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Dynamic mechanical analysis (abbreviated DMA) is a technique used to study and characterize materials.It is most useful for studying the viscoelastic behavior of polymers.A sinusoidal stress is applied and the strain in the material is measured, allowing one to determine the complex modulus.
The ratio of the loss modulus to storage modulus in a viscoelastic material is defined as the , (cf. loss tangent), which provides a measure of damping in the material.
A Mooney viscometer MV 2000 Mooney Viscometer. A Mooney viscometer or rotating disk viscometer is an instrument used for measuring the Mooney viscosity of rubbers. [1] Invented in the 1930s by Melvin Mooney, [2] it contains a rotating spindle and heated dies, the substance encloses and overflows the spindle and the mooney viscosity is calculated from the torque on the spindle.
An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus (E) and high failure strain compared with other materials. [1]
Rubber elasticity is the ability of solid rubber to be stretched up to a factor of 10 from its original length, and return to close to its original length upon release. This process can be repeated many times with no apparent degradation to the rubber. [1] Rubber, like all materials, consists of molecules.
For instance, a rubber band is disordered in the initial state of this region. When stretching the rubber band, you also align the structure to be more ordered. Therefore, when releasing the rubber band, it will spontaneously seek higher entropy state hence goes back to its initial state.
Thermoplastic vulcanizates were first reported in 1962 by A.M. Gessler and W.H. Haslett. [4] In 1973, W.K. Fisher reported the dynamic vulcanization process through his prior work on polypropylene and EPDM rubber-based TPVs with peroxides as a cross-linking agent.
Crazing in polymers This is a cartoon representation of failure mechanisms in epoxy resins. The numbers correspond to the following. "(1) shear band formation, (2) fracture of rubber particles, (3) stretching, (4) debonding and (5) tearing of rubber particles, (6) transparticle fracture, (7) debonding of hard particles, (8) crack deflection by hard particles, (9) cavitated rubber particles ...