Liquid rubber resins

Liquid rubber resins are excellent for realizing soft to gel-like compounds despite their high hydrophobicity. Such systems are extremely advantageous for the encapsulation of sensitive electronic components. The mechanical load on such components is low when subjected to thermal shock.

Potting compounds that are mainly based on so-called polybutadiene polyols (Fig. 1) are known as liquid rubber casting resins. Due to the very non-polar character of these casting resins, they have a pronounced hydrophobicity. This has an extremely positive effect on factors such as water absorption and diffusion permeability to water and moisture. Low gas permeability is another favorable property of the liquid rubber systems.

In addition, the non-polar character of this potting compound in many cases results in comparatively good adhesion to non-polar surfaces that are considered difficult in terms of adhesion. Another characteristic is excellent low-temperature flexibility, which is equivalent to that of silicones. Typical values for the glass transition point are in the range of - 50°C. Values as low as -80°C can be achieved through specific formulations and curing of the system.

By using suitable additives, the resistance to UV radiation and the limited temperature stability can be significantly increased. By adding thinners to the formulation, the comparatively high viscosities can be reduced to a very practicable level.

Product overview - liquid rubber resins

Below you will find a selection of our casting resins.  Many other modifications are available on request.

For further information and data sheets, please click on the respective product.

Liquid rubber cast resins can be divided into two classes:

1. polyurethane liquid rubber cast resins

These are systems that are cured using isocyanates. They have good hydrolysis stability, as there are no unstable groups in the underlying polyol and water is virtually not absorbed due to the low polarity of the casting resin. Glass transition points here are usually in the range of approx. -50°C.

2. polyester - liquid rubber resins

These are built up by the reaction of a polybutadiene polyol (Fig. 1) and a maleicised polybutadiene. The maleic anhydride groups react with the hydroxyl groups to form an ester bond. The exothermicity of the reaction is very low, so that no component stresses occur. Nevertheless, casting resins of this type can be adjusted to very short processing temperatures using suitable catalysers. Many of the properties mentioned above apply to these pure polybutadiene polyesters in an even more pronounced form, as the hardener component here is also a non-polar polybutadiene. The glass transition temperatures of these systems can be as low as -80°C.

The advantage of these systems is that they do not require the use of an isocyanate. This means that they are not subject to labelling under current German law.

These cast resins are characterized by special properties that are difficult to achieve with conventional casting resins based on polyether/polyester polyols.