Strain
crystallization is a phenomenon in which an initially amorphous solid material undergoes a
phase transformation due to the application of strain. Strain crystallization occurs in
natural rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
, as well as other
elastomers and
polymers.
The phenomenon has important effects on strength and fatigue properties.
How strain crystallization occurs
Strain crystallization occurs when the chains of
molecules in a material become ordered during deformation activities in some polymers and elastomers. The three primary factors that affect strain crystallization are the molecular structure of the polymer or elastomer, the
temperature, and the
deformation
Deformation can refer to:
* Deformation (engineering), changes in an object's shape or form due to the application of a force or forces.
** Deformation (physics), such changes considered and analyzed as displacements of continuum bodies.
* Defo ...
being applied to the material.
If a
polymer's molecular structure is too irregular, strain crystallization can not be induced because it is impossible to order the chains of molecules.
In order to induce strain crystallization, the polymer or elastomer is stretched while its temperature is kept above its
glass transition temperature. It is also necessary for the
yield point
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...
of the polymer to be exceeded by the stretching activity. This in turn will ensure that the chains of molecules are straightened.
In general, the greater the
deformation
Deformation can refer to:
* Deformation (engineering), changes in an object's shape or form due to the application of a force or forces.
** Deformation (physics), such changes considered and analyzed as displacements of continuum bodies.
* Defo ...
applied to the material, the higher the rate of crystallization.
Effects of strain crystallization
The
mechanical properties
A materials property is an intensive property of a material, i.e., a physical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one material versus another ...
of materials are greatly affected by the orientation of the crystals in their
micro-structure.
The process of strain crystallization directly affects the micro-structure of the material by adding crystalline structures. Strain crystallization's effect on the micro-structure greatly increases the strength of the polymer or elastomer it is induced in.
This effect of strain crystallization can be viewed in vulcanized natural rubber, a material that is known for its
toughness and tensile
stress.
Measuring strain crystallization
There are various techniques for measuring crystallization in rubber, including:
x-ray diffraction,
specific heat
In thermodynamics, the specific heat capacity (symbol ) of a substance is the heat capacity of a sample of the substance divided by the mass of the sample, also sometimes referred to as massic heat capacity. Informally, it is the amount of heat ...
changes, and
density changes. Crystallization can also be observed indirectly through its effects on stress–strain and fatigue behavior.
See also
*
Crystallization of polymers
Crystallization of polymers is a process associated with partial alignment of their molecular chains. These chains fold together and form ordered regions called lamellae, which compose larger spheroidal structures named spherulites. Polymers can ...
;Some polymers that strain crystallize
*
Polyethylene
*
Polyethylene Terephthalate
;Some elastomers that strain crystallize
*
Natural rubber
Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
(
polyisoprene
Polyisoprene is strictly speaking a collective name for polymers that are produced by polymerization of isoprene. In practice polyisoprene is commonly used to refer to synthetic ''cis''-1,4-polyisoprene, made by the industrial polymerisation of i ...
)
*
Polychloroprene
Neoprene (also polychloroprene) is a family of synthetic rubbers that are produced by polymerization of chloroprene.Werner Obrecht, Jean-Pierre Lambert, Michael Happ, Christiane Oppenheimer-Stix, John Dunn and Ralf Krüger "Rubber, 4. Emulsion ...
;Some elastomers that do not strain crystallize
*
Polybutadiene
Polybutadiene utadiene rubber BRis a synthetic rubber. Polybutadiene rubber is a polymer formed from the polymerization of the monomer 1,3-butadiene. Polybutadiene has a high resistance to wear and is used especially in the manufacture of tir ...
*
Styrene-butadiene
References
Sources
*Chapter 1, Engineering with Rubber, Ed. A. N. Gent, Hanser, 1992. .
*B. Huneau, STRAIN-INDUCED CRYSTALLIZATION OF NATURAL RUBBER: A REVIEW OF X-RAY DIFFRACTION INVESTIGATIONS, Rubber Chem. Technol. 84, 425 (2011);
*Mars, W. V. (2009). Computed dependence of rubber's fatigue behavior on strain crystallization. Rubber Chemistry and Technology, 82(1), 51–61.
Chapter 10 – Strength of Elastomers A.N. Gent, W.V. Mars, In: James E. Mark, Burak Erman and Mike Roland, Editor(s), The Science and Technology of Rubber (Fourth Edition), Academic Press, Boston, 2013, Pages 473–516, {{ISBN, 9780123945846, 10.1016/B978-0-12-394584-6.00010-8
*Rao, I,J; Rajagopal, K.R. (2001–02). "A study of strain-induced crystallization of polymers". ''International Journal of Solids and Structures. 38 (6-7): 1149-1167 https://doi.org/10.1016/S0020-7683(00)00079-2. ISSN 0020-7683.''
*Battjes, Kevin P.; Kuo, Chung-Mien; Miller, Robert L.; Saam, John C. (1995-05). "Strain-induced Crystallization in Poly
ethyl3,3,3-trifluoropropyl)siloxane] Network". ''Marcromolecules'' 28 (3): 790-792
Strain-Induced_Crystallization_in_Poly[methyl(3,3,3-trifluoropropyl)siloxaneNetworks.html" ;"title="ethyl(3,3,3-trifluoropropyl)siloxane">Strain-Induced Crystallization in Poly[methyl(3,3,3-trifluoropropyl)siloxane
Networks">ethyl(3,3,3-trifluoropropyl)siloxane">Strain-Induced Crystallization in Poly[methyl(3,3,3-trifluoropropyl)siloxane
Networks ISSN 0024-9297
*Toki, S.; Fujimaki, T.; Okuyama, M. (2000–06). "Strain-induced crystallization of natural rubber as detected real-time by wide-angle X-ray diffraction technique". ''Polymer.'' 41 (14): 5423-5429
Strain-induced crystallization of natural rubber as detected real-time by wide-angle X-ray diffraction technique ISSN 0032-3861.
*"Crystallization". ''polymerdatabase.com''. Retrieved 2018-12-08.
Rubber properties