Vibration-Damping Properties

The main factors that affect the damping capability of polymers were reported elsewhere [248]. The theory of frequency-dependent attenuation of vibrations by viscoelastic polymers was presented [249]. hi review [55] there are some data on dynamic mechanical properties and on the damping characteristics, which are tightly cormected. 

To quantify damping performance, the area imder the tan 5 or vs temperature curves may be used. The loss area is given [250] as  

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The resonant beam test technique forms the basis of the ASTM Standard E756-83 for measuring the viscoelastic properties of damping materials. Fundamentally, the beam test requires that the resonant frequencies of a metal-beam, mounted in cantilever fashion, be determined as a function of temperature and frequency the beam is then coated with a polymer and the resonant frequencies and corresponding modal damping of the composite beam are determined as a function of temperature and frequency. From these two data sets, the vibration damping properties of the polymer can be evaluated. The ASTM Standard provides the necessary equations to obtain the complex modulus data from the collected test data and also provides guidelines for the proper choice of the specimens (1.21. The principal difference between the beam test and the other methods used here is that the beam test calculates the material properties from the test results on the metal beam and the composite beam whereas the... 

However, they are basically brittle materials, and many types of additives and modifiers have been developed to improve some of their properties. While working to develop special-purpose phenolic materials, the authors found that the compounds being produced had excellent vibration-damping properties (high loss tangent values), and that these properties were preserved to higher temperatures than elastomers generally used for the... 

Another application is to include microencapsulated polymer mixtures with various glass transition temperatures. The incorporation of such material into a coating leads to a change in vibrational damping properties this is important for coated textiles used, for example, as transportation belts in industrial machinery. 

The figure gives the results of testing composite reeds of different fibers and epoxy. The figure clearly shows the superior vibration damping properties of Dyneema composites. 

Kaolin is used only in small quantities in PR The anisotropic particle geometry of wollastonite and mica reinforces the pol)uner. The latter is applied more extensively in USA and Canada due to the closer location of mining facilities. Barite-filled PP has excellent vibration damping properties due to the high density of this filler. Wood flour filled PP is occasionally applied in the automotive industry for the preparation of door panels. Water absorption of this filler creates problems in processing and application. The most important characteristics of mineral fillers are collected in Table 2. 

It is important to note that, although the loss is a maximum at the point of inflection in the modulus curve, the tails extend considerably into both the glass and the rubber regions. It is this latter that gives rubbers their energy absorbing, vibration damping properties. 

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