Effect of temperature on bakelite properties used for standard RPC chambers

Bruni, Fabio; Hull, G.; Mari, Stefano Maria

doi:10.1016/j.nuclphysbps.2006.07.008

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“…The bond dissociation energy of CH 2 , CH, OH, OH − , and OH (phenyl) groups was found to be 24.12 kJ mol −1 , 19.26 kJ mol −1 , 24.23 kJ mol −1 , 26.24 kJ mol −1 , and 26.76 kJ mol −1 , respectively . However, there is a rapid increase in o‐Ps lifetime (τ 3 = 86.50 ps) and free volume ( V f = 7.52 Å 3 ) from 200 to 270°C, which is attributed to the cleavage of bonds, and this may leads to the depolymerization of Bakelite . This is also evident from both DSC and FTIR Spectra; particularly a prominent transition at 200°C is seen in DSC thermogram of Bakelite (Figure ).…”

Section: Resultsmentioning

confidence: 85%

Thermally induced microstructural changes and its influence on electrical conductivity of a polymer‐based bakelite RPC detector material: A positron lifetime study

Veedu

Basavaraju

Ranganathaiah

2013

J of Applied Polymer Sci

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Annealing studies have been carried out to understand the temperature induced microstructural changes in Bakelite (P-120 NEMA LI-1989 Grade XXX) Resistive Plate Chamber (RPC) detector material using Positron annihilation lifetime spectroscopy (PALS), Fourier transform infrared spectroscopy (FTIR), and XRD. The variation of positron lifetime parameters viz., ortho-Positronium lifetime (s 3 ) and free volume size (V f ) increases marginally above glass transition temperature T g as a result of structural changes due to segmental mobility. The drastic increase of free volume parameters above 240 o C attributed to the reduction in strength of CAH bond of the aliphatic bridges and cleavage of methylene bridges of the polymer network, which is supported by the FTIR results. The XRD results show the reduction in crystallinity and average crystallite size of Bakelite on annealing correlates well with the free volume and electrical conductivity. The temperature induced electrical conductivity and activation energy is also correlated with the positron lifetime parameters.Generally, RPCs are operated at high voltages (about 8-10 kV) and due to the variation of temperature under experimental conditions, might lead to changes in microstructural properties of the Bakelite over a period of time. It was noticed that the Bakelite resistivity changes as a function of temperature and humidity. 8,9 This is the indication that Bakelite RPCs are expected Additional Supporting Information may be found in the online version of this article.

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Section: Resultsmentioning

confidence: 85%