C1-Emulsion Flashcards
Multi-Homo composition
two stirring elements ( anchor stirrer, spiral stirrer and a homogeniter
anchor stirrer
equipped with two scraping arms
which flow does the anchor stirrer creats?
tangential flow inside the vessel
vigorous radial mixing of materials
spiral stirrerr
axial mixing of matrial and efficient vetical heat transfer
homogenizer
it is installed and operated independently of the two stirring elements
on what does the function of homogenzier based
rotor-stator principle
what’s the importance of vigorous radial mixer?
a strong suction force draws the material from th vessel into the whirl chamber of the homogenizer
when does the actual homogenization process takes place?
as the materials are pushed to the outside through the gap space between the rotor and stator
Stephan composition?
one stirring element, which is the centrally rotating knife
what are the movements of the centrally rotating knife?
radial and axial movements
Ultra-turrax is based on?
rotor stator principle
what’s the main different between the ultra-turrax and the multi-homo
ultra-turrax has a higher circumferential speed
movement of the ultra-turrax
frequency shear, mechanical impact, collision, hydrodynamic potential gradients and turbulent fluid movements
Bernoulli equation and cavitation
it states that the total energy of a flowing fluid
what’s the bernoulli effect?
an increase in the flowing speed of a fluid (increase in kinetic energy) will be accompanied by a decrease in it static pressure (decrease pressure energy)
what’s the resulting effect of the bernoulli effect
the phenomenon of cavitation
what happend when the local pressure inside the gap area drops the vapor pressure
the liquid vaporizes and forms gas bubbles
what happend after exiting?
the static pressure of the liquid increases and surpasses the vapor pressure, gas bubbles will violently implode
what is the results of the implosions?
it leads to cavitation fragmentation , helps to break down liquid droplets
high pressure homogenizer
primary function of this device is to homogenize and not to generate an emlsion from starting materials
requirement of the HPH
has to be pre-emulsified mixture
three major types of force in the HPH
fragmentation, cavitation, shear and turbulence
cavitation fragmentation
pressure outside the gap is higher than the vapor pressure, whereas the pressure inside the gap is smaller,
shear fragmentation
the tiny gap disrupts movement of the fliud and gives rise to a high shear force
tubulence fragmentation
when existing the gap, the liquid forms a jet and the disintegration of this jet leads to small eddies
two main parameter of the HPH?
homogenization pressure and the number of homogenization cycles
what is the quantification of the laser diffraction with droplet size of emulsions
the droplet size is directly proportional to the intensity of light scattered by a droplet and inversely proportional to the angle of the laser beam
how is the DSD measured in emsulsions?
Laser differecation analysis, by measuring the angular variation in intensity of light scattered as a laser beam passes through a sample
how are smaller droplets in emulsions generated?
by using equipment with high mechanical energy, becuase to a certain extent smaler droplets can be generated
why are emulsion just meta-stable and how do you achieve the meta stable state?
With a emulsifier, the emulsions can be stabilizied kinetically, refereing to as a meta stable state
how can the particle velocity be decrease?
accoring to the stokes’ law,
reduction of the particle size or increase the viscosity of the external phase
defination of emulsion?
disperse system of two immiscible liquid
continental method?
emulsifier is tured into a suspension by dispersing it in the internal phase
then adding of the external pahse
english method: emulsifier dissolved in the external phase
what is responsible for the formation of droplet using emulsion divices?
solely on the mechanical energy input, which will lead to the phase inversion
opaque and translucent occure with which equipment?
stephan translucent and multi-homo, Ultra Turrax and homogenizer opaque
transulcent is an indication for?
creaming
meaurement of the dropelt size of an transulcent and opaque system?
light is less likely to be scattered in a transulcent systme compared to the opque system
why was autoclave carried out?
for sterilization at 121°C for 15 min at 2 bar
why do we have an entlargment of droplets after autoclave?
Due to decrease of the viscosity, resulating to an increase of the creaming rate
increase of the particle velosity
what is the critical micelle concentration?
it is the limit at which a larger amount of emulsifer may futher lower the interfacial energy, thefore delay creaming
which model can be used in a FFD and CCD?
a linear model for FFD quadratic correlations (CCD)
CCd consist of ?
FFC, central point and star points
rotatable design?
give very narrow confidence intervalts, depends on the vector length but not direction
orthogonality?
prevents collinearity by an independent estimation of the coeefficient
why is rotation more important than othogonality
becuase the design can be easily transofrmed into an orthogonal design by addition of runs, but not the other way around
equation for rotation
do you know it?
equation for total numbers of runs for oth
do you know it?
equation forstar points?
do you know it?
Q2 is?
it takes the ability of the model to predit values into account
what are gels?
liquid immobilized by a suitbale gelling agent
gels properties?
spreading properties under shear stress and great elastic pressure
what’s the critical property of gels?
yield point
behaviour of a viscous fluid happend when?
when the applied shear stress is higher than the yield point
below the yield point?
elastic solid
what’s the immobilizing mechanism if the gel?
it is it’s swelling in water to reduce, increasing the system’s viscosity
example for a gelling agent?
carbomers, high molecular-weight polyacrylic acid slight cross-linked with polyalkene ethers of surga or polyalcohols
what happend water water ia added to carbomers?
it takeup water to sweel and uncoil it polymer chains
the addition of base to the carbomers?
chains will reple each other due to electrostatci repulsions, results to complete uncoiling and stretching of the polymer chains
what’s the diiferent in energy input for emulsion and gel preparations?
smaller energy is used for gel compared to emulsions
why smaller input of energy in gel?
because it is thermodynamically stable systems
what happend when more energy is used during the gel pre.
leads to disruption if the 3-D network and results in a loss of consistent gel structure
