Sun G, Zhang Z
School of Chemical Engineering, The University of Birmingham, Edgbaston, UK.
J Microencapsul. 2001 Sep-Oct;18(5):593-602. doi: 10.1080/02652040010019541.
The mechanical properties of melamine-formaldehyde (M-F) microcapsules were studied using a micromanipulation technique. Single microcapsules with diameters of 1-12 microm were compressed and held between two parallel planes, compressed and released, and compressed to burst at different speeds, whilst the force being imposed on the microcapsules and their deformation were measured simultaneously. This force increased as single microcapsules were compressed and then relaxed slightly as they were held. When the microcapsules were repeatedly compressed and released, a pseudo yield point was found for each microcapsule. Before the microcapsules were compressed to this point, the deformed microcapsules recovered to their original shape once the force was removed. However, when the deformation was beyond the 'yield point' there was profound hysteresis and the microcapsules showed plastic behaviour. As the microcapsules were compressed to burst at different speeds, ranging from 0.5-6.0 microm/s, it was found that their mean bursting forces did not change significantly. The deformations at the pseudo yield point and at bursting were also independent of the compression speed. On average, these melamine-formaldehyde microcapsules reached their 'yield point' at a deformation of about 19 +/- 1%, and burst at a deformation of 70 +/- 1%.
采用微操纵技术研究了三聚氰胺 - 甲醛（M - F）微胶囊的力学性能。将直径为1 - 12微米的单个微胶囊压缩并夹在两个平行平面之间，以不同速度进行压缩、释放以及压缩至破裂，同时测量施加在微胶囊上的力及其变形情况。随着单个微胶囊被压缩，该力增大，随后在保持过程中略有松弛。当微胶囊被反复压缩和释放时，每个微胶囊都出现了一个假屈服点。在微胶囊被压缩到该点之前，一旦去除力，变形的微胶囊会恢复到其原始形状。然而，当变形超过“屈服点”时，会出现明显的滞后现象，微胶囊表现出塑性行为。当微胶囊以0.5 - 6.0微米/秒的不同速度被压缩至破裂时，发现它们的平均破裂力没有显著变化。假屈服点和破裂时的变形也与压缩速度无关。平均而言，这些三聚氰胺 - 甲醛微胶囊在变形约19±1%时达到其“屈服点”，并在变形70±1%时破裂。
