NR is a natural product and is produced from the white milky juice (latex) of the rubber tree. The artificially manufactured kind is designated isoprene rubber (IR) and is made up of isoprene (2-methyl-1,3-butadiene) as a monomer. NR is an entirely 1,4 cis isomer. The 1,4 polyisoprene is also a natural product called gutta-percha. For more on cis-trans isomerism. Carbon black is often added in order to increase the tensile strength and abrasion resistance of the material, as well as for coloring.
|DSC 204 F1 Phoenix®
|IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase
|Al, pierced lid
|N2 (40 ml/min)
Natural rubber (NR) is mainly amorphous with a small amount of crystalline (hard) segments. This can be seen from the Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.glass transition step at -63°C (2nd heating, red, midpoint) which is overlapped by an enthalpy RelaxationWhen a constant strain is applied to a rubber compound, the force necessary to maintain that strain is not constant but decreases with time; this behavior is known as stress relaxation. The process responsible for stress relaxation can be physical or chemical, and under normal conditions, both will occur at the same time. relaxation, and from the shallow, broad melting transition between -10°C and 50°C (peak temperature: approx. 28°C, 2nd heating) with a heat of fusion of only 1.5 J/g. An even smaller melting enthalpy of 0.5 J/g was observed in the 1st heating (blue).