Isothermal crystallization behavior and properties of polypropylene/EPR blends nucleated with sodium benzoate

The effect of sodium benzoate on the isothermal crystallization behavior of isotactic polypropylene (iPP)/ethylene–propylene rubber(EPR) blends was investigated using differential scanning calorimetry. Dynamic mechanical and physical properties of the iPP/EPR blends nucleated with sodium benzoate were also measured. It was found that the crystallization behavior and physical properties such as heat deflection temperature (HDT), flexural modulus, and impact strength were strongly affected by the competition between the nucleating effect of EPR attributed to its partial compatibility with iPP and the simple addition of the amorphous component, as well as the nucleating effect of sodium benzoate. High impact strength was achieved by addition of EPR and sodium benzoate to iPP. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 201–211, 2002     

Low‐temperature photoinitiation solution polymerization behavior of N‐vinylcarbazole in tetrahydrofuran

N‐Vinylcarbazole (VCZ) was solution‐polymerized in tetrahydrofuran (THF) at ?20, 0, and 20°C using the photoinitiation method; the effects of the amount of solvent, polymerization temperature, and photoinitiator concentration were investigated. On the whole, the experimental results corresponded to predicted ones. Low polymerization temperature using photoinitiation proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of a high molecular weight with a smaller temperature rise during polymerization; nevertheless of free radical polymerization by 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN). The photo‐solution polymerization rate of VCZ in THF was proportional to the 0.47 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ prepared in THF at ?20°C using a photoinitiator concentration of 0.00005 mol/mol of VCZ, a weight‐average molecular weight of 510,000 was obtained, with a polydispersity index of 1.73, and a degree of lightness converged to about 99%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3667–3672, 2002     

Photoluminescent and tough hydrogels from silk fibroin and polyacrylic acid complexed with europium

Biocompatible, tough, and photoluminescent hydrogels are highly desirable for biomedical applications in vivo. Herein, hybrid hydrogels prepared from silk fibroin (SF) and polyacrylic acid (PAA) and complexed with europium, named as SF-PAA-Eu³⁺ hydrogels, exhibit good comprehensive properties. Owing to the intensive molecular interactions among SF, PAA, and Eu³⁺, SF-PAA-Eu³⁺ hydrogels show a greatest tensile strength of 0.58 MPa, elongation of 443%, and work of fracture of 1.65 MJ/m. In vivo imaging experiment in a mouse subcutaneous implantation model revealed excellent and sustained photoluminescence of the SF-PAA-Eu³⁺ hydrogels for 24 h. The work provides a strategy for designing functional SF-based hydrogels for imaging applications in vivo.     

Enhancing the carbon sink in European agricultural soils: including trace gas fluxes in estimates of carbon mitigation potential

The possibility that the carbon sink in agricultural soils can be enhanced has taken on great political significance since the Kyoto Protocol was finalised in December 1997. The Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere. Thus, forestry activities (Article 3.3) and changes in the use of agricultural soils (Article 3.4) that are shown to reduce atmospheric CO₂levels may be included in the Kyoto emission reduction targets. The European Union is committed to a reduction in CO₂ emissions to 92% of baseline (1990) levels during the first commitment period (2008–2012). We have shown recently that there are a number of agricultural land-management changes that show some potential to increase the carbon sink in agricultural soils and others that allow alternative forms of carbon mitigation (i.e. through fossil fuel substitution), but the options differ greatly in their potential for carbon mitigation. The changes examined were, (a) switching all animal manure use to arable land, (b) applying all sewage sludge to arable land, (c) incorporating all surplus cereal straw, (d) conversion to no-till agriculture, (e) use of surplus arable land to de-intensify 1/3 of current intensive crop production (through use of 1/3 grass/arable rotations), (f) use of surplus arable land to allow natural woodland regeneration, and (g) use of surplus arable land for bioenergy crop production. In this paper, we attempt for the first time to assess other (non-CO₂) effects of these land-management changes on (a) the emission of the other important agricultural greenhouse gases, methane and nitrous oxide, and (b) other aspects of the ecology of the agroecosystems. We find that the relative importance of trace gas fluxes varies enormously among the scenarios. In some such as the sewage sludge, woodland regeneration and bioenergy production scenarios, the inclusion of trace gases makes only a small (<10%) difference to the CO₂-C mitigation potential. In other cases, for example the no-till, animal manure and agricultural de-intensification scenarios, trace gases have a large impact, sometimes halving or more than doubling the CO₂-C mitigation potential. The scenarios showing the greatest increase when including trace gases are those in which manure management changes significantly. In the one scenario (no-till) where the carbon mitigation potential was reduced greatly, a small increase in methane oxidation was outweighed by a sharp increase in N₂O emissions. When these land-management options are combined to examine the whole agricultural land area of Europe, most of the changes in mitigation potential are small, but depending upon assumptions for the animal manure scenario, the total mitigation potential either increases by about 20% or decreases by about 10%, shifting the mitigation potential of the scenario from just above the EU's 8% Kyoto emission reduction target (98.9 Tg C y⁻¹) to just below it. Our results suggest that (a) trace gas fluxes may change the mitigation potential of a land management option significantly and should always be considered alongside CO₂-C mitigation potentials and (b) agricultural management options show considerable potential for carbon mitigation even after accounting for trace gas fluxes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Adhesion properties of soy protein with fiber cardboard

Adhesion properties of soy protein isolate (SPI) on fiber cardboard and effects of press conditions, pre-pressing drying time, and protein concentrations on gluing strength were investigated. Shear strength increased as press time, press pressure, and/or press temperature increased. The effect of temperature on shear strength became more significant at high press pressure. The shear strength of the SPI adhesive on fiber cardboard decreased by 12–25% after water soaking. Shear strength increased as pre-pressing drying time increased and reached its maximal value at about 10 min. An SPI/water ratio of 12∶100 (w/w) gave the highest gluing strength. The specimens showed complete cohesive failure (fiber cardboard failure) except for soaked specimens pressed at low press temperature, low pressure, and short press time. Specimens pressed at 25°C and 2 MPa for 5 min with pre-pressing drying time of 10 min and an SPI/water ratio of 12∶100 (w/w) had T-peel strength and tensile bonding strength of 1.15 N/mm and 0.62 MPa, respectively, without water soaking, and 1.11 N/mm and 0.24 MPa, respectively, with water soaking.     

In vitro skin permeation and cellular protective effects of flavonoids isolated from Suaeda asparagoides extracts

The objective of this study was to compare astragalin (kaempferol-3-O-glucoside) isolated from Suaeda asparagoides extract with kaempferol, an aglycone of astragalin showing the anti-oxidative activity, the cellular protective effect, and skin permeability. Kaempferol was superior to (+)-α-tocopherol and l-ascorbic acid known as strong antioxidants in the antioxidative activity by DPPH method and chemiluminescence assay. Astragalin and kaempferol exhibited more prominent cellular protective effect than the lipid peroxidation chain blocker, (+)-α-tocopherol. In this in vitro permeation experiment of astragalin and kaempferol through the ICR mouse skin, kaempferol permeated deeper into the skin than astragalin. These results indicate that kaempferol and astragalin can function as antioxidants in biological systems, particularly skin exposed to solar radiation, and protect cellular membranes against reactive oxygen species.     

Novel conventional and chelating anion exchange resins with amino ligands for sorption of silver

ABSTRACT

The polymeric resins containing diethylenetriamine, tetraethylenepentamine, 2-(diethylamino)ethanol, 1-methylimidazole, and 1,2-dimethylimidazole ligands have been synthesized from vinylbenzyl chloride-divinylbenzene copolymers and used in the removal of Ag(I) from chloride solution. The best Ag(I) sorption was reached in the case of 1-methylimidazole resin. Resins retain their capacity towards Ag(I) in five consecutive sorption/desorption cycles. The resins with imidazole ligands were highly selective for Ag(I) from synthetic chloride solution and they did not sorb chloride complexes of Cu(II). Additionally, the recovery of Ag(I) was tested from real chloride solution coming from leaching of the copper concentrate from Lubin Concentrator (KGHM Polska Mied? S.A.).     

Thermo-rheological analysis of various chain extended recycled poly(ethylene terephthalate)

Three chain extenders, pyromellitic dianhydride (PMDA), ethylene carbonate (EC), and a polymeric-epoxide, were investigated for improving recycled p(ethylene terephthalate) (r-PET) properties with melt extrusion. The amount of additives and processing temperatures were also varied to check for melt degradation. Small amplitude oscillatory shear experiments were performed to probe rheological changes with different chain extenders. Capillary rheometry with haul-off was also performed to measure extensional viscosity and melt strength. Higher loadings of the chain extenders were found to improve properties of r-PET. These chain extenders definitely increased melt viscosities when incorporated at the higher level of the ranges examined, matching that of virgin PET. EC addition resulted in high shear thinning of the polymer. Epoxy and PMDA added to r-PET produced products with the same extensional viscosity as v-PET. Haul-off experiments demonstrate superior performance by epoxy-modified r-PET compared to v-PET.     

Improving the flame retardancy of polypropylene foam with piperazine pyrophosphate via multilayering coextrusion of film/foam composites

A series of 16-layer polypropylene/flame retardant (PP/FR) film/foam composite structures were produced by microlayer coextrusion. A highly branched PP was used in the foam layers to increase strain hardening and cell stability, while the PP used in the film layers was a high shear viscosity grade to confine bubble growth. In addition to improved tensile properties, the PP/FR composite film/foams exhibited five times the compression modulus of PP/FR composite foams at each FR loading level. The thermal stabilities of the composites were investigated, exhibiting three step decompositions. The FR particles were effective in decreasing flammability by forming intumescent char. The PP/FR-film/foam-20 showed self-extinguishing behavior in a modified vertical burn test, while the PP/FR-foam-20 sample continued to burn. Cone calorimetry demonstrated that PP/FR film/foams had lower heat release than PP/FR foams due to the unique alternating film/foam structure of PP/FR film/foams. Scanning electron microscopy imaging of the residual chars from fire testing that the PP/FR composite film/foams showed a more continuous protective char surface when compared with PP/FR composite foams at each FR concentration. The combined data indicate that the formation of a surface film on top of a foam ensures a robust intumescent fire protective barrier for partly foamed materials and shows a new way toward lightweight materials with improved fire safety performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48552.