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Monomer cast polyamide 6 composites and their treatment with high-energy electrons

: Engelmann, G.; Gohs, U.; Ganster, J.


Journal of applied polymer science 123 (2012), Nr.2, S.1201-1211
ISSN: 0021-8995
ISSN: 1097-4628
Fraunhofer IAP ()

At first, the impact of selected spherically structured nanofillers made of different polar materials (carbon, silicon carbide, surface-modified silica, 2 wt % each) on mechanical properties of monomer cast polyamide 6 (MCPA6) was examined. Only the low-polar carbon-based nanofiller showed an average particle size below 100 nm in the liquid phase before polymerization was initiated. With regard to neat MCPA6, mechanical properties of the composite loaded with the carbon nanoparticles like tensile strength, Young's modulus, and heat distortion temperature could be improved by 6.4%, 13.5%, and 27.5%, respectively. The efficiency of carbon as filler material for MCPA6 was also shown for carbon short-cut fibers. A fiber content of 15% improved tensile strength from 78 to 93 MPa (19%) and Young's modulus could be doubled from 2660 MPa to nearly 5300 MPa. Regardless of the improved mechanical properties, the composites showed reduced degrees of crystallinity. Therefore, elect ron beam irradiation was applied to crosslink the polymer chains as an alternative to improve material properties. Crosslinking was supported by the application of a curing agent (CA). Two strategies for crosslinking experiments were tested: (1) Irradiation of CA-containing neat MCPA6 to find the most effective dose and subsequent treatment of the composites under this special condition; (2) Optimization of the properties by irradiation of the composites itself at graduated dose values. The second way was more convenient and showed, with regard to the composites without CA, improvements of tensile strength and Young's modulus of 6% each.