Oil–Extended Natural Rubber (OENR)
Petroleum oils are used in rubber, either as a process aid or as an extender. When the oil added is below 10 parts per hundred rubber it is termed as process aid and above that is termed extender, which cheapens the product. Natural rubber, which contains oil as an extender is termed oil extended natural rubber. In tyres OENR can impart high skid resistance on wet road, and resistance to wear and groove cracking. Oil addition to rubber can be carried out in latex or dry stage.
Latex Carbon Black Masterbatch
It is made by mixing carbon black in the form of dispersion in latex and the resultant rubber-black mixture is coagulated, dried and baled. Latex stage mixing of carbon black in rubber can save energy.
Thermoplastic Natural Rubber (TPNR)
Thermoplastic elastomers (TPE) are a new class of materials which posses the processing characteristics of thermoplastics and properties of vulcanised rubbers at room temperature. TPEs can soften reversibly with heat like thermoplastics, but possess considerable resilience and flexibility, a characteristic of vulcanised rubbers. Thermoplastic natural rubber made from a blend of NR and polypropylene (PP) with certain definite composition can function as a TPE. The elastic properties of TPNR could be improved, with partial crosslinking of the rubber phase, known as dynamic vulcanisation. TPNR is generally resistant towards heat and ozone. TPNR may find application in footwear, sports goods, automobiles etc.
Superior Processing (SP)Natural Rubber
Superior processing (SP) rubber consists of an intimate mixture of vulcanised and unvulcanised rubber. It is made by mixing vulcanised latex with preserved field latex in different proportions, followed by coagulation and drying. Typical grades are SP 20, PA 80 and PA 57. SP 20 – A blend that contains 20 parts vulcanised and 80 parts unvulcanised NR. It is available in sheet and crepe forms. PA 80 – A blend of 80 parts vulcanised and 20 parts unvulcanised NR. PA-57 – An oil extended version of PA 80. Superior processing rubbers find application in extruded products as it can reduce die swell, especially in lightly filled components.
Deproteinized Natural Rubber (DPNR)
DPNR is a highly purified form of natural rubber with very low nitrogen and ash contents. It is suitable for electrical and engineering applications. Removal of proteins from NR reduces its moisture sensitivity thereby improving its engineering properties. Deproteinization is usually effected by an enzymic means. Enzymes hydrolyse the proteinaceous non-rubber materials into water soluble forms, which are then washed away during subsequent processing.