Low-density polyethylene (LDPE)/barium sulfate (BaSO 4 ) composites with different contents of BaSO 4 nanoparticles after modification by stearic acid (SA) were prepared. Characterizations of morphology, thermal, and mechanical properties of the LDPE/SA-BaSO 4 composites were systematically performed by scanning electron microscope, thermal gravimetric analysis, tensile and flexural tests. Specially, the X-ray radiographic and developable properties were examined by the X-ray fluoroscopy test and the ageing resistant properties were analyzed by the simplified protocol of accelerated aging. It was found that the Young's modulus and tensile strength of the composites were increased by 24.6 and 11.0% while flexural modulus and flexural strength were increased by 10.8 and 14.0%, respectively, together with the elongation at break of 455.1% 6 26.3% which was 74.4% of LDPE when the SA-BaSO 4 content reached 25 wt%. By contrast, when accelerated ageing for 5 years, the retention ratios of Young's modulus, tensile strength and elongation remained at 89.3, 69.5, and 69.6%, respectively. In addition, X-ray radiographic and developable properties of the composites were also improved by the addition of SA-BaSO 4 , making it possible to achieve some applications in medical devices such as intrauterine devices and body brackets which could be easily implanted into human bodies and enable accurate external monitoring using an X-ray medical diagnostic machine. POLYM. COMPOS., 37:1396-1406, 2016

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A new compound was synthesized by chemical combination of (3-mercapto)propyl-heptaisobutyl polyhedral oligomeric silsesquioxane (POSS-SH) and 1,3:2,4-bis(3,4dimethylbenzylidene) sorbitol (DMDBS) via epichlorohydrin while hydroxyl groups were still retained in the product POSS-DMDBS. The prepared POSS-DMDBS was introduced into isotactic polypropylene (iPP) to improve crystallization behaviors of iPP and obtain nanocomposites with suitable mechanical properties. Crystallization and mechanical properties of iPP/POSS-DMDBS were systematically investigated by wide-angle X-ray diffraction, polarization microscopy, atomic force microscopy, differential scanning calorimetry, and tensile tests. The spherulite size of the modified iPP was obviously decreased with the addition of POSS-DMDBS, while the crystallization temperature was increased by 58C to 98C depending on the content of POSS-DMDBS incorporated. POSS-DMDBS exhibited relatively higher nucleating efficiency on iPP which is similar to that of DMDBS, confirmed by the increased crystallization temperature. It was also found that the tensile modulus of iPP after adding POSS-DMDBS increased significantly with respect to pristine iPP, but the elongation values decreased. Introduction of POSS-DMDBS in content less than 1 wt% could bring about effective influence on the crystallization behaviors of iPP, demonstrating its potential applications. POLYM. ENG. SCI.,