Influence of the Processes Parameters on the Properties of The ...

Chapter 3.
Analytical Methods and Designs <strong>of</strong> Experiments
Poly(L lactide): K = 5.45×10 -4 dL/g and a = 0.73 in chlor<strong>of</strong>orm at 30°C.
Poly(D,L lactide): K = 2.21×10 -4 dL/g and a = 0.77 in chlor<strong>of</strong>orm at 30°C.
Poly(D,L lactide-co- L lactide): K = 1.29×10 -5 dL/g and a = 0.82 in chlor<strong>of</strong>orm at 25°C.
Poly(D,L lactide-co-glycolide): K = 5.45×10 -4 dL/g and a = 0.73 in chlor<strong>of</strong>orm at 25°C;
For hyaluronic acid, <strong>the</strong> Mark-Houwink constants are K = 5.07510 -5 dL/g and a = 0.716, in 200
mM NaCl at 20°C [Gura et al., 1998] and K = 2.22610 -5 dL/g and a = 0.796, in chlor<strong>of</strong>orm at 25°C
[Source Javene]..
3 Laser Granulometry Method
3.1 Granulometry
Laser granulometry dates back to <strong>the</strong> 1970s. It is a technique for measuring <strong>the</strong> size distribution <strong>of</strong>
particles contained in a powder. If this one contains particles <strong>of</strong> different sizes, it permits to determine <strong>the</strong>
proportion <strong>of</strong> each size class.
The measure is based on <strong>the</strong> <strong>the</strong>ory <strong>of</strong> single scattering and laser diffraction. Beam laser is
obtained by collimating a beam from Helium – Neon gas tube. This beam is sent to a sensor in which <strong>the</strong>
particles are kept in constant movement so that each particle passes at least once in front <strong>of</strong> <strong>the</strong> laser beam
during <strong>the</strong> measurement time (cf. Figure 3.6).
(A)
(B)
Figure 3.6: (A) Mastersizer 2000 (Malvern Instruments) (B) Schematic diagram showing <strong>the</strong> main
components <strong>of</strong> a laser diffraction particle size analyzer.
[Storti and Balsamo, 2009]
3.2 Principle <strong>of</strong> Laser Analysis
It uses <strong>the</strong> following hypo<strong>the</strong>ses: spherical particles are considered to be non porous and non
opaque at laser radiation and <strong>the</strong>se particles have a diameter superior to <strong>the</strong>ir wave length, are in constant
random motion and diffract light efficiently regardless <strong>of</strong> <strong>the</strong>ir size.
When a laser beam sheds light on a particle, diffraction patterns can be observed. The intensity <strong>of</strong>
<strong>the</strong> diffracted radiation and <strong>the</strong> deviation angle differ according to <strong>the</strong> size <strong>of</strong> <strong>the</strong> particles (cf. Figure 3.7).
Thus, particles with large sizes diffract large light quantities on small angles, while small
particles diffract small light quantities on large angles. The light angle and intensity permit to
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