CRYSTALLIZATION BEHAVIOR continued
Figure 2 – Crystallization exotherms for cap samples.
Figure 1 – Example of Avrami analysis using linear form from X(t) = 0.2 to X(t) = 0.8.
Experimental Samples Samples used were marker pen caps in various colors purchased from a
local office supplier. (They are polypropylene but the author does not have access to the formulation; the base resin is likely the same formulation.) Sample colors include black, red, yellow, brown, orange, green, blue and purple. A cap made from polypropylene containing no pigments was used as a reference.
Instrument and experimental parameters 1. Instrument: Discovery DSC 2500 (TA Instruments, New Castle, Del.)
2. Sample mass: 5 mg nominal 3. Purge gas: N2
at 50 mL/min
Table 2 – Summary of single-point Avrami analysis Sample Red
TC
Brown Black
Purple Blue
Orange Green Yellow
No colorant °C
122.7 113.9 124.2 130.8 129.4 122.8 127.0 121.9 110.7
n
2.053 2.956 2.786 1.896 2.472 2.103 2.271 2.287 3.094
Figure 3 – Crystallized fraction as a function of temperature.
k
2.507 3.071 6.088 3.282 6.515 5.421 6.299 6.992 1.200
t1/2
(min)
0.535 0.604 0.458 0.440 0.404 0.376 0.378 0.364 0.837
τ (reciprocal half-time-min-1 1.87
1.66 2.18 2.27 2.48 2.66 2.65 2.75 1.19
)
AMERICAN LABORATORY
12
JANUARY/FEBRUARY 2017
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