Noise damping

Noise pollution can be reduced by controlling the dampening characteristics of a material. The dampening material converts the energy of vibration to heat rather than emitting it to air. Incorporation of fillers gives such characteristics. 

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When one polymer of an IPN was plastic and the other was rubber, the combination showed synergistic properties reinforced rubbers, impact resistant plastics, or noise damping materials were reported. Because of the macroscopic network structure formed in IPN s, they are thermoset and cannot be molded. However IPN s have been made by emulsion polymerization so that each individual emulsion particle is an IPN in miniature form containing both networks (75, 76, 77, 78, 82, 83). Emulsion polymerization allows the molding of IPN s if the crosslink density of the miniature IPN s is not too high. 

Fibrillated aramid (Kevlar and Twaron ) pulps are widely used as a moderately heat-resistant reinforcement in friction formulations. Aramid pulps provide briquettability for preforms, improve friction and wear characteristics, help modify compressibility, and aid in noise damping. However, these flbers are one of the most expensive raw materials used in friction materials. 

Friction dusts are cured coarse powders composed of polymerized cashew nut shell liquids. These materials are added to friction materials to confer friction stability, resiliency, and noise damping. Rubber and abrasive modified friction dusts are also available. Friction dusts tend to absorb solvents, causing the friction material to spring back after forming. This limits the use of cashew friction dusts to dry mixes or solvent-free wet mixes. 

Rubber particles of various origins are used in friction materials to provide friction and wear improvement, noise damping, and as a cost-reducing filler. Powders made from tire peel and other recycled rubber products and partially cross-linked acrylonitrile powders are the most widely used products in friction materials. 

Figure 2. Shot noise damping in a simple model circuit demonstrates why macroscopic linear conductors are usually free from this type of noise. The circuit is a series connection of N ideal current noise generators paralleled by ideal resistors. Anticorrelations in elementary transport events arise from the voltage fluctuations in connectors between generators.

Noise-damping coating. [Data from Wesch, K. Ruch, K., us Patent 5,756,555, May 26,... 

This is sprayable plastisol which can be used for coating substrates which require noise-damping especially of high-frequency components. 

MAJOR APPLICATIONS The rubbery polymers are useful as vibration and noise damping materials. Also for oil spill recovery, sound barrier materials, and for soft seals and gaskets. 

L. H. Sperling, J. A. Grates, J. E. Lorenz, and D. A. Thomas, Noise damping with methacrylate/acrylate latex interpenetrating polymer networks, Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 16(1), 274 (1975). Methacrylic/acrylic latex IPNs. Broad-temperature noise-damping characteristics. 

The number of applications suggested in the patent literature is large— and growing. Included are impact-resistant plastics, ion exchange resins, noise-damping materials, a type of thermoplastic elastomer, and many more. 

Hutchinson and coworkers examined a wide range of IPNs, SINs and semi-IPNs that were useful as reinforced elastomers. PU/PMMA semi-IPNs prepared by bulk polymerization are used in shaping polymer articles. Epoxy/PU semi-IPNs are used as adhesives. Ion exchange resins are prepared from chloromethyl PS/sulfonate PS IPNs. PS/PS IPNs are used to prepare optically smooth plastic surfaces. Poly(ethyhnethacrylate)/poly(ra-butyl acrylate) prepared by Sperling et find the applications as noise damping coatings. 

The material obtained by the above-stated processing of waste buffing dust from chrome tanned leather is potentially applicable on cemented soles, wrapping sheets, lagging and noise damping materials, sealing materials, antivibration pads, and so on. 

An advanced detailed non-hnear computation model of the mobile antinoise wall has been used. The computation model of the motorcar has been selected from the database of test vehicle models. The analysis has been carried out using a specially developed procedure. Fulfilling certain specified criteria, the computer analysis substitutes the actual impact test of the vehicle crashing into the restraint system. Following the results of computations, the construction details of the mobile noise damping wall structure have been properly modified. Advanced is a method of global sensitivity analysis that allows us to analyze the higher order interaction effects. 

Phenolic resin-laminated mats and sheet made from glass fiber and other mineral fiber materials are among the most important noise damping and thermal insulation materials. The liquid resins used to manufacture these insulation materials provide both excellent mechanical strength and good thermal and moisture resistance. 

Specify, if required, suitable surfacing materials (metals, ceramics, mastics, deck covering underlays, cements, fillers, noise damping and anti-condensation compounds, plastic and reinforced... 

Application of special-purpose coatings (anti-condensation, noise damping, etc.). 

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