Characterization of HDPE-g-MA/clay nanocomposites prepared by different preparation procedures: Effect of the filler dimension on crystallization, microhardness and flammability

Abstract Nanocomposites of maleic anhydride-grafted HDPE (HDMA) and the organoclay Cloisite 20A (20A) have been prepared by melt-compounding, solution-blending and static annealing of polymer/clay powder mixtures. It has been shown that solution-blending of HDMA with 20A fails to produce intercalated composites. Fast intercalation was observed when solution-blending HDMA/clay composites were annealed. The nanocomposites prepared in the melt under shear were found to possess high levels of exfoliation. The dependence of the crystallization behaviour, microhardness and flammability of the composites on the preparation conditions has been studied by differential scanning calorimetry, microhardness tests and determination of limiting oxygen index. The results have shown that the reduction of the flammability and the microhardness of HDMA/20A nanocomposites prepared by melt compounding and composite annealing are higher than those for composites prepared by solution blending. Moreover, a nucleation effect of the clay on the polymer matrix crystallization for some samples has been observed. The results have been interpreted by different levels of clay dispersion and degree of clay intercalation/exfoliation, achieved during different preparation procedures

Effect of Nanoadditives on Bitumen Aging Resistance: A Critical Review

Starting from the eighties, the use of nanoadditives registered an increasing attention in the scientific and patent literature, especially for the case of polymeric nanocomposites. In the last decade, this involved bituminous materials, modified either with nanosized fillers or with polymeric nanocomposites. One of the expected benefits is an increased resistance of the binder to aging. After a short introduction underlining the uncertainties and risks of artefacts in aging tests, a review is given, focusing on the antiaging properties of layered silicates, which are by far the most important nanoadditives for bitumens. Together with layered silicates, other materials such as nanohydrated lime, nanosilica, and layered double hydroxides are mentioned. Preparation and characterization of the binary bitumen/layered silicate and ternary bitumen/layered silicate/polymer systems are described in order to individuate the aspects that influence the antiaging effect. Even if the available literature is quite abundant and unanimously confirms that nanoadditives may improve bitumen durability, there is a lack of studies clarifying the involved mechanisms. As it is for conventional fillers, it seems to be a combination of physical and chemical interactions. Nanoadditives with different chemistries, porosities, and interlayer spacings differently absorb the polar components from the bitumen, thus affecting their predisposition to oxidative aging

Azidated Ether-Butadiene-Ether Block Copolymers as Binders for Solid Propellants

Polymeric binders for solid propellants are usually based on hydroxyl-terminated polybutadiene (HTPB), which does not contribute to the overall energy output. Azidic polyethers represent an interesting alternative but may have poorer mechanical properties. Polybutadiene–polyether copolymers may combine the advantages of both. Four different ether-butadiene-ether triblock copolymers were prepared and azidated starting from halogenated and/or tosylated monomers using HTPB as initiator. The presence of the butadiene block complicates the azidation step and reduces the storage stability of the azidic polymer. Nevertheless, the procedure allows modifying the binder properties by varying the type and lengths of the energetic blocks

Synthesis of GAP and PAMMO Homopolymers from Mesylate Polymeric Precursors

In azidic binders for solid propellants, the N3 functionality is introduced by substitution of a halogen or tosyl group, but recently the mesyl group has been suggested as an alternative. The mesylate group has two advantages, mainly related to its small dimensions and low cost. Poly(glycidyl azide) and poly 3-azidomethyl-3-methyl oxetane were prepared by using both tosylate and mesylate precursors. The azidation kinetics were studied at three different temperatures while keeping all other operating parameters the same. The results confirmed the good potential of the mesylate precursors for the production of azidic binders

Microstructure and rheological response of laboratory-aged SBS-modified bitumens

Polymer additives are widely used to improve the performance of road bitumens including their resistance to hardening during oxidation, although their oxidative inhibitor effect has not been well documented. This study aims to investigate the effect of laboratory-simulated ageing on the microstructure, and rheological properties of Polymer Modified Bitumens (PMBs) prepared with a Styrene-Butadiene-Styrene (SBS) copolymer and sulphur as a cross-linker. The laboratory ageing was conducted through the Rolling Thin Film Oven (RTFO) and the Pressure Aging Vessel (PAV) procedures. The unaged and aged binders were characterised using the Multiple Stress Creep and Recovery (MSCR) test, Gel Permeation Chromatography (GPC) and fluorescence microscopy. The MSCR test showed that the cross-linked polymer had a higher capability of mitigating the effect of bitumen hardening on the rheological response, while for the PMBs without cross-linking, the polymer effects decreased significantly after RTFOT ageing. The GPC results showed that the aromatics, resins and asphaltenes fractions of the unmodified bitumens shifted towards heavier molecules after one cycle of PAV ageing but showed limited variation with further ageing. Similar behaviour was observed for the uncross-linked polymer binders, while for the cross-linked polymer binder, the behaviour depended on the polymer concentration

agronomic evaluation of green biodegradable mulch on melon

A two-year research was carried out in 2004-2005 in order to evaluate the effects of biodegradable green mulch on melon ( Cucumis melo L. var. reticulatus Naud.) yield and quality. The loss of quality due to the presence of spot caused by the residues of biodegradable plastics was also investigated. The research was conducted over two years, in open field, at S. Piero a Grado, Pisa, Italy, (lat. 43.67498, long. 10.34737), from the beginning of May to the end of July of each year. The films tested in the first year experiment were two biodegradable ones with different colours (black and green) compared with a low-density polyethylene (LDPE) film, while in 2005 three biodegradable films, (two green and one black) were compared with a traditional LDPE film. The two green biodegradable films had different properties related to the biodegradation rate, faster in film Cv205 , because of a different degree of Mater Bi polymer inside the film. In each year a randomized block design with four replications was followed. Green biodegradable films allowed obtaining a higher yield than LDPE films maybe because of the higher soil temperatures reached, and excellent fruit quality, especially for the soluble solids content and the ripening process. At the same time, the presence of residues on the fruit skin was rather low because of the degradation of films occurred at the ripening time. In the first year, the percentage of spotted fruits was low for every kind of film, while in the second one the green film showed a higher presence of residues on skin compared with the black one. The biodegradable materials covered the soil for the whole crop cycle with a good mulching effect, and the successive degradation allowed to avoid the removal and disposal of plastic film, with a certain economic advantage

Quantitative Effects of Repeated Muscle Vibrations on Gait Pattern in a 5-Year-Old Child with Cerebral Palsy

Objective. To investigate quantitatively and objectively the effects of repeated muscle vibration (rMV) of triceps surae on the gait pattern in a 5-year-old patient with Cerebral Palsy with equinus foot deformity due to calf spasticity. Methods. The patient was assessed before and one month after the rMV treatment using Gait Analysis. Results. rMV had positive effects on the patient's gait pattern, as for spatio-temporal parameters (the stance duration and the step length increased their values after the treatment) and kinematics. The pelvic tilt reduced its anteversion and the hip reduced the high flexion evidenced at baseline; the knee and the ankle gained a more physiological pattern bilaterally. The Gillette Gait Index showed a significant reduction of its value bilaterally, representing a global improvement of the child's gait pattern. Conclusions. The rMV technique seems to be an effective option for the gait pattern improvement in CP, which can be used also in very young patient. Significant improvements were displayed in terms of kinematics at all lower limb joints, not only at the joint directly involved by the treatment (i.e., ankle and knee joints) but also at proximal joints (i.e., pelvis and hip joint)

Glucan particles loaded with a NIRF agent for imaging monocytes/macrophages recruitment in a mouse model of rheumatoid arthritis

Glucan Particles (GPs) are hollow pseudo-microspheres (average diameter 3?5 mm) obtained from common baker´s yeast Saccharomyces cerevisiae, in which mannan, lipids and proteins are removed through a process of chemical extraction. GPs shell is mostly made of 1,3-b-D-glucan that allows for their prompt in vivo uptake by immune system cells. In this work, the inner cavity of the particles has been loaded with two amphiphilic fluorescent dyes (based on cyanine for in vivo imaging purposes and rhodamine for ex vivo microscopy experiments) through a sudden change in solvent polarity that allowed the entrapment of the molecules as microemulsion. The ability of fluorescent GPs to label immune cells in vivo and report on their recruitment in inflamed sites has been successfully demonstrated in a mouse model of rheumatoid arthritis (CIA) by NIRF imaging. Besides providing the visualization of the mononuclear cell infiltration in the lesion, the fluorescent signal well correlated with the clinical score associated with the disease. Very interestingly, the signal detected in lesions with the same clinical score allowed the assessment of the time evolution (progression or remission) of the pathology.Fil: Garello, Francesca. Universitã â  Di Torino; ItaliaFil: Arena, Francesca. Universitã â  Di Torino; ItaliaFil: Cutrin, Juan Carlos. Universitã â  Di Torino; Italia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Cardiológicas (i); ArgentinaFil: Esposito, Giovanna. Universita di Torino; ItaliaFil: D'angeli, Luca. University Of London; Reino UnidoFil: Cesano, Federico. Universita di Torino; ItaliaFil: Filippi, Miriam. Universitã â  Di Torino; ItaliaFil: Figueiredo, Sara. Universitã â  Di Torino; Italia. Universidad de Coimbra; PortugalFil: Terreno, Enzo. Universita di Torino; Itali

Comparison of Standard 1.5 T vs. 3 T Optimized Protocols in Patients Treated with Glatiramer Acetate. A Serial MRI Pilot Study

This study explored the effect of glatiramer acetate (GA, 20 mg) on lesion activity using the 1.5 T standard MRI protocol (single dose gadolinium [Gd] and 5-min delay) or optimized 3 T protocol (triple dose of Gd, 20-min delay and application of an off-resonance saturated magnetization transfer pulse). A 15-month, phase IV, open-label, single-blinded, prospective, observational study included 12 patients with relapsing-remitting multiple sclerosis who underwent serial MRI scans (Days −45, −20, 0; the minus ign indicates the number of days before GA treatment; and on Days 30, 60, 90, 120, 150, 180, 270 and 360 during GA treatment) on 1.5 T and 3 T protocols. Cumulative number and volume of Gd enhancing (Gd-E) and T2 lesions were calculated. At Days −45 and 0, there were higher number (p < 0.01) and volume (p < 0.05) of Gd-E lesions on 3 T optimized compared to 1.5 T standard protocol. However, at 180 and 360 days of the study, no significant differences in total and cumulative number of new Gd-E and T 2 lesions were found between the two protocols. Compared to pre-treatment period, at Days 180 and 360 a significantly greater decrease in the cumulative number of Gd-E lesions (p = 0.03 and 0.021, respectively) was found using the 3 T vs. the 1.5 T protocol (p = NS for both time points). This MRI mechanistic study suggests that GA may exert a greater effect on decreasing lesion activity as measured on 3 T optimized compared to 1.5 T standard protocol