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Strain crystallization is a phenomenon in which an initially amorphous solid material undergoes a crystal phase transformation due to the application of strain. Strain crystallization occurs in natural rubber, as well as other elastomers and polymers. The phenomenon increases the strength and fatigue properties of the material..

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 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 of the polymer to be exceed by the stretching activity. This in turn will ensure that the chains of molecules are straightened. In general, the greater the deformation applied to the material, the higher the rate of crystallization.

Effects of Strain Crystallization
The mechanical properties of materials are greatly affected by the 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 affect 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 changes, and density changes. Crystallization can also be observed indirectly through its effects on stress–strain and fatigue behavior.

Some Polymers that Strain Crystallize

 * Polyethylene
 * Polyethylene Terephthalate

Some Elastomers that Strain Crystallize

 * Natural rubber (polyisoprene)
 * Polychloroprene

Some Elastomers that do not Strain Crystallize

 * Polybutadiene
 * Styrene-butadiene

Plans and Sources
Strain Crystallization

Elastomers that strain crystallize

Elastomers that do not strain crystallize

Add information regarding how strain crystallization is done (the process behind it).

More detail regarding how strain crystallization affects the material.

Check citation regarding the kinds of elastomers that do or do not strain crystallize

Explain why some elastomers strain crystallize and why some do not.

Do other kinds of materials (polymers) experience this.

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Sources to use:

A study of strain-induced crystallization of polymers

https://doi.org/10.1016/S0020-7683(00)00079-2

Strain-induced crystallization of natural rubber as detected real-time by wide-angle X-ray diffraction technique

https://doi.org/10.1016/S0032-3861(99)00724-7

Strain-Induced Crystallization in Poly[methyl(3,3,3-trifluoropropyDsiloxane] Networks1

https://pubs.acs.org/doi/pdf/10.1021/ma00107a019

Effect of draw ratio and temperature on the strain-induced crystallization of poly (ethylene terephthalate) at fast draw rates

https://doi.org/10.1016/S0032-3861(98)00770-8

Elastomers that strain crystallize.
Vulcanized Rubber (Toki)

Natural Rubber (Hevea) (Toki)

Polymers that Strain crystallize.
polyethylene (Rao)

polyethylene terephthalate (Rao)

Products that contain Strain crystallized material.
Plastic bottles (Rao)

Add information regarding how strain crystallization is done (the process behind it).
Semi-crystalline materials can be created from multiple kinds of polymers (Rao).

The amorphous or semi-crystalline micro structure of polymer depends on the molecular structure as well as the cooling rate (Rao).

It has been demonstrated that the rate of crystallization is enhanced due to flow, and is accelerated by deformation by multiple studies (Rao).

Stretch a film of at a constant rate of extension, this creates a rapid increase in stress as crystallization begins (Rao).

In experiment with a constant stretching force, it takes extreme amounts of deformation to enact crystallization (Rao).

Crystallization by deformation in rubber has been studied numerous times (Toki).

At 200% strain at 25°C, strain induced crystallization begins in rubber (Toki).

When retracting after applying a load, crystallization continues to occur (Toki).

Temperature in itself can induce crystallization (toki).

Strain crystallization when the chains of molecules in a material are ordered as the material is stretched (Kevin).

More detail regarding how strain crystallization affects the material.
The mechanical properties of the materials is greatly affected by the orientation of the crystals (Rao).

The strength of the material can exponentially increase when undergoing strain crystallization (Rao).

The ext ream toughness and tensile stress associated with vulcanized natural rubber is because of the strain induced crystallization that it experiences (Toki).

Explain why some strain crystallize and why some do not.
Polymers are able to strain crystallize when there molecular structure is regular. polymers with irregular molecular structures are unable to crystallize because it is to random to organize into packing (Rao).