Influence of Cross-Linking Agent Concentration/Beta Radiation Surface Modification on the Micro-Mechanical Properties of Polyamide 6

Abstract

This study focuses on the problematic of polyamide 6 containing various concentrations of cross-linking agent that was exposed to electron radiation. It is important to improve the material properties of polymers as much as possible. This endeavor can be realized by numerous methods, one of which is radiation exposure. This study investigates the effect of electron beam radiation in doses ranging from 66 to 132 kGy on the micro-mechanical properties of polymers, specifically polyamide 6 filled with 1, 3 and 5 wt.% of cross-linking agent triallyl isocyanurate (TAIC). The changes in the material brought by the radiation exposure were quantified by measurements of indentation hardness and modulus, which were the main measured micro-mechanical properties. Furthermore, thermo-mechanical analysis (TMA) was chosen to confirm the results of the material cross-linking, while the effect of degradation was investigated by Fourier-transform infrared spectroscopy (FTIR). In pursuit of complete evaluation, the topography of the test subject’s surface was explored by atomic force microscopy (AFM). The optimal concentration/radiation ratio was found in polyamide 6 enriched by 5 wt.% concentration of TAIC, which was irradiated by 132 kGy. Material treated in such a way had its indentation hardness by 33% and indentation modulus improved by 26% in comparison with the untreated material. These results were subsequently confirmed by the TMA and FTIR methods.

The Modification of Useful Injection-Molded Parts’ Properties Induced Using High-Energy Radiation

“…The actuator of these changes was the cross-linking process, which resulted in the creation of free radicals (breakup of C-H bonds) that subsequently recombined into a spatial network due to the linking of two free radicals together (C-C bond) with neighboring chains. As a result, mechanical properties were changed, which corresponds with the conclusions of other authors [ 18 , 24 , 25 , 26 ]. In the case of some polymers, an addition of a polyfunctional monomer is necessary to increase the initiation and recombination tendency of its radicals.…”

“…However, this universality is strongly dependent on the absorbed radiation dose, especially the ratio between both coexisting processes, i.e., cross-linking and degradation (oxidation). Up to now, many important studies have been written on the topic of the influence of high-energy radiation on the useful properties of polymer materials, e.g., studies of Holik, Danek, Manas et al [33,34] and other authors [5,[18][19][20][21][22][23][24][25][26][27][28][29]. Nevertheless, the aforementioned correlation between the absorbed radiation dose and the required surface and mechanical properties has not yet been comprehensively investigated.…”

Tribological and Micro-Mechanical Properties of Injected Polypropylene Modified by Electron Radiation

“…The Indentation hardness H IT represents the degree of resistance to permanent deformation or damage. Indentation hardness H IT is generally defined as the maximum loading force P max divided by the area of contact (A p ) between the indentor and test sample [29,30].…”

“…In general, the indentation modulus can be determined from the slope of the tangent line used for the calculation of the indentation hardness H IT . The calculations involve the Poisson number (v s ), which is usually between 0.2 and 0.4 for metal materials and 0.3 and 0.4 for polymer materials [29,30].…”

“…Equation ( 6) contains h 1 , which is the indentation depth in t 1 , the time when the maximum load is reached. Furthermore, h 2 is the depth reached in t 2 during the hold on constant maximum testing load phase [29,30].…”