3.3. Thermogravimetric analysis
Fig. 4 shows TGA curves of pure components and blends.
Decomposition of pure components takes place in one step, however
in the case of blends this process occurs in two steps: the first
one is related to wax decomposition and the second one to HDPE.
This degradation behaviour is typical of immiscible blends whose
components have very different decomposition temperatures.
The starting and ending degradation temperatures of HDPE, PW
and their blends can be examined in Table 2. Pure HDPE has the
highest thermal stability and its decomposition begins at 410 C.
Thermal stability of blends is lower than HDPE but their decomposition
range is enlarged if it is compared with pure components.
A similar behaviour is found in the case of blends of polypropylene
and paraffin wax [15,18,19]. This characteristic is beneficial for
blends used in powder injection moulding technology because it
favours a gradual decomposition of the binder [20,21]. On the other
hand, the mass loss percentages can be clearly correlated to the
initial amount of components of the blends which is another evidence
of no wax loss during processing.