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The recyclability of two commercial nylon 66/PPO [poly(phenylene oxide)] alloys has been investigated by examining the effects of multiple and abusive melt processes upon the impact strength. The loss of performance associated with these exposures has been correlated, in one instance, with the thermal degradation of polybutadiene-based impact modifier. The degradation of the rubber has been quantified using an indirect measurement of rubber mobility obtained from the NMR free induction decay of mobile and rigid protons in the material. Substitution of the unsaturated rubber modifier with a saturated hydrocarbon resulted in improved recyclability. Both formulations provide evidence of changes in morphology related to instability of the dispersed PPO phase. The coalescence of PPO particles, evident in later stages of prolonged thermal exposure, appears to cause further loss of impact strength. Currently the chemical and/or physical changes responsible for the increase in average PPO particle size are not known. It is probable that the thermal stability of the compatibilizer, formed during the reactive extrusion manufacturing process, may be insufficient to provide a durable morphology for repeated recycling of these alloys., INTRODUCTION The recyclability of thermoplastic materials is contingent upon numerous technical factors including life history prior to recycling and the effects of multiple processing operations upon the physical and chemical [...]

Abnormal degradation of matrix components due to dysregulated expression of matrix metalloproteinase (MMP)-9 in macrophages has been linked to progression of acute cerebral ischemia and atherosclerosis. We report that lithium chloride (LiCl) or CHIR99021, inhibitors of Wnt signaling pathway, enhance phosphorylation of glycogen synthase kinase-3beta and suppress lipopolysaccharide-mediated upregulation of MMP-9 expression in murine macrophage RAW264.7 cells in a dose-dependent manner. Suppression of MMP-9 expression by LiCl or CHIR99021 did not result after inhibition of kinases involved in NFκB or AP-1 family proteins, but from changes in the activity of histone deacetylases. Beneficial effects on atherosclerosis or cerebral ischemia in animal studies caused by LiCl may be in part explained by the suppression of MMP-9 gene expression. [ABSTRACT FROM AUTHOR]

This study examined the electrical and self-sensing capacities of ultra-high-performance fiber-reinforced concrete (UHPFRC) with and without carbon nanotubes (CNTs). For this, the effects of steel fiber content, orientation, and pore water content on the electrical and piezoresistive properties of UHPFRC without CNTs were first evaluated. Then, the effect of CNT content on the self-sensing capacities of UHPFRC under compression and flexure was investigated. Test results indicated that higher steel fiber content, better fiber orientation, and higher amount of pore water led to higher electrical conductivity of UHPFRC. The effects of fiber orientation and drying condition on the electrical conductivity became minor as sufficiently high amount of steel fibers, 3% by volume, was added. Including only steel fibers did not impart UHPFRC with piezoresistive properties. Addition of CNTs substantially improved the electrical conductivity of UHPFRC. Under compression, UHPFRC with a CNT content of 0.3% or greater had a self-sensing ability that was activated by the formation of cracks, and better sensing capacity was achieved by including greater amount of CNTs. Furthermore, the pre-peak flexural behavior of UHPFRC was precisely simulated with a fractional change in resistivity when 0.3% CNTs were incorporated. The pre-cracking self-sensing capacity of UHPFRC with CNTs was more effective under tensile stress state than under compressive stress state., Competing Interests: The authors declare no conflict of interest.