Structure and mechanical investigation of the effect of proton irradiation in Makrofol DE 7-2 polycarbonate

Research highlights: → Makrofol is a candidate for applications requiring its bending without breaking. → The carbonyl groups (C=O) are the most sensitive groups to proton irradiation. → The irradiation of Makrofol causes crosslinking that increases the molecular mass. → The standard chains and a great number of chain ends weaken under proton irradiation. - Abstract: Makrofol-DE 7-2 polycarbonate is a class of polymeric solid state nuclear track detectors which has many applications in various radiation detection fields. In the present work, Makrofol samples were irradiated using different fluences (2.5 x 1013 to 2.5 x 1015 p cm-2) of 1 MeV protons at the University of Surrey Ion Beam Center, UK. The structural modifications in the proton irradiated Makrofol samples have been studied as a function of fluence using different characterization techniques such as X-ray diffraction, FTIR spectroscopy, intrinsic viscosity and mechanical properties. The results indicate that the carbonyl group (C=O) is the most sensitive group towards proton irradiation, where it degraded under irradiation up to 2.5 x 1015 p cm-2. This degradation is also reported by FTIR spectroscopy and enhanced the degree of ordering in the degraded samples as revealed by XRD technique. Additionally, this degradation decreases the intrinsic viscosity from 0.68 to 0.41 at 35 deg. C, indicating a decrease in the average molecular mass. Above 7.5 x 1013 and up to 2.5 x 1015 p cm-2, the free radicals produced from scission are chemically active, can be used in chemical reactions that lead to the enhancement of the crosslinking process. Thus the proton irradiation in the fluence range 7.5 x 1013 to 2.5 x 1015 p cm-2 led to a more compact structure of Makrofol polymer resulted in an enhancement in its mechanical properties.