Molybdenum Disulfide, simply known as Moly, is used both independently as a dry lubricant and as an additive in lubricating greases. Dry lubricants reduce friction between two sliding surfaces without the need for an oil medium. Dry lubricant molecules have a natural attraction to metal and adhere themselves to metal surfaces. These molecules create a layer of protection that prevents wear and tear as well as significantly improve lubricity of metallic surfaces.
How Does Moly Work?
When used on its own, Moly is impregnated into the surfaces of metal parts to improve the lubricity and protect the parts themselves. When used in greases and lubricants, the Moly attracts itself to the metal surfaces as an anti-wear surface coating. When used in lubricants, Moly’s efficacy is limited if the additive remains suspended. It is important to ensure that the Moly is compatible with the oil or grease. If it is not compatible, the compounds could drop out and plug oil passages and filters.
Moly has a variety of unique properties that distinguish itself from other solid lubricants and solid additives. These include:
An inherently low coefficient of friction
Strong affinity for metallic surfaces
Film forming structure
Stability in the presence of most solvents
Effective lubricating properties from cryogenic temperatures to 350 C in air
Efficacy in vacuum and aerospace applications
Moly Greases
Moly greases can have concentrations from anywhere from 1 to 20%. Typically, Moly greases typically contain 3 to 5% Moly. Moly greases are generally used in operations where high pressure metal surfaces are sliding against each other. These include roller bearings that have very heavy loads and shock loading. Moly greases are also recommended in slow or oscillating motion that is used in universal and CV joints. Moly greases used in high-speed bearings can create problems such as “skidding,” where a bearing roller fails to rotate a full 360 degrees.
Due to its lubricating abilities in vacuums, Moly and Moly greases are popular in aerospace applications. Temperature limitations for Moly are much higher in space (1200 C compared to 350 C in air) thus can withstand extreme temperatures in space. Moly is used for low speed systems such as solar array drives, sensors, and antenna scanners.
Conclusion
As a solid lubricant, Molybdenum disulfide (Moly) serves as a better lubricant and additive than graphite because of its ability to operate under very heavy loads and in vacuum environments. If your machine’s manual calls for a moly grease, it is important to ensure a moly grease is used and the moly grease is compatible with other lubricants in your equipment.
As the world’s petroleum reserves are extracted, scarcity increases, thus driving oil and lubricant prices higher. This economic burden will force end-users and manufacturers to develop alternatives that are cost effective, readily available, and sustainable. The answer to these concerns are biodegradable lubricants.
Biodegradable Lubricants Defined
Biodegradable lubricants have the ability to degrade naturally by the actions of biological organisms. Petroleum is naturally occurring and is considered inherently biodegradable. However, that does not mean they can be marketed, sold, and treated as biodegradable. When we refer to biodegradable lubricants, we are discussing lubricants that are readily biodegradable.
Determining Biodegradability
Biodegradable lubricants must meet the ISO 9439 or OECD 301B standards. These standards state that a lubricant that has degraded by more than 60% within 28 days is readily biodegradable. The tests involve treating a lubricant sample with microorganisms in the presence of oxygen and measuring the CO2 produced by the microorganisms. As mentioned before, petroleum-based lubricants are inherently biodegradable, but not readily biodegradable because they fail to meet these standards. Petroleum-based lubricants naturally degrade at a rate of 15-35% in 28 days, falling short of the required 60%.
Additionally, the lubricant must be of “low toxicity.” There are a variety of tests used to determine toxicity. These tests involve fish, daphnia, and other organisms. In their pure form, mineral oil and vegetable oil show little toxicity, but lubricants are not just pure oil. As additives are incorporated into formulations, the toxicity increases. Additives are added to make up for any performance shortcomings of biodegradable base stocks.
Types of Biodegradable Base Stocks
Most biodegradable lubricants use vegetable oil, synthetic esters, polyalkylene glycols (PAGs), or a combination of these as base stocks. Vegetable oils have been used for years when petroleum was in short supply. They were popular during World War I and World War II due to oil rationing and came back in popularity during oil embargo in the 1970s. Vegetable oils declined in popularity due to the availability of low-cost oil after Desert Storm. Their popularity is beginning to rise as more manufacturers and end-users are faced with climate change and sustainability concerns. Some common vegetable oils used are soybean oil, cottonseed oil, olive oil, sunflower oil, and canola oil. To improve performance, farmers are beginning to grow genetically modified crops that are designed and engineered for use in lubricants.
Synthetic base stocks, such as esters and PAGs, are also used to boost performance when vegetable oils cannot get the job done. PAGs are effective, however they have a few issues that should be considered. PAGs are incompatible with other oils and can cause problems if inadvertently mixed with non-PAG oils. PAGs can also react poorly with seals and paints. This is why synthetic esters are preferred for biodegradable lubricants. Synthetic esters are typically added to vegetable-oil based lubricants to improve low temperature properties. These serve better than light mineral oils as synthetic esters are less toxic and more biodegradable.
Biodegradable Lubricant Products
Many applications and machines now can be lubricated with biodegradable lubricants and meet all performance requirements. Products that can be composed of soybean oils include:
Tractor transmission and industrial hydraulic fluids
Chainsaw bar oils
Gear lubricants
Compressor oils
Transmission and transformer line cooling fluids
Many more products are in development and could become viable in lubricant markets soon. These include:
Two-cycle engine oils
Metalworking fluids
Specialty lubricants
With more resources and demand for biodegradable lubricants, engineers and manufacturers can research and develop more products that perform more applications, perform better than mineral oils, and remain price competitive.
Biodegradable lubricants are highly popular in applications and industries where environmental and safety concerns are high. Marine and agricultural industries need these lubricants as contamination could have devastating effects. According to Total Lubricants, a single liter of oil can pollute as much as 1,000,000 liters of water. In those applications, biodegradable lubricants are essential. Some government regulations ensure that these industries use biodegradable lubricants that do not harm consumers and operators in the event of leakage.
Twin Specialties Offers Biodegradable Lubricants
No matter your application or environmental requirements, Twin Specialties can meet your manufacturing, marine, or agricultural needs. We offer a variety of lubricants including: Shell Naturelle, Castrol Performance Bio, and various Food Grade lubricants. Contact Twin Specialties for a quote.
Used for over 3000 years, grease is a key lubricant used to operate a variety of machines and bearings. Over 80% of the world’s bearings are lubricated with grease. Grease is an excellent lubricant to use when liquid lubricants fail to do the job. Greases are made of three main components: base oil (70-95%), thickener (3-30%), and additives (up to 10%). We are going to examine the second component: thickeners. Thickeners are essential as they are the “sponge” that holds the base oil and additives.
What are Thickeners?
When combined with the base oil and additives, the thickener forms a semi-fluid structure. Conventional thinking suggests the structure indicates the grease is mainly thickener, however, the thickener is a material that holds the lubricant until it is dispersed. As mentioned above, the overwhelming majority of any grease is composed of base oil. There are many types of compounds that can be used as thickeners.
Greases are classified into two major families: soap and non-soap thickeners. Over 90% of greases worldwide are classified as soap thickeners. Soap-based thickeners are produced via an acid-base reaction known as saponification. The end-result is a soap and water mixture. The water is removed and the remaining soap is used as a thickener for grease. The type of soap thickener will depend on which acids and bases are used in saponification. Some common compounds used are:
High molecular weight fatty acids: Stearic and 12 Hydroxy Stearic Acid (12 HSA)
Short chain complexing acids: Tallow, Azelaic, and Sebacic Acid
Most bases are a metallic hydroxide compound (i.e. lithium, calcium, etc.).
Types of Soap Thickeners
Simple Soap: This results from the reaction of one fatty acid and a metallic hydroxide. The most common soap, lithium soap, is produced
Types of Soap Thickeners – Source: NYE Lubricants
with 12 HSA and lithium hydroxide. The metallic hydroxide defines the thickener and other types besides lithium can be used.
Mixed Soap: Less common than simple soap, mixed soap is created in similar fashion as simple soap. However, the “mixed” characteristic is derived from mixing multiple metallic hydroxide compounds with a fatty acid. A common mixed soap is Ca/Li soap, which is made with calcium hydroxide and lithium hydroxide.
Complex Soap: Like simple soaps, complex soaps use a single metallic hydroxide. In order to create the complex-thickened grease, a fatty acid is combined with a short chain complexing acid. The acid mixture is then combined with a metallic hydroxide to for a complex thickener. Lithium complex grease, the most popular in North America, is made with lithium hydroxide, 12 HSA, and azelaic acid. These thickener types have an advantage over simple soap because of better high-temperature properties.
Types of Non-Soap Thickeners
Urea: Also known as polyurea, these thickeners are a reaction product of di-isocyanate combined with mono and/or diamines. The ratios of the ingredients will determine the characteristics of the thickener. This classification includes diurea, tetraurea, urea-urethane and others. Since there are no metallic elements in polyurea grease, the grease is ashless and subsequently more oxidatively stable. Polyurea greases are the most popular non-soap grease today.
Organophilic Clay: Also referred to as organo clay or clay thickeners, these thickeners are mineral based usually made from bentonite, hectorite, or montmorillonite. The minerals are purified into a clay and treated to be compatible with organic chemicals. The clay is dispersed in a lubricant to form a grease. Clay greases have no melting point and are traditionally used in high-temperate greases (however the oil will oxidize quickly at elevated temperatures).
Other: Polyurea and clay thickeners are the most used non-soap greases, but there are some other specialty thickeners that are used. These include:
Teflon
Mica and silica gel
Calcium sulfonate
Polytetrafluoroethylene (PTFE)
Carbon blacks
NLGI Grades – Source: Noria
NLGI Classifications
In addition to composition, the other key classification for grease is quite obvious: thickness. Defined as consistency, a grease’s consistency is its resistance to deformation by applied force. This is measured by penetration. A standard test, specifically ASTM D217, measures cone penetration after five (5) seconds for a grease at 77 F (25 C). The unit of measure is tenths of a millimeter and the NLGI classifies grease based on its penetration. The range of grades is 000 to 6. See the chart to the left for a full breakdown NLGI grades.
Most greases today fall in between the 1 and 3 grades with NLGI 2 being the most common. High penetration greases such as 00 and 0 can be used in central systems and colder environments.
Selecting the Appropriate Thickener and Grade
The right grease could vary greatly depending on your application, operating environment, and other factors. High temperature environments may require firmer (higher NLGI grade) greases and certain thickeners with high-temperature properties. It is best to consult OEM guides or speak with your grease manufacturer or distributor to get a recommendation.
Switching and mixing greases could either prove to be extremely costly. Most thickeners do not mix together and there are specific greases that are not compatible with others. It is recommended to match “like-for-like.” If you plan to make a switch, it is best to completely drain your equipment before applying new grease.
Lubricants are a critical component to any machine, engine, or tool. How you manage and store the lubricants is as important, if not more so than the actual lubricant selection. In controlled situations, higher quality lubricants will consistently outperform their inferior counterparts. This difference is clearly seen in comparisons of oil-based lubricants (Group I-III) and synthetic lubricants (Group IV – V). However, controlled tests are not going be perfectly replicated in the work environment. Proper storage and monitoring can be the difference between high performance and early breakdowns.
The shelf life for lubricants depends on a variety of factors such as: base oil, additives and thickeners. It is often best to consult the manufacturer to determine the shelf life for your lubricants. Regardless of the lubricant’s shelf life, it will never be actualized if it is not stored properly. This leads to many problems on the manufacturing floor that have a major impact on the bottom line. This can lead to increased costs, machine breakdowns and lower-than-expected productivity.
Consistency is Key
What is the key characteristic for storage best practices? Consistency. By having consistent and routine storage practices, you will have the confidence that your lubricants will perform up to manufacturer’s stated standards. A consistent and controlled environment can also help you diagnose and remedy issues that may arise in your lubricant. For example, if your oil analysis shows that there are higher levels of moisture, you can more effectively diagnose the root cause of moisture. In poor conditions, there are many factors that can affect moisture found in oil-based lubricants, but controlled environments eliminate many of these root causes or isolate them to one-off instances (e.g. a loose oil cap, a small leak or the occasional spill).
Creating the Ideal Environment
The best way to ensure an optimal environment is to dedicate a room solely for lubricant storage. The room should be climate controlled thus protecting lubricants from the heat or the cold. As temperatures reach extremes on either end, the lubricant can breakdown and fall short on performance and shelf life. This is especially important with greases where low temperatures can affect additives. Indoor storage also protects lubricants from airborne moisture. Moisture in lubricants reduces reliability and performance and will lead to more machine breakdowns and downtime.
The storage room should be further away from any external entrance such as a shipping and receiving area or an employee exit. Lubricants near these areas are at risk to exposure outdoor weather and particle contamination. Particles in the lubricants must be filtered out or else machinery will experience greater wear and a reduce life expectancy. By storing lubricants away from shipping and receiving areas, this allows facilities to have less congested work areas and allow for efficient movement or parts, supplies, products and people.
What is the ideal environment for storing lubricants? We recommend a cool, dry area that protects the products from moisture and extreme temperatures. This means storing them in a room or floor area that is away from any external windows or doors, in a well ventilated area, and clearly separated from any workstation.
Improving Storage for End-Users
The lubricant storage room should efficiently use space, but also have the capability to expand. It is important to have all lubricants to be easily accessible so you can properly fill up the right amount of lubricant without spilling and potentially contaminating other lubricants. Many machine breakdowns occur when two incompatible lubricants are mixed. This error is preventable and the best way to ensure proper collection is to have clear and visible labels on each container. This includes having manufacturers labels clearly displayed, having color-coded labels to indicate product type, end-use or receiving date.
Another good idea is to organize containers based who uses them at their workstation. If one person uses the majority of a certain lubricant, it is sensible to store that product close to other products he or she may use. This creates an efficient process for people to collect their lubricants and reduces potential confusion and human error.
One of the greatest root causes of lubricant mismanagement and machine breakdown is human error. It happens to all of us. We are not perfect, but it is critical to strive to improve and implements rules and procedures to minimize these errors. Having properly tuned equipment ensures lubricants are properly measured out each time. Another good measure is to limit who has access to the lubricant room and ensure it is locked when not in use. When access is well controlled this reduces spillage, waste and in some cases, theft.
Conclusions
Theses some of the basic measures that can be taken to ensure a stable and consistent environment. We cannot control the weather, but we do have authority on the thermostat. Storing the lubricants in cool, dry area will ensure maximum shelf life. The additive packages will work properly and the performance you seek from a lubricant, will be realized and performance will improve.
Accidents happen and we learn from our mistakes. The most important thing to learn is preventing similar accidents in the future. This may involve changing processes, reworking access, or using different equipment. Making these changes ensure that mistakes are limited. It is important to regularly assess these processes ensure your lubricants are up to specifications and waste or damage is reduced. By following these best practices, your facility will be cleaner, organized and more efficient.
