Lubricants exudation

Visible exudation or efflorescence on the surface of a plastic caused by plasticizer, lubricant, etc. Spacer or filler material in a mold. 

Additive, slip An additive modifier that acts as an internal lubricant which exudes to the surface of the plastic during and immediately after processing providing the necessary lubricity to reduce or eliminate coefficient of friction in molded parts, film, etc. products. 

On a related theme, we can take advantage of the diffusion of molecules incorporated into a polymer to its surface. Thus we can blend lubricants, bactericides, and antiblock agents into polymers, which slowly exude to the surface where they perform a useful role. 

Originally a mixture of 88% cyclonite with 12% lubricating oil was employed. This mass however was not sufficiently plastic and lost its plasticity readily by exuding the oil at a high temperature. It was therefore replaced by a mixture named Composition C-3 of 77% cyclonite and 23% gel made out of liquid nitro compounds (e.g. liquid DNT) and nitrocellulose or of butyl phthalate and nitrocellulose. 

The pleural, pericardial, and peritoneal cavities normally contain a small amount of serous fluid that lubricates the opposing parietal and visceral membrane surfaces. Inflammation or infections affecting the cavities cause fluid to accumulate. The fluid may be removed to determine if it is an effusion or an exudate, a distinction made possible by protein or enzyme analysis. The collection procedure is called paracentesis. When specifically apphed to the pleural cavity, the procedure is a thoracentesis if applied to the pericardial cavity, a pericardiocentesis. Paracenteses shordd be performed only by sldlled and experienced physicians. Pericardiocentesis has now been largely supplanted by echocardiography. 

The mechanism of plate-out is still unknown. A stieky deposit is formed on the surface of calender rolls which require cleaning. The deposit is also transferred to the product leaving marks, blemishes, or stains on the product s surface. These deposits are most likely due to incompatibility of stabilizers and lubricants which exude to the surface. Changes in temperature and pressure are considered to trigger the processes of separation... 

Hand Layup (Contact Molding or Open Mold Process). The oldest and simplest technique is primarily manual. An open mold is waxed to lubricate it. The surface of the proposed product is applied to the mold, usually as an unreinforced gel coat or sometimes as a thermoformed plastic sheet. A layer of fabric is hand cut and hand laid into the mold. Catalyzed resin is poured over the fabric and worked into it with brush, roUer, and squeegee to eliminate air bubbles. Another layer of fabric is laid over this, often oriented in a specific direction to optimize properties. Again, catalyzed resin is poured over it and worked into it. The process is repeated as many times as required to build up the desired thickness and optimum orientation of the layers. If the cure reaction is inhibited by air, a wax may be dissolved in the resin it exudes to the surface and forms a barrier to exclude air and permit complete cure. The resin may be allowed to cure at room temperature, or the assembly may be heated to complete or hasten the cure reaction. 

Slip agents are added to polymers for film production. They exude to the surface of the film and lubricate if keeping the films from sticking to each other and making it easier for them to slide over each other and to separate from each other. This is helpful in processing, both for speeding production and to avoid distortion. 

It is common to distinguish between internal and external lubricants. The worst definition is based on who adds the lubricant if the supplier added it, it comes to the processor as an internal lubricant if the processor must add it himself, it is an external lubricant. A semimeaningful distinction an internal lubricant is compounded into the polymer an external lubricant is applied to the surface of the mold. The proper distinction is based on miscibility/immiscibility of the additive in the polymer an internal lubricant is miscible with the polymer and acts like a small amount of plasticizer to increase molecular flexibility and mobility, and to help the disentanglement and flow of tbe polymer molecules in the melt. An external lubricant is immiscible in the polymer and tends to exude to the surface of the plastic and form an abhesive (nonstick) interface between the polymer and the steel process equipment, or it tends to come to the surface of the finished plastic product and give it continual lubricity in the use of the product. 

Some lubricants are purely internal some are purely external. Many exhibit a balance of intemal/extemal activity, which depends both on the lubricant and on the polymer in which it is used. This depends on the relative polarity of the polymer and the lubricant. If they have very similar polarity, the lubricant is completely soluble in the polymer and acts as an internal lubricant. If they have very different polarity, the lubricant is insoluble in the polymer and exudes to the surface, where it acts as an external lubricant. If the lubricant... 

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