Abstract
Urea resin moulding compounds belong to the class of thermosetting materials. They undergo a chemical crosslinking reaction in the mould, giving them outstanding heat resistance. In contrast to thermoplastic materials, thermosets need a critical cure time before the glass transition temperature shifts sufficiently for the hot parts to be stable enough to be demoulded. The cycle times are therefore significantly longer. One possible means of reducing the cycle time would be to increase the mould temperature. As is generally known, increasing the temperature by 10 K doubles the reaction rate. However, a faster reaction rate reduces the time window available for demoulding the cured parts, and the whole process becomes more vulnerable to variations in process parameters and compound composition. By the use of an online cure monitoring system it should be possible to control the process even at higher mould temperatures. In this article the dielectric cure monitoring method is tested in the manufacture of injection moulded parts and its potential for process control is discussed.
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