Probing the Effect of Linear and Crosslinked POE-g-GMA on the Properties of Asphalt

The copolymer ethylene-octene (POE) has good aging resistance and is an inexpensive asphalt additive compared to the styrene-butadiene-styrene copolymer (SBS). However, POE is easy to segregate in asphalt during storage at high temperatures. Grafting glycidyl methacrylate (GMA) onto the molecular backbone of POE (i.e., POE-g-GMA) may solve this problem, for the epoxy groups in GMA can react with the active groups in asphalt. Asphalt modified with linear and crosslinked POE-g-GMA were prepared, and the hot storage stability, physical properties and thermal oxidation aging properties were discussed in detail. The results show that linear and low-degree crosslinked POE-g-GMA-modified asphalts are storage-stable at high temperatures via measurements of the difference in softening points and small-angle X-ray scattering (SAXS) characterizations from macro and micro perspectives. The difference in softening points (ΔSP) between the upper and lower ends is no more than 3.5 °C for modified asphalts after 48 h of being in an oven at 163 °C. More importantly, the crosslinking modification of POE-g-GMA can further increase the softening point and reduce the penetration as well as rheological properties via conventional physical property, dynamic shear rheometer (DSR) and multiple-stress creep recovery (MSCR) tests. Furthermore, asphalt modified with crosslinked POE-g-GMA reveals better aging resistance via measurements of the performance retention rate and electron paramagnetic resonance (EPR) characterizations after a rolling thin film oven test (RTFOT). This work may provide further guidelines for the application of polymers in asphalt.

Synthesizing of Metallized Acrylic Containing Both Gadolinium and Lead as a Transparent Radiation Shielding Material and Its Physical Properties

In this study, a series of optically transparent metallized acrylics containing Gd and Pb were synthesized by the bulk polymerization of Gd(MAA)3, Pb(MAA)2 and AM according to different polymerization procedures. The variation of their optic transmittance and mechanical performance with Gd contents was investigated. Then, quasi-static uniaxial tensile tests under different strain rates and temperatures were performed to study the influence of strain rate and temperature on the mechanical properties of radiation-shielding metallized acrylic containing both Gd and Pb. The tensile responses of this material distinctly exhibit nonlinear characteristics and strongly depend on both temperature and strain rate. Based on the experimental results, a modified Zhu–Wang–Tang (ZWT) constitutive model, in which the standard elastic component was replaced by the Mooney–Rivlin hyperelastic model, was implemented to characterize the observed both hyperelastic and viscoelastic behaviors. The constitutive parameters were expressed as functions of temperature and determined by experimental data. The model fitting results indicate that the selected constitutive model can accurately describe the nonlinear tensile stress–strain responses of metallized acrylic containing Gd and Pb. Furthermore, the great difference in constitutive parameters implies that the viscoelastic behavior of the as-prepared metallized acrylic affects the response to quasi-static tensile loading the most.