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Plastic lubricants for hydraulic seals

by:ORK      2022-10-14
Additives that are added to plastic ingredients to reduce friction and improve processing properties in plastic molding, called lubricants. Plastic lubricants are divided into external lubricants and internal lubricants. 1. External lubricant and internal lubricant 1. External lubricant External lubricant is used to reduce the friction or adhesion between materials or products and the metal surface of processing equipment during plastic processing. For example, reducing the friction between the melt and the injection molding machine, the extruder screw or the barrel, the friction between the product and the mold shape, etc. The requirements for external lubricants are: 1) The surface tension is small, which can reduce the friction between the polymer and the metal surface. 2) The compatibility with the polymer is small, and it is easy to migrate to the surface of the material during the plastic processing. 3) Contains metal-friendly polar groups, which can form a polar lubricating layer oriented toward the metal on the polymer surface. In addition to being added to the plastic ingredients, the external lubricant can also be rubbed on the metal mold. In this case, it is called a release agent or an anti-sticking agent, which is generally not included in the list of plastic additives. 2. Internal lubricants Internal lubricants are used to reduce the friction between resin macromolecules during plastic melt processing, reduce melt viscosity, and increase the fluidity of molten materials, which is beneficial to plastic processing. The requirements for the internal lubricant are: it should have appropriate compatibility with the resin macromolecules, and the compatibility at room temperature is small. With the increase of temperature, the compatibility increases. At the melting temperature of the polymer, it has better compatibility with it. compatibility. The difference between internal lubricants and plasticizers is that although internal lubricants can promote the flow of plastic fluids, they do not affect the physical and mechanical properties of the material in the solid state, because the amount of lubricants is very small, generally only a few thousandths of the ingredients. , far less than the amount of plasticizer. Internal lubricants can only be added to plastic formulations. Most lubricants have the dual functions of internal and external lubricants. 2. Varieties of lubricants Lubricants for plastics include the following types of compounds. 1. Fatty acids and their esters For example, the most commonly used ones are stearic acid CH3(CH2)16COOH, 12-hydroxystearic acid CH3(CH2)10CHOH(CH2)5COOH, 9,10-dihydroxystearic acid CH3(CH2 ) 7CHOHCHOH(CH2)7COOH, methyl stearate CH3(CH2)16COOCH3, butyl stearate CH3(CH2)16COO(CH2)3CH3, methyl 2-hydroxystearate CH3CHOH(CH2)15COOCH3, etc. 2. The commonly used varieties of fatty acid amides are: stearic acid amide, oleic acid amide, palmitic acid amide CH3(CH2)14CONH2, caprolamide CH3(CH2)4-CONH2, caprylamide CH3(CH2)6CONH2, capric amide CH3 (CH2) 8CONH2 etc. 3. Metal soaps Stearates of metals such as calcium, magnesium, barium, lithium, zinc, and lead are all external lubricants for plastics. In addition, lead n-octoate, lead laurate, and lead myristate are also commonly used lubricants. 4. Hydrocarbon hydrocarbon lubricants include paraffin (the main component is alkane with a carbon number of 18-30, and the molecular weight is about 250-450), liquid paraffin (alkane with a carbon number of about 10-18, and a molecular weight of about 10-18). between 150-250) and polyethylene wax (low molecular weight polyethylene with average molecular weight between 1500-5000). 5. Silicone organic compounds Mainly methyl silicone oil (polydimethylsiloxane) and ethyl silicone oil (polydiethylsiloxane). It should be pointed out that MoS2, graphite, etc., which are used for plastic friction parts (such as gears and bearings) to reduce friction and wear, can also be included in the list of external lubricants, but are generally not included in the category of plastic additives. Company website:
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