Hello and welcome to a new post on design properties for engineers. In today’s post we discuss the storage modulus E’ measured by DMA of the ultra performance polymer Polybenzimidazole (PBI). Check out my other post on DMA of high performance polymers here. DMA is an essential tool for polymer material selection, allowing you to immediately capture the mechanical behaviour over a wide temperature range.
What is Polybenzimidazole (PBI)?
PBI is the ultra high performance plastic which was developed in cooperation with NASA to have a lightweight, high heat, low friction, high chemical and radiation resistant polymer which can be used in space and aircraft applications. Nowadays the application field of PBI is much broader and it is used in electric & electronic appliances too. Its unique structure, consisting of a repeating benzimidazole unit, imparts these remarkable characteristics. PBI has a glass transition point of 427°C and its high purity makes it ideal for cable insulation powder coatings, friction parts and housings.
Storage Modulus E’ of PBI and PBI-blends
Figure 1 shows the storage modulus vs. temperature behaviour of PBI, PBI-PEEK blend, PAI, and PEI. They all show a significant drop in modulus in the glass transition region, expect of PBI. Before reaching the Tg, the neat PBI polymer still has a storage modulus of 3 GPa, where else the other presented polymers have already reached the zero level at this temperature. Blending PBI with PEEK makes it easier for melt processing and still up to 200°C a high level of modulus can be achieved. Among the amorphous high performance polymers, PAI has with 275 °C the highest glass transition temperature. A continuous use temperature of 260°C is feasible. PAI is melt processable in an injection moulding machine and needs an annealing step after moulding.
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| Figure 1: Storage modulus E' of PBI and PBI blends [1] |
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