Lum S K, Duncan-Hewitt W C
Faculty of Pharmacy, University of Toronto, Ontario, Canada.
Pharm Res. 1996 May;13(5):692-700. doi: 10.1023/a:1016087214032.
We hypothesize that if the kinetics and the mechanisms involved in tablet compression are more fully understood and quantified, the parameters which influence tablet behavior in production may be controlled. The objective of our work was to obtain two deformation kinetic parameters for the predominant barrier to deformation, the activation volume (Vact) and the activation energy (Eact) of poly (methyl methacrylate-co-methacrylic acid) (PMMA/coMAA), a viscoelastic polymer similar to the commercial Eudragit.
Stress relaxation studies were performed and monitored at varying temperatures on compacts using an instrumented Instron testing apparatus. Solid density, microindentation hardness and contact area testing served to quantify the shear stress rates.
The Vact was found to be 64.4 +/- 4 b(3), 63.8 +/- 11 b(3) and 79.1 +/- 8 b(3) for the applied strain rates of 1, 2, and 5 mm/min. The Eact for flow was determined to be 145 +/- 7.7, 235 +/- 8.0, and 506 +/- 2.8 x 10(1) kJ/mole(-1) for the applied strain rates of 1, 2, and 5 mm/min respectively.
The average activation energies are indicative of strain hardening effects. The activation volumes and energies obtained will serve as estimates of these state variables for input into a particle deformation model of time-dependent compaction which is underway.
我们假设，如果能更全面地理解和量化片剂压制过程中的动力学和机制，那么生产中影响片剂性能的参数就可以得到控制。我们工作的目标是获得两个与主要变形障碍相关的变形动力学参数，即聚（甲基丙烯酸甲酯 - 共 - 甲基丙烯酸）（PMMA/coMAA）的活化体积（Vact）和活化能（Eact），PMMA/coMAA是一种类似于市售尤特奇的粘弹性聚合物。
使用配备仪器的英斯特朗测试设备，在不同温度下对压片进行应力松弛研究并监测。固体密度、微压痕硬度和接触面积测试用于量化剪切应力速率。
对于施加应变率为1、2和5毫米/分钟的情况，活化体积分别为64.4±4 b(3)、63.8±11 b(3)和79.1±8 b(3)。对于施加应变率为1、2和5毫米/分钟的情况，流动活化能分别确定为145±7.7、235±8.0和506±2.8×10(1) kJ/摩尔(-1)。
平均活化能表明了应变硬化效应。所获得的活化体积和能量将作为这些状态变量的估计值，输入到正在进行的与时间相关的压制颗粒变形模型中。
