Cross-linking of LDPE/wax Blends in the Presence of Dicumyl Peroxide

Thermal properties of cross-linked and uncross-linked LDPE/wax blends were investigated. The blends were prepared by thoroughly mixing the powdery ingredients, followed by pressing at 180 ºC for ten minutes. The extent of cross-linking was determined by means of gravimetric analysis of the gel content of the samples. The thermal properties were determined by differential scanning calorimetry (DSC). The analyses of cross-link density of the samples indicated that increased amounts of peroxide gives rise to more efficient cross-linking, but only the PE phase in the blends is cross-linked. The DSC results indicated that LDPE and wax are probably miscible in the crystalline phase at low wax concentrations, but at higher wax concentrations the wax is only partially miscible in the crystalline phase. South African Journal of Chemistry Vol.55 2002: 34-4

Influence of the modification, induced by zirconia nanoparticles, on the structure and properties of polycarbonate

Melt compounding was used to prepare polycarbonate (PC)-zirconia nanocomposites with different amounts of zirconia. The effect of the zirconia loading, in the range of 1-5 wt.%, on the structure, mechanical properties and thermal degradation kinetics was investigated. The zirconia nanoparticle aggregates were well dispersed in the PC matrix and induced the appearance of a local lamellar order in the polycarbonate as inferred by SAXS findings. This order could be a consequence of the intermolecular interactions between zirconia and the polymer, in particular with the quaternary carbon bonded to the methyl groups and the methyl carbon as inferred from the NMR results. The presence of zirconia caused a decrease in the storage and loss moduli below the glass transition temperature. However, the highest amount of zirconia increased the modulus. The presence of zirconia in PC slightly increased the thermal stability, except for the highest zirconia content which showed a decrease. The activation energies of thermal degradation for the nanocomposites were significantly lower than that for pure PC at all degrees of conversion

Twelve-month observational study of children with cancer in 41 countries during the COVID-19 pandemic

Introduction Childhood cancer is a leading cause of death. It is unclear whether the COVID-19 pandemic has impacted childhood cancer mortality. In this study, we aimed to establish all-cause mortality rates for childhood cancers during the COVID-19 pandemic and determine the factors associated with mortality. Methods Prospective cohort study in 109 institutions in 41 countries. Inclusion criteria: children <18 years who were newly diagnosed with or undergoing active treatment for acute lymphoblastic leukaemia, non-Hodgkin's lymphoma, Hodgkin lymphoma, retinoblastoma, Wilms tumour, glioma, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, medulloblastoma and neuroblastoma. Of 2327 cases, 2118 patients were included in the study. The primary outcome measure was all-cause mortality at 30 days, 90 days and 12 months. Results All-cause mortality was 3.4% (n=71/2084) at 30-day follow-up, 5.7% (n=113/1969) at 90-day follow-up and 13.0% (n=206/1581) at 12-month follow-up. The median time from diagnosis to multidisciplinary team (MDT) plan was longest in low-income countries (7 days, IQR 3-11). Multivariable analysis revealed several factors associated with 12-month mortality, including low-income (OR 6.99 (95% CI 2.49 to 19.68); p<0.001), lower middle income (OR 3.32 (95% CI 1.96 to 5.61); p<0.001) and upper middle income (OR 3.49 (95% CI 2.02 to 6.03); p<0.001) country status and chemotherapy (OR 0.55 (95% CI 0.36 to 0.86); p=0.008) and immunotherapy (OR 0.27 (95% CI 0.08 to 0.91); p=0.035) within 30 days from MDT plan. Multivariable analysis revealed laboratory-confirmed SARS-CoV-2 infection (OR 5.33 (95% CI 1.19 to 23.84); p=0.029) was associated with 30-day mortality. Conclusions Children with cancer are more likely to die within 30 days if infected with SARS-CoV-2. However, timely treatment reduced odds of death. This report provides crucial information to balance the benefits of providing anticancer therapy against the risks of SARS-CoV-2 infection in children with cancer

Recommendations on basic requirements for intensive care units: structural and organizational aspects

OBJECTIVE: To provide guidance and recommendations for the planning or renovation of intensive care units (ICUs) with respect to the specific characteristics relevant to organizational and structural aspects of intensive care medicine. METHODOLOGY: The Working Group on Quality Improvement (WGQI) of the European Society of Intensive Care Medicine (ESICM) identified the basic requirements for ICUs by a comprehensive literature search and an iterative process with several rounds of consensus finding with the participation of 47 intensive care physicians from 23 countries. The starting point of this process was an ESICM recommendation published in 1997 with the need for an updated version. RESULTS: The document consists of operational guidelines and design recommendations for ICUs. In the first part it covers the definition and objectives of an ICU, functional criteria, activity criteria, and the management of equipment. The second part deals with recommendations with respect to the planning process, floorplan and connections, accommodation, fire safety, central services, and the necessary communication systems. CONCLUSION: This document provides a detailed framework for the planning or renovation of ICUs based on a multinational consensus within the ESIC

Influence of Different Waxes on the Physical Properties of Linear Low-density Polyethylene

The influence of three different waxes on the thermal and mechanical properties of linear low-density  polyethylene (LLDPE) was investigated. The samples were prepared through melt blending in a Brabender  mixer. The thermal properties of the samples were determined using differential scanning calorimetry  (DSC) and thermogravimetric analysis (TGA). The tensile and flow properties of all the samples were  determined and compared. The polymer-wax miscibilities differed with the type of wax used, and with the amount of wax mixed into the polymer. These miscibilities, and accompanying morphologies, had a  strong influence on the flow properties, thermal stabilities and tensile properties of the corresponding  blends.H1wax andM3wax (which are both Fischer-Tropsch paraffin waxes produced by Sasol Wax) both  reduce the apparent viscosity of LLDPE more than EnHance (a Fischer-Tropsch paraffin wax produced by SasolWax as a polyethylene processing lubricant).M3wax had the strongest influence on the melt flow rates (MFI) of the blends, and it had the least influence on the tensile properties of LLDPE. It did, however, strongly reduce its thermal stability.H1 wax, on the other hand, had only a small influence on the thermal stability of LLDPE, but like EnHance it strongly increased the modulus.KEY WORDS: LLDPE, paraffin wax, melt flow, thermal stability, tensile properties

Investigation of the morphology and properties of the polypropylene/low-density polyethylene/wood powder and the maleic anhydride grafted polypropylene/low-density polyethylene/wood powder polymer blend composites

The properties of polypropylene/low-density polyethylene and maleic anhydride grafted polypropylene/low-density polyethylene blends, and their wood powder composites are compared in this study. The blends contained equal amounts of polymers, and the wood powder was added into the blends to form polypropylene/low-density polyethylene/wood powder and maleic anhydride grafted polypropylene/low-density polyethylene/wood powder ternary systems. The Fourier-transform infrared analysis of the blends and composites did not provide any evidence of significant interactions between the different components, although the rest of the results clearly showed that maleic anhydride grafted polypropylene and wood powder significantly interacted, and that there was some interaction between maleic anhydride grafted polypropylene and low-density polyethylene. The differential scanning calorimetry and dynamic mechanical analysis results confirmed the immiscibility of polypropylene and low-density polyethylene, and polypropylene and maleic anhydride grafted polypropylene, and indicated that wood powder was distributed in both the low-density polyethylene and polypropylene phases in the polypropylene/low-density polyethylene blend, but most probably only in the maleic anhydride grafted polypropylene phase in the maleic anhydride grafted polypropylene/low-density polyethylene blend. The polypropylene/low-density polyethylene and maleic anhydride grafted polypropylene/low-density polyethylene blends were found to be more thermally stable than the neat polymers, while the presence of wood powder in both polymer blends further increased the thermal stability of the polymers. The blends and composites with maleic anhydride grafted polypropylene showed higher tensile modulus values and lower elongation at break values than the composites with polypropylene, while the stress at break values of the two sets of samples were comparable.Scopu

Composites of linear low density polyethylene and short sisal fibres: The effects of peroxide treatment

Influence of sisal fibre content and different concentrations of dicumyl peroxide (DCP) on the thermal, mechanical and viscoelastic properties of short sisal fibre - linear low-density polyethylene (LLDPE) composites was investigated. Significant improvement of tensile strength was found after peroxide induced grafting between fibres and PE matrix. The stress relaxation measurements also suggest better stability upon prolonged loading of the samples prepared with 1% of DCP. It was shown, on the other hand, that higher DCP concentrations could have detrimental effects on the PE matrix, especially at low fibre contents. (C) 2004 Kluwer Academic Publishers

The influence of wax content on the physical properties of low-density polyethylene-wax blends

\The influence of wax content on the thermal, mechanical and viscoelastic properties of low-density polyethylene (LDPE)-oxidized wax miscible blends have been investigated. It was found that small concentrations of wax improved physical properties such as thermal stability, elastic modulus and yield stress. At higher concentrations, however, due to crystal phase separation, wax deteriorates the thermal as well as the mechanical properties. It was also shown that a formerly established two-process model for the stress relaxation in semicrystalline polymers could be used for the explanation of the viscoelastic behaviour of the blends. (C) 2003 Society of Chemical Industry