Study of morphology of natural rubber particles by scanning electron microscope (SEM)
Electron microscopic examination of rubber particles (28) has indicated that NR particles consist of hydrophobic rubber polymers enclosed by a monolayer membrane. This membrane consists of lipids, proteins and other components that are associated with the good mechanical properties of NR. Therefore, the physical and chemical characteristics of natural rubber particles were investigated to clarify the rubber particle membrane. The method, developed for determining the size and shape of rubber particles using SEM, involves air-drying of a particle suspension after fixation in osmium tetroxide.
The scanning electron micrographs of fresh latex, centrifuged latex, deproteinized latex, saponified latex and small rubber are shown in Fig. 6. In the micrographic image, small features can be seen on the rubber particle surface. In comparison, air-dried preparation of particles from freshly tapped latex from mature Hevea trees remained their natural shape and size. Hevea rubber particles were spherical, occurring predominantly as discrete individual particles in a range of sizes. Size measurements for Hevea particles placed the particles in 0.10–0.75 μm range, which agrees with previously reported values for particle size in this species 28. and 29..