Mechanical, flow and electrical properties of thermoplastic polyurethane/fullerene composites: Effect of surface modification of fullerene

Thermoplastic polyurethane (TPU) composites with fullerene loadings varying from 0.5 to 2 weight% were prepared by melt-mixing method. Nitric acid oxidation and silanization were applied to fullerene surface to improve interfacial interactions with TPU matrix. The influence of surface modifications of fullerene on mechanical, melt flow and electrical properties of TPU based composites were investigated. Incorporation of fullerene leads to nearly twofold increase in tensile strength and Young's modulus of the composites in addition to enhancing the flexibility. The best results are obtained in nitric acid and silane modified fullerene containing composites at the lowest concentration (0.5%). Higher MFI values were observed for composites loaded with surface treated fullerenes compared to pristine fullerene because of their better dispersion in TPU. Electrical properties of TPU also improved by the addition of surface modified fullerene particles. Surface oxidation and silanization gave rise to dispersion homogeneity which may be the reason of both tensile strength and strain improvements at the same time

Effect of LiClO4 Salt on Dielectric Properties of Acrylonitrile-Methyl Methacrylate and Acrylonitrile-Isobutyl Methacrylate Copolymers

Poly(acrylonitrile-co-isobutyl methacrylate), PAN-co-PIBMA, and poly(acrylonitrile-co-methyl methacrylate), PAN-co-MMA copolymers are synthesized by emulsion polymerization. The structural characterization is done by FTIR and H-1-NMR spectroscopy and thermal analyses are performed by thermogravimetric analysis (TGA). After various amounts of LiClO4 salt loading into copolymer films, the dielectric properties of these films at different temperatures and frequencies are determined. The effects of different methacrylate groups and salt content on the dielectric properties of copolymers are investigated. It is found that the dielectric constant increases systematically with increasing MMA and IBMA content in the copolymer. The samples with higher salt content show higher ac-conductivities

Preparation and characterization of acrylonitrile-ethyl methacrylate copolymers and the effect of LiClO4 salt on electrical properties of copolymer films

Copolymers of poly(acrylonitrile-co-ethyl methacrylate), P(AN-EMA), with three different EMA content and parent homopolymers were synthesized by emulsion polymerization. The chemical composition of copolymers were identified by FTIR, H-1-NMR and C-13-NMR spectroscopy. The thermal properties of copolymers were modified by changing the EMA content in copolymer compositions. Various amounts of LiClO4 salt loaded (PAN-co-PEMA) copolymer films were prepared by solution casting. The dielectric properties of these films at different temperatures and frequencies were investigated. It was found that the dielectric constant and ac-conductivity of copolymer films were strongly influenced by the salt amounts and EMA content in copolymers. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 201

The synthesis of covalent bonded single-walled carbon nanotube/polyvinylimidazole composites by in situ polymerization and their physical characterization

Single-walled carbon nanotube (SWCNT) polyvinylimidazole (PVI) composites have been prepared by in situ emulsion polymerization. Dispersion of raw SWCNTs in the PVI matrix was improved by surface modification of the SWCNTs using nitric acid treatment and air oxidation. The carbonyl-terminated SWCNTs were covalently bonded to PVI by in situ polymerization and the SWCNT/PVI composite was thus obtained. The morphological and structural characterizations of the surface-functionalized SWCNTs and SWCNT/PVI composites were carried out by Fourier transform infrared spectroscopy, X-ray diffraction, conductivity measurements, scanning, and transmission electron microscopy. Thermograms of the materials were determined by the differential scanning calorimetry technique. The characterization results indicate that PVI was covalently bonded to SWCNTs and a new material was then obtained. The functionalized SWCNTs showed homogenous dispersion in the composites, whereas purified SWCNT resulted in poor dispersion and nanotube agglomeration. SWCNT/PVI composites exhibited chemical stability enhancement in many common solvents. IV curves of the samples exhibit an ohmic character. Conductivity values for pure SWCNTs, pure PVI and SWCNT/PVI composite were measured to be 3.47, 2.11 X 10-9, and 2.3 X 10-3 S/m, respectively. Because of resonance, a large dielectric constant is obtained for SWCNT/PVI composite, which is not observed for ordinary materials

Mechanical, electrical, and melt flow properties of polyurethane elastomer/surface-modified carbon nanotube composites

Carbon nanotube-reinforced polyurethane elastomer composites were prepared by melt-mixing. Nitric acid oxidation and silanization were applied to carbon nanotube surfaces to achieve better interfacial interactions with polyurethane elastomer. Tensile and hardness tests, differential scanning calorimetry, melt flow index test, dielectric measurements, and morphological studies of composites were reported. The best results were obtained for surface-modified carbon nanotubes containing composites with lower loading levels. Addition of carbon nanotubes leads to almost two-fold increase in strain and modulus compared to pristine polyurethane elastomer. Tensile strength of composites was also improved by inclusion of carbon nanotubes. However, strength values drop down with increasing carbon nanotube content. Shore hardness increased with the inclusion of modified carbon nanotube to polyurethane elastomer while pristine carbon nanotube caused remarkable decrease in hardness of polyurethane elastomer. Relatively higher melting points and slightly lower glass transition temperatures were observed for carbon nanotube-loaded composites compared to polyurethane elastomer because of plasticizing effect of carbon nanotube. Incorparation of carbon nanotube to polyurethane elastomer matrix caused reduction in melt flow index values due to formation of agglomarates, and n the contrary, surface modifications of carbon nanotube exhibited increase in melt flow index thanks to enhanced interfacial interactions between carbon nanotube and polyurethane elastomer. Significant increase in dielectric constant of composites was observed. Better dispersion of surface modified carbon nanotubes into polyurethane elastomer was also concluded from SEM micrographs of composites

Epileptic seizures in cerebral venous sinus thrombosis: Subgroup analysis of VENOST study

Purpose: The aim of this study is to evaluate the presence and prognostic impact of early seizures in cerebral venous sinus thrombosis patients (CVST).Method: VENOST is a retrospective and prospective national multicenter observational study. CVST patients with or without epileptic seizures (ES) were analyzed and compared in terms of demographic and imaging data, causative factors, clinical variables, and prognosis in a total of 1126 patients.Results: The mean age of the patients in the ES group was 39.73 +/- 12.64 and 40.17 +/- 14.02 years in the non-ES group (p > 0.05). Epileptic seizures were more common (76.6 %) in females (p < 0.001). Early ES occurred in 269 of 1126 patients (23.9 %). Epileptic seizures mainly presented in the acute phase (71.4 %) of the disease (p < 0.001). Majority of these (60.5 %) were in the first 24 h of the CVST. The most common neurological signs were focal neurologic deficits (29.9 %) and altered consciousness (31.4 %) in the ES group. Superior sagittal sinus (SSS) and cortical veins (CV) involvement were the most common sites of thrombosis and the mostly related etiology were found puerperium in seizure group (30.3 % vs 13.9 %). Patients with seizures had worse outcome in the first month of the disease (p < 0.001) but these did not have any influence thereafter.Conclusions: In this largest CVST cohort (VENOST) reported female sex, presence of focal neurological deficits and altered consciousness, thrombosis of the SSS and CVs, hemorrhagic infarction were risk factors for ES occurrence in patients with CVST

Epileptic seizures in cerebral venous sinus thrombosis: Subgroup analysis of VENOST study

Purpose: The aim of this study is to evaluate the presence and prognostic impact of early seizures in cerebral venous sinus thrombosis patients (CVST). Method: VENOST is a retrospective and prospective national multicenter observational study. CVST patients with or without epileptic seizures (ES) were analyzed and compared in terms of demographic and imaging data, causative factors, clinical variables, and prognosis in a total of 1126 patients. Results: The mean age of the patients in the ES group was 39.73 +/- 12.64 and 40.17 +/- 14.02 years in the non-ES group (p > 0.05). Epileptic seizures were more common (76.6 %) in females (p < 0.001). Early ES occurred in 269 of 1126 patients (23.9 %). Epileptic seizures mainly presented in the acute phase (71.4 %) of the disease (p < 0.001). Majority of these (60.5 %) were in the first 24 h of the CVST. The most common neurological signs were focal neurologic deficits (29.9 %) and altered consciousness (31.4 %) in the ES group. Superior sagittal sinus (SSS) and cortical veins (CV) involvement were the most common sites of thrombosis and the mostly related etiology were found puerperium in seizure group (30.3 % vs 13.9 %). Patients with seizures had worse outcome in the first month of the disease (p < 0.001) but these did not have any influence thereafter. Conclusions: In this largest CVST cohort (VENOST) reported female sex, presence of focal neurological deficits and altered consciousness, thrombosis of the SSS and CVs, hemorrhagic infarction were risk factors for ES occurrence in patients with CVST.WOS:0005375741000192-s2.0-85083703251PubMed: 3235381

Assessment of Patients with Intracerebral Hemorrhage or Hemorrhagic Transformation in the VENOST Study

PubMed: 33130674Introduction: Cerebral venous and sinus thrombosis (CVST) may lead to cerebral edema and increased intracranial pressure; besides, ischemic or hemorrhagic lesions may develop. Intracerebral hemorrhages occur in approximately one-third of CVST patients. We assessed and compared the findings of the cerebral hemorrhage (CH) group and the CVST group. Materials and Methods: in the VENOST study, medical records of 1,193 patients with CVST, aged over 18 years, were obtained from 35 national stroke centers. Demographic characteristics, clinical symptoms, signs at the admission, radiological findings, etiologic factors, acute and maintenance treatment, and outcome results were reported. the number of involved sinuses or veins, localizations of thrombus, and lesions on CT and MRI scans were recorded. Results: CH was detected in the brain imaging of 241 (21.1%) patients, as hemorrhagic infarction in 198 patients and intracerebral hemorrhage in 43 patients. Gynecologic causes comprised the largest percentage (41.7%) of etiology and risk factors in the CVST group. in the CH group, headache associated with other neurological symptoms was more frequent. These neurological symptoms were epileptic seizures (46.9%), nausea and/or vomiting (36.5%), altered consciousness (36.5%), and focal neurological deficits (33.6%). mRS was ?3 in 23.1% of the patients in the CH group. Discussion and Conclusion: CVST, an important cause of stroke in the young, should be monitored closely if the patients have additional symptoms of headache, multiple sinus involvement, and CH. Older age and parenchymal lesion, either hemorrhagic infarction or intracerebral hemorrhage, imply poor outcome. © 2020 S. Karger AG, Basel. All rights reserved

Headache as the sole presenting symptom of cerebral venous sinuses thrombosis: Subgroup analysis of data from the VENOST study

Objectives: Headache is the most common complaint in cerebral venous sinus thrombosis (CVST) and it may sometimes be the only symptom in these patients. This retrospective and prospective study was an investigation of any differences in terms of clinical risk factors, radiological findings, or prognosis in patients with CVST who presented with isolated headache (IH) and cases with other concomitant findings (non-isolated headache [NIH]). Methods: A total of 1144 patients from a multicenter study of cerebral venous sinus thrombosis ( VENOST study) were enrolled in this research. The demographic, biochemical, clinical, and radiological aspects of 287 IH cases and 857 NIH cases were compared. Results: There were twice as many women as men in the study group. In the IH group, when gender distribution was evaluated by age group, no statistically significant difference was found. The onset of headache was frequently subacute and chronic in the IH group, but an acute onset was more common in the NIH group. Other neurological findings were observed in 29% of the IH group during follow-up. A previous history of deep, cerebral, or other venous thromboembolism was less common in the IH group than in the NIH group. Transverse sinus involvement was greater in the IH group, whereas sagittal sinus involvement was greater in the NIH group. The presence of a plasminogen activator inhibitor (PAI) mutation was significantly greater in the IH group. Conclusion: IH and CVST should be kept in mind if a patient has subacute or chronic headache. PAI, which has an important role in thrombolytic events, may be a risk factor in CVST. Detailed hematological investigations should be considered. Additional studies are needed