The Effect of Compaction Properties on Swelling and Erosion Characteristics of HPMC and PEO Compacts

Hydrophilic polymers are frequently employed to develop matrices for controlled release applications. The physicochemical properties of these polymeric materials can have an impact on their compaction behaviour. Hence, the degree and extent of deformation and consolidation of these polymers can influence the compaction pressure dependant attributes that include, but are not limited to, porosity, surface roughness, compact internal microstructure and interparticulate bonding and packing. It is anticipated that these aforementioned tabletting attributes could influence the performance and functionality of hydrophilic matrices, although limited studies have been conducted in this regard. Therefore, two polymers hydroxypropyl methylcellulose (HPMC K4M), polyethylene oxide (PEO WSR N60K) and their mixture (1:1 w/w) were selected. These polymers have appreciable different compression properties but comparable molecular size and this study was carried out to understand the role of tabletting attributes on swelling and erosion characteristics. It is evident from the findings that the changes in compression pressure affect the tensile strength, porosity, bulk and apparent density, microstructural properties, bonding strength and surface roughness of all types of matrix tablets. Increase in compression pressure has monotonically enhanced the swelling rate and degree of erosion of the matrix tablets, however, in the case of HPMC K4M and HPMC K4M: PEO WSR N60K (1:1 w/w) based matrices the swelling and erosion rate become steady after 150 MPa compression pressure. All the tabletting attributes such as swelling and erosion rate, average pore diameter, surface roughness and interparticulate bonding capacity are inter-linked (mostly R2 lies in the range of 0.74 - 0.99 ) and greatly affect each other. It can be concluded from the findings that a careful comprehension of tableting attributes associated with compressed matrix tablets might be valuable in developing successful hydrophilic matrices for control drug release applications.