Mechanical Properties of Multiblock Polyamide-Polyoxirane Copolymers

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Abstract
The mechanical properties of alternating polyamide-polyoxirane copolymers (P1-P2)n were evaluated. The polyamide component of these copolymers consisted of poly(lactams), of poly(N-methyllactams) or of their statistical copolymers with a molecular weight ranging from 1,400 up to 15,000. Two different molecular weights (1,400 and 9,000) were chosen for the polyoxirane component. The dynamic mechanical spectra were determined with a Rheovibron viscoelastometer at a frequency 110 Hz and within a temperature range from - 190°C to 60°C. The stress-strain curves were measured with a table model of an INSTRON tester at room temperature. The dynamic mechanical behaviour indicates a reduced crystallinity of N-methyl substituted polyamides with respect to unsubstituted polyamides and a microdomain structure of some of the polyamide-polyoxirane copolymers. The stress-strain curves reflect the temperature position of the main transition, the fraction and molecular weight of the polyoxirane component and the possibility of a strain hardening of the material. The copolymer samples exhibited both plastic and viscoelastic deformation mechanism which was reflected in a delayed elasticity after unloading. Some of the samples exhibited an unusually high strain-at-break, i.e. up to 1,500%. A repeated testing of fragments of once broken test pieces showed that after drawing there was a large increase in tensile strength of some samples, up to six times the original value.

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