The applications and uses for thermosetting plastics have grown substantially over recent years. The benefits of this type of plastic are largely due to its favourable plastic properties. Thermoset plastic polymers cross-link together when being cured and so form an irreversible chemical bond.
Closed-meshed, cross-linked thermoset molecules require a completely different temperature profile to thermoplastics. The compound is injected from a cold cylinder module into a hot mould. Further heating and melting of the compound in the mould causes a decrease in viscosity that is only reversed when cross-linking increases. The finished component is then irreversibly cross-linked, which makes it extremely hard.
The temperature reached within a thermoset injection mould tool is significantly higher than a thermoplastic version. As such, the electrical connectors that are surface mounted to the tools, and carry the temperature monitoring thermocouple contacts, will experience temperatures of 30 to 40degC higher than the typical standard connector working temperature of 125degC. As a result, there is a tendency that these connectors will have a reduced operating life.
These potential connectivity component failures can occur during the plastic component assembly process, which means critical mould temperatures will cease to be controlled. Consequently, in some high-volume production conditions, parts may come off the line which do not meet quality standards, resulting in increased and costly waste materials.
Harting has recently launched a new high temperature version of its Han series multipole connectors that addresses these issues through its extended maximum working temperature capability. This significantly extends the operational lifetime of the thermoset plastic injection mould tools, reducing potential tooling maintenance and service periods, line downtime and ultimately, operating costs.
Harting has used its considerable technical expertise to develop special connectors which provide reliable options for these high-temperature environments.
For example, bulkhead connector seals must not melt or adhere to other integrated component parts over the full operating temperature range. Consequently, Harting has opted for a non-stick coated high-temperature-resistant rubber version, which avoids bonding between the hood and housing even if they are left mated for several years.
Many of the hoods and housing coatings and lacquers available on the market are not suitable for long-term use at high temperatures as they can cause melting, which can lead to mated parts sticking together. Thanks to the application of a special surface treatment to the aluminium die-cast hoods and housings, Harting has been able to dispense with any additional, separately applied, detrimental protective coating finish.
The connector insert and contacts must withstand the high ambient conditions of the location and the additional heat generated inside the housing when under mated load. Harting has selected high-temperature-resistant copper alloy contacts that maintain constant electrical properties when heated. In addition the high-temperature LCP plastic inserts ensure a longer service life.
As a result of these features, Harting’s Han High Temp connectors can permanently withstand operating ambient conditions of +200degC, providing extended operating lifetimes and ensuring reduced line downtime, compared with competitor offerings.
Learn more about Harting’s Han High Temp connectors at www.harting.co.uk.