Swelling Of Compacts Research Articles

Development of a novel method utilising dissolution imaging for the measurement of swelling behaviour in hydrophilic matrices

A variety of imaging techniques are currently used within the field of pharmaceutics to help understand and determine a wide range of phenomena associated with drug release from hydrophilic matrix tablets. This work for the first time aims at developing an appropriate testing imaging methodology using a surface dissolution imaging instrument (SDI2) for determining the swelling of whole compacts using hypromellose as a model hydrophilic matrix former. The influence of particle morphology (CR and DC grades) and two compressional forces (5 and 15 kN) on the initial swelling behaviour of hypromellose were investigated. The results showed that a lower absorbance of 50 mAu with a wider measurement zone proved successful in determining the edge of the gel layer and growth measurements in real-time with high level of details under flow. Despite the differences in the morphology of the grades of hypromellose tested, it was however discovered that gel growth was statistically similar between them which may be attributed to their similar chemistry. This novel method also highlighted differences in the hydrated polymer’s appearance which may have been as a result of differences in porosity and solid fraction. This information is of great importance to a formulator as gel growth plays a crucial role in determining drug release from polymer compacts.

Evaluation about wettability, water absorption or swelling of excipients through various methods and the correlation between these parameters and tablet disintegration

Objective: To evaluate parameters about wettability, water absorption or swelling of excipients in forms of powders or dosage through various methods systematically and explore its correlation with tablet disintegration.Material and methods: The water penetration and swelling of powders with different proportions of excipients including microcrystalline cellulose (MCC), mannitol, low-substituted hydroxypropyl cellulose (L-HPC), crospolyvinylpyrrolidone (PVPP), carboxymethyl starch sodium (CMS-Na), croscarmellose sodium (CCMC-Na) and magnesium stearate (MgSt) were determined by Washburn capillary rise. Both contact angle of water on the excipient compacts and surface swelling volume were measured by sessile drop technique. Moreover, the test about water absorption and swelling of compacts was fulfilled by a modified method. Eventually, the disintegration of tablets with or without loratadine was performed according to the method described in USP.Results and discussion: These parameters were successfully identified by the methods above, which proved that excipient wettability or swelling properties varied with the structure of excipients. For example, MgSt could improve the water uptake, while impeded tablet swelling. Furthermore, in the present study it is verified that tablet disintegration was closely related to these parameters, especially wetting rate and initial water absorption rate. The higher wetting rate of water on tablet or initial water absorption rate, the faster swelling it be, resulting in the shorter tablet disintegration time.Conclusion: The methods utilized in the present study were feasible and effective. The disintegration of tablets did relate to these parameters, especially wetting rate and initial water absorption rate.

Sintering Behavior of Nanocrystalline Al6063 Powders Prepared by High-Energy Mechanical Milling

Nanocrystalline Al6063 powders were synthesized by high-energy mechanical milling of gas-atomized powders for 22.5 h. The powders were uniaxially compacted at various compaction pressures ranging 200–1325 MPa and then were sintered at temperatures between 550 and 650 °C for 1 h. The densification and microstructural evolutions during both solid phase sintering and supersolidus liquid phase sintering are studied. Ultrafine-grained (UFG) Al alloy compacts show superior sinterability compared with coarse-grained (CG) compacts due to the higher defect density and larger specific surface area of the mechanically-milled powders. The densification parameter and hardness of both CG and UFG Al6063 compacts enhances as the compaction pressure increases. Nevertheless, applying high compaction pressures has an adverse effect on the sintered density and results in the swelling of compacts. The results point out an optimum sintering temperature at ~600 °C for achieving the highest sintered density and hardness with minimal grain coarsening and slumping.

Carbon Monoxide Reduction and Accompanying Swelling of Iron Oxide Compacts.

Pure Fe2O3 compacts were fired at 1373K for one hour then reduced with CO at 973-1373K. Reduction was followed up by means of weight-loss technique whereas volume change was measured by displacement method. The structure of the fired and reduced compacts was examined by reflected light microscope while the different phases were identified by X-ray diffraction technique. These measurements together with kinetic data were correlated for better understanding the gas-solid reaction mechanisms and the accompanying swelling phenomenon. A highest swelling value of 176% was obtained for compacts completely reduced at 1173K whereas a maximum swelling of 224% was obtained for compacts 90% reduced at the same temperature. At all reduction temperatures swelling increased with the increase in reduction extent up to 90% where a maximum swelling value was obtained followed by a small decrease in swelling when compacts were completely reduced. Excessive swelling was attributed to the carbon in metallic iron and/or iron carbide formed and their reactions with oxygen forming CO and/or CO2. A mechanism of disintegration of iron grains and swelling of the compacts has been proposed and correlated with reduction conditions.

Swelling of compacts formed from copper coated iron powders: H.S. Yang et al (Chonnam National University, Kwang-Ju, Korea), J Korean Inst of Metals, Vol 30, No 10, 1992, 1205–1210. (In Korean).

Swelling of compacts formed from copper coated iron powders: H.S. Yang et al (Chonnam National University, Kwang-Ju, Korea), J Korean Inst of Metals, Vol 30, No 10, 1992, 1205–1210. (In Korean).

電解銅圧粉体の異方性膨張に及ぼす加圧・焼結条件の影響

The swelling of cylindrical compacts, 10 mm(d)×10 mm (h) in size, was measured with a micrometer during each production process; after pressing at 2-8 t/cm2 (196-784 MPa), after dewaxing at 500°C (773K) for 30 min, and after sintering at 900°C (1173 K) for 5-180 min.Compacts pressed under higher pressures (588-784 MPa) swelled during sintering, while those pressed under lower pressures (196-392 MPa) shrank. Both the swelling and the shrinkage of compacts pressed with die-wall lubrication and sintered in cracked ammonia gas were larger than those of compacts pressed with powder lubrication or sintered in argon gas. Dimensional change during sintering was larger in swelling or smaller in shrinkage, in the pressing direction than in the lateral direction.The sintering time for the swelling of electrolytic copper powder compacts in argon gas was longer than that of the compacts sintered in cracked ammonia gas or of the compacts made from atomized copper powder.