Bloom (phase)

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In polymer chemistry, materials science, and food science, bloom refers to the migration of one component of a solid mixture to the surface of an article. The process is an example of phase separation or phase aggregation.

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Materials science

EU food contact material symbol: used for marking materials intended to come into contact with food in the European Union as defined in regulation (EC) No 1935/2004 EU food contact material symbol.svg
EU food contact material symbol: used for marking materials intended to come into contact with food in the European Union as defined in regulation (EC) No 1935/2004

Blooming is commonly encountered in polymer additives such as stabilizers. [1] Many polymers are essentially pure hydrocarbons whereas additives are often significantly more polar, this results their being forced out via hydrophobic forces. The blooming of additives may be desirable or undesirable. For example, the migration of antioxidants to the polymer surface may help it resist degradation. Conversely, the leaching of additives from packaging materials into foods, or the blooming of additives in biomedical devices is often of high concern. [2] Regulations exist in many counties that require both the levels of blooming and the materials involved to be of a safe level, for example the international symbol for materials approved for food contact is a wine glass and a fork symbol.

Sulfur bloom

Sulfur bloom refers to the migration of sulfur, usually as S8, to the surface of a rubber article either before or after vulcanization. Blooming is undesirable in rubber processing. When sulfur bloom appears before vulcanization, the rubber is deprived of the crosslinking agent. Sulfur bloom after vulcanization indicates incomplete vulcanization. [3] In rubber processing, ingredients other than sulfur can "bloom", including antioxidants, fatty acids, and accelerators.

Food science

Chocolate bloom

Chocolate bloom refers two types of whitish coating that can appear on the surface of chocolate: fat bloom, caused by changes in the fat crystals in the chocolate; and sugar bloom, due to crystals formed by the action of moisture on the sugar. Chocolate that has "bloomed" remains edible but may have an unappetizing appearance and texture.

See also

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<span class="mw-page-title-main">Vulcanization</span> Process of hardening rubber

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<span class="mw-page-title-main">Ebonite</span> Highly vulcanized rubber that is generically known as "hard rubber"

Ebonite is a brand name for a material generically known as hard rubber, obtained via vulcanizing natural rubber for prolonged periods. Ebonite may contain from 25% to 80% sulfur and linseed oil. Its name comes from its intended use as an artificial substitute for ebony wood. The material has also been called vulcanite, although that name formally refers to the mineral vulcanite.

Bloom or blooming may refer to:

<span class="mw-page-title-main">EPDM rubber</span> Type of synthetic rubber

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<span class="mw-page-title-main">Photodegradation</span> Alteration of materials by light

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<span class="mw-page-title-main">Silicone rubber</span> Elastomer

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<span class="mw-page-title-main">Chocolate bloom</span> Coating that can appear on chocolate

Chocolate bloom is either of two types of whitish coating that can appear on the surface of chocolate: fat bloom, caused by changes in the fat crystals in the chocolate; and sugar bloom, due to crystals formed by the action of moisture on the sugar. Fat and sugar bloom damage the appearance of chocolate but do not limit its shelf life. Chocolate that has "bloomed" is still safe to eat, but may have an unappetizing appearance and surface texture. Chocolate bloom can be repaired by melting the chocolate down, stirring it, then pouring it into a mould and allowing it to cool, bringing the sugar or fat back into the solution.

<i>N</i>-Isopropyl-<i>N</i>-phenyl-1,4-phenylenediamine Chemical compound

N-Isopropyl-N′-phenyl-1,4-phenylenediamine (often abbreviated IPPD) is an organic compound commonly used as an antiozonant in rubbers. Like other p-phenylenediamine-based antiozonants it works by virtue of its low ionization energy, which allows it to react with ozone faster than ozone will react with rubber. This reaction converts it to the corresponding aminoxyl radical (R2N–O•), with the ozone being converted to a hydroperoxyl radical (HOO•), these species can then be scavenged by other antioxidant polymer stabilizers.

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Sulfur vulcanization is a chemical process for converting natural rubber or related polymers into materials of varying hardness, elasticity, and mechanical durability by heating them with sulfur or sulfur-containing compounds. Sulfur forms cross-linking bridges between sections of polymer chains which affects the mechanical and electronic properties. Many products are made with vulcanized rubber, including tires, shoe soles, hoses, and conveyor belts. The term vulcanization is derived from Vulcan, the Roman god of fire.

References

  1. Zweifel, Hans; Maier, Ralph D.; Schiller, Michael (2009). Plastics additives handbook (6th ed.). Munich: Hanser. ISBN   978-3-446-40801-2.
  2. Nouman, Micheal; Saunier, Johanna; Jubeli, Emile; Yagoubi, Najet (September 2017). "Additive blooming in polymer materials: Consequences in the pharmaceutical and medical field". Polymer Degradation and Stability. 143: 239–252. doi:10.1016/j.polymdegradstab.2017.07.021.
  3. Barlow, Fred W. (1993). Rubber Compounding: Principles: Materials, and Techniques (Second ed.). M. Dekker. ISBN   0824789687.