Band 32, Heft 4

A multivariate sensor (MVS) is described for measurement of melt temperature, melt pressure, melt velocity, and melt viscosity. Melt pressure and temperature are respectively obtained through the incorporation of a piezo-ceramic element and infrared thermopile. Melt velocity is derived from the initial response of the melt temperature as the polymer melt flows across the sensor lens. The apparent melt viscosity is then derived based on the melt velocity and the time derivative of the increasing melt pressure. The response of the MVS is analyzed using an instrumented mold including piezoelectric pressure sensors, an infrared pyrometer, and thermocouples. A 12-run, blocked half-fractional design of experiments (DOE) was run to characterize the effect of melt temperature, mold temperature, packing pressure, and ram velocity. The results show that the MVS provides excellent measurement of melt temperature and pressure. The accuracy of the melt velocity estimations depended on the ram velocity set-point, yielding a coefficient of determination of 0.91 for the lower ram velocities, and reaching saturation for melt velocities about 450 mm/s. The apparent melt viscosity estimated by the MVS are close to those predicted by the Cross-WLF model, exhibiting appropriate shear thinning but behavior but inconsistent temperature dependence.

This paper deals with the work done on friction stir welding of thermoplastic material PA 6,6. A specially designed welding tool was used for this polymer. The major process parameters like tool rotational speed, feed rate were varied to understand the physical changes of the polymer and to carry out characterization studies. In this study, an attempt was made to optimize the process parameters by using L9 orthogonal array approach. ANOVA analysis was used to explore the effect of process parameters. Tensile testing was performed to analyze the joint strength. Thus, in new exploration of using polyamide 6,6 as base material, a maximum joint strength of 37 MPa has been achieved. Optimum combination of process parameters were found by using ANOVA studies. Microstructure of the friction stir welded joints using scanning electron microscopy was done. The X-ray diffraction and the thermogravimetric analysis were done to determine the degree of crystallinity and the level of degradation of the friction stir welded joints.

The co-kneader is a particular single-screw extruder with pins fixed on the barrel, interrupted screw flights, and a screw with both rotational and reciprocating motions. The co-kneader is principally used for its excellent mixing capacities. In order to calculate the flow in the co-kneader, we developed a simplified Hele-Shaw model which takes into account the mixing pins and the reciprocating motion of the screw. In this paper we describe the model and the effects of the reciprocating motion and the presence of mixing pins on the polymer flow.

The interplay of screw speed and residence time during polymer blend extrusion profoundly influences blend properties. Herein, blends of styrene-ethylene-butylene-styrene (SEBS) and polystyrene (PS) containing 30% by weight PS were prepared at a constant feed rate but different screw speeds (50, 100, 200 and 300 min −1 ). The blend produced at 100 min −1 (B100) possessed a finer morphology, better mechanical and rheological properties, attributed to suitability of residence time and viscosity ratio. When batch foamed with carbon dioxide at 110°C and 100°C, all blends produced stable foams. B100 foams exhibited higher volume expansion ratio (VE) due to higher complex viscosity and storage modulus. When foaming was conducted at 35°C, all foams shrank. B100 foams possessed higher cell density, lower VE and showed faster shrinkage due to increased nucleation and hindered expansion by the finely dispersed stiff PS aggregates during selective foaming of the elastomeric phase.

In the current study, an assessment of the melt-compounding approach upon the behavior of blast furnace slag (BFS) filled polypropylene (PP) is reported. Two melt-compounding technologies are compared in terms of thermodynamic considerations as well as final behavior of the produced compounds. For this comparison, three PP-BFS formulations are introduced, where non-treated BFS is melt-mixed with PP via (1) internal lab mixer (IM) and (2) co-rotating twin-screw compounder (TSC). PP-BFS compounds from both processes are formed into plates via compression molding, characterized and tested for rheological, thermal and mechanical behavior. Processing parameters were evaluated for both processes such as specific shear work, residence time and shear rates. In addition, the rheological, thermal and mechanical behavior of comparable compounds are evaluated. The calculated specific shear work values for IM and TSC are 0.15 and 0.1 kW · h · kg −1 . Calculated residence time for TSC is 55 s. Regarding the rheological behavior, it was found that melt mixing via both technologies did not show major differences in complex viscosity or storage- and loss moduli values. DSC findings show that crystallization and melting temperatures of IM- and TSC formulations are comparable. Decreased strain values are noticed for TSC compounds, while tensile modulus is found to be independent of process variation.

Long fiber-reinforced thermoplastic (LFRT) composites are a very important lightweight material for practical use by the automotive industry because their mechanical performance is superior to that of short fibers. Microstructures of LFRT products, including fiber orientation state and fiber length distribution, strongly affect their mechanical properties and testing. Prior numerical approaches were limited by their inability to analyze many complex flows. Currently, the 3D numerical technology is able to analyze a varying geometry flow. We therefore aim to derive accurate predictions of fiber microstructure in a reliable 3D flow simulation of an injection molded LFRT composite part, with the use of objective fiber orientation and fiber length models. In addition, the microstructure data imported to calculate appropriate mechanical properties effectively improves the prediction accuracy of structural performance for an LFRT part. In such an integrative simulation, the predictive results are compared to related experimental data for the purpose of evaluation.

With polymer-metal hybrids becoming more commonly used as structural components it was investigated how they perform in complex environments with combined thermal, media, and mechanical loads. Special attention was put on media tightness under said loads. This paper sums up the activities of the polymer technology research group of the University of Kassel on hybrids produced by overmolding metal inserts. Investigations concerning joint strength and influence of (cyclic) temperature loads and chemical corrosion on media tightness of the joint were undertaken with different polymer-metal hybrid specimen geometries (simple and complex). In order to enhance adhesion and joint strength, different bonding agents and adhesives were used in the experiments. It could be shown that all joints of polymer-metal hybrids lost their tightness after being exposed to temperature ranges from 30 to +150°C due to their highly different thermal expansion behavior. An elastomeric intermediate layer of certain minimum thickness in order to compensate the relative movement of plastic and metal and thus maintain integrity of the joint regardless of temperatures is proposed.

In the last decades polymer sheets have been developed and used for various purposes, for example with electronic devices or solar cells. After polymer processing, they present a high residue of polymer solvent that should be reduced. Indeed, a high presence of solvent could affect their electrical properties or cause high levels of pollution. In addition, uncontrolled drying process can cause bubble formation with consequent film breakage. The aim of this work is to simplify the phenomena involved in the drying process in order to develop a mathematical model able to predict the time evolution of the composition and the mass of the polymer sheet. The model proposed here, therefore, is aimed at stimulating the industrial process and the results were verified against experimental data collected with cellulose acetate-based polymeric sheets. In addition, thanks to its simplicity and to the very low system requirements and central processing unit (CPU) time, our model gives immediate views of the system behavior.

The purpose of this paper is to shed light on how and when 3D simulations are preferable over 2D simulations in order to predict the replicated height of nanocavities via plastic injection moulding. Simulations are necessary since not all the cavity is copied depending on geometrical and injection conditions. A 3D simulation is preferable over a 2D simulation in two cases: (i) when the heat transfer through the walls parallel to the simulated domain is not negligible and (ii) when the polymer final shape is relevant. This work explains when 2D simulations like the more commonly found in the literature are not enough to obtain reliable results and how to obtain such results by means of a 3D simulation.

This study is concerned with the mathematical modelling of the vibration response characteristic of a special dissimilar composite beam based on experimental modal analysis. Here, experimental modal analyses of three different dissimilar polyamide 6 composite beams, which are connected to each other by hot plate welding are performed. The measured natural frequencies are compared with finite element predictions for verification purposes. Modal information obtained by experiments is used to construct a mathematical model representing vibration response characteristic of beams by applying multi degree of freedom curve fitting method. The model showing modal characteristics of dissimilar beams is now ready to be used in different kinds of excitations to predict the frequency response of vibration.

In this project we performed a theoretical study of the electrospinning process. The electrospinning process typically consists of two phases. For the first part, we have studied Feng's model (2003) and used Phan-Thien Tanner (PTT) rheological model instead of Giesekus model which was used by Feng. A theoretical model for the jet is derived by using a thin filament approximation, and the resulting differential equations are solved numerically. For the second part of the jet, the basis of the modeling is the bead-spring approach first proposed by Reneker et al. (2000) and we added the evaporation effect to Reneker's model. The three dimensional equations describing the dynamics of the bending of electrospun jets are derived and the calculated behavior is compared with experimental observations of jets.

This study empirically examined the influences of electrospinning process factors (applied voltage, feed rate of the polymer solution and tip-to-collector distance) and the polymer solution concentration on the diameters of electrospun polyacrylonitrile (PAN) nanofibers. To examine this, the polymer solution concentration, applied voltage, feed rate of the polymer solution and tip-to-collector distance were specified as parameters with four levels. In order to optimize these parameters, Taguchi's L 16 orthogonal design (4 parameters, 4 levels) was applied to the experiential design. In order to describe the optimum production conditions for electrospun PAN nanofibers, the signal-to-noise (S/N) ratio was used, which was calculated from the diameters of electrospun PAN nanofibers using the “smaller-the-better” approach. By using the S/N ratio response results, the most influential parameter determining the nanofiber diameter was identified as the polymer solution concentration. The nanofiber diameter at the optimum conditions was 163.6 nm. In addition, homogeneous nanofibers with no observed beads were obtained by means of the newly designed adjustable rotary plate collector. In conclusion, the Taguchi technique was seen to be an efficient technique to optimise the crucial electrospinning process factors used in nanofiber production.

Herein, we describe the synthesis of polyfuran, polyaniline, and their copolymer nanocomposites by in-situ oxidative polymerisation of corresponding monomers in the presence of montmorillonite, using ammonium persulfate as an oxidant. The obtained nanocomposites were characterised by Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and UV-vis spectroscopy.