Layer Damping with IPNs

Methacrylic/acrylic latex IPNs, Section 5.4.1, yield convenient semicompatible compositions. Tables 8.15 and 8.16 ° delineate several experimental and commercial compositions. Poly(vinyl acetate) copolymers, appropriately plasticized and filled, are the most important group of the latter materials. 

The advantages of the latex IPN constrained layer damping system are twofold  

G IPN (9-co-21)/(21-co-49) poly (ethyl methacrylate-co-ethyl acrylate)/(n-butyl acrylate-co-ethyl acrylate) 

H random copolymer 55/45 ethyl acrylate/methyl methacrylate 

J random copolymer 70/30 ethyl acrylate/methyl methacrylate 

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Fig. 1. Oscilloscope traces of vibration decay. Characteristics of an undamped reed(a), and a damped reed(b). Steel reed damped with an IPN constrained layer system. (Reprinted with permission from ref. 5. Copyright 1975 Wiley.)...

Sound and vibration damping research with IPNs began in the early 1970 s and resulted in the formation of a constrained layer damping system with the inner damping layer a latex IPN paint (3 ). The constrained layer system results in a shearing effect within the IPN layer along with flexural and extensional motions as the composite panel vibrates. The added shear mechanism, not present in extensional applications, increases the amount of energy that is dissipated in each vibrational cycle. 

Figure 13.13. Proposed use of gradient IPN s as constrained layer damping materials. Left, A is the substrate to be damped, B is a gradient IPN with the plastic component increasing in concentration toward the outside, as shown on the right.

The damping of an IPN constrained layer system based on an acrylic/methacrylic IPN and an epoxy constraining layer is compared with several other commercial homopolymers and statistical copol5miers in Figure 21 (78). Hitachi Chemical has a high temperature sound and vibration damping material based on vinyl-phenolic compositions (79). 

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