REACTION INJECTION MOULDING (RIM)

Dispensing systems for the production of plastic moulded parts

Though we may not pay it much attention, products and components made in the Reaction Injection Moulding (RIM) process form a significant part of our everyday lives. Typically, these items would be found in consumer goods, as well as household or electrical appliances, for example in the form of cases and housing in kitchen appliances or telephones. Vehicles contain numerous plastic moulded components too, in both their interior and exterior (consoles, switches, bumpers, etc.) and even prototype and small series productions often make use of this plastic processing method. That is why RIM is nowadays considered one of the classic applications in low-pressure metering technology.

The basis of the RIM process is usually a two-part, low viscosity polyurethane. The two parts – polyol and isocyanate – are precisely metered first and then homogeneously mixed (reaction). Subsequently, the material is injected at a low pressure (injection) into a closed mould, where it cures within a few minutes (moulding).

METER MIX® offers a reliable metering and mixing solution perfectly suited to the specifics of polyurethane processing in RIM processes. The PAR 50 system can be connected directly to the mould, while material injection can be partially automated.

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BONDING AND SEALING

Complex, yet strikingly effective applications

No matter which industry we look at – be it electronics, automotive or aviation – we will notice that bonding has replaced the established joining methods such as welding or screwing. For example, up to 18 kilograms of adhesive are used in the production of a single car. The electronics industry relies on adhesives for potting or sealing of components. In any case, bonding is a complex technique and requires significant specialist knowledge. Material manufacturers are constantly working on new adhesives and increasingly often they are also tailoring them to specific applications. In many cases, bonding is the only viable technique of binding modern materials.

ADHESIVE BONDING WITH EPOXY RESIN, POLYURETHANE AND SILICONE

Adhesive material can be based on epoxy resins, silicones, polyurethanes or methacrylates and it can be a one or a multi-part substance. Multi-component adhesives are metered and mixed by dispensing systems according to a fixed mixing ratio. Polyurethane adhesives often perform a sealing function, are easy to process and have a very good chemical resistance. Most commonly used are epoxy adhesives. They can be processed very well at room temperature and are highly resistant.

METERING METHACRYLATE ADHESIVES

Methacrylate adhesives usually have a very short pot life, which can complicate their processing. On the other hand, they offer the advantage of short curing times and particularly high strength. They are an excellent alternative for the joining of metal, glass and duromeric plastics.

PRE AND POST-TREATMENT OF COMPONENTS

Adhesives do not adhere easily to all components. Depending on the component properties, a pre-treatment such as by corona flame, corona primer or brushing, may be required. The subsequent application of the adhesive can be carried out in various ways, for example in a dot or bead form. After the components are joined, curing systems such as infrared light, ultraviolet light or continuous furnace can be used to accelerate the bonding reaction and speed up the time in which the components are available for the next production step.

In summary, the bonding and sealing process is a relatively complex one with many factors at play. The selected material must be a perfect fit for the application, the application parameters must be clearly and precisely defined and lastly, a metering solution capable of processing the selected material in the defined way needs to be identified. METER MIX® offers robust and proven metering systems which are continuously adapted to the evolving demands of adhesive technology. They present an accessible solution to process-reliable and high-quality processing of adhesive materials.

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