Polyurethane-based embedding compounds

Information

Synthetic embedding compound is a two-component material and is supplied in double containers with the A and B components in the appropriate mixing ratio. For smaller jobs, the material is generally applied manually. Both components in the containers supplied are mixed homogeneously and then poured under the rail from the sheet steel container. Pouring is carried out from one side so that it is possible to monitor on the other side whether the pourable, self-leveling material is indeed filling up the entire space underneath the foot of the rail. As the material begins to react as soon as the components are mixed, the limited application time must be taken into account when applying manually. The material reacts more quickly as the temperature rises. At outdoor temperatures above about 30°C work should be stopped, as above this temperature the application time is very short. For larger jobs and if construction time is short, it can be advantageous to install the embedding compound by machine. Application is by means of a special device in which both components are brought together and applied through a nozzle via a mixing head. This mixing and dosing system is installed in a vehicle and can be driven. The embedding material is applied from barrels containing approx. 200 l. One advantage of machine application is that relatively large quantities can be processed and applied in a relatively short space of time. Another is that high quality can be expected, as mixing is adjusted to a fixed ratio within the machine, which means that mixing errors cannot occur. The device is also fitted with a warning signal, visual or acoustic, if tolerances are exceeded when processing or applying.
Synthetic products are divided into elastic (polyurethane) and non-elastic (epoxy resins). Epoxy resins cannot be installed while rail traffic is running and do not reduce vibration. They are therefore rarely used. The polyurethane-based elastic compounds offer many advantages.
They are good to very good at reducing vibration and their long-term performance and electric insulation are also very good. PU embedding compounds can also generally be installed while rail traffic is still running. PU-based embedding compounds are used by many public transport companies, due in particular to their very good vibration and noise reduction and because of their excellent durability. Synthetic materials also offer advantages if for example a single set of points is to be exchanged. As the material is installed cold, the points or rails hardly expand at all and need no additional fastening. No melting pot or similar equipment is needed during application, as PU materials are mixed in the delivered container and poured straight from the container. Problem-free application saves time and as a rule no space for equipment is needed. It should be taken into account that these products make high demands on the application process and are relatively expensive to purchase. But because of the outstanding long-term qualities these extra costs pay for themselves within a relatively short space of time.