Project #8
Silver Bullet Testing - solvent blends to replace TCE
02/28/2022
Small
Less than 1 lb
Trichloroethylene
TCE is generally used in degreasing operations because of its high boiling point, which allows the solvent to remove soils and waxes that lower-boiling solvents may not. The stability of TCE makes it particularly useful in airless degreasing systems. TCE is also used in “cold” degreasing applications, where the liquid is applied to the contaminant directly.
TCE is a highly versatile solvent that works on a lot of soils and end user applications. TCE is an effective solvent for a variety of organic materials. The solvent is also forgiving of operator inexperience, easy to use, and relatively inexpensive. In addition, for military, aerospace, and other stringent processes it is a well-known and proven solvent.
Identifying a substitute for solvents in cleaning applications is not an easy task. There are thousands of formulations from which to choose. The variability of literature for these products changes from vendor to vendor as well as from product to product, making the search for an applicable substitute nearly impossible. Even after selecting a potential product, there is no guarantee that it will work with the company’s specific soils, parts and process.
Solvent replacement for TCE identified using HSPiP. Evaluated on soils from past TCE projects
Used Immediately
The HSP values represent the bond energy from the dispersion, polarity and hydrogen bond forces respectively; the solutes and solvents possess greater compatibility when these values are more closely aligned (i.e., the concept of “like dissolves like”).
HSP consists of three intermolecular bonding forces (i.e., parameters) to characterize the interaction of a chemical with other components. These parameters are the dispersion parameter (∂D), the polarity parameter (∂P), and the hydrogen bonding parameter (∂H) [12]. The HSP values of a solvent blend is calculated based on the sum of individual solvent component HSP values multiplied by their respective volume fractions.
HSP values can also indicate similar solubility properties of solvents based on the location of each solvent; the nearer that solvents are positioned to each other in HSP space, the more alike they are in terms of solutes that they can dissolve.
The theoretical concepts and approaches proposed for this type of project are innovative to the identification and assessment of new solvent blends used to replace hazardous solvents. The proposed research will utilize the application of Hansen solubility parameters as the underpinning theoretical model to identify and screen potential alternative chemicals for replacing TCE. The Hansen solubility parameters are typically used for product reformulation to increase the technical performance or decrease the costs of the product. However, the primary goal of applying the Hansen solubility parameters for this research will be to identify solvent blends that are less hazardous than TCE. Therefore, only solvents with a desirable environmental, health, and safety profile will be considered as potential ingredients for a solvent blend developed using Hansen solubility parameters. The HSP will be used to characterize the solvency of TCE and potential alternatives for the target solute.
Past HSP efforts have focused on identifying azeotrope blends that would allow the solvent mixtures to be used in vapor degreasing operations. Limited success in these efforts has only produced less than desirable solvents and low operating performance. The focus of the current work at the TURI Lab is on identifying mixtures that can be used for other operations (immersion, ultrasonic, or wipe cleaning).
After identifying a product, solvent, or solvent mixture that has effective performance and environmental health and safety, a site –specific pilot test is conducted at the facility (based on the results of the lab testing). Products and bench scale equipment are made available to conduct “on-site” piloting. The TURI Cleaning Lab and company workers jointly responsible for the cleaning process. The client must try out the alternative in their current or new equipment and provide feedback on scale-up feasibility. If the alternative works in real-world application, the client will then connect with the vendor and provide training for the updated cleaning process. If the alternative does not work, the process is repeated, or upstream changes are considered are conducted to allow for more flexibility for alternatives.