Search results for "Melt flow index"
showing 10 items of 33 documents
Long-term thermomechanical degradation of molten polystyrene
1985
Abstract Rheological data on polystyrene samples processed for long periods under various mechanical stresses are presented. The data indicate that thermomechanical degradation occurs and that the rate of thermal degradation is increased by the applied stress. Moreover degradation does not reach a limiting value even at high processing times.
Photooxidation Behavior of a LDPE/Clay Nanocomposite Monitored through Creep Measurements
2017
Creep behavior of polymer nanocomposites has not been extensively investigated so far, especially when its effects are combined with those due to photooxidation, which are usually studied in completely independent ways. In this work, the photooxidation behavior of a low density polyethylene/organomodified clay nanocomposite system was monitored by measuring the creep curves obtained while subjecting the sample to the combined action of temperature, tensile stress, and UV radiation. The creep curves of the irradiated samples were found to be lower than those of the non-irradiated ones and progressively diverging, because of the formation of branching and cross-linking due to photooxidation. …
Grafting of Maleic Anhydride onto Isotactic Polypropylene in the Presence of Supercritical Carbon Dioxide as a Solvent and Swelling Fluid
2004
Grafting of maleic anhydride (MA) onto isotactic polypropylene (iPP) was carried out by thermal decomposition of dicumylperoxide (DCP) using supercritical carbon dioxide (scCO2) as a solvent and swelling fluid. Provided that the initial concentration of anhydride dissolved in scCO2 is higher than 1% w/w, the grafting occurs without significant molecular weight modification of the polymer, and with a proper selection of the operative conditions, a grafting level higher than 0.5% w/w with respect to the polymer mass was obtained. The amount of grafted MA was determined by FT-IR spectroscopy and polymer degradation was monitored by dynamic mechanical tests in the melt state. The effect of MA a…
Prediction of the growth interface shape in industrial 300mm CZ Si crystal growth
2004
Abstract A model approach for a modification of the effective heat conductivity in the turbulent melt flow simulation for 28″ Si CZ crucibles is presented, which helped to overcome deficiencies in the growth interface shape prediction for industrial 300 mm Si CZ growth. The model has been incorporated into a CZ simulation tool based on the simulation software codes FEMAG for the global heat transfer and CFD-ACE for the turbulent melt flow simulation. The model predictions are compared to results from 300 mm Si CZ growth experiments with 200 kg charge weight in 28″ crucibles in a growth parameter range covered by standard industrial processes. The model is an engineering approach. Neverthele…
Numerical simulation and analysis of heat and mass transfer processes in metallurgical induction applications
2009
Comprehensive knowledge of the heat and mass transfer processes in the melt of induction applications is required to realize efficient metallurgical processes. Experimental and numerical studies of the melt flow in induction furnaces show that the flow pattern, which comprise several vortexes of the mean flow, and the temperature distribution in the melt are significantly influenced by low-frequency large scale flow oscillations. Two- and three-dimensional hydrodynamic calculations of the melt flow, using two-equation turbulence models based on Reynolds Averaged Navier-Stokes approach, do not predict the large scale periodic flow instabilities obtained from the experimental data. That's why…
Melt flow instability and vortex structures in Czochralski growth under steady magnetic fields
2002
Abstract The hydrodynamics of melt motion in the CZ-process of silicon single crystal growth in axial and axial–radial magnetic fields is studied using a physical model. The modeling liquid is eutectics InGaSn. Most attention is paid to the problem of flow stability. A multi-channel system gathering data is used to define the pattern and dynamics of velocity disturbances. Instant spatial distributions of the electric potential induced by motion in the melt are obtained. Temporal evolution of the instant distributions in vertical and horizontal planes of the working volume is under investigation.
Physical modelling of the melt flow during large-diameter silicon single crystal growth
2003
Abstract The reported investigations concern physical modelling of Czochralski growth of silicon large-diameter single crystals. InGaSn eutectic was used as a modelling liquid, employing actual criteria of the real process (Prandtl, Reynolds, Grashof numbers, etc.) and geometric similarity. A multi-channel measuring system was used to collect and process the temperature and flow velocity data. The investigations were focused on the study of heat transfer, in particular, the instability of the “cold zone” of the melt at the crystallization front.
Modelling of electromagnetic heating and mixing conditions in glass melt output equipment
2011
PurposeThe purpose of this paper is to investigate the outlet of a special glass melting system, which is used to control melt flow and modify flow pattern.Design/methodology/approachNumerical calculations in ANSYS and ANSYS CFX were used to study electromagnetic, thermal, hydrodynamic and chemical mixing processes, results are validated by comparison with experimental data.FindingsObtained results show that investigated approach can improve glass melt chemical homogeneity significantly – Lorentz force driven melt movement in conjunction with diffusion process ensures good mixing quality.Research limitations/implicationsThe mixing in glass melt is present only in azimuthal direction (in cyl…
Numerical 3D study of FZ growth: dependence on growth parameters and melt instability
2001
Three-dimensional modelling of the floating zone (needle-eye) crystal growth process is carried out to analyse numerically the stability of the melt flow and the influence of the crystal rotation rate and inductor slit width on the 3D flow field and on the grown crystal resistivity. The unsteadiness of the melt is simulated and it is found that for the considered growth parameters a steady-state flow can be a reasonable approximation to the unsteady melt motion. The parametric studies have shown that increasing the rotation rate essentially changes the flow pattern and weakens the rotational striations, while the inductor slit width has a more local influence on these characteristics.
Effect of stress and temperature on the thermomechanical degradation of a PE-LD/OMMT nanocomposites
2014
Thermomechanical degradation of nanocomposites is a topical issue that has not been fully investigated as demonstrated by the low number of papers available in the literature regarding this spe- cific aspect. In particular, with regards to low density polyethylene/clay nanocomposites, the degrada- tion behavior is very complex since it involves the degradation paths of both the polymer matrix and the organomodified nanoclay. In the present work, the effects of mechanical stress and temperature on the thermomechanical behavior of PE-LD/organomodified clay nanocomposites and the degradation paths were investigated by rheological, FT-IR and mechanical methods. The results have shown that the t…