A Thorough Comparison of Water Based Cleaners and Solvent Cleaners
As water-based cleaning chemistries and new solvent technologies gain popularity, the ongoing discussion about which is better, water-based or solvent cleaners, continues to be a subject of debate.
Companies that need to meet specific cleaning requirements in industrial, precision, and specification-driven applications face the task of choosing the most suitable cleaning material for their operations. This decision is crucial for ensuring optimal performance and success in their respective industries.
To make an informed decision about which cleaning material is best for your application, it is essential to have the necessary knowledge and understanding. In this article, we will delve into the distinctions in properties, performance, cost, safety, and regulatory implications between these two cleaning materials. By exploring these factors, we aim to provide you with valuable insights that will simplify the decision-making process and enable you to make an informed choice for your specific needs.
THE DIFFERENCE BETWEEN A WATER-BASED CLEANER AND A SOLVENT CLEANER
When we talk about solvent cleaners or solvent degreasers, we're referring to a type of cleaner that uses a liquid to dissolve dirt and grime. These cleaners can utilize one type of solvent or a combination of multiple solvents and compounds to achieve optimal performance for specific cleaning tasks. Solvents can be classified into different categories like alcohols, ketones, and aliphatic hydrocarbons, each with its own unique characteristics and solvency properties. By combining various compounds and mixtures, a wide range of solvents and cleaning solutions are created for commercial use. These solvents can be tailored to effectively remove specific types of dirt while minimizing any impact on other materials. You may be familiar with some solvents like acetone and butyl acetate, which are commonly found in local hardware stores. Other examples include alcohols like isopropanol and ethanol, as well as gasoline, which is composed of hydrocarbons.
Water, as a solvent, falls under the category of solvents. Water-based degreasers primarily rely on water as the main solvent, but they can also contain any of the solvents mentioned earlier, along with detergents, pH modifiers, builders, chelating agents, and other compounds. Depending on the specific compounds used, water-based cleaners can be highly effective or milder in their cleaning action. They can range from potentially hazardous to relatively safe for use, although they typically require a rinsing step. The diversity and complexity of water-based cleaners are extensive. Both solvent-based and water-based cleaners find applications in various fields, including degreasing, precision cleaning, ultrasonic cleaning, and medical device assembly cleaning, among others.
SOLVENT CLEANERS
Solvents work by dissolving dirt and grime, breaking it down into smaller particles and carrying it away from the surface being cleaned. Many solvents offer the advantage of quick cleaning, as they can swiftly dissolve and remove soils without requiring extensive preparation, processing, or drying time. Solvent-based cleaners are widely used in industrial applications due to their strong cleaning power, capable of tackling thick layers of baked-on oils, dirt, contaminants, solder flux, and greases. Examples of potent cleaning solvents include acetone, methyl ethyl ketone, toluene, nPB, and trichloroethylene (TCE). On the other hand, mild solvents like isopropyl alcohol, glycerine, and propylene glycol are commonly used for gentler cleaning tasks. It's important to note that the terms "strong" and "mild" are arbitrary and depend on factors such as the type and amount of soil to be removed, as well as the desired level of cleanliness.
Solvent-based cleaners can be fast evaporating or slow evaporating, high in odor or low in odor, plastic safe or very aggressive. The wide array of solvents has allowed the creation of very specific cleaning chemistries for removing specific soils from substrates. For example, some cleaners are capable of removing a specific ink on a plastic substrate while leaving others completely untouched.
FLAMMABLE SOLVENTS VERSUS NONFLAMMABLE SOLVENTS
When deciding on a solvent cleaner, a key consideration is whether to opt for a flammable or non-flammable solution. If it is safe to use flammable solvents and appropriate precautions can be taken, such as ensuring good ventilation, eliminating ignition sources, and following safety protocols, flammable solvents tend to be more cost-effective compared to non-flammable alternatives. However, if safety concerns arise or if it is not possible to meet the necessary safety requirements, there are plenty of non-flammable solvents available as alternatives.
EVAPORATION RATE OF SOLVENTS
Solvents have different rates of evaporation. Some evaporate quickly at room temperature, which is useful for minimizing process downtime. Others evaporate slowly and are better suited for applications involving elevated temperatures. It's important to note that there isn't a single solvent that works for all applications. Additionally, solvents with slower evaporation rates are less likely to be volatile organic compounds (VOCs), but they may require an additional drying process.
SURFACE TENSION OF SOLVENTS
Surface tension refers to a liquid's ability to form droplets or spread out on a surface. When a material has low surface tension, it easily spreads and wets a surface, resulting in a thin and even coating. On the other hand, high surface tension causes the liquid to gather and form droplets. In general, solvents have lower surface tension compared to water-based cleaners. This property allows solvents to penetrate into narrow spaces and effectively remove dirt without getting trapped.
SAFETY CONCERNS OF SOLVENT CLEANERS
It is important to handle all solvents and cleaners with caution and use appropriate personal protective equipment, such as gloves and goggles, to minimize any potential exposure. Additionally, it is essential to work in well-ventilated areas to ensure proper air circulation. To ensure safe usage, it is advisable to follow the recommendations provided in the manufacturer's Safety Data Sheet (SDS), which provides important information on handling, storage, and potential hazards associated with the product.
A rising concern regarding solvents is the presence of Volatile Organic Compounds or VOCs. These are substances that easily evaporate and turn into gas at normal room temperatures. VOCs can contribute to the formation of smog and have potential negative impacts on the environment and personal health. That's why the use of low or no VOC solvents is gaining importance. Companies are adopting these solvents to meet air quality standards and promote the well-being of their workers.
When using solvents that do not contain VOCs, there are certain tradeoffs to consider. One drawback is that these solvents may have a longer drying time compared to those containing VOCs. This applies to both water-based and solvent-based systems. To reduce the VOC impact of a cleaner, slow-evaporating solvents can be added to the mixture, minimizing the release of VOCs into the environment. These slow-evaporating solvents can be substances that have oil-like properties or even water mixtures. However, incorporating these solvents may necessitate additional processes such as rinsing, using drying heat tunnels, or implementing reclamation procedures to meet the required process parameters.
There are alternative solvents called VOC exempt materials, including acetone, siloxanes, and PCBTF, which have their own set of tradeoffs. These solvents are generally effective at cleaning, but they come with certain considerations. Acetone is an affordable option but is flammable and has a strong odor. PCBTF and siloxanes, on the other hand, are more expensive. Additionally, there are VOC exempt materials like HFC-43-10mee, which may not have sufficient cleaning power on their own and require mixing with stronger solvents to enhance their effectiveness in removing most types of dirt and grime.
WATER-BASED CLEANERS
Water-based cleaners are effective at removing dirt and grime by using two methods: dissolving contaminants and chemically reacting with them to make them easier to dissolve in water. Different materials respond differently to the pH of the cleaning solution. For example, acidic solutions with a pH of 7 or lower are better at reacting with or dissolving certain materials. You can find acidic materials in everyday items like lemons (citric acid), vinegar (acetic acid), soft drinks (carbonic and phosphoric acid), and even car batteries (sulfuric acid). On the other hand, materials that react or dissolve more readily in solutions with a pH above 7 prefer caustic or alkaline solutions. Common caustic materials include ammonia, bleach (sodium hypochlorite), lye (sodium hydroxide), and oven cleaners (which contain sodium hydroxide).
Most aqueous cleaners contain a variety of other components to enhance the cleaning profile. These other materials can include [2]:
1. Detergents or surfactants – materials that have wetting and emulsifying properties, and can carry soils into a solution that they would not otherwise dissolve into.
2. Builders – materials that increase the efficacy of detergents in water by adding alkalinity to solutions.
3. Emulsifiers – liquids that can carry oils into water solutions, creating a liquid in liquid solution.
4. Saponifiers – materials that will react with fatty acids and other carboxyl groups to form water-soluble soaps that can dissolve into the water solution.
5. Sequestering agents – bind with calcium, magnesium and other metals in hard water that detract
from the overall cleaning ability of the cleaner. Sequestering agents can bind with more than one metal ion at a time.[3]
6. Chelating agents – similar to sequestering agents, but bind to one metal ion only. The combination of water, solvents, surfactants, and saponifiers can be as effective as solvent cleaning, but often requires a change in the cleaning process. In a high precision application where residues cannot be tolerated, a rinsing process is often required with water-based chemistries. Batch or in-line cleaning systems generally have rinse and dry cycles to overcome these issues.
DIFFERENCES WHEN USING WATER-BASED CLEANERS
Aqueous cleaners can achieve very similar cleaning levels as solvent-based cleaning chemistries, but there are certain differences:
1. Evaporation: Water-based cleaners function in a much narrower range of evaporation time when compared to solvent cleaners. While solvent cleaner’s evaporation time can range from milliseconds to months, water-based degreasers usually operate in a much narrower range. They typically are not left to evaporate on their own, and can normally be used in a cold or hot soak application.
2. Temperature profile: Cleaning temperatures for water-based chemistries can range from room temperature up to about 80C, depending on the specific cleaner and its formulation. Although this provides a great deal of process variability, this is much more limited when compared to solvent cleaners. Solvent temperature cleaning range can be much wider just based on the variety of solvents available, from below 0C to above 200C.
3.Higher surface tension: In general, water-based cleaners have higher surface tensions when compared to solvents. Raising the temperature, using different surfactants and emulsifiers, and incorporating spray and drying systems can overcome much of this shortcoming. However, for the tightest clearance areas, solvents with low surface tension are superior in their abilities to wet into and evaporate out of tight spaces.
4.Reactive additives: Some of the reactive additives incorporated into aqueous cleaners can be very aggressive to different metals, plastics, or inks. Once the part is cleaned, validation of material compatibility with the parts must be checked. This includes making sure no reactive material is left behind from the rinse process, and verifying that the product will function in the expected manner and in all expected environments. Trace quantities of some of these reactive materials may contribute to electrical leakage, coating dewetting, and a variety of other defects.
5.Rinse and Drying: As noted above, rinsing and drying removes any cleaner components and solubilized contaminants. While some solvent cleaning systems also require a rinse and dry process, water-based systems are usually more involved with respect to the rinse and dry process in the context of vapour degreasing applications.
6. Environmental Impact: Here again, environmental impact concerns apply to both solvent and aqueous cleaners. Global, national, state and municipal regulations continue to limit the cleaning choices available to manufacturers:
• Montreal and Kyoto protocols limit categories of substances like CFC’s (chlorofluorocarbons), HCFC’s
(hydro chlorofluorocarbons), and HFC’s (hydro fluorocarbons) due to ozone depletion, global warming, and other environmental concerns.
• EPA (Environmental Protection Agency) and state agencies like Cal-OSHA (California OSHA) limit personnel exposure to toxic chemicals.
• CARB (California Air Review Board) restricts smog-producing VOCs (volatile organic compounds) in cleaners based on specific cleaning categories.
• Hazardous Air Pollutants (HAPs). Hazardous air pollutants (HAPs) are those pollutants that are known or suspected to cause either environmental damage or other serious health effects (i.e. reproductive complications, birth defects, and cancer).[4] Some solvents are considered a HAP, and in general water- based chemistries do not contain HAPs.
• Priority Pollutant List[5]. These are a set of chemicals that the EPA regulates, and has analytical test methods for detecting under the Clean Water Act. Once again, several solvents are on this list, while aqueous cleaning chemistries are not. These regulatory pressures force manufacturers to evaluate new cleaners and cleaning processes to overcome policy-related hurdles. As a result, water-based cleaners are becoming more common in the industry.
WHICH CLEANING CHEMISTRY IS BEST FOR YOU?
Both cleaning technologies, whether it's solvent-based or water-based, have the potential to be highly effective in terms of cleaning performance. However, the effectiveness depends on various factors such as the type of substance being cleaned, the surface or material being cleaned, and the specific constraints and requirements of the cleaning process. It's important that all three of these parameters are considered and aligned properly in order to achieve the best possible cleaning results.
To choose between an aqueous cleaner vs. a solvent, one must evaluate your unique application, requirements, and goals. Then, you must consider safety, performance, and cost of the solution. A good cleaning agent that is made specifically for removing handling soils may not remove machine greases, a cleaner that works well on stainless steel may not be compatible with glass lenses, and a cleaner that removes machining oil may not be clean enough for a liquid oxygen line. The bottom line is that it’s impossible to make an overall credible judgment of the superiority of either solvent or water-based cleaners without evaluating the unique situation of the user. Luckily, even with the ever-mounting regulations, there's an array of choices that include both solvents and water-based cleaners. There you have it - our comparison of solvent and aqueous cleaners. Be sure to post your questions and comments below. And if you still need assistance choosing between a solvent cleaner and water base, speak with one of our product specialists. They’ll help you get the right product for your application.
