Polyurethane resins are widely used within underground coal mining, to assist in the consolidation and stabilisation of fractured and broken ground conditions. Ground consolidation techniques using injectable resins are a common tool for the reinforcement of roof and wall corners, as well as for stabilising side walls and long wall faces. One of the primary performance parameters for injectable resins is the maximum reaction temperature, as an indicator of the total heat released during the exothermic resin curing process.
As defined within MDG 3608 ‘Non-metallic materials for use in underground coal mines’ (NSW Resources Regulator, 2012), the maximum reaction temperature must remain below 150°C in order for product certification to be granted. Standardised methods for testing the maximum reaction temperature are based on small scale mixing tests conducted within a laboratory environment. Similarly, other key material properties tests for the cured polyurethane are also reacted and cured under laboratory conditions.
This paper presents new considerations for exothermic testing of polyurethane resins. Within the underground environment, heat will flow away from the polymerisation reaction and into the rock mass, altering the resultant exothermic temperature. To explore this effect, a new experimental method has been developed to assess the influence of heat transfer on the exothermic reaction. Data generated using this experimental method clearly aligns with thermodynamic principles and subsequently provides fresh insight into this field of application. Correspondingly, considerations arise for the true nature of the exothermic reaction and resultant material properties within the underground environment, in comparison with reported properties from existing test standards.