Specifically formulated, concrete mix viscosity modifiers allow concrete to achieve optimum viscosity by providing the right balance between agility and resistance to delamination, opposite properties that come with the addition of water.
At the end of 2007, BASF Construction Chemicals introduced a new development, Smart Dynamic Construction TM concrete mix technology, designed to upgrade P4 and P5 concrete to a higher level. Concrete produced in accordance with this technology has all the properties of self-compacting concrete, while the process of its production is no more complicated than that of ordinary concrete.
The new concept meets today's ever-increasing need for more flexible concrete mixes and offers a wide range of benefits:
Economic: due to the unique process occurring in concrete, the binder and fillers with fraction< 0.125 мм. Стабильная и высокоподвижная бетонная смесь является практически самовыравнивающейся и при укладке не требует уплотнения. Процесс укладки достаточно прост, чтобы производиться при помощи одного оператора, что экономит до 40% рабочего времени. Кроме того, процесс производства почти так же прост, как и изготовление обычного бетона, поскольку смесь малочувствительна к изменениям водосодержания, которые происходят по причине колебания уровня влажности заполнителей.
Environmental: The low content of cement (less than 380 kg), the production of which is accompanied by the emission of CO 2, increases the environmental friendliness of concrete. In addition, due to its high mobility, the concrete completely covers the reinforcement, thus preventing its external corrosion. This characteristic increases the durability of concrete and, as a result, the service life of the reinforced concrete product.
Ergonomic: Due to its self-compacting properties, this type of concrete does not require the use of vibration compaction, which helps workers avoid noise and health-damaging vibration. In addition, the composition of the concrete mixture provides concrete with low stiffness, increasing its workability.
When a stabilizing additive is added to the concrete mixture, a stable microgel is formed on the surface of the cement particles, which ensures the creation of a "bearing skeleton" in the cement paste and prevents the concrete mixture from delamination. At the same time, the resulting "bearing skeleton" allows the aggregate (sand and crushed stone) to move freely, and thus the workability of the concrete mixture does not change. This technology of self-compacting concrete makes it possible to concrete any structures with dense reinforcement and complex geometric shapes without the use of vibrators. The mixture in the process of laying self-compacts and squeezes out the entrained air.
Organic peroxides and others are used as viscosity modifiers. They increase or decrease the viscosity of the polymer. Viscosity modifiers include cross-linking agents.
crosslinking agents. Cross-linking agents are substances that cause the formation of cross-links in the polymer. The result is a stronger and tougher coating. Commonly used crosslinkers include isocyanates (forming polyurethanes), melamines, epoxides and anhydrides. The type of crosslinking agent can greatly affect the overall properties of the coating. IsocyanatesIsocyanates are found in a number of industrial materials known as polyurethanes. They form a group of neutral derivatives of primary amines with the general formula R-N=C=O.
The most commonly used isocyanates are 2,4-toluene diisocyanate, toluene 2,6-diisocyanate, and diphenylmethane 4,4"-diisocyanate. Less commonly used are hexamethylene diisocyanate and 1,5-naphthylene diisocyanate.
Isocyanates spontaneously react with compounds containing active hydrogen atoms, which migrate to nitrogen. Compounds containing hydroxyl groups spontaneously form esters of substituted carbon dioxide or urethane.
Application
The main application of isocyanates is the synthesis of polyurethanes in industrial products.
Due to their durability and strength, methylene 2 (4-phenylisocyanate) and 2,4-toluene diisocyanate are used in aircraft, tanker and trailer coatings.
Methylene-bis-2 (4-phenylisocyanate) is used to bond rubber and viscose or nylon, as well as in the production of polyurethane varnish coatings, which can be used in some car parts, and in the production of patent leather.
2,4-Toluene diisocyanate is used in polyurethane coatings, in putties and finishes for floors and wood products, in paint and concrete aggregates. It is also applied to the production of polyurethane foams and polyurethane elastomers in ceramic pipe seals and coated materials.
Cyclohexane is a structural agent in the manufacture of dental materials, contact lenses and medical adsorbents. It is also found in car paint.
Properties and applications of some of the most important isocyanatesIsocyanate | Melting point, °С | Boiling point, °С (pressure in mmHg *) | Density at 20 ° C, g / cm 3 | Application |
Ethyl isocyanate C 2 H 5 NCO | ||||
Hexamethylene diisocyanate OCN(CH 2) 6 NCO | Production of elastomers, coatings, fibers, paints and varnishes |
|||
Phenyl isocyanate C 6 H 5 NCO | ||||
n-Chlorophenplisocyanate | Synthesis of herbicides |
|||
2,4-Toluene diisocyanate | 22 (freezing point) | Production of polyurethane foams, elastomers, paints and varnishes |
||
Diphenylmethanedinozocyanate-4.4" | 1.19 (at 50°C) | Same |
||
Diphenyl diisocyanate-4.4" | ||||
Triphenylmethanetriisocyanate-4.4", 4" | Glue production |
It is claimed that low-viscosity oils provide protection even for forced diesel engines. What are the features of this statement? Let's try to figure it out.
In order for low-viscosity oils to provide sufficient protection for diesel engines of heavy equipment and trucks, it is important to study the shear stability in detail. Isabella Goldmints, Lead Scientist for Friction Modifiers at Infineum, talks about some of the steps being taken to investigate the ability of various multigrade motor oils to maintain their viscosity.
Concerns about environmental and economic issues have given impetus to significant changes in the design of uprated diesel engines, especially in terms of emission control, noise control and power supply. New requirements are putting more stress on lubricants, and modern lubricants are increasingly expected to provide superior engine protection over long drain intervals. Adding to the challenge are the requirements of engine manufacturers (OEMs) to provide lubricants with fuel savings through reduced friction losses. This means that the viscosity of engine oils for heavy equipment and trucks will continue to decrease.
Multigrade oils and viscosity modifiers
The Kurt Orban 90 cycle test has been successfully used to determine the shear stability of oils.
Viscosity improvers (VII) are added to engine oils to increase the viscosity index and provide multigrade oils. Oils containing viscosity modifiers become non-Newtonian fluids. This means that their viscosity depends on the shear rate. Two phenomena are associated with the use of such oils:
- Temporary loss of viscosity at high shear rate - polymers align in the direction of flow, resulting in reversible thinning of the oil.
- Irreversible shear losses where polymers break - resistance to such breakage is a measure of shear stability.
Since their introduction, multigrade oils have been constantly tested to determine the shear stability of both new and existing oils.
For example, to simulate a constant loss of viscosity in forced diesel engines, a test is carried out on an injector stand according to the Kurt Orban method for 90 cycles. This test has been successfully used to determine the shear stability of oils and has been firmly correlated with results from use in 2003 and later engines.
However, boosted diesel engines are changing, exacerbating conditions that cause lubricant viscosity shifts. If we want oils to continue to provide reliable wear protection throughout the entire drain interval, we need to fully understand the processes that take place in the most modern engines.
Engine design needs further testing
To comply with NOx emissions regulations, engine manufacturers first introduced Exhaust Gas Recirculation (EGR) systems. The exhaust gas recirculation (re-supply) system contributes to the accumulation of soot in the crankcase, and in most engines manufactured before 2010, soot contamination of drained oils was 4-6%. This led to the development of API CJ-4 oils that could withstand heavy soot contamination and not exhibit excessive viscosity growth.
However, to meet near-NOx exhaust gas requirements, manufacturers are now equipping modern engines with more sophisticated exhaust aftertreatment systems, including Selective Catalytic Reduction (SCR) systems. This innovative technology delivers more efficient engine performance and greatly reduces soot formation compared to pre-2010 engines, meaning that soot contamination now has negligible effect on oil viscosity.
These changes, along with other significant advances in engine technology, mean that it is now important to explore the potential of commercial viscosity modifier additive packages that are added to modern API CJ-4 oils used in those engines that meet the new emission standards.
At the same time, it is necessary to understand whether the laboratory tests we use to evaluate the performance of lubricants are still effective and correlate well with the actual results of using these materials in modern engines.
One of the most important properties of an oil is its viscosity retention throughout the drain interval, and it is more important than ever to understand the function of a viscosity modifier in multigrade oils. With this in mind, Infenium conducted a series of laboratory and field tests of a viscosity modifier (hereinafter referred to as MV) to investigate in detail the performance of modern lubricants.
Field test of wear protection
The first stage of the research work was the establishment of the performance characteristics of the lubricant when applied in the field. To do this, Infineum conducted a field test of various types of MW for different viscosity oils. Engines used were highly shear-friendly and low-soot engines, typical models found in today's trucks or heavy equipment.
The two most popular types of MF are hydrogenated styrene-butadiene copolymers (HBRs) and olefin copolymers (SPOs). The SAE 15W-40 and 10W-30 viscosity grades used in the test contained these polymers and were formulated from Group II base oils with an API CJ-4 compliant additive package. During the test, the oils were changed at intervals of approximately 56 km, at which time samples were taken, which were tested for a number of parameters. The first was that all oils used retained both kinematic viscosity at 100°C and high temperature high shear viscosity at 150°C (HTHS), regardless of their MW content.
Metal wear products have also been given special attention, as low viscosity oils are used to provide adequate fuel economy, and some manufacturers have raised concerns about the ability of these low viscosity oils to adequately protect against wear. However, during the test, there were no wear issues with either oil sample, as measured by the wear metal content of the used oil - no actual difference between oils with different types of MW or different viscosities.
All of the oils used in the field test were quite effective in protecting against wear throughout the test. Also, during the entire oil change interval, there was a minimal drop in viscosity.
Future PC-11 oils
However, the viscosity of lubricants continues to decline, and it is important to prepare for the next generation of motor oils. In North America, the PC-11 category has been adopted, within which a new “fuel-efficient” subcategory, PC-11 B, is being introduced. The oils corresponding to it in viscosity will be classified as SAE xW-30 with a dynamic viscosity at high temperature (150 ° C) and high shear rate (HTHS) of 2.9-3.2 mPa s.
In order to assess the prerequisites for the future appearance of PC-11 oils, several test samples were mixed so that their high temperature viscosity at high shear rate was 3.0-3.1 mPa·s. They passed 90 cycles of the Kurt Orban test and after that their kinematic viscosity (CV 100) and high temperature viscosity at high shear rate (HTHS viscosity at 150°C) were measured. The HTHS-CV relationship for these oils is similar to that observed for oils with high high temperature viscosity at high shear rate. However, since these samples are at the lower end of the SAE viscosity grades, after shearing, their CV100 is more likely to fall below the viscosity grade limit than the HTHS viscosity. This means that when developing PC-11 B oils, it will be more important to keep the KB100 within the viscosity grade limits for kinematic viscosity at 100°C than to keep the HTHS viscosity at 150°C.
The result of such tests shows that viscosity loss can be dependent on the viscosity and type of base oil, lubricant viscosity and polymer concentration. In addition, it is clear that lower viscosity oils have better polymer shear stability even at 90 cycles in the Kurt Orban test.
Comparison of field and bench test results
To confirm the results obtained in the laboratory, Infenium analyzed intermediate samples and samples taken after the 56 km replacement interval in field trials. A comparison of bench and field test data shows that the ASTM method makes it possible to accurately predict polymer shear in the field, even in today's highly accelerated diesel engines.
This study shows that one can be sure that the Kurt Orban bench test over 90 cycles is a good indicator of the viscosity loss and viscosity grade retention that can be expected when oils are used in modern diesel engines.
In our opinion, since lubricants are intended not only to provide protection against wear, but also to reduce fuel consumption, it is important not only to choose a viscosity modifier whose composition and structure will give high shear stability, but also to pay great attention to kinematic viscosity.
How does a viscosity modifier work?
You may have come across a "red oil can" - a motorist's horror story, one of the most likely reasons for its appearance is the irreversible destruction of the viscosity modifier. A smooth decrease in pressure in the engine over the life of the oil also indicates an unplanned destruction of the polymer (MB).
Unfortunately, this does not happen so rarely, due to the fact that all components for creating motor (and not only motor) oil are on the open market, in addition to base oil and an additive package containing ready-made products that meet manufacturers' requirements, you can also find viscosity modifiers on sale.
There is only one problem - the raw material base from which the finished product will be formulated varies greatly in quality, and product stability studies can take many months (sea trials) and significant funds.
No organoleptic analysis, no taste, no color, no smell, will help the consumer to separate a quality product from a low-quality one. The consumer can only trust the manufacturer, and therefore should carefully choose the manufacturer of the base oil and additives. The right technology is not just adding additives, but working on all raw materials.
Chevron does more than just create exclusive base oils. The corporation's specialists also develop unique additive systems, which provide Texaco lubricants with excellent performance properties. The Chevron holding includes its own division for the development and production of additives - this is Chevron Oronite. The research and development activities of the company are concentrated in Ghent (Belgium), where in 1993 a completely new technology center was opened, equipped with the most modern equipment, the laboratories of the center conduct hundreds of thousands of oil analyzes per year to provide quality assurance to the consumer.
What is Viscosity?
Viscosity is the resistance of a fluid to flow. When one layer of fluid slides through another layer of the same fluid, there is always some level of resistance between these flows. When the value of this resistance is high, the liquid is considered to have a high viscosity and, as a result, flows in a thick layer, for example, like honey. When the fluid flow resistance is low, the fluid is considered to have a low viscosity and its layer is very thin, such as olive oil.
Because the viscosity of many fluids changes with temperature, it is important to consider that the fluid must have the right viscosity at different temperatures.
Viscosity for engine oil.
Engine oils must lubricate engine components throughout the engine's normal operating temperature range. Low temperatures tend to thicken the flow of engine oil, making it more difficult to pump. If the lubricant is slowly getting to the main parts of the engine, oil starvation will lead to their excessive wear. In addition, thick oil will make it difficult to start a cold engine due to the added resistance.
On the other hand, heat tends to thin the oil film and in extreme cases can reduce the oil's protective capabilities. This can lead to premature wear and mechanical damage to the piston rings and cylinder walls. The trick is finding the right balance of viscosity, oil film thickness and fluidity. Solution viscosity modifiers can achieve this. Viscosity modifiers are polymers specifically designed to help control the viscosity of a lubricant over a specific temperature range. They help the lubricant provide adequate protection and fluidity.
The video will help illustrate three key points of viscosity:
- Thin oil flows faster than thick oil.
- Low temperatures thicken oils and slow down their fluidity compared to higher temperatures.
- An oil viscosity modifier can affect its performance.
Viscosity control by polymers.
Two different engine oils: high performance oil (with modifiers) and low performance oil. Both viscosity grades are SAE 10W-40. The beaker on the left corner shows the viscosity of high performance engine oil at room temperature. The second beaker from the left shows how low performance motor oil can thicken during use. The third beaker shows how high performance oil retains fluidity at -30°C. The beaker at the far right illustrates the reduced fluidity of low performance motor oil at -30°C.
When studying chemistry in school, remember that a polymer is a large molecule that is made up of many repeating subunits known as monomers. Natural polymers such as amber, rubber, silk, wood are part of our everyday life. Man-made polymers first came into general use in the 1930s. Synthetic rubber and nylon stockings :) By 1960, the benefits of adding carbon based polymers, which are often used as viscosity modifiers, were universally recognized.
Throughout this period, Lubrizol has been a leader in polymer chemistry for passenger car and truck engine oils. Today, viscosity modifiers (VMS) are key ingredients in most motor oils. Their role is to assist lubrication, achieve the required viscosity and mainly to positively influence changes in the viscosity of the lubricant when subjected to temperature fluctuations.
Viscosity grades
Simply put, viscosity grade refers to the thickness of the oil film. There are two types of viscosity grade: seasonal and all-weather. Oils such as SAE 30 are designed to provide engine protection at normal operating temperatures, but will not flow at low temperatures.
Multigrade oils usually use viscosity modifiers to achieve greater flexibility. They have an identified viscosity range, such as SAE 10W-30. The "W" indicates that the oil has been tested for use in both cold weather and normal engine operating temperatures.
For a deeper understanding of viscosity grades, it is helpful to use examples. Since multigrade oils are the engine oil standard for most cars and heavy trucks around the world today, we'll start with them.
SAE 5W-30 is an all-season engine oil viscosity grade most widely used in passenger car engines. Operates as SAE 5 in winter and as SAE 30 in summer. The value of 5W (W stands for winter) tells us that the oil is fluid, and the engine will be easier in cold temperatures. The oil flows quickly to all parts of the engine and fuel economy is improved because there is less viscous drag from the oil on the engine.
30 part SAE 5W-30 makes the oil more viscous (thicker film) for high-temperature protection during summer driving, keeping the oil from becoming too thin, preventing metal-to-metal contact inside the engine.
Severe-duty diesel oils currently use higher SAE viscosity grades than passenger car engine oils. The most widely used viscosity grade worldwide is SAE 15W-40, which is more viscous (and film thicker) than SAE 5W-30. Winter (5W vs 15W) and summer (30 and 40). In general, the higher the SAE viscosity grade numbers, the more viscous (thicker film) the oil.
Seasonal oils, such as SAE 30 and 40 grades, do not contain polymers to modify viscosity with temperature changes. The use of a multigrade motor oil containing viscosity modifiers allows the user to have the double benefit of ease of flow and starting while maintaining a high degree of engine protection. In addition, unlike seasonal motor oils, the consumer does not have to worry about switching from a summer grade to a winter grade due to seasonal temperature fluctuations.
polymeric viscosity modifiers.
Types of viscosity modifiers:
Polyisobutylene (PIB) was the predominant VM for motor oil 40 to 50 years ago. PIB is still used in gear oils due to its outstanding wear characteristics. PIBs have been replaced by olefin copolymers (OCPs) in motor oils due to their superior efficiency and performance.
Polymethacrylate (PMA) the polymers contain alkyl side chains that inhibit the formation of paraffin crystals in the oil, providing excellent low temperature properties. PMAs are used in fuel economy motor oils, gear oils and transmissions. As a rule, they have a higher cost than OCP.
Olefin polymers (OCP) have found wide application in motor oils due to their low cost and satisfactory performance. Many OCPs on the market vary in molecular weight and ratio of ethylene to propylene content. OCPs are the main polymer used for viscosity modifiers in motor oils.
Styrene Maleic Anhydride Ester Copolymers (Styrene Esters). The combination of different alkyl groups provides excellent low temperature properties. Typical use cases are: efficient fuels, engine oils for automatic transmissions. As a rule, they have a higher cost than OCP.
Hydrogenated Styrene-Diene Copolymers (SBR) characterize fuel economy benefits, good low temperature properties, and performance superior to most other polymers.
Hydrogenated Radial Polyisoprene polymers polymers have good shear stability. Their low temperature properties are similar to those of OCP.
Viscosity measurement, kinematic viscosity
The lubricant industry has created and improved laboratory tests that can measure viscosity parameters and predict how modified motor oils will perform.
Kinematic viscosity is the most common measurement of viscosity used for motor oils and is a measure of fluid flow resistance to gravity. Kinematic viscosity has traditionally been used as a guide in selecting oil viscosity for use at normal operating temperatures. A capillary viscometer measures the flow of a fixed volume of liquid through a small orifice at a controlled temperature.
A high pressure capillary viscometer test that is used to simulate the viscosity of motor oils in crankshaft bearing applications to measure high temperature high shear viscosity (HTHS) levels. HTHS may be related to engine durability under high load and severe service conditions
Rotational viscometers measure the resistance of a fluid to flow using torque on a rotating shaft at a constant speed. Cold Cranking Simulator (CCS). This test measures viscosity at low temperatures to simulate starting an engine at low temperatures. Oils with high CCS viscosity can make it difficult to start the engine.
Another common rotary viscometer test is the Mini-Rotary Viscometer (MRV). This test examines the pump's ability to pump oils after a specified thermal history, which includes warming, slow cooling, and cold soak cycles. MRVs are useful in predicting engine oils that are prone to failure under slow cooling (overnight) field conditions in cold climates.
Motor oil is sometimes evaluated by pour point (ASTM D97) and cloud point (ASTM D2500) measurements. Pour point is the lowest temperature at which movement is observed in the oil when the sample in the glass tube is tilted. Haze is the temperature at which a cloud from the formation of paraffin crystals is first observed. These last two methods are no longer used today and have been replaced by specifications for low temperature pumping and gelatinization index.
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Concrete viscosity modifiers (stabilizers)
Thanks to a specially formulated formulation, concrete mix viscosity modifiers allow concrete to achieve optimum viscosity by providing the right balance between agility and resistance to delamination, the opposite properties that come with the addition of water.
In late 2007, BASF Construction Chemicals introduced a new development, Smart Dynamic ConstructionTM concrete mix technology, designed to upgrade P4 and P5 concrete to a higher grade. Concrete produced in accordance with this technology has all the properties of self-compacting concrete, while the process of its production is no more complicated than that of ordinary concrete.
The new concept meets today's ever-increasing need for more flexible concrete mixes and offers a wide range of benefits:
Economical: thanks to the unique process that takes place in concrete, the binder and fillers with a fraction are saved<0.125mm. Стабильная и высокоподвижная бетонная смесь является практически самовыравнивающейся и при укладке не требует уплотнения. Процесс укладки достаточно прост, чтобы производиться при помощи одного оператора, что экономит до 40% рабочего времени. Кроме того, процесс производства почти так же прост, как и изготовление обычного бетона, поскольку смесь малочувствительна к изменениям водосодержания, которые происходят по причине колебания уровня влажности заполнителей.
Environmental: The low content of cement (less than 380 kg), the production of which is accompanied by the emission of CO2, increases the environmental friendliness of concrete. In addition, due to its high mobility, the concrete completely covers the reinforcement, thus preventing its external corrosion. This characteristic increases the durability of concrete and, as a result, the service life of the reinforced concrete product.
Ergonomic: Due to its self-compacting properties, this type of concrete does not require the use of vibro-compacting, which helps workers avoid noise and health-damaging vibration. In addition, the composition of the concrete mixture provides concrete with low stiffness, increasing its workability.
When a stabilizing additive is added to the concrete mixture, a stable microgel is formed on the surface of the cement particles, which ensures the creation of a "bearing skeleton" in the cement paste and prevents the concrete mixture from delamination. At the same time, the resulting "bearing skeleton" allows the aggregate (sand and crushed stone) to move freely, and thus the workability of the concrete mixture does not change. This technology of self-compacting concrete makes it possible to concrete any structures with dense reinforcement and complex geometric shapes without the use of vibrators. The mixture in the process of laying self-compacts and squeezes out the entrained air.
Materials:
RheoMATRIX 100
High performance viscosity modifier additive (VMA) for poured concrete
Technical description RheoMATRIX 100
MEYCO TCC780
Liquid viscosity modifier to improve the pumpability of concrete (Total Consistency Control system).
Technical description MEYCO TCC780
