What factors affect the lyophilization effect of the four-ring lyophilization experimental freeze dryer

The four-ring lyophilization experimental type lyophilizer is to pre-freeze the aqueous items, and then sublimate the moisture in a vacuum state to obtain the dried items
.
Freeze-dried items are easy to store for a long time, mainly used in the pharmaceutical, biological, chemical and food industries, for heat-sensitive substances and other biological products
。 In the process of lyophilization, what factors will affect the lyophilization effect, that is to say, what are the factors that determine the success or failure of the four-ring lyophilization experimental lyophilizer? 1.
Eutectic point In the process of product prefreezing, for the crystallization system, as the temperature continues to decrease, when the product reaches below the freezing point, an ice core is formed in the system, the ice core is gradually growing, the concentration of solute in the rest of the solution will gradually increase, and when it reaches supersaturation, crystals will precipitate, and the temperature continues to decrease until the remaining solution is completely solidified into a crystalline mixture of ice and solute, and the temperature at this time is the eutectic point
.
But there is a situation where the eutectic point of some substances is not a specific temperature value, but a temperature range
.
2.
Glass conversion temperature In the process of pre-freezing of products, for the amorphous system, when the temperature of the product drops to a certain extent, the ice crystals formed will no longer continue to increase, the concentration of the residual solution will become larger, and the solute and the remaining moisture form a glass state with a large viscosity, and the temperature at this time is also the glass transition temperature
.
3.
Eutectic point In the drying process of vacuum freeze-drying mechanism, as the temperature gradually increases, the completely solidified solute and solvent begin to melt continuously, and the temperature at this time is the eutectic point
.
4.
Collapse temperature In the drying process of the product, when the temperature of the drying layer rises to a certain value, the ice crystals in the material will gradually disappear, and the space originally occupied by the ice crystals will become holes, so the drying layer is a porous honeycomb-like sponge structure
.
When the solid matrix temperature of the honeycomb structure is high, its rigidity decreases
.
When the temperature reaches a certain critical value, the rigidity of the solid matrix is not enough to maintain the honeycomb structure, the solid matrix wall of the hole will collapse, and the original vapor diffusion channel is closed, preventing the sublimation process, resulting in a high
moisture content of the finished product.
This critical temperature is also known as the collapse temperature
.