Types and functions of polyether defoamers
1、GP type defoamer
It is made by addition polymerization of propylene oxide or a mixture of ethylene oxide and propylene oxide with glycerol as the initiator
GP type defoamer has poor hydrophilicity and low solubility in the foaming medium, so it is suitable for use in thin fermentation broth. Its antifoaming ability is superior to its defoaming ability, and it is suitable for addition to the basic culture medium to inhibit the generation of foam during the entire fermentation process.
2、GPE type defoamer is also called foam enemy
Adding ethylene oxide to the end of the polypropylene glycol chain segment of the GP type defoamer, it becomes polyoxyethylene oxypropylene glycerol with a hydrophilic group at the chain end, also called. According to the addition amount of ethylene oxide of 10%, 20%, … 50%, it is called GPE10, GPE20, … GPE50 respectively.
GPE type defoamer has good hydrophilicity, is easy to spread in the foaming medium, has strong defoaming ability, but has high solubility and short defoaming activity maintenance time, so it is better to use it in viscous fermentation broth.
3、GPES type defoamer: There is a new polyether defoamer, which uses a hydrophobic stearate to cap the chain end of the GPE type defoamer, thus forming a block copolymer with hydrophobic chains at both ends and a hydrophilic chain in the middle. The molecules of this structure tend to be horizontally aggregated at the gas-liquid interface, so the surface activity is strong and the defoaming efficiency is high.
The function of the defoamer is to trap air at the interface. The function of the defoamer is to make the tiny air (microbubbles) dispersed in the coating quickly rise to the surface during and after the coating process. However, this distinction is often not made clearly in practical applications. Defoamers can also eliminate microbubbles to a certain extent. The defoaming mechanism of defoamers in water-based coatings and inks is discussed below.
For defoamers to show their effects, they must meet certain requirements. One of them is that they must be able to destroy the above-mentioned foam stabilization mechanism. For this reason, the defoamer must have a certain degree of incompatibility in the system and be able to migrate to the air interface. Of course, serious side effects such as shrinkage caused by the use of defoamers should not occur.
