Direct bonding technology by chemical reactions at the interface & the applications of polyamide elastomers (PEBA)

Thermoplastic polyamide elastomer (PAE) [also PEBA: polyether block amide] is one of the most recently developed of the thermoplastic elastomers: a multiblock polymer with polyamide hard segments, it uses longchain polyether diol or polyester diol of low Tg for its soft segments. Polyamide 6 or polyamide 12 (PA12) is the main polyamide component used, while the soft segments are mostly provided by a polyether diol exemplified chiefly by poly(tetramethylene)glycol and poly(oxypropylene)glycol. The synthesis of PAE is generally split into two: formation of a polyamide oligomer, and chain extension by esterification. Figure 1 shows schematically the most usual synthetic route to PAE with PA12 hard segments. A broad comparison of the physical properties of PAE with other thermoplastic elastomers is presented in Table 1. Its outstanding features assure that PAE is widely used in automotive, sports, consumer electrical and other industrial applications [1]. As a step in the development of materials of higher functionality, the author and co-workers have recently sought to confer on PAE and other polyamides the ability to bond with dissimilar materials. The basis for the project was the “K&K” thermoplastic to rubber direct bonding technology [2, 3] we have been working on since 1999, progress with which has led to the successful development of a new PAE and PA12 that allow direct bonding to TPU in a combination of thermoplastic resins [4].