1. Environment friendly
The general rules of the relationship between biodegradability and its molecular structure are as follows: the degree of hydrophobicity is high and easy to degrade; The length of hydrophobic chain has influence on the degradability; Ethoxyl chain is short and easy to degrade; Alkyl benzene sulfonates are easy to degrade by increasing the distance between the ends of sulfonic group and hydrophobic group. For anionic emulsifiers, alkyl sulfate (as) is the most easily degraded. Linear alkylbenzene sulfonate (LAS) is most easily degraded in C6-C12 chain length. The alkyl chain has branched chains and the longer it is close to the main chain, the more difficult it is to degrade. For non-ionic emulsifiers, short chain alkyl, straight chain alkyl, no phenol group in the molecule, less Po and EO units are easy to degrade, and EO chains with the same length are easier to degrade than Po chains.
The toxicity of anionic emulsifiers is relatively low. For as, those with carbon number less than 8 or more than 14 are less toxic than their homologues. The toxicity of most non-ionic emulsifiers is lower than that of anionic emulsifiers. Polyethylene glycol (PEG) is the lowest, followed by sugar esters, fatty alcohol polyoxyethylene ether (AEO), sorbitol fatty acid esters and their adducts with ethylene oxide (span, Tween). For EO type non-ionic emulsifiers, the general ester type (Tween, a polyoxyethylene compound of sorbitol dehydrated) is less toxic than the ether type (AEO and APEO). Polyol types such as sorbitan and glyceride can be expected to be basically non-toxic.
The order of skin irritation of some anionic emulsifiers: ABS (LAS) > as > AOS（ α－ Alkenyl sulfonate) > AES (fatty alcohol polyoxyethylene ether sulfate). Comparing the skin irritation intensity of as, Las and AOS with different chain lengths, on the whole, c10-14 emulsifier has strong skin irritation, and C12 chain length has the greatest irritation. The irritation of Tween in EO type non-ionic emulsifier is less than that of AEO; Homologues of various EO emulsifiers, with the increase of the number of ethylene oxide added, the irritation decreases. The introduction of polyethylene glycol (PEG) groups into molecules can greatly reduce the irritation of emulsifiers.