Why vulcanization is important

The active sites are allylic hydrogen atoms; that means they are hydrogen atoms connected to the first saturated carbon atom connected to the carbon-carbon double bond. During vulcanization the eight-membered ring of sulfur breaks down in smaller parts with one to eight sulfur atoms. These small sulfur chains are quite reactive.

At each cure site on the rubber molecule, such short sulfur chain can attach itself, and eventually reacts with a cure site of another rubber molecule, and so forming a bond between two chains. This is named a cross-link. These sulfur bridges are typically between two and eight atoms long.

The number of sulfur atoms in a sulfur crosslink has a strong influence on the physical properties of the final rubber article.

Short sulfur crosslinks, with just one or two sulfur atoms in the crosslink, give the rubber a very good heat resistance. Crosslinks with higher number of sulfur atoms, up to six or seven, give the rubber very good dynamic properties but with lesser heat resistance.

Dynamic properties are important for flexing movements of the rubber article, e. Without good flexing properties these movements will rapidly lead to formation of cracks and, ultimately, to failure of the rubber article. There are various vulcanization methods. The economically most important method i. A typical vulcanization temperature for a passenger tire is 10 minutes at dgrees C. This type of vulcanization is an example of the general vulcanization method named compression moulding.

The rubber article is intended to adopt the shape of the mold. Other methods for instance those used to make door profiles for cars use hot air vulcanization or microwave heated vulcanization both continuous processes. Although vulcanization is a 19th century invention, the history of rubber cured by other means goes back to prehistoric times. The name "Olmec" means "rubber people" in the Aztec language. Ancient Mesoamericans, spanning from ancient Olmecs to Aztecs, extracted latex from Castilla elastica , a type of rubber tree in the area.

The juice of a local vine, Ipomoea alba , was then mixed with this latex to create an ancient processed rubber as early as BC [1]. The first reference to rubber in Europe appears to be in , when Edward Nairne was selling cubes of natural rubber from his shop at 20 Cornhill, London. The cubes, meant to be erasers, sold for the astonishingly high price of 3 shillings per half-inch cube. In the early 19th century rubber was a novelty material, but it did not find much application in the industrial world.

It was used first as erasers, and then as medical devices for connecting tubes and for inhaling medicinal gases. With the discovery that rubber was soluble in ether , it found applications in waterproof coatings, notably for shoes and soon after this, the rubberized Mackintosh coat became very popular. Nevertheless, most of these applications were in small volumes and the material did not last long. The reason for this lack of serious applications was the fact that the material was not durable, was sticky and often rotted and smelled bad because it remained in its uncured state.

Most textbooks point out that Charles Goodyear — invented vulcanization of rubber as used today by the addition of sulfur in high heat. Depending on what you read, the Goodyear story is one of either pure luck or careful research. Goodyear insists that it was the latter, though many contemporaneous accounts indicate the former. Goodyear claimed that he discovered vulcanization in , but did not patent the invention until June 15, , and did not write the story of the discovery until in his autobiographical book Gum-Elastica.

Describe about tetrahalides, Q. S, Se, Te Functions of triglycerides - biomolecules, functions of triglycerides T Write Your Message! Email id. Verfication Code. Featured Services. Online Tutoring. Project Development. Exam Preparation. Course Help. Assignment Help. Popular Subjects. HR Management. Computer Science. Web Design. Submit Assignment. The essence of the rubber vulcanization process are as followings.

Therefore, the vulcanization now refers to the crosslinking process between many chemicals, including sulfur and rubber. Vulcanization is the last process where rubber products manufacturing process.

During the process, the rubber undergoes a complex series of chemical changes. From ancient Mexican civilisations to modern-day tyre manufacture, the story of vulcanised rubber stretches back thousands of years. Along the way, such notable luminaries as Charles Goodyear and Charles Macintosh played a major role in its development. Vulcanisation is the process of curing elastomers. It involves the treatment of natural rubber with sulphur or other curatives such as peroxide and metal oxides to form cross-links between sections of a polymer chain to produce a rubberised material boasting excellent rigidity and durability.