Influence of the Processes Parameters on the Properties of The ...
Influence of the Processes Parameters on the Properties of The ...
Influence of the Processes Parameters on the Properties of The ...
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Chapter 4.<br />
Experimental Procedures and Protocols for Analyses<br />
PLA<br />
B<br />
PLA<br />
Polymer<br />
granulates<br />
C<br />
Ground fine<br />
powder<br />
Screened<br />
powder<br />
PLGA<br />
A<br />
Granulates in<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> chamber<br />
Knife mill with<br />
water circulati<strong>on</strong><br />
Screening mesh:<br />
SS frame & Cloth<br />
Overall height = 1-3/4"<br />
Depth to cloth:<br />
1-1/4" (32 mm)<br />
PLGA<br />
Figure 4.1: Polylactide granulates size reducti<strong>on</strong> by knife mill.<br />
Few tens <str<strong>on</strong>g>of</str<strong>on</strong>g> grams <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> chosen polymers were introduced in <str<strong>on</strong>g>the</str<strong>on</strong>g> knife mill which was <str<strong>on</strong>g>the</str<strong>on</strong>g>n<br />
closed. Cold water was allowed to circulate in <str<strong>on</strong>g>the</str<strong>on</strong>g> mill double jacket. Copolymers such as PLGA 85:15 (PLG ,<br />
PLG 8531, LG 857 S, … ) are granules, that must be initially pre-ground in batches, in <str<strong>on</strong>g>the</str<strong>on</strong>g> knife mill for a<br />
specified time that more than 95% <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> ground material is recovered. Each material was ground in <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
knife mill for alternative time On/Off <str<strong>on</strong>g>of</str<strong>on</strong>g> 60 s to avoid melting or degradati<strong>on</strong>. Times required to recover<br />
95% <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> initial polymer depends <strong>on</strong> its inherent viscosity. <strong>The</strong>n, <str<strong>on</strong>g>the</str<strong>on</strong>g> pre-ground product was recovered<br />
and sieved according to <str<strong>on</strong>g>the</str<strong>on</strong>g> procedure presented.<br />
Waxes used were pre-ground in knife mill but <strong>on</strong>ly for 30 s. <strong>The</strong> wax obtained was very fine that<br />
100% <str<strong>on</strong>g>of</str<strong>on</strong>g> wax removed after pre-grinding passed through 500 mesh sieve. This wax will be utilized latter <strong>on</strong><br />
as porogen for preparing a mixture with polymer to obtain better scaffolds.<br />
1.1.2 Tumbling Ball Mill Grinding<br />
<strong>The</strong> pre-ground and sieved product was ground in a tumbling ball mill Prolabo ® (cf. Figure 4.2) to<br />
several tens <str<strong>on</strong>g>of</str<strong>on</strong>g> micrometers, value <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> size that could not be reached with <str<strong>on</strong>g>the</str<strong>on</strong>g> knife mill. <strong>The</strong> tumbling<br />
ball mill has a grinding chamber with a capacity <str<strong>on</strong>g>of</str<strong>on</strong>g> 5 liters, a height <str<strong>on</strong>g>of</str<strong>on</strong>g> 32 cm and a diameter <str<strong>on</strong>g>of</str<strong>on</strong>g> 27 cm.<br />
Sieved polymer<br />
powder<br />
Balls <str<strong>on</strong>g>of</str<strong>on</strong>g> 9.6, 19.0 and<br />
34 mm diameter<br />
B<br />
Gloves<br />
Stop watch<br />
Ceramic lid<br />
Closing plate<br />
Crushing<br />
chamber<br />
Balance<br />
C<br />
D<br />
Tumbling ball mill with<br />
accessories<br />
Metallic<br />
rollers<br />
Joint seal<br />
Speed regulator<br />
Electric switch<br />
A<br />
E<br />
Tumbling Ball Mill Descripti<strong>on</strong><br />
Filler<br />
F<br />
Sieve<br />
Co-ground<br />
Material / Mixture<br />
Cleaning<br />
brush<br />
Spatula<br />
Ethanol<br />
Gloves<br />
Figure 4.2: Milling process in tumbling ball mill.<br />
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