Noise and vibration damping with plastics

In numerous technical applications, noise and vibration damping play an important role. Whether in mechanical engineering, in vehicles, in medical technology or in household appliances – uncontrolled vibrations can shorten the service life of components, impair the precision of systems and cause disruptive noise.

Plastics offer a wide range of possibilities for damping vibrations, isolating oscillations and reducing the transmission of structure-borne noise. Depending on the application, their material properties make them an economical and high-performance alternative to metals or classic elastomers.

Fundamentals of noise and vibration damping

Noise is generated by mechanical vibrations that are transmitted to adjacent components or to the air. If no damping occurs, these vibrations can spread throughout the entire system and place stress on people, machines and structures.

Plastics can act on several levels: they convert part of the vibration energy into heat through internal friction, absorb or scatter sound waves and can simultaneously decouple components from one another.

A distinction must be made here between vibration damping and vibration isolation. In damping, vibration energy is reduced within the material. In vibration isolation, by contrast, as little vibration energy as possible should be transmitted from a source to adjacent components or sensitive parts.

The effectiveness depends on, among other things, the density, hardness, modulus of elasticity, temperature behaviour, duration of load and the molecular structure of the material. Targeted material selection, compounds or suitable additives for plastics can additionally influence specific properties.

Suitable plastics and damping materials

Which plastic is suitable as a damping material depends strongly on the load, temperature, frequency, installation situation and desired resilience. There is therefore no universally optimal material.

Thermoplastics

Many thermoplastics such as polyamide or polycarbonate have higher internal damping than metallic engineering materials.

Polyamide, for example, is used for bearings, gears, rollers or covers where, in addition to noise reduction, wear resistance and mechanical load capacity are also required.

Polycarbonate stands out for its high toughness and impact strength and is suitable, among other things, for housings, panelling or covers where vibrations occur and a high impact strength is simultaneously required.

Thermoplastic elastomers (TPE)

TPE combine the properties of thermoplastics with elastomeric behaviour. Their elasticity and resilience make them particularly interesting for components that must repeatedly absorb vibrations and then largely return to their original shape.

Typical applications are:

• vibration buffers
• elastic mountings
• seals
• stops
• decoupling elements
• vibration-damping interlayers

Particularly in the case of industrial vibration dampers under continuous load, not only the initial elasticity but also the long-term behaviour must be considered. Creep, relaxation, temperature and static preload can influence the resilience of a soft-elastic plastic.

Polyurethanes (PUR)

PUR is one of the classic material groups for vibration and noise damping. Depending on the formulation, very different degrees of hardness and mechanical properties are possible.

PUR is used, among other things, for conveyor rollers, machine elements, elastic mountings, buffers and shock absorbers.

For industrial vibration damping, PUR is particularly interesting when a combination of elasticity, load capacity, wear resistance and defined resilience is required.

Elastic PUR elements can also help to reduce the transmission of structure-borne noise and vibrations to adjacent structures when decoupling machines and technical systems.

High-performance plastics

Materials such as PEEK, PPS or polyimides offer special mechanical properties in addition to high temperature and chemical resistance.

They are used when conventional plastics reach their limits due to high temperatures, chemical exposure or demanding mechanical conditions.

Particularly in aerospace, low weight, temperature resistance and reliable long-term behaviour play an important role. In the vibration isolation of components, the focus is often not merely on pure damping, but on the combination of mechanical stability, low mass and resistance to extreme operating conditions.

Fibre-reinforced plastics

By combining a plastic matrix with glass or carbon fibres, components with very high strength and stiffness can be produced.

However, the reinforcement can change the damping behaviour. For this reason, stiffness and internal damping must be considered together in structures subjected to vibration.

Hybrid structures can be useful when high mechanical load capacity is to be combined with targeted vibration damping.

Foamed plastics

Open-cell and closed-cell foams made of PE, PU or other polymeric materials are also used for noise and vibration reduction.

Open-cell foams are particularly suitable for absorbing airborne sound. Closed-cell materials, by contrast, can serve as elastic interlayers and reduce impacts or vibrations.

Which damping materials are suitable for industrial vibration dampers?

Elastic or soft-elastic materials in particular come into consideration for industrial vibration dampers. The selection should not be based on hardness alone.

Important criteria are:

• desired resilience
• static and dynamic load
• vibration frequency
• temperature range
• compressive load
• chemical environment
• permissible deformation
• creep and relaxation behaviour
• wear resistance
• desired service life

TPE and PUR, for example, can offer high resilience. Under high continuous load, however, it must be checked how much the respective material deforms over a longer period.

Engineering thermoplastics such as polyamide, in turn, can be useful when, in addition to a certain inherent damping, significantly higher stiffness or wear resistance is required.

The material selection should therefore always be based on the specific load.

Application areas

Area	Typical applications	Advantages of use
Mechanical and plant engineering	drives, pumps, gearboxes, fans, housings and vibration buffers	reduction of operating noise and vibration transmission
Automotive industry	engine mounts, interior trim, chassis components	more driving comfort and lower noise transmission
Household appliances	washing machines, dishwashers, vacuum cleaners, refrigerators	reduced operating noise
Construction industry	elastic interlayers, pipe systems, technical mountings	reduction of structure-borne noise and vibration transmission
Medical technology	analysis devices, pumps, compressors	improved precision through lower vibrations
Electronics	fan decoupling, housing damping	protection of sensitive components
Energy plants	wind turbines, compressor stations	protection against continuous vibration loads
Aerospace	mountings, housings, technical functional parts	lightweight construction and vibration control under demanding conditions

Vibration isolation in mechanical and plant engineering

Machines, pumps, compressors and drives generate dynamic forces during operation. If these are transmitted directly into frames, foundations or adjacent components, structure-borne noise, resonances and additional mechanical loads can result.

Elastic plastic elements can be inserted between the vibration source and the structure in order to reduce this transmission. What is decisive here is a design matched to the machine weight, frequency and installation situation.

Vibration isolation in buildings

Constructive decoupling is also relevant for technical systems in buildings. Ventilation systems, pumps, compressors or other units can introduce vibrations into the building structure.

Elastic damping elements or interlayers can help to reduce transmission to floors, ceilings or adjacent components. However, the requirements differ significantly from classic plastic components in mechanical engineering and must be designed accordingly.

Advantages of plastics compared with metals

Compared with metals, plastics offer several properties that can be advantageous in noise and vibration damping.

Their low weight supports lightweight construction. At the same time, many polymers have higher internal damping than metallic materials and therefore transmit vibrations differently.

Further advantages can be:

• low weight
• corrosion resistance
• electrical insulation
• great freedom of design
• different hardness and elasticity ranges
• good machinability
• adaptable material properties

Compounds, fillers and additives allow materials to be additionally tailored to specific operating conditions.

Challenges and limits

In the case of damping plastic components, long-term behaviour in particular must be taken into account.

High temperatures can change the mechanical properties and thus also the damping behaviour. Chemical media, UV radiation and high mechanical loads can also influence the service life.

Another important variable is the relaxation of plastics. If a plastic is permanently deformed or loaded, the stress in the material can decrease over time. Under constant load, creep can also occur.

In the case of vibration dampers, elastic mountings and permanently preloaded components, therefore, not only short-term characteristic values but also temperature, time and continuous load must be taken into account.

Designing noise and vibration damping in a targeted way

Plastics offer a wide range of possibilities for reducing noise and vibrations in technical applications. Depending on the task, engineering thermoplastics, TPE, PUR, foamed plastics or high-performance plastics can be used.

For a reliable solution, however, damping, resilience, load, temperature and long-term behaviour must be considered together.

Martan Plastics supports you in selecting suitable engineering plastics for industrial applications and in implementing suitable semi-finished products and components.

FAQ

Which plastics are particularly suitable for vibration damping?

Depending on the application, PUR, thermoplastic elastomers, polyamides and other engineering plastics in particular come into consideration. The decisive factors are load, temperature, desired elasticity and vibration frequency.

Which soft-elastic plastic is suitable for industrial vibration dampers with good resilience?

TPE and PUR are typical material groups for elastic damping elements. Which material is suitable depends, among other things, on compressive load, temperature, vibration frequency and continuous load. Particularly under continuous load, creep and relaxation behaviour should be taken into account.

What is the difference between vibration damping and vibration isolation?

In vibration damping, vibration energy is reduced within the system. In vibration isolation, by contrast, the focus is on reducing vibration transmission between a source and an adjacent component.

How can vibrations in machines be damped?

Possibilities include elastic mountings, vibration buffers, damping elements, flexible interlayers or constructive decoupling. Material and geometry must be matched to the mass, load and frequency of the machine.

Is felt suitable for industrial vibration damping?

Felt can reduce noise and light vibrations and is used in certain technical applications. Under defined dynamic loads or high continuous stress, however, specially designed elastic plastics or elastomers are often used, whose mechanical behaviour can be tailored more precisely to the application.

What role does vibration isolation play in aerospace?

In aerospace, sensitive components must be protected against dynamic loads and vibration transmission. At the same time, high requirements apply to weight, temperature resistance and mechanical reliability. For this reason, specially selected engineering and high-performance plastics are often used there.

What does relaxation mean in plastics?

Relaxation describes the reduction of mechanical stress under a deformation held constant over a longer period. In permanently loaded damping elements, this behaviour can influence the preload and long-term function.

Why are plastics often better suited to damping tasks than metals?

Many plastics have higher internal damping and can dissipate vibration energy better than rigid metallic materials. In addition, they offer advantages such as low weight, corrosion resistance and great freedom of design.