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Regarding thicker adhesives,such as certain silicones or SMP-polymers, they can be difficult to measure using dynamic viscosity testing. Another type of measurement for flow can be used instead, extrusion rate. This value is usually listed in units such as g/min or ml/s. What is measured is the amount of material extruded from a certain apparatus during a specific time and pressure.Īpart from viscosity values, you will often also find a mention of the consistency of of the adhesive in its specification. Some terms commonly used are flowing/free-flowing, paste/non-flowing and thixotropic. Please note that it can be quite difficult to compare viscosities of different adhesives due to the fact that any values will depend on the method or standard used when measuring, such as the rpm. The viscosity is also dependent on outer factors including temperature. Some examples of questions to ask yourself: When choosing an adhesive, it is important to consider that the adhesive itself as well as its viscosity is suitable for both the final product and the gluing process. Does the adhesive need to flow out to a bigger surface area than the string of glue I dispense? Or du I want it to stay put?.Do I need to build up a certain thickness of the adhesive bond? (Tip: look in the technical data sheet where the recommended maximum gap fill is usually stated).How will I dispense the adhesive? Is any type of equipment already determined?.What does it mean if an adhesive is thixotropic?Ī fluid is thixotropic when its viscosity is affected by movement (shear stress) and also is dependent of the time during which this movement takes place. In reality, this means that the viscosity is lowered more when the fluid is stirred for longer. It also means that an adhesive that is thixotropic will not flow. Instead, it will maintain the shape it had when you dispensed it. When the adhesive is not exposed to shear stress, it will stop flowing. But as you stir it, or dispense it for that matter, it will start to get more thin until you stop (with a delay). Ketchup is an example of a thixotropic fluid. As a result, 0W-20 and 5W-30 oils have been developed for colder climates while 15W-40 and 20W-50 oils have been developed with hotter climates in mind.A thixotropic adhesive does not really tell you anything about the adhesive viscosity. Thin oils that are less prone to thickening in low temperatures will help you start your engine more quickly in winter while thick oils that are less prone to thinning in hot temperatures will help your engine perform better in summer. When comparing oils, it is important to take into account the location in which the car will be used. During summer and in hotter regions, your engine will benefit more from oil with higher viscosity at 100 degrees Celsius. Oil with a 5W-30 grade thins out more quickly at high temperatures as compared to oils with a 5W-40 grade.ĭuring winter and for cars used in cooler regions, your engine will benefit from using oil with low winter viscosity. The numbers after the “XW” indicate viscosity at 100 degrees Celsius and represent the oil’s resistance to thinning at high temperatures.įor instance, oil with a 5W-30 grade thickens less than oil with a 10W-30 grade in cold weather.
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The lower the number, the less the oil thickens in cold weather. The number preceding the “W” (winter) rates the oil’s flow (viscosity) at zero degrees Fahrenheit (-17.8 degrees Celsius). Viscosity is notated using the common classification “XW-XX”. The Society of Automotive Engineers developed a scale for both engine (motor oil grades) and transmission oils.
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Thick oils are better at maintaining film strength and oil pressure at high temperatures and loads. Thin oils reduce friction in engines and help engines start quickly during cold weather. Thin oils have lower viscosity and pour more easily at low temperatures than thicker oils that have a higher viscosity. TotalEnergies Automotive Repair & Maintenance WorkshopsĮngine oil viscosity refers to how easily oil pours at a specified temperature.Agricultural machinery engine oil e-brochure.