Roberts R J, Rowe R C
J Pharm Pharmacol. 1986 Aug;38(8):567-71. doi: 10.1111/j.2042-7158.1986.tb03082.x.
The effect of punch velocity over the range 0.033-300 mm s-1 on the compaction properties of lactose, microcrystalline cellulose and a drug substance (a phthalazine derivative) for a range of particle sizes has been studied using the yield pressure derived from the Heckel relationship and a strain rate sensitivity index (SRS index), as the criteria to describe their behaviour. For lactose, a material which deforms by a mixed mechanism of particle fracture and plastic deformation at the contact points, the yield pressure increased and the SRS index decreased as particle size decreased, due to a reduction in the amount of fragmentation of the particles. For microcrystalline cellulose, a material which is known to deform plastically, the yield pressure and the SRS index were independent of particle size. For the phthalazine derivative the yield pressure increased as particle size decreased; however the SRS index reduced from 41% to zero, indicating that the deformation mechanism was changing from plastic flow to brittle behaviour. This decrease in the SRS index has been explained in terms of the relative amounts of strain-hardened material produced as milling severity increased, resulting in an increasing resistance to deformation and thus an apparent increase in brittle behaviour as particle size decreased.
在0.033 - 300毫米/秒范围内，冲头速度对一系列粒径的乳糖、微晶纤维素和一种药物物质（酞嗪衍生物）的压实特性的影响，已通过从赫克尔关系得出的屈服压力和应变率敏感性指数（SRS指数）进行研究，以此作为描述它们行为的标准。对于乳糖这种通过颗粒破碎和接触点塑性变形的混合机制变形的材料，由于颗粒破碎量减少，屈服压力随粒径减小而增加，SRS指数则降低。对于已知会发生塑性变形的微晶纤维素，屈服压力和SRS指数与粒径无关。对于酞嗪衍生物，屈服压力随粒径减小而增加；然而SRS指数从41%降至零，表明变形机制从塑性流动转变为脆性行为。SRS指数的这种降低已根据随着研磨强度增加产生的应变硬化材料的相对量来解释，这导致对变形的阻力增加，从而随着粒径减小脆性行为明显增加。
