What is strain induced crystallization?

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, as well as other elastomers and polymers. The phenomenon has important effects on strength and fatigue properties.

Is natural rubber crystalline?

Natural rubber becomes crystalline when stretched or when cooled, yet the structure of this ordered form has never been satisfactorily determined.

What is strain induced?

Strain-induced crystallisation (SIC) is the phenomenon of elastomers to experience a pronounced nonlinearity under large deformations of several hundred percentages of strain, which is advantageous for industrial applications due to the resulting positive properties such as increasing crack growth resistance and …

Can rubber crystalize?

The tough elastic properties of natural rubber (NR) are thought to originate from its ability to crystallize rapidly upon stretching, which has been known since the 1920s.

How do polymers crystallize?

Polymers can crystallize upon cooling from melting, mechanical stretching or solvent evaporation. Crystallization affects optical, mechanical, thermal and chemical properties of the polymer.

What is the composition of natural rubber?

Natural rubber consists almost entirely of the cis-1,4 structure and hence is, chemically, cis-1,4 polyisoprene. When the chain units in a polymer consists of the same isomer it is said to be stereoregular.

Is natural rubber a natural polymer?

Rubber can be found in nature and harvested as a latex (milky liquid) from several types of trees. Natural rubber coming from tree latex is essentially a polymer made from isoprene units with a small percentage of impurities in it.

How does vulcanization process take place?

Vulcanization is a chemical process in which the rubber is heated with sulphur, accelerator and activator at 140–160°C. The process involves the formation of cross-links between long rubber molecules so as to achieve improved elasticity, resilience, tensile strength, viscosity, hardness and weather resistance.

What ingredient is a must as compounding agent for chloroprene rubber?

Firstly, volatile ingredients that may exist in CR include mainly chloroprene monomer (CM), toluene and butadiene (BD), in most cases, in addition to some lead-containing products (i.e., lead oxide) used as compounding agents, and thiourea and lead from the curing system (Ethylene Thiourea, Report on Carcinogens, 2002) …

Which polymer is more likely to crystallize?

Linear polymers are more likely to crystallize that branched ones. In addition, polymers having isotactic structures will normally have a higher degree of crystallinity that those having atactic structures. Increasing a polymer’s crystallinity leads to an increase in its tensile modulus.

What makes a polymer more likely to crystallize?

Structural Regularity. To crystallize a polymer chain must be linear, although limited crystallization can take place if a small number of branches are present. Crystallization is favored by a regular arrangement along the polymer chain giving the structure a high degree of symmetry.

How is natural rubber processed?

Rubber processing consists of four basic steps: (1) mastication, when the elastomer is sheared and the molecules are broken down to give easier flow, (2) mixing, usually carried out immediately after mastication, when additives are incorporated, (3) shaping of the viscous mass, for example, by extrusion or molding, and …

Does strain-induced crystallization occur in natural rubber?

Strain-induced crystallization (SIC) of natural rubber (NR) samples with different strain rates at a fixed strain was investigated by synchrotron radiation X-ray diffraction measurements, which provided the evolution trends of crystal sizes and crystallinity during the SIC process.

What is the crystallization of rubber?

Rubber is an indispensable raw material due to its high elasticity. Several types of rubber can crystallize when exposed to external stretching, 1, 2, 3, 4 such as natural rubber (NR), polychloroprene rubber and polyisoprene rubber (IR).

What can we learn from strain-induced crystallization for advanced industrial applications?

For some particular applications, strain-induced crystallization has resulted in the development of polymers for advanced industrial applications, which are briefly summarized at the end of the chapter. 1. Introduction

Can X-ray diffraction detect strain-induced crystallization of rubber?

Toki, S., Fujimaki, T. & Okuyama, M. Strain-induced crystallization of natural rubber as detected real-time by wide-angle X-ray diffraction technique. Polymer 41, 5423–5429 (2000).