polymer chemistry Polymer chemistry is a sub-discipline of chemistry that focuses on the structures, chemical synthesis, and chemical and physical properties of polymers and macromolecules. The principles and methods used within polymer chemistry are also applic ...

materials science Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries. The intellectual origins of materials sci ...

, and

food science Food science (or bromatology) is the basic science and applied science of food; its scope starts at overlap with agricultural science and nutritional science and leads through the scientific aspects of food safety and food processing, informing ...

, 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 Phase separation is the creation of two distinct Phase (matter), phases from a single homogeneous mixture. The most common type of phase separation is between two immiscible liquids, such as oil and water. This type of phase separation is kn ...

or phase aggregation.

Materials science

Blooming is commonly encountered in

polymer additive Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptabi ...

s such as stabilizers. 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. 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 Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

, usually as S₈, to the surface of a rubber article either before or after

vulcanization Vulcanization (British English: vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to ...

. 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. To prevent sulfur blooming, rubber industry utilizes amorphous, polymeric forms of sulfur referred to as "insoluble sulfur" for sulfur vulcanisation. It remains insoluble in uncured rubber, thereby preventing migration and blooming. In rubber processing, ingredients other than sulfur can also "bloom", including antioxidants, fatty acids, and accelerators.

Food science

Chocolate bloom

{{main, 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.

References

Rubber Sulfur Polymer chemistry

Materials science

Sulfur bloom

Food science

Chocolate bloom

See also

References