Potting of a sensor with a polyurethane.
The all-rounder among plastics
Since their discovery, polyurethanes have developed into a technically important class of plastics with a wide range of applications. In addition to their use as functional materials in the field of insulating materials in upholstered furniture, sports articles or in the interiors of vehicles, polyurethanes have been proving their worth for many years in the field of electronics manufacturing (full encapsulation of control units and semiconductor elements) and also as 1C assembly adhesives (foam in the construction sector or window assembly in automotive and rail vehicle construction).
Polyurethanes are characterized by a wide range of applications, which results from the broad chemical basis of the possible base polymers (resin). In addition, they are often less expensive than comparable epoxies or silicones in terms of material costs.
Polyurethanes are advantageous wherever a certain flexibility of bonding or potting application is required. Very soft elastomers (up to 8 MPa) as well as medium-strength duromers (25 MPa) are possible as end products. Compared to epoxies and silicones, polyurethane plastics do not achieve the same high media and temperature resistance and are more sensitive to UV light and environmental influences. However, modern thermoset formulations can also achieve heat resistance of up to 180 °C.
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Application areas and requirements
2C self-leveling casting resins and adhesive
In the field of low-viscosity electro casting resins, polyurethanes are comparable to epoxies and are often formulated as a 2C system. Like all polyaddition systems, polyurethanes are very sensitive to variations in the mixing ratio. The quantity ratio specified by the manufacturer in the data sheet must be strictly adhered to in order to maintain the required quality standards of the end products.
Usually, the mostly higher viscosity A-component (polyol) contains fillers. The B component (isocyanate) corresponds to the crosslinker. While epoxy resins are relatively tolerant of environmental parameters and the components during processing, polyurethanes are highly sensitive to moisture. During processing and preparation, the resin and hardener must be adequately protected from moisture. When exposed to moisture, various defect patterns can basically occur.
Our experts from the Technology Center will advise you on the correct way to store and process your adhesive system.
Pasty 1C/2C adhesives based on polyurethane
A widely used class of assembly and structural adhesives in the field of polyurethane-based systems are the 1C moisture-curing variants. Their most prominent application is in window assembly in the field of automotive and rail vehicle production. Here, the reaction of the isocyanates with moisture is exploited as a curing reaction. It is important for the processing of moisture-curing polyurethanes to consistently exclude moisture in the area of dispensing components and material preparation. Only by taking these measures can trouble-free operation be guaranteed.
bdtronic offers with the container discharge PPS an elegant solution to convey moisture-sensitive adhesives safely and protected under a water-free atmosphere without bubbles.
If you take a dispensing system for moisture-curing materials out of operation for a longer period of time, remember to dispense some material from time to time in order to remove diffusing water from the system through screw connections and sealing surfaces. Contact us. We will support you in working out a relocation or decommissioning concept.
In addition to moisture-curing systems, hot-curing PU-based materials are also offered, which are not sensitive to moisture. These consist of an already premixed quantity of resin and isocyanate, which has been chemically inactivated. If the assembly is now heated (approx. 80-100° C) after successful application and joining process, the inactivation is thermally cancelled and the curing reaction proceeds as usual.
Benefit from our expertise and many years of experience. Develop the optimum process for your requirements together with us. We are specialists for different applications and processes.