Polyisoprene

Polyisoprene (IR)
The polyisoprene (IR) is the synthetic version of natural rubber, polymerized with a Ziegler catalyst have "cis" contents of about 98%. The last few percentages of non-cis polymer, which makes IR different from natural rubber (NR), are very important for the physical properties of vulcanizates. Among the various types, 1,4-cis polyisoprene is the most important because of the elastic and mechanical properties it imparts to vulcanization, properties that derive from the high degree. of isomeric purity of the material which, in the case of natural rubber, is constituted by values greater than 99% by the 1,4-cis unit. The prefix ¨cis¨ indicates that the methyl group and a hydrogen atom are on the same side of the C = C double bond, ¨1, 4¨ indicates that the chemical units that are repeated in the polymer chain are covalently bound to the first and fourth carbon atoms. The very high isomeric purity of the natural polymer determines its remarkable tendency to crystallize already at room temperature; The maximum degree of crystallinity that the material can have is limited to 25-30%, a value more than enough to increase its Mooney hardness and viscosity over time.
Symbols			Structure
IR PI 1,3-butadiene, Isopentadiene Beta-methylbivinyl 2-methylbutadiene 2-methyl-1,3-butadiene; 2-methyldivinyl; 2-methylethene Nsc 9237 Cis -1,4- polyisoprene 2 methylbutadiene Polyisoprene Polyisoroprene rubber Cas nr- 78-79-5 C₅H8
Characteristics of Polychloroprene rubber
Good chemical resistance High resistance to aging and ozone Better wear resistance than natural rubber (NR) Cost higher than that of natural rubber (NR) Hardness 20 ÷ 95 ShA It is self-extinguishing and does not spread the flame Good mechanical and abrasion properties Acceptable resistance in vulcanizates with hardness from 60º Shore Conveniently protected presents a good resistance to temperature and ozone Hardness 20 ÷ 90 Sh Working temperature -20 +100 ° C (with tips of 120 ° C) Glass transition temperature -50 ° C
Rubber Physical-Mechanical properties Polychloroprene
Excellent mechanical properties, excellent resistance to abrasion, tearing and fatigue. Excellent resistance to UV radiation, ozone, oxygen, atmospheric agents and hot aging, but hardened by prolonged reductions in the presence of oxygen. Discrete resistance at low temperatures, high impermeability to many gases. The vulcanized chloroprene rubber with ordinary composition shows a tendency to absorb water; when it is a problem, it is less than NBR and SBR.
Applications of rubber Polysoroprene
Polyisoprene, with a very low level of branching and a relatively narrow molecular weight distribution that contributes to a lower heat buildup compared to natural rubber. For this reason, certain grades of polyisoprene can be used without sacrificing abrasion resistance, groove cracking, rib tearing, cold bending properties or weather resistance. Footwear and mechanical goods are also important uses. Due to the high purity of the polyisoprene and the high tensile strength of the rubber (without filler) of its compounds, it is widely used in medical products and articles in contact with food. These include nipples for baby bottles, milk tubes and hospital sheets.