Share on Facebook Share on Twitter Email
Answers.com

adhesion

 
Dictionary: ad·he·sion   (ăd-hē'zhən) pronunciation
n.
  1. The act or state of adhering.
  2. Attachment or devotion; loyalty.
  3. Assent or agreement to join.
  4. Medicine.
    1. A condition in which bodily tissues that are normally separate grow together.
    2. A fibrous band of scar tissue that binds together normally separate anatomical structures.
  5. Physics. The physical attraction or joining of two substances, especially the macroscopically observable attraction of dissimilar substances.

[French adhésion, from Latin adhaesiō, adhaesiōn-, from adhaesus, past participle of adhaerēre, to adhere. See adhere.]


Search unanswered questions...
Enter a question here...
Search: All sources Community Q&A Reference topics
Thesaurus: adhesion
Top

noun

    The close physical union of two objects: adherence, bond, cohesion. See connect.

Dental Dictionary: adhesion
Top
(adh′zhən)
n

1. the attraction of unlike molecules for one another. 2. the molecular attraction existing between surfaces in close contact. 3. the condition in which a material sticks to itself or another material. 4. the abnormal joining of tissues, generally by fibrous connective tissue, to each other after repair of an injury.

Architecture: adhesion
Top


1. The joining of two surfaces as pieces of wood, metal, plastic, or other construction materials, by means of a viscous, sticky composition such as cement or glue.
2. The sticking together of two surfaces by means of physical and chemical forces such as those which bind a paint film to a surface.


An abnormal union of separate tissues, commonly resulting from inflammation or haemorrhage. Adhesions may affect the synovial membranes of joints or form in and around muscle after a sports injury. Manipulation is often necessary to breakdown an adhesion and prevent loss of normal function. Many sports doctors advocate aggressive rehabilitation involving early mobilization (e.g. by using continuous passive motion exercises on the injured joint) to minimize the formation of adhesions.

Science Dictionary: adhesion
Top

The molecular (see molecule) attraction that holds the surfaces of two dissimilar substances together. (Compare cohesion.)

Veterinary Dictionary: adhesion
Top

Union of two surfaces that are normally separate; also, any fibrous band that connects them. Surgery within the abdomen sometimes results in adhesions. As an organ heals, fibrous scar tissue forms around the incision. Fibrinous exudate and scar tissue may cling to the surface of adjoining organs, causing them to kink. Adhesions are usually painless and cause no difficulties, although occasionally they produce obstruction or malfunction by distorting the organ. They can also occur following peritonitis and other inflammatory conditions. They may also occur in the pleura, in the pericardium, and around the pelvic organs. Surgery is sometimes recommended to relieve adhesions.

  • bowel a. — see peritoneal adhesion (below).
  • cervical a's — adhesions in the uterine cervix; they usually result from infection and in mares encourage the development of pyometra.
  • interthalamic a. — the midline union of the two halves of the thalamus; during development of the brain the two thalami encroach into the primitive disk-shaped third ventricle transforming it into a ring.
  • intestinal a. — takes the form of nonelastic bands between loops of intestine or between the intestine and other organs, or of constricting bands around the intestine. They often cause no clinical signs. Long bands may cause intermittent colic due to obstruction of the intestinal lumen which is relieved spontaneously. When they are not relieved they are life-threatening. Cicatricial bands within the wall of the intestine are more likely to cause persistent, subacute abdominal pain. See also equine colic.
  • pericardial a's — fibrous adhesions that restrict the action of the heart and that follow late stages of pericarditis. This may cause cardiac inefficiency that leads to congestive heart failure.
  • peritoneal a. — part of the healing process in peritonitis, and disruption by surgical means or by violent activity may result in recrudescence of peritonitis. In the late cicatrization stage, adhesions may, by contraction, cause partial obstruction of the intestine and chronic or intermittent pain; a common cause of chronic colic in horses.
  • pleural a. — develops in the healing stages of pleurisy but is soon attenuated by constant thoracic movement and causes little respiratory insufficiency.
  • reticular a. — if extensive, can restrict the movements of the reticulum so much that the reticular groove cannot open to allow emptying of the rumen through the reticulo-omasal orifice. Chronic distention and frothy bloat result.
  • vaginal a's — common only in mares. Interfere with mating by preventing penetration of the penis, or with fertilization by blocking the movement of spermatozoa. Vaginal and rectal examination reveal bands of adhesion across the passage, or transverse partitions that completely block it. In the latter there may be an accumulation of exudate or secretion cranial to it. Three-dimensional adhesions convert the vagina into a solid mass with a similar obstructive effect. See also vaginal.
Wikipedia: Adhesion
Top
Dew drops adhering to a spider web

Adhesion is the tendency of certain dissimilar molecules to cling together due to attractive forces. In contrast, cohesion takes place between similar molecules.

Contents

Mechanisms of adhesion

Cohesion causes water to form drops, surface tension causes them to be nearly spherical, and adhesion keeps the drops in place.
Water droplets are flatter on a Hibiscus flower which shows better adhesion.

Five mechanisms of adhesion have been proposed to explain why one material sticks to another:

Mechanical adhesion

Adhesive materials fill the voids or pores of the surfaces and hold surfaces together by interlocking. Sewing forms a large scale mechanical bond, velcro forms one on a medium scale, and some textile adhesives form one at a small scale. This is similar to surface tension.

Chemical adhesion

Two materials may form a compound at the join. The strongest joins are where atoms of the two materials swap (ionic bonding) or share (covalent bonding) outer electrons. A weaker bond is formed if a Hydrogen atom in one molecule is attracted to an atom of Nitrogen, Oxygen, or Fluorine in another molecule, a phenomenon called Hydrogen bonding.

Dispersive adhesion

In dispersive adhesion, also known as physisorption, two materials are held together by van der Waals forces: the attraction between two molecules, each of which has a regions of slight positive and negative charge. In the simple case, such molecules are therefore polar with respect to average charge density, although in larger or more complex molecules, there may be multiple "poles" or regions of greater positive or negative charge. These positive and negative poles may be a permanent property of a molecule (Keesom forces) or a transient effect which can occur in any molecule, as the random movement of electrons within the molecules may result in a temporary concentration of electrons in one region (London forces).

In surface science, the term "adhesion" almost always refers to dispersive adhesion. In a typical solid-liquid-gas system (such as a drop of liquid on a solid surrounded by air) the contact angle is used to quantify adhesiveness. In the cases where the contact angle is low, more adhesion is present. This is due to a larger surface area between the liquid and solid and results in higher surface energy. The Work of Adhesion explains the interactive force between the liquid and solid phases and the Young-Dupree equation is used to calculate the Work of Adhesion. The contact angle of the three-phase system is a function not only of dispersive adhesion (interaction between the molecules in the liquid and the molecules in the solid) but also cohesion (interaction between the liquid molecules themselves). Strong adhesion and weak cohesion results in a high degree of wetting, a lyophilic condition with low measured contact angles. Conversely, weak adhesion and strong cohesion results in lyophobic conditions with high measured contact angles and poor wetting.

Electrostatic adhesion

Some conducting materials may pass electrons to form a difference in electrical charge at the join. This results in a structure similar to a capacitor and creates an attractive electrostatic force between the materials.

Diffusive adhesion

Some materials may merge at the joint by diffusion. This may occur when the molecules of both materials are mobile and soluble in each other. This would be particularly effective with polymer chains where one end of the molecule diffuses into the other material. It is also the mechanism involved in sintering. When metal or ceramic powders are pressed together and heated, atoms diffuse from one particle to the next. This joins the particles into one.

What makes an adhesive bond strong?

The strength of the adhesion between two materials depends on which of the above mechanisms occur between the two materials, and the surface area over which the two materials contact. Materials that wet against each other tend to have a larger contact area than those that don't. Wetting depends on the surface energy of the materials. Well-known examples of adhesion are tape, glue, and stickers.

See also

References

  • John Comyn, Adhesion Science, Royal Society of Chemistry Paperbacks, 1997
  • A.J. Kinloch, Adhesion and Adhesives: Science and Technology, Chapman and Hall, 1987

External links

  • Definition of dispersive adhesion Glossary definition of related surface science terms including dispersive adhesion, Work of Adhesion, wettability, cohesion, and surface energy, with diagrams.

Translations: Adhesion
Top

Dansk (Danish)
n. - fastklæben, fastklæbning

Nederlands (Dutch)
vergroeiing (door verwonding), het vastkleven, het kleverig zijn, contact tussen wielen en wegdek, (het geven van) steun

Français (French)
n. - (Méd, Tech) adhérence, (fig) adhésion

Deutsch (German)
n. - Verwachsung, Zusammenwachsen

Ελληνική (Greek)
n. - προσκόλληση, στερεή εφαρμογή (κν. γερό πιάσιμο), (ιατρ.) σύμφυση

Italiano (Italian)
adesione, aderenza, saldatura

Português (Portuguese)
n. - adesão (f) (Fís.) (Med.), aderência (f), fidelidade (f)

Русский (Russian)
прилипание, притяжение, сцепление

Español (Spanish)
n. - adhesión, cicatrización, adherencia

Svenska (Swedish)
n. - vidhäftningsförmåga

中文(简体)(Chinese (Simplified))
粘着, 皈依, 固守, 附着

中文(繁體)(Chinese (Traditional))
n. - 黏著, 皈依, 固守, 附著

한국어 (Korean)
n. - 접착[력], 유착, 응착, 착생

日本語 (Japanese)
n. - 付着, 粘着, 癒着

العربيه (Arabic)
‏(الاسم) إلتصاق, إلتحام‏

עברית (Hebrew)
n. - ‮דבקות, דביקות, תמיכה, הידבקות (של שטחי-פנים בשל פציעה או דלקת), שמירה על היצמדות בין צמיגים לכביש‬


 
 

 

Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Thesaurus. Roget's II: The New Thesaurus, Third Edition by the Editors of the American Heritage® Dictionary Copyright © 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Architecture. McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Science Dictionary. The New Dictionary of Cultural Literacy, Third Edition Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Adhesion" Read more
Translations. Copyright © 2007, WizCom Technologies Ltd. All rights reserved.  Read more