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Selecting Solvent Substitutes

WHAT TO LOOK FOR

Identifying a substitute for solvents in cleaning applications is not an easy task. There are thousands of formulations to choose from. The variability of the literature for these products changes from vendor to vendor and 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.

Part of SSL's mission is to test and evaluate the effectiveness of different cleaning chemistries and equipment on a variety of substrates and soils. The objective of the Lab is to develop and promote environmentally-friendlier, safer alternatives to hazardous solvents. The determination of a chemical's overall risk is based on the health and environmental indicators of:

  • TURI's "Safer" Alternative Cleaners
  • Non-Ozone Depleting Substances
  • Non-Volatile Organic Compounds
  • Zero Global Warming Potential
  • HMIS/NFPA Rating <3 (scale 0 low, 4 high)
  • pH between 2.5 and 11

The SSL has been aiding companies in the search for safer alternatives for more than fifteen years and has performed over 1500 process specific trials. The other part of SSL's mission is to provide technology transfer of these innovative and effective cleaning systems. The results from these simulated cleaning tests have been compiled into an extensive database designed to make solvent substitution in surface cleaning easier and faster. Database searches can be run for companies based on a few important parameters. In order to select the proper criteria, a simple test request form needs to be filled out. This form consists of three major sections designed to help a company to better understand their current cleaning systems, what are their major shortcomings with system, and what they are trying to accomplish by switching to an alternative cleaning system.

 KNOWING YOUR PROCESS

More specifically, the first portion of the form aims to describe the parts to be cleaned. In selecting an alternative cleaner, compatibility of the cleaning solution with material of the part is very important. If the component is made of several different materials, the selection process must find a chemical mix that will not pose potential harm to the most sensitive material. For instance, if the part to be cleaned is made of stainless steel and aluminum, the cleaning chemical selection would be focused on a product that would be compatible with aluminum. Usually a product that can be safely used on aluminum would also work well with the more durable stainless steel. The configuration of the part is almost as important as the surface materials. The shape of the parts may provide insight into what type of equipment may have to be used to ensure adequate cleaning can be achieved. Following the description of the parts to be cleaned, questions about the current cleaning process help to further guide the input for the cleaning product selection.

The types of contaminants that need to be removed from the parts are just as important as the materials and configuration of the parts are. In addition to the dirt, identifying the types of cleaning equipment available provides direction for the selection process. Furthermore, this section provides information about the after cleaning requirements, such as rinsing and drying procedures. Both are important for process specific testing which will take place once the alternative cleaners have been selected.

The third section asks directed questions about what is wrong with the system and the purpose of why they are cleaning the parts. It also provides the company an opportunity to raise areas of concern not covered by the form which the company feels should be addressed during the selection process.

 FINDING AN ALTERNATIVE

All of these parameters provide the necessary information for identifying potential alternatives for surface cleaning. Initially, SSL selection procedure for cleaning alternatives relied on the general data based on traditional technical data sheets and Material Safety Data Sheets (MSDSs).

In an effort to make identifying potential replacements, SSL has established a directory of vendors which provided detailed information from both the technical data sheets and MSDSs. This database provided a comprehensive listing of potential cleaning solvent alternatives.

From the process specific testing performed in the lab, a second database was designed to enhance the data provided by vendors. The use of the new databases allowed for SSL to search for evaluations which closely match new requests.

This type of alternative selection procedure has increased the effectiveness of choosing a cleaning chemical that worked. To illustrate, prior to the database almost a quarter of the trials performed resulted in ineffective cleaning and after the database improved selection process, nearly 93% of the tests performed yielded an effective alternative. Using the information compiled about the process, the search begins by entering the most important criteria into both databases.

Most often, the two essential pieces of data are the material of the parts and the contaminant to be cleaned off of the part. A third input may be the inclusion of a particular type of cleaning equipment being used or requested. After executing the database query, two lists of products are generated and compared to each other. From this list, usually six to eight cleaning blends are selected for laboratory evaluation.

 VERIFYING THE ALTERNATIVE

Phase I of testing should attempt to minimize all the cleaning variables. From the vendor supplied information, similar concentrations (low) should be used. Cleaning concentrations (5%), times (<5minutes) and agitation types (immersion) need to be the same for all the cleaners tested. Thus, the only component being investigated is the chemistries. In this phase of testing, actual parts are not required. In place of the parts, coupons of similar construction material (substrate) will be used. To simplify complex substrates, use the most sensitive material. The dirty coupons should then be reweighed to determine the amount of contaminant applied. With the leading mixtures at the designated temperature and concentration, at least three coupons should be cleaned in each solution for selected time period. Rinsing and drying methods should closely match the previously determined methods used. Obtain a "clean" weight of the coupons once the parts have completely dried (if heated, wait until coupons are at room temperature before weighing). The table displays the set of calculations used to yields the effectiveness of the experiment.