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Some types are synthetic liquid lubricants that have been used in the aerospace industry for over 30 years. [1] The main properties of PFPE are being temperature resistant between −58 °C (215 K) and 257 °C (530 K) (depending on specific composites), having very low outgassing compared to other fluids ( vapour pressure of 6 × 10 −8 Torr ...
A highly viscous cubic phase gel made of polysorbate 80, water, and liquid paraffin. Lyotropic liquid crystals result when amphiphiles, which are both hydrophobic and hydrophilic, dissolve into a solution that behaves both like a liquid and a solid crystal. This liquid crystalline mesophase includes everyday mixtures like soap and water. [1] [2]
Consistency and viscosity affect the adhesion and retention property of the gel, and are important in ensuring the gel is retained at the site of application and effective delivery of the drug. [3] The ingredients in topical gel formulation can be broadly categorized into four types: gelator, solvent, drug, and excipients.
Mechanics of gelation describes processes relevant to sol-gel process. In a static sense, the fundamental difference between a liquid and a solid is that the solid has elastic resistance against a shearing stress while a liquid does not. Thus, a simple liquid will not typically support a transverse acoustic phonon, or shear wave. Gels have been ...
The sol–gel process is a wet-chemical technique used for the fabrication of both glassy and ceramic materials. In this process, the sol (or solution) evolves gradually towards the formation of a gel-like network containing both a liquid phase and a solid phase.
CMC serves to both thicken the solution and add a lubricating effect, and often silicone-based lubricants are added for additional lubrication. The most familiar example of this type of lubricant, used as a surgical and personal lubricant , is K-Y Jelly .
Both gas and liquid lubricants can transfer heat. However, liquid lubricants are much more effective on account of their high specific heat capacity. Typically the liquid lubricant is constantly circulated to and from a cooler part of the system, although lubricants may be used to warm as well as to cool when a regulated temperature is required.
At that point in the reaction, which is defined as gel point, the system loses fluidity and viscosity becomes very large. The onset of gelation, or gel point, is accompanied by a sudden increase in viscosity. [3] This "infinite" sized polymer is called the gel or network, which does not dissolve in the solvent, but can swell in it. [4]