NR natural rubber is made from trees that grow in tropical climates. Rubber-bearing plants produce a rubber hydrocarbon, abbreviated as NR. Aqueous colloidal dispersions, or latexes, contain approximately 30-38% solids. Their amount in aqueous dispersions varies and depends on many factors. The content is influenced by the age of the tree and the period of the year when the raw material is harvested. Latex, apart from rubber, also contains resins and proteins, fatty acids, carbohydrates and a small amount of mineral salts. During the coagulation of raw rubber, a number of other substances are precipitated, which can also be used in industry.
Natural rubber is grateful for further chemical treatment. It is very often hydrogenated, chlorinated, and subjected to the processes of hydrogenation, cyclization and reactions with resins. The rubber can be grafted as an adhesive. This material is also subjected to epoxidation, i.e. the oxidation of the double bond in the molecule, thanks to which an epoxide is formed. Epoxy is a resin that can also be used in industry.
What does the abbreviation NR stand for?
Natural rubber is a flexible hydrocarbon polymer derived from latex. Latex is a milky colloid the source of which is rubber trees. Piercing, cutting the bark of a tree causes the sap to ooze, resembling milk. When refining, a rubber with a wide range of applications is obtained. In industry, natural rubber is marked with the abbreviation NR, it is a multiparticulate polymer of isoprene. According to ASTM, it is marked with the symbol 1418 – WR. Trade names under which natural rubber can be found are RSS, SMR, CREPE, DYNAT.
Where does natural rubber come from?
The sticky discharge of caoutchouc plants is the basis for the formation of natural rubber. Many polysaccharides and starch were isolated in their composition. Latexes are obtained when the plant is injured and plant mucus flows out of the injured tissue. The occurring phenomenon consisting in the formation of rubber infiltrates on plants is called gum disease. This process is the plant’s defensive reaction to external injuries. Rubber trees are typical plants planted in industrial plantations. These trees are resistant to the changes of the seasons and do not shed leaves each year. These trees belong to the spurge family and their bark is naturally latex. Only this latex is processed into natural rubber. The use of latex was first mentioned in ancient Indian times, but the real rubber madness started in the 19th century. Currently, natural rubber is used in every area of life.
Latex is produced in milk cells in selected plants, it is created thanks to the transformation of sucrose into a type of polyisoprene. Podczas działania czynników środowiska naturalnego (zakwaszenia lub zmrożenia, dodania soli mineralnych) lateks koaguluje do miękkiego i elastycznego materiału, który stabilizuje się w obecności substancji alikalicznych, jakimi jest na przykład amoniak. The presence of ammonia also blocks spontaneous coagulation. Centrifugation or evaporation of part of the water results in the production of natural latex.
Currently, the basic raw material from which natural rubber is most often produced is Brazilian rubber. This tree can grow up to 30 meters, and it does best in a warm and humid climate. It is not resistant to drought and frost. The flesh of this tree is poisonous due to the content of cyanogenic glycosides, which are released in the form of hydrogen cyanide. This compound is used as an ingredient in paints, varnishes and soaps. The tree can also be used to make animal feed (seed expeller) and use it as fuel. However, the basic material obtained from this tree is latex.
The technology of obtaining natural rubber by emulsion polymerization was patented in 1929.
Natural rubber – Properties
Natural rubber is very flexible. For this reason, it is widely used in everyday life. It is a resilient material. However, it is not stable in an environment of high temperatures. However, it shows good elasticity at low temperatures. It also has good abrasion resistance, which is considered satisfactory in many industries. However, it is not a very resistant rubber. It is also not very resistant to ozone and weather conditions. It is also not fireproof. Swells in the presence of mineral oils, fuels. Natural rubber is much more stable in the presence of alcohols, esters, glycols and ketones.
Natural rubber – Application
Natural rubber is used in the vulcanization industry, especially when it comes to the production of tires, it is often used as a component of adhesives, carpets, paper, rubbers, inner tubes. In principle, in every area of life you can find elements manufactured on the basis of natural rubber.