For the past few decades, FBE has been widely applied on pipes for transporting gas, oil and water. Due to the depletion of crude oil supplies, crude oil from greater depth and more inadequate areas has to be extracted, which means higher temperature of the crude oil, therefore new FBE is required to protect the pipes in high temperatures. Normally, FBE has Tg below 110 oC, in temperatures higher than the Tg, the mechanical properties of FBE such as its toughness, flexibility and adhesiveness are reduced. Due to these factors, general FBE may not effectively protect pipes in temperatures over 110 oC. This paper reports evaluation methods for these high Tg FBE, and the performance differences between the high Tg FBE and general FBE.
Most pipes are used for transporting crude oil. With a temperatures around 80 oC. Standard FBE with Tg below 110 oC is suitable for this appication. However, due to the recent depletion of crude oil, crude oil with high temperatures from deeper location needs to be extracted. This crude oil has temperatures between 80~150 oC, therefore the existing FBE may not effectively protect the pipes. High Tg FBE is required which can protect pipes effectively in high temperatures.1 To achieve high Tg, either cross-linking density is increased, or new resins with different backbone is used. However, as the cross-linking density increases, mechanical properties such as flexibility is reduced.2 In this paper, several methods were used to determined the glass temperature, the performance difference between standard FBE and high Tg FBE were also reported.
Glass Transition Glass Transition is a method to characterize a property of a polymeric material. The glass transition is the temperature where the polymer goes from a hard, glass like state to a rubber like state. If FBE is exposed to the temperature higher than its Tg, the properties of FBE will be changed. Tg is one of most important character of FBE. The best way to envision this type of transition is to put a rubber band (rubber like state, very flexible) into a container of liquid nitrogen. When removed the rubber band is solid and inflexible (glass state) and in fact the rubber can be shattered. Upon standing and warming to room temperature the rubber band will again become flexible and rubbery(rubber like state).3
DSC (Differential Scanning Calorimeter) defines the glass transition as a change in the heat capacity as the polymer matrix goes from the glass state to the rubber state. This is a second order endothermic transition (requires heat to go through the transition). DSC the transition appears as a step transition and not a peak such as might be seen with a melting transition. TMA (Thermo Mechanical Analysis) defines the glass transition in terms of the change in the coefficient of thermal expansion (CTE) as the polymer goes from glass to rubber state with the associated change in free molecular volume.3
