The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
The rheological properties of various TPV's have been studied in shear flow using dynamical mechanical spectrometry, capillary rheometry, transient stress buildup and shear creep. The TPV's which are commercial dynamically vulcanised PP/EPDM blends show a typical rheological behaviour with an apparent yield stress value at low shear rates, a shear-thinning viscosity at high(er) shear rates and, moreover, they do not obey the Cox-Merz law. This study revealed that the observed phenomena could be explained by the role of the three main components: PP, EPDM and oil.
A rugged new process rheometer employs a cam rotating in a cylindrical cavity containing a flush mounted pressure transducer. The cam generates excess hydrodynamic pressure in the wedge-shaped region between its outer edge and the cavity wall. As the cam passes the transducer, the measured pressure increases, reaches a maximum and then decreases. The amplitudes of the pressure fluctuations are proportional to viscosity. The shear rate of the viscosity measurement is the cam speed divided by the gap distance. The instrument continuously records and analyzes pressure versus time profiles. For dual shear rate measurements, two cams are keyed to an extruder screw or the shaft of a gear pump. For continuous shear rate sweeps, external variable speed drive motors can be used with side stream and reactor vessel versions. In-line and referee lab data are presented for typical polymers and rheometer configurations.
Polyolefins such as polypropylenes need to be stabilized effectively against UV radiation in order to have a useful product life. The use of hindered amine light stabilizers (HALS) in polypropylene fibers and molded articles has been gaining popularity. Specific applications include automotive bumpers, medical devices and polypropylene fibers for carpets. A novel method was developed to detect the presence of a hindered amine light stabilizer (HALS), based on silicon technology in polypropylene. The method consists of extracting the HALS from the polypropylene matrix followed by detection and quantification using proton NMR spectroscopy.
A theoretical method is proposed for optimum design of a crosshead annular die used for medical tubing. According to this method, the geometric variables are determined to minimize the change in gapwisely-averaged flow velocities due to the variation in flow patterns inside the transitional region of the flow channel of the die, namely the gum space. To achieve this, a numerical approach to flow analysis is put forward based upon the simplified motion and energy equations as well as the approximation of the flow channel using a series of varying annular slits, each having constant geometric parameters. Accordingly, the numerical schemes for flow analysis and design optimization are established, and the computer program is developed using Microsoft Visual C++ 6.0. For an optimum die design, the heat adhesion between the cold-fed inner tube and the hot melt during the over-extrusion is evaluated based upon the temperature rise and pressure profile of the melt in the die land. Based upon the optimum die design obtained from the method, the flow is well balanced with enhancement of extrusion quality. Also, it is found that the optimum die designs are less sensitive to extrusion conditions within a certain range.
Supercritical carbon dioxide (scCO2) was added during compounding of polystyrene and poly(methyl methacrylate) (PMMA) and the resulting morphology development was observed. The compounding took place in a twin screw extruder. Viscosity reduction of PMMA and polystyrene were measured using a slit die rheometer attached to the twin screw extruder. Carbon dioxide was added at 0.5, 1.0, 2.0 and 3.0 wt.% based on polymer melt flow rates. A viscosity reduction of up to 80% was seen with PMMA and up to 70% with polystyrene. A sharp decrease in the size of the minor (dispersed) phase was observed near the injection point of CO2. However, further compounding led to coalescence of the dispersed phase. De-mixing of the dispersed phase occurred upon CO2 venting. The resulting morphology was similar to that without the addition of CO2. Adding small amounts of fillers (e.g. carbon black, calcium carbonate, or nano-clay particles) tended to slow down the de-mixing of the polymer blend system when the CO2 was released. The comparison of morphology and mechanical properties for various polymer blends with and without CO2 considerations will be reported.
In this study the effect of polyolefin composition, i.e. ethene/propene ratio, on MA grafting and branching/crosslinking or degradation was investigated both in the melt and solution. The MA grafting content for PE and EPM was similar, but low for polymers with a high propene content. An increase of the ethene content results in a transition from degradation to branching/crosslinking.
Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or system design has been universally accepted, and the manufacturing systems continue to produce defective components during production. This paper provides an overview strategies in polymer process control, and discusses some of the difficulties posed by the complex and distributed processes. Objectives for 'intelligent' process control are presented. Finally, the potential benefits of integating product and process design are demonstrated.
Several topics will be covered in the Take Home Information" to aid the reader in a better understanding of optical brighteners use in extrusion coating applications. They include: • What is an optical brightener? • What is the mechanism? • How to formulate with optical brighteners in an extrusion coating grade copolyester resin. "
The on-line monitoring system of Raman spectroscopy was developed to monitor the grafting identification and level of grafting of glycidyl methacrylate (GMA) onto low density polyethylene (LDPE). The reactive extrusion and melting behavior of GMA and LDPE was monitored by a fiber optic probe through the glass windows mounted on the model non-intermeshing counter rotating twin screw extruder. Monitoring concentration of GMA along the screw extruder was carried out to determine the reaction level.
Obtaining high quality parts in injection molding requires the understanding of the many interactions that exist between the molding parameters. Cavity pressure and part mass are good indicators for maintaining high product quality and obtaining good machine control performance. The effect on cavity pressure and part mass was investigated by varying the molding conditions using a two-phase screw-plunger injection molding machine. The molding parameters that were perturbed included the barrel temperature, injection velocity and hold pressure. The results provided a good understanding of the effect of changing the molding conditions on cavity pressure and part mass for a two-phase injection machine.
The self-affine behavior of fracture surfaces of polypropylene, PP, and polystyrene, PS, were analyzed applying the variable bandwidth method to the height profiles generated with an atomic force microscope, AFM. The roughness exponent, ?, obtained with this method was 0.788-0.008 for PP samples and V=0.81-0.023 for PS. These results are in very good agreement with the claimed universal value of V=0.8 reported in the literature for other non-polymeric materials. Melted PP was crystallized following two different cooling rates and the crystalline surfaces were also analyzed, obtaining similar roughness exponents. This fact probably means that, for this case, the self-affine behavior could be independent of the crystallization rate.
Laser welding, an innovative, flexible technology for joining of thermoplastics, now starts to make its way from scientific laboratories into industrial series production. There has been intense research on weld strength de-pending on polymer, butt design, fillers and absorption behavior. Nevertheless, a considerable lack of knowledge concerning the fundamental relationship between the process and its influence on thermal loading of the weld plane and resulting morphology still exists. Actual results of laser transmission welding experiments - including thermal and microscopic analysis of the weld plane - could contribute to a better understanding of the process itself and to success in practical applications.
Plastic cog-wheels may run completely without lubricants. When using plastic cog-wheels a service life dependent on the application is to be guaranteed. Because the service life of the cog-wheel is limited by the wear of the flank of the cog-wheel, the specification of the wear is required for dimensioning plastic gears. Caused by frictional processes at the surface of the cog, heat is produced. Like the mechanical properties of plastics, the wear also strongly depends on temperature. Therefore, it is necessary to determine the temperature of the cog. Plastic gears are tested and the cog temperature is measured by means of a thermal camera. Polyacetal cogwheels with a modulus of 1 mm are examined. It will be shown, that the cog temperature can be calculated on the basis of heat balances with a known coefficient of friction.
Unknown properties of recycles are the problem in the field of recycling thermoplastics. The off-line determination of selected properties (basicpolymer, colour and mechanical properties) is not sufficient to qualify recyclates. Important for the characterization is an almost complete knowledge of the material properties when producing recyclates that are supposed to be competitive as construction materials. Therefore the implementation of tools for the detection and assurance of material properties on-line during extrusion is a promising conception. This presentation shows and discusses the basic ideas of on-line property determination, the achieved results of material determination, and the resulting process control.
Composite fiber of PAN and chitosan was obtained by hydration-melt spinning process. The fiber showed a fibrillar structure which can be converted easily into pulp-like structure by beating. PAN/chitosan pulp showed much higher amount of acid dye uptake than chitosan powder or activated carbon which is used for the color removal from the waste water of dyeing industry. This better sorption for the composite fiber is considered to result from the relatively large surface area due to its pulp-like shape.
This paper presents the motivation for using fiber-reinforced plastics in automotive applications and the advantages and limitations concomitant therewith. Applications of fiber-reinforced plastic components in current and future vehicles have been selected for discussion to provide examples of how these materials can be used to support the drive toward the continuous improvements in performance, energy-efficiency, manufacturing cost, and environmental conservation.
Various macrokinetic models; namely the Avrami, Tobin, and Malkin macrokinetic models, were applied to describe the kinetics of isothermal crystallization from the melt state of syndiotactic polypropylene (sPP). Data analysis was carried out using a direct data-fitting method, in which the experimental data were directly fitted to each macrokinetic model using a non-linear multi-variable regression program. The results suggested that the experimental data can be best described by the Avrami model, followed by the Malkin and Tobin models, respectively.
Binary blends of ethylene-styrene interpolymers (ESIs) were studied over a range of styrene concentration. The miscibility composition map was determined primarily from the morphology as imaged with AFM, and when possible confirmed by analysis of the Tg behavior using DMTA and DSC. A difference in styrene content of about 8 wt% marked a transition from miscible to immiscible behavior for amorphous ESIs. The miscibility criterion extended to blends of semicrystalline ESIs. It was also found that molecular weight affects the observed domain morphology.
The surface tension of a low molar mass liquid crystal (LMMLC) was measured as a function of temperature (56.0°C to 79.5°C), using the pendant drop method. The surface tension presented a behavior described by two distinct curves for the different phases (isotropic and nematic). Also the contact angles of LMMLC on plates of PS and of a liquid crystal polymer were measured at different temperatures (from 62.4°C to 89.0°C). The angle presented a discontinuity nearby the nematic to isotropic transition temperature when measured on PS, whereas it remained constant on the LCP. The interfacial tension between the LMMLC and the polymers were estimated.
Heating experiments were carried out in order to investigate the significance of the different process parameters on susceptibility to stress cracking. With the help of wetting tests, different crack lengths were generated in the heated sheet and subsequently compared with the various process parameters by means of multiple regression analysis. Another focal point is the estimation of the normal stress difference (?x – ?y) at each point of the specimen by means of 2D photoelastic stress analysis. In both cases the marked correlations between the process parameters and the phenomenon of stress cracking are recognisable, and the results can be used to minimise stress cracking.
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Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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