Poly(ether-b-amide)(PEBA)/Montmollionite(MMT) composites(C-PEBA) were prepared with isocyanate(NCO-) terminated poly(tetramethylene glycol)(PTMG) and amine(NH2-) terminated polyamide12(PA12)/MMT nanocomposites oligomer(M-PA). The PA12/MMT nanocomposites was synthesized by in-situ polymerization of 4,4’-methylenebis(cyclohexylamine) containing 0 ~ 10 wt% of MMT and 12-aminododecanoic acid to control the molecular weight of the PA12. The MMT contents of the PEBA/MMT composites were adjusted in the MMT contents of the PA12/MMT nanocomposites applied. The reaction completion was identified by confirming the presents of the specified chemical group on the chemical structures of the reactants and PA12/MMT nanocomposite.
PEBA as a thermoplastic elastomer performing engineering grade elasticity has been known for an elastomer having relatively high melting point due to crystalline PA hard segment. Therefore, It is believed that the MMT incorporated into the crystalline PA12 hard segment affects the properties of C-PEBA. Degree of MMT intercalation between in-situ polymerization with MMT and simple blending MMT after polymerization was examined by using XRD anaysis with alteration of the specified 2theta(θ) values to explain the effects on the thermal and mechanical properties of C-PEBA corresponding to the same structure of PEBA/MMT composite(B-PEBA) simply blended MMT after reaction. The 2θ of gallery spacing for the M-PA appeared at a lower degree than those of MMT and the simple blends.
As the results of DSC analysis the crystalline melting temperature(Tm) and the fusion enthalpy(ΔH) increased up to 3 wt% in case of M-PAs while the Tm of C-PEBAs increased up to 5wt%, then both decreased with increasing the MMT content. In addition the Tm and ΔH values of the C-PEBA were higher than those of the pristine and the B-PEBAs. This means that in-situ polymerization leads to a better separation to the soft amorphous phase and give rise to a more rigid and larger crystalline phase. Thermal stability analyzed by using TGA indicated that MMT influenced on the thermal decomposition temperature positively, The maximum strain and strength of the C-PEBA were shown at 3wt% of MMT content and the corresponding values to the B-PEBA at the same MMT content were at a lower level. The permanent setting of C-PEBA decreased with the increasing the MMT, especially more than at 5wt%, similar or less than those of Pebax®4033 commercialized PEBA and a typical polyurethane thermoplastic elastomer(TPU). In general elastic property of PEBA presenting multi-phase morphology is strongly dependant on the degree of phase separation and on the rigidity of hard domain consisting of the PA segment. Thus, a better elastic recovery is presumably ascribed to a better phase separation brought by intercalation of the PA12 segment into MMT effectively.