What is a polymer damping material?

Damping material is a special material with vibration and noise reduction and certain sealing properties, and polymer damping material is the most effective type of damping material, which is widely used due to its unique structure. Damping materials have been widely used for shock absorption and noise reduction of aircraft, rockets, various aircraft, armored vehicles, tanks, cars, and other transportation vehicles, as well as for wave absorption and stealth of submarines, and environmental protection.

Polymer materials generally have significant damping near the glass transition temperature (Tg). When polymers are in a glass state, their modulus is very high, and molecules can hardly move, therefore they cannot absorb mechanical energy; In high elastic states, molecules move easily and cannot absorb sufficient mechanical energy; However, near Tg, the modulus of the polymer significantly decreases, accompanied by obvious mechanical damping characteristics. Mechanical vibration is converted into the motion of macromolecular chains or segments, and mechanical energy is converted into thermal energy through internal friction between molecules, achieving damping effect.

The phase angle difference between strain and stress δ It is called the mechanical loss angle, commonly known as the tangent tan of the mechanical loss angle δ (also known as damping factor) to represent the magnitude of internal friction. The relationship between mechanical loss and damping performance is very close, and the greater the internal friction of the polymer, the better the damping effect δ The relationship between energy storage modulus E 'and loss modulus E' is as follows:

Tan δ= E "/E '

Damping factor tan δ The larger the damping temperature range, the better the damping performance of the material.

Factors affecting damping performance

The morphology and structure (compatibility) of damping materials, the Tg of each polymer component, the damping capacity of each polymer component, crosslinking degree, fillers, and environmental temperature all have an impact on the damping performance of the material.

(1) Compatibility

A fully compatible polymer network (IPN) is similar to a single component polymer, with a widened glass transition temperature range, but E ″, tan δ The value change presents a single peak; Completely incompatible IPNs are similar to blends, with poor interpenetration and compatibility of the network, presenting two isolated peaks and a lower tan in the middle region δ； The Tg of semi compatible IPN migrates inward and approaches each other, while the damping values E ″ and tan in the intermediate transition region are significantly affected by the synergistic effect of interpenetration δ There is a significant increase. Proper compatibility can improve damping performance.

(2) Temperature

Select a suitable polymer or blend based on the ambient temperature at which the damping material is used, so that its Tg is consistent with the ambient temperature, so that the damping material can have the maximum damping effect in the specified environment.

(3) Copolymerization

Copolymers prepared through grafting and block copolymerization can exhibit good damping properties over a wide range. Increasing the number of side chains and increasing the polarity of side chains can both improve the damping performance of the graft copolymer.

(4) Tg of each component polymer

For the design of damping materials in a wide temperature range, it is required that the Tg of the damping material components be far apart. In theory, the damping temperature range of damping composite materials cannot exceed the temperature range of the upper and lower limits of the two components Tg. Considering the internal displacement effect of Tg after the formation of a composite system, the Tg of the two components should be sufficiently far apart. If each component has high damping performance, there is no doubt that damping composite materials will have excellent damping performance.

(5) Crosslinking degree

As the degree of crosslinking increases, the compatibility of the two components increases. Therefore, by selecting the appropriate crosslinking degree, high damping performance can be achieved over a wide temperature range.

(6) Filler

Fillers can increase the damping performance of polymers, as the friction between particles occurs when the filler particles come into contact with each other. The friction between particles and polymers occurs at the interface, which increases the internal friction of polymers near the interface, thereby improving the damping performance.