Abstract
Using ethyl p-hydroxybenzoate (Et-POB), methyl p-hydroxybenzoate (Me-POB) and lactose, the effect of temperature on the tensile strength as well as the surface area was examined.
For Et-POB and Me-POB, it was found that the tensile strength (σ) increased and surface area (Sw) decreased with an increase in heating time. These results can be explained in terms of the sintering mechanism.
The tensile strength for both powders showed maxima between a homologous temperature of 0.9 and 0.95. This observation suggests that the packing structure of a powder bed alters at temperatures closer to their melting point; that is, agglomerates may be formed by a marked increase in the adhesive force between particles.
There is an approximately linear relationship between the reduction in surface area (ΔSw) and the tensile strength (σ). This may be attributed to the fact that the increase in tensile strength is due to the increase in contact area between particles which is proportional to ΔSw.
For lactose, the results were complicated by the evolution of water of crystallization at above about 120°C, although the results in the lower temperature region are almost identical to those of Et-POB or Me-POB.
