We investigate the gradual changes of the microstructure of two blends of high-density polyethylene (HDPE) and polyamide 6 (PA6) at opposite composition filled with increasing amounts of an ...organomodified clay. The filler locates preferentially inside the polyamide phase, bringing about radical alterations in the micron-scale arrangement of the polymer phases. When the host polyamide represents the major constituent, a sudden reduction of the average sizes of the polyethylene droplets was observed upon addition of even low amounts of organoclay. A morphology refinement was also noticed at low filler contents when the particles distributes inside the minor phase. In this case, however, keep increasing the organoclay content eventually results in a high degree of PA6 phase continuity. Rheological analyses reveal that the filler loading at which the polyamide assembles in a continuous network corresponds to the critical threshold for its rheological transition from a liquid- to a gel-like behaviour, which is indicative of the structuring of the filler inside the host PA6. On the basis of this finding, a schematic mechanism is proposed in which the role of the filler in driving the space arrangement of the polymer phases is discussed. Finally, we show that the synergism between the reinforcing action of the filler and its ability to affect the blend microstructure can be exploited in order to enhance relevant technological properties of the materials, such as their high temperature structural integrity.
Display omitted
Display omitted
•Nanocomposites based on commercial biodegradable polymer were investigated.•Effect of the orientation during non-isothermal elongational flow was assessed.•Different clay nanofillers ...lead to different rheological behaviour due to their polarity.•Mechanical properties are significantly dependent on the draw ratio.•Nanocomposites subjected to significant non-isothermal elongational flow can behave like a polymer blend.
The recent increasing interest towards biodegradable polymers has favoured the investigation on these systems, showing also their limits. On the other hand, the success achieved by nanocomposites has fostered the search for new systems where the polymer matrix is biodegradable. The final properties can depend on a number of factors, including the biodegradable polymer used as well as the nanosized filler, their mutual compatibility, the filler dispersion and the processing conditions. In this work, nanocomposites based on a starch-derived matrix and three different lamellar silicates were prepared, and the effects of the elongational flow on the dispersion, the improvement of intercalation/exfoliation and the possible aligning of the nanosilicate particles along the flow direction was investigated. Rheological, morphological and tensile tests showed that the properties were significantly different upon varying the compatibility between the polymer matrix and the nanofiller, as well as the draw ratio and therefore the orientation degree.
Polymer films based on biodegradable polymers, polyethylene (PE) and modified PE with oxo-degradable additive were prepared by film blowing. Carbon black (1%) was added to all the films. Commercial ...biodegradable Ecovio
and Mater-Bi
samples were used. Mechanical properties, soil burial degradation and surface wettability were investigated, before and after UV irradiation. Chemical modifications induced by UV and soil degradation, or a synergic effect, were highlighted by Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR). Photo-oxidized film samples with an elongation at break equal to 50% and 0.5 the initial value were selected for the soil burial degradation test at 30 °C. Weight loss measurements were used to follow biodegradation in soil. Predictably, the degradation in soil was higher for biodegradable polymer-based films than for the PE-based ones. UV irradiation increased surface wettability and encouraged the disintegration in soil of all the samples. In fact, photo-oxidation produced a molar mass reduction and hydrophilic end groups, thus increasing surface erosion and weight loss. This paper not only supplies new criteria to evaluate the performance of biodegradable films in agriculture, before and after lifetime, but also provides a comparative analysis on the soil burial degradation behaviour with traditional ones.
There is considerable evidence that multiple sclerosis (MS) is an immune‐mediated disease characterized by infiltration of inflammatory cells into the CNS and demyelination. Several myelin proteins ...may be encephalitogenic, including myelin basic protein, proteolipid protein and myelin oligodendrocyte glycoprotein (MOG), the latter being expressed on the external layer of myelin sheaths and hence accessible to antibody attack. We investigated MOG autoreactivity in serum and cerebrospinal fluid (CSF) by ELISA, employing the recombinant extracellular domain of MOG as antigen. We tested serum samples from 262 MS patients (175 relapsing‐remitting, 43 primary progressive and 44 secondary progressive), 131 patients with other neurological diseases (OND) and 307 healthy controls. No patients or controls were receiving immunomodulating treatments. We found anti‐MOG antibodies in the serum of 13.7% MS patients, mainly in those with secondary progressive MS (25%), in 13.7% of OND patients and in 6.2% of controls. We found a direct correlation (R2 = 0.6, P = 0.002) between disease severity and anti‐MOG titer only in patients with primary and secondary progressive MS. Anti‐MOG antibodies were present in the CSF of 11.4% MS patients and 18.9% OND patients. Intrathecal synthesis of anti‐MOG antibodies was demonstrated in four (4.5%) of MS patients and no OND patients. Anti‐MOG antibodies are not specific for MS; however, they may characterize a subset of MS patients and this may be revealed by serial assays in relation to changing disease phase.
The preliminary results of a post-marketing study on relapsing-remitting multiple sclerosis patients treated with immunomodulating agents attending the Lombardia Region's Multiple Sclerosis Centers ...are presented. A total of 294 patients treated with Betaferon (67), Avonex (115), Rebif 22 (45), Rebif 44 (18) and Copaxone (49) were included. Relapse frequency consistently decreases at 1 year and continues to decrease after 5 years of treatment, without differences between therapeutic groups. Eighty-seven out of 294 patients (29.6%) discontinued treatment for different reasons. Forty-eight of them shifted to a second therapeutic agent. A different trend, to lower or higher doses of interferon or immunosuppression, according to reasons of discontinuation, was observed.
The efficacy of dexamethasone (DX) and methylprednisolone (MP) at high (HD) and low (LD) dose in acute multiple sclerosis (MS) relapses was evaluated by a double-blind trial in 31 patients followed ...for 1 year. DX and HDMP were similarly efficacious in promoting recovery, while LDMP was ineffective in the short-term outcome and was followed by an early clinical reactivation. The different outcomes seem to be related to different immunomodulating effects, mainly on cerebrospinal fluid (CSF) IgG synthesis and on peripheral blood and CSF CD4+ lymphocyte subsets.
Polymer nanocomposites are gaining a growing interest both in the academia and in the industrial field, because of some specific properties they can assure. However, the rise in the attention from ...the industry is also leading to concerns about their processing, which can involve issues which are not present in traditional polymers processing; furthermore, additional issues can arise when nanocomposites are based on a polymer blend rather than a single polymer. In this work, a systematic study on thermomechanical degradation and reprocessing behaviour of LDPE/PA6/Cloisite 15A systems has been performed. The characterization was based on rheological, mechanical and morphological analysis. The investigation revealed a complex degradation behaviour, including the degradation phenomena involving the filler and those involving the two components of the polymer blend; furthermore, these phenomena are strongly dependent on the specific processing conditions.
To evaluate the incidence and dose-dependency of mitoxantrone (MTX)-associated acute myelocytic leukemia (AML) in the network of Italian multiple sclerosis (MS) clinics.
We performed a multicenter ...retrospective cohort study of patients treated with MTX in MS centers under the Italian national health care system between 1998 and 2008. Demographic, disease, treatment, and follow-up information were collected using hospital records.
Data were available for 3,220 patients (63% women) from 40 Italian centers. Follow-up (mean ± SD) was 49 ± 29 months (range 12-140 months). We observed 30 cases of AML (incidence 0.93% 95% confidence interval 0.60%-1.26%). The mean cumulative dose was higher in patients with AML (78 vs 65 mg/m(2), p = 0.028). The median interval from the start of therapy to AML diagnosis was longer than expected at 33 months (range 13-84 months); 8 patients (27%) developed AML 4 years or more after the first MTX infusion. The rate of mortality associated with AML was 37%.
This higher than expected risk of AML and related mortality requires that treatment decisions must be made jointly between clinicians and patients who understand their prognosis, treatment options, and treatment-related risks. The now large exposed MS population must be monitored for hematologic abnormalities for at least 6 years from the end of therapy, to ensure the rapid actions needed for early diagnosis and treatment of AML.
PDF
