity. grade increased. The mean yield pressures of HPMC K100, HPMC K4M and HPMC K15M were independent of particle size but the mean yield pressures of HPMC K100M were affected by the particle size. The mean yield pressure of EC was significantly increased as the particle size of EC increased indicating more ductile and less brittle behaviour with the smaller sized particles. The tensile strengths of tablets compressed at different compression forces from 5 to 20 kN increases with moisture content from 0 to 14.9% w/w. The compression characteristics of powder ed HPMC polymers, namely particle packing and deformation, are related to moisture distribution effects mainly due to the particle size changes and to some extent, due to the methoxy/hydropropoxy substitution? ratio changes while no dependence nz the molecular size is evident The mean yield pressures increased as the moisture content decreased. For each viscosity grade of HPMC 2208 an increase in compression speed from 15 to 500 mm/s generally, decreased the tensile strength of the tablets. The tensile strength of HPMC K100 tablets or the lowest molecular weight of HPMC and EC tablets was more sensitive to changes in compression speed than those of the the other grades. HPMC F4M produced the highest tablet tensile strength compared with the other substitution types. | |
