Lubricant bloom

Lubricant bloom See bloom. The term lubricant bloom should only be used when the exudation is known to be caused by a lubricant contained in the plastic compound or applied to it during processing. 

Bloom Visible exudation or efflorescence on the surface of a plastic caused by plasticizer, lubricant, etc. 

Although we made no attempt to elucidate the mechanism of friction decreases in rubbers after surface fluorination, it seems to us that apart from the substitution of H atoms to F in the polymer macromolecule, which forms a fluoropolymer on the surface, there is another phenomenon that makes a significant contribution to the friction decreases, i.e., fluorination of carbon black, which is used in rubber recipes for reinforcement. It appears that when the carbon black in the surface of the rubber is fluorinated it produces a lubricating effect, followed by blooming on the surface of the treated rubber while it is under a friction load. So, in our opinion, two effects contribute to friction decrease of carbon-filled rubbers fluorination of the rubber macromolecules and fluorination of the carbon black rubbers that do not contain carbon black show a much smaller decrease in friction after XeF2 treatment. 

Slip additives act at the surface of a polymer film or article to reduce the friction between it and another surface. In a variety of plastics, such as polyolefins, polystyrene, and polyvinyl chloride, fatty-acid amides are applied as slip additives. Fatty-acid amides, such as oleamide, stearamide, erucamide, and oleyl palmitamide, are added to plastic formulations where they gradually tend to bloom to the surface, imparting useful properties including lubrication, prevention of films sticking together, and reduction of static charge. 

Three properties that contribute the most to migration are (1) incompatibility with the resin, (2) low melt point, and (3) low molecular weight. Examples of noncolorant additives that are prone to migrate are (1) lubricants/dispersants such as metal stearates and bis-stearamides, (2) mold release and slip agents, and (3) antistatic agents. All of these ingredients serve useful purposes in color formulations. If you exceed their solubility limit in the end-use resin, however, you risk blooming and its consequences. 

In PVC-P applications, the plasticiser acts as an internal lubricant and external lubricants can be added to increase output etc. Excessive levels or incorrect choice can cause problems with post treatment, e.g., printing or blooming on ageing. 

Surface treatment can also affect the amount of bloom or surface migration of various active surface agents (lubricants, slip and antislip additives, etc.) and either subsequent migration into a product by surface abrasion or chemical removal, solubility, etc. 

Waxes act as internal lubricants in rubber and increase the scorch safety somewhat. Unfortunately, waxes have a number of shortcomings. First, they are ineffective under dynamic stress conditions. This is likely due to a lack of adhesion between the wax film and the rubber and to the inextensibility of the wax bloom. 

Furthermore, many factors affect the frictional force measured. These include sample hardness, the load and speed used in the test, and the particular material and surface morphology of the surface against which the sample is pressed. Compounding differences of polymer type and especially additives (which can bloom to the surface) have major effects. Lubrication of surfaces by light oils or soapy water can render them very slippery. 

A fully optimized formulation provides high outputs, low scrap rates, high-quality finished products and the required compound physical properties. Deficient or excessive amounts of lubricant lead to reduced processing efficiencies or can even shutdown the operation. A balanced lubricant system (right amounts of both internal and external lubrication) provides control over the compound fusion and thermal stability times, output rate, blooming, compound clarity and physical properties. 

Slip additives are used with packaging plastics such as polyolefins, polystyrene and PVC to impart lubrication, prevent films (such as cling-film) from sticking together and to reduce static charges. They are usually surfactants such as fatty add amides which have the desired rate of blooming to the polymer surface where their action is needed. 

Areas in which X-ray photoelectron spectroscopy might be expected to perform best are the detection of surface effects (e.g. blooming), surface active additives (e.g. release and slip agents, lubricants, surfactants, etc.), rapidly migrating additives (e.g. plasticisers), or thin-film contaminants. XPS detection limits for additives (0.5 vol.%) are unfavourable for... 

Ester lubricants ate based frequently on pentaerythritol. The mixed mono- and distearate ester blend is particularly useful in wire and cable compounds for improving output and providing a smooth surface without bloom. It is often used in combination with low-MW PE wax in high-speed extmsions. Some use has also been made in rigid PVC profile extmsions, for similar reasons. The latter application has also seen use of pentaerythritol tetrastearate, a lubricant of somewhat lower cost than the mono/diblend. The tetrastearate is, however, more external in rigid PVC and thus more prone to bloom or deposit. 

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