No abstract

No abstract

No abstract

Low-density polyethylene (LDPE) modified asphalts with improved high-temperature storage stability are prepared by incorporating silica into the LDPE compounds. The effect of silica on the high-temperature storage stabilities, dynamic rheological and mechanical properties, and morphologies of the modified asphalts are studied. It is found that the LDPE/silica ratio in the compound has a great effect on the high-temperature storage stability. The modified asphalts are stable when the ratio of LDPE/silica is around 100/60 (w/w). The silica content in the modified asphalts is less than 3.2%, and it has a slight influence on the mechanical properties of the modified asphalts. Silica can improve the rheological properties of the modified asphalt to some extent. The high-temperature storage stability can be increased by a decreasing density difference between the LDPE/silica compound and the asphalt or in terms of equalizing the polarity differences between asphalt and LDPE by silica.

With the increasing ratio of waste tire powder (WTP) to low-density polyethylene (LDPE), the hardness and tensile strength of the WTP/LDPE blends decreased while the elongation at break increased. Five kinds of compatibilizers, such as maleic anhydride-grafted polyethylene (PE-g-MA), maleic anhydride-grafted ethylene-octene copolymer (POE-g-MA), maleic anhydridegrafted linear LDPE, maleic anhydride-grafted ethylene vinyl-acetate copolymer, and maleic anhydride-grafted styrene-ethylene-butylene-styrene, were incorporated to prepare WTP/LDPE blends, respectively. PE-g-MA and POE-g-MA reinforced the tensile stress and toughness of the blends. The toughness value of POE-g-MA incorporating blends was the highest, reached to 2032.3 MJ/m 3 , while that of the control was only 1402.9 MJ/m 3 . Therefore, POE-g-MA was selected as asphalt modifier. The toughness value reached to the highest level when the content of POE-g-MA was about 8%. Besides that the softening point of the modified asphalt would be higher than 60 C, whereas the content of WTP/LDPE blend was more than 5%, and the blends were mixed by stirring under the shearing speed of 3000 rpm for 20 min. Especially, when the blend content was 8.5%, the softening point arrived at 82 C, contributing to asphalt strength and elastic properties in a wide range of temperature. In addition, the swelling property of POE-g-MA/WTP/LDPE blend was better than that of the other compalibitizers, which indicated that POE-g-MA /WTP/ LDPE blend was much compatible with asphalt. Also, the excellent compatibility would result in the good mechanical and processing properties of the modified asphalt.

Poly(vinylidene difluoride) (PVDF)/Fe 3 O 4 magnetic nanocomposite was prepared by a simple coprecipitation method, and was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and ultraviolet visible spectroscopy (UV-Vis). The SEM images showed that Fe 3 O 4 nanoparticles were dispersed in the PVDF matrix as some aggregates with the sizes of 50 nm-2 lm, and the XRD curves showed the incorporation of the

No abstract

In this study, the different encapsulation methods involving emulsification and coaxial electrospinning were both utilized to fabricate a series of core/sheath composite, nanoparticles (NPs) and Nanofibers (NFs) separately, for drug delivery on potential biological and therapeutic applications. Bovine serum albumin (BSA) was employed as an active pharmaceutical ingredient model for core; poly(L-lactic acid) (PLLA) and methoxy poly(ethyleneglycol)-Poly lactic acid (mPEG-PLA) were selected as the encapsulation matrix for sheath. Attributed to the optimized fabrication procedures, the obtained NPs and NFs had the small average diameters and narrow size distributions with uniform structures and smooth surface morphologies. Based on the drug release profiles, both the NPs provided a burst release process followed by a drug diffusion manner, while for the NFs, the drug diffusion was the predominant factor in drug release. In particular, the mPEG-PLA NFs were fabricated with excellent hydrophilicity and highly neutralized surface resulting in a sustained release of BSA over 10 days. In addition, mPEG-PLA NFs also provided a better zero-order drug release profiles during the release time from 8 to 72 h, and a one-dimensional Fickian diffusion pattern during the whole BSA release period. A cytotoxicity study suggested that the two drug delivery systems were both safe to cells. In conclusions, the synergism of PEGylation with coaxial electrospinning may be an effective way to retard the release of drugs in a more sustained manner.