Scholarly record

CONVEYOR BELT RUBBER AGING MEASURED BY DIELECTRIC SPECTROSCOPY

J. Nedbal

Abstract

Rubbers used in conveyor belt transport undergo an aging caused by the aggressive character of external environment during their operation. The main changes of conveyor belts due to the aging process appear firs tly on their surface being in an immediate contact with the cargo transported and/or with an ambient air. Chemical changes caused by the aging are reflected in changes of physical properties of belt components such as network density, glass transition temperature Tg and other. Determination of physical properties of conveyor belt rubbers is comm only realized by expe rimental methods – mainly by mechanical and dielectric spectro scopy. Both noticed methods are suitable because the changes of network density and Tg temperature are visible on the mechanical and dielectric frequency and/or temperature spectra. Classical mechanical and dielectric measurements are usually performed on bulk samples. Such laboratory measurements require obtained samples of conveyor belt rubbers which mean that the cutting is not possible during the course of op eration. While in the mechanical case it is for the time being necessary to use the mentioned geometry of sample, in the dielectric one we have an opportunity to use a system of planar so called interdigital system of (comb) electrodes. Dielectric spectroscopy is a well establis hed method that is used many years for characterization of non- or only low-conduc tive materials. As mentioned above, classical dielectric measurements require disc-like samples placed between the parallel plates of a measuring condenser. The main advantage of this arrangement consists in the fact that the outer excitation electric field applied to the condenser plates is homogenous and enabling an accurate eval uation of measured material permittivity. On the other hand, there are some limitations of this clas sical approach as e.g. necessity of cutting samples (non in situ non-destructive meas urements), insensitivity to the spatial inhomogenities (material heterogeneity). In the last years a new experimental method so called interdigital dielectrom etry has been developed which is based on a planar configuration of the electrode system. This new method is used more often for non- destructive determination of ma terial characteristics, such as monitoring of humidity, density, porosity, cure processes, aging. To its main features belong a single sided access to the measured material and the possi bility to measure its spatial profiling by means of sensors with different spatial period icity. Some limitation, th at is balanced by 11th International Multidisciplinary Scientific GeoConference SGEM2011 www.sgem.org International Multidisciplinary Scientific GeoConference SGEM 2011 752 a possibility to measure in situ during opera tion of conveyor belt transport, mirror the inhomogenity of electric field between driven and sensing electrodes and therefore the uncertainty in determinati on of material permittivity. To obtain and optimize the maximum information about measured material it is necessary to design the geometry of coplanar electrode system for any concrete application, in our case for the monitoring of an aging process in conveyor belt rubbers . The requisite information mainly the information about the behaviour of conveyor belt rubbers in different distances from surface Therefore we have fixated to study the effect of the sequential changes: the geometry of used sensors, their total size, th e amplitude of outer electric field, the air gap between the electrode system and the surface of measured belts, the pressure of planar electrode system to the surface during measurements without an air gap.

Publication Impact Profile

• Citations
• CrossRef - Citation Indexes: 3

• Captures
• Mendeley - Readers: 6

PLUMX see details

DOI resolver: doi.org/10.5593/sgem2011/s03.113

Publication details

Back to publication list