Part I of ‘Solvents, Scents, and Sensibility: Sequestering and Minimizing’ was presented on Friday and encouraged the use of Pemulen TR – 2 in cleaning as an alternative to solvents or as a vehicle for solvents.
The topic of Part II was substituting safer solvents for more hazardous ones. Chris Stavroudis began the talk with a warning: There is no perfect substitute for Xylenes. He did, however, address some alternatives later in his talk.
Some of the harmful solvents that Chris suggested replacing were:
Benzene (a carcinogen) – can be replaced with xylene or toluene (although these alternatives are also hazardous)
n-Hexane (a neurotoxin) – can be replaced with n-Heptane
DMF – replace with n-methyl-2-pyrrolidone (NMP), although this may also be hazardous
Methanol – replace with Ethanol
Cellosolve and Cellosolve Acetate – just don’t use them! May be able to substitute butyl Cellosolve
Chlorinated Solvents – don’t use them. 1,1,1 trichloroethane is the least of the evils, but is terrible for the environment
Xylenes (it is a mixture of isomers and contains varying levels of ethyl benzene) – It may be safer to use xylene (single isomer) but this hasn’t been adequately tested.
Stavroudis stressed the fact that there is a difference between a safe solvent and an untested solvent. The two should not be confused and proper safety precautions must be made. He gave multiple examples of solvents that were once considered to be safe and that we now know can be hazardous (ex: d-limonene).
The use of silicone solvents was encouraged because they are versatile, as they can be cyclic or linear, and have a very low polarity. Silicone solvents may be safer than alternative solvents. They are found in make-up, are practically odorless (although this makes exposure difficult to gauge).
Another safer solvent that Chris mentioned was Benzyl Alcohol which has aromatic and alcoholic functionality, although it is toxic to the eyes.
Chris ended his talk with a review and discussion of solubility theory, including the Hildebrand and Hansen Solubility parameters and the TEAS diagram. This review was focused on the problem of finding a replacement for Xylene, a solvent that would have the same solubility characteristics. Chris’ Modular Cleaning Program is a greener and healthier technique/tool and includes Hildebrand, Hansen, and TEAS solubility theories. Using these theories the solvent mix that most closely matches the solubility characteristics of Xylene is a mixture of nonane and benzyl alcohol. There is more experimentation to be done and the next version of MCP can help you experiment with solvent mixtures and solubilities.