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.
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The Effect of Process Aids on the Rheological Properties of Rigid PVC Melt
This work presents an overview on the role of process aids on the rheological properties of rigid PVC. A new rheological approach is introduced to allow a better assessment of the role of these additives. This system comprises a combination of a Couette-type cell and a capillary rheometer. The former allows a good control of the thermo-mechanical history of the compound prior to injection into the capillary barrel where a viscosity measurement is performed. The results showed that rigid PVC undergoes a fusion and gelation processes during the early stages of processing. In this step, the particles are agglomerated under the influence of heat and mostly shear. There seems to be an optimal morphological state where the best mechanical properties are obtained. Additional work showed that the addition of high molecular weight impact modifiers which also act as “binders” in the matrix promote the fusion and gelation of PVC. The results are supported by impact testing and microscopy.
Practical Application of a Portable Rheometer
A portable rheometer has been developed for characterizing plastic melts for different measurement purposes. The rheometer is intended particularly for use with rigid PVC processing, but can be used for other materials too. Measurements showing the accuracy of the instrument and its reproducibility are discussed. Comparisons are made between measurements on a conventional laboratory capillary rheometer and ones on the rheometer developed, using polypropylene. The practical application of the rheometer is also shown. This is used in combination with a twin-screw extrusion line to evaluate the rheological data of different pressure pipe and profile PVC formulations in order to develop new die geometries.
Microrheology and Melt Index Calculations of Polymer Melts
There is a demand for the development of techniques for viscosity measurements of very small polymer samples. Traditional rheological equipment and standard tools are limited in their capabilities to measure milligram samples of polymers. This paper outlines methods and tools used to measure the melt viscosity of polymer samples as small as 5 mg. Special, small diameter parallel plates are used to quantify the shear rheology of these samples. The data is fit to several GNF models, and the melt index is calculated from these parameters. Results from this technique are compared to results from actual melt index measurements.
Rheological Changes in CO2 Impregnated Polystyrene Reinforced with Nanoclays
The addition of small quantities of plate-like nanoclay can substantially increase the polymer melt viscosity, while adding dissolved gases such as CO2 can reduce the viscosity of a polymer melt. The combined effect of nanoclay and CO2 on polymer melt rheology was investigated for an extrusion process. The shear viscosities of polystyrene/CO2/nanoclay melts were measured using an extrusion slit die rheometer with a backpressure regulator. Our results show, without the presence of CO2, that the viscosity of the nanocomposite increases with nanoclay loading. However, when the nanocomposite melt is swelled by CO2, the nanoclay acts to reduce viscosity compared to the pure polystyrene/CO2 system. A possible explanation is that a significant amount of CO2 is adsorbed on the surface of the nanoclay to lubricate the flow due to the existence of surface modifier and a unique nanoclay particle layering structure.
A Novel Device for Characterizing Polymer Flows in Uniaxial Extension
A novel extensional rheometer has been developed for use in characterizing the flow behavior of polymers in uniaxial extension. The device has been designed as a fixture for use on a commercial rotational rheometer and incorporates dual wind-up drums that allow for a truly uniform extensional deformation during flow measurement. The miniature unit can be accommodated within the oven chamber of almost any rotational rheometer such that the extensional flow properties of filled and unfilled polymers can be measured over a very wide range of extensional rates, deformations, and temperatures. Validation results with this robust instrument are in excellent agreement with published data in the literature. These and other results indicate the potentially invaluable impact that this novel device could have as a polymer characterization tool.
An Investigation into Collection and Recycling of Blow Moulded Motor Oil Bottles in Australia
This paper presents an investigation on the strategies to increase the post consumer HDPE recycling of extrusion blow molded oil containers in Australia and proposes a novel oil drain rack designed to drain out the residual oil effectively from the used oil containers, based on the requirements of the clients.
Combined Effects of Temperature and Sulfuric Acid Exposure on the Degradation of Nylon 6,6
Temperature effects combined with the chemical effects of sulfuric acid on Nylon 6,6 result in significant degradation of the mechanical performance of the material. Several techniques including weight gain studies and neutron activation analysis (NAA) have permitted the calculation of diffusion coefficients and activation energies of diffusion as well as the modelling of the degradation over extended periods of time.
Melting Aspects of Filled Compounds in a Modular Co-Rotating Twin Screw Extruder
Polymers containing fillers are an important in the polymer compounding industry. Melting mechanisms were studied in master batched polymer compounds using an intermeshing co-rotating twin screw extruder. Calcium carbonate or aluminum powder was master batched with linear low density polyethylene. The compounds filled with particles have higher thermal conductivities and viscosities than neat polyethylene. We determined rates and mechanisms of melting of polyethylene compounds by removal and characterization of carcasses in the melting region.
Effect of Barium Sulphate on Rheological Behaviour and Mechanical Properties of Metallocene Catalysed Polyethylenes used in Medical Devices
The incorporation of radiopaque barium sulphate (BaSO4) in medical tubing products is a challenge to extrusion processers. The effect of BaSO4 concentration (0-25% by weight) on the rheology and mechanical properties of three different metallocene catalysed polyethylenes were studied. The results show significant change in melt viscosity, tensile properties and phase transition (Tan ? max) with increase in BaSO4 concentration.
Effect of Isotacticity on the Simultaneous Equibiaxial Stretching of Isotactic Polypropylene Films
A laboratory film stretcher that closely simulates the stretching conditions encountered on the industrial biaxial tenter-frame stretching process was utilized to investigate the simultaneous biaxial stretching of isotactic polypropylene films in the partly molten sate. The effects of chain tacticity of the polypropylene resins on the biaxial deformation behavior and the resulting mechanical properties were studied. Correlations were found and explained between the deformation behavior, end-film properties and the morphological characteristics of the partly molten state.
Selectivity of Extensional Viscosity Measurement under Different Conditions – Melt Elongation Versus Converging Flow
Elongational viscosity becomes more and more important due to increasing processing velocities in industrial processing. For film blowing, blow moulding and spinning process it is inevitable to consider elongational properties. The most important requirements for industrial application areFast testing with easy useHigh selectivityElongation rates similar to processingOnline measurement.Several methods of measurement have been analyzed and some are introduced on the market but not under all aspects mentioned above.First an online elongational viscosity measurement on the basis of the so called “Rheotens” is presented in this work. This method of melt elongation is then compared with converging flow method (entrance pressure loss), were different calculations of elongational viscosity are used. Different lots of polyolefine types are selected for elongational viscosity measurement. The selectivity of both methods to material differences are compared discussing measurement uncertainty.
Low-Coherence Interferometry Applied to Uniaxial Elongational Rheometry
The relevance of transient uniaxial elongational viscosity determination of polymers to industrial processes such as film blowing and foam extrusion is now being well recognized. Elongational rheometry is also beginning to be well documented, but it remains a delicate measurement technique, with reliability of the equipment and reproducibility of the data still being of prime concern.Recent developments in experimental evaluation coupled with state-of-the art optical techniques extend a step further the capabilities of generating reliable response in elongation, especially for large Hencky strains where dimensions of the sample being stretched is subjected to uncertainty. This paper will review the current approaches used and present a new way of monitoring in real time the true elongational response of polymeric materials, which exhibits enhancement of both the accuracy and the rapidness of the data acquisition.
An Evaluation of Elongational Viscosity of Polyethylenes Obtained from a Semi-Hyperbolic Die
A semi-hyperbolic (SHPB) die attached to capillary rheometer has been proposed as a method to obtain extensional viscosity data for polymer melts at high extension rates and strains. There has been very little confirmation that data obtained from this type of device is a true measure of the extensional viscosity, ?e. Values of ?e+(transient extensional viscosity) were obtained on a Münstedt device for several polyethylenes (PE) at extension rates which overlapped with those obtained from a semi-hyperbolic die. For a highly branched PE the values obtained on a SHPB die were qualitatively in agreement with those from the extensional rheometer. However, for a linear and a sparsely branched PE the values were an order of magnitude higher than those obtained from the Münstedt device. A new analysis was carried out relating the pressure drop to the extensional viscosity which included a correction term for the variation of pressure along the die wall.
Investigation of the Predictive Capability of Advanced Differential Constitutive Equations for Polymer Melts under Different Flow Conditions
The predictive capabilities of three models (modified White-Metzner model, eXtended Pom-Pom model and newly proposed modification of the Leonov model) are tested for steady shear and uniaxial extensional flows of LDPE, mLLDPE and PVB melts. The input low-shear-rate viscosity data was measured on ARES Rheometrics parallel plate rheometer, whereas RH7-2 capillary rheometer was used for the determination of shear viscosity (capillary), first normal stress coefficient (slit die) and uniaxial elongational viscosity (Cogswell method). A newly proposed ‘effective entry length correction‘ has been applied to deal with all extensional viscosity data.
Ultrasonic and NIR Determination of Filler Concentration in Polymer Melt Flows in Extrusion
The work detailed here describes techniques for improving the accuracy of previous ultrasonic methods used in determining filler concentration (up to 20 wt.%) in polymer melt flows. Results from preliminary investigation into the application of in-line transmission Fourier Transform Near Infra red (FT-NIR) for determination of filler concentration real-time during processing is also presented.
Properties and Processing of Thermal Conductive Thermoplastics
The increase of at least 60 Vol.-% high thermal conductive filler in thermoplastics is an innovative approach for direct adjustment of a plastic part´s heat transfer. The filler content and high thermal conductivity affects directly the flow- and cooling-conditions during injection moulding. The paper presents basic influencing variables onto processing an part properties and shows new ideas for the construction and intelligent injection moulding processtechnology.
The Effect of PIB Molecular Weight on the Cling Characteristics of Polyethylene/PIB Films for Stretch and Cling Film Applications
The effect of molecular weight on the migratory characteristics of polyisobutylene (PIB) additive from the bulk to the surface of a range of mono-layer and multi-layer extruded polyethylene films was analysed by FTIR-ATR and peel cling analysis. Migration rates were shown to be higher for low molecular weight additive and cling strength increased as the PIB molecular weight increased.
A Rheological Model for Thermoplastic Resins Melt
A new rheological model of polymer melt was developed to describe viscosity-shear rate curves utilizing a four parameters equation based on Guassian processes approach for regression description of melt properties. Four parameters of the model (Newtonian viscosity at “zero” shear rate, viscosity and shear rate at inflection point, and dispersion of the rate of change of the viscosity) were found to be a function of polymer chain structure, molecular weight and temperature. The model provides precision description in a wide range of conditions of shear deformation of the polymer melts, solutions, blends and alloys.
Experiments in Micro-Welding of Polycarbonate with Laser Diodes
Polymer use in micro-devices, especially in the medical industry has been rapidly increasing. During assembly of micro-devices it is desirable to produce weld joints that are about 100 ?m in width. This paper reviews the use of fiber coupled laser diodes in conjunction with special lenses to produce spot sizes between 25 and 50 ?m in diameter for through transmission infrared welding technique. Studies were completed to evaluate the effect of travel speed, power density and pressure on weld quality for polycarbonate and polystyrene. It was found that process parameters are extremely critical in producing consistent welds. In addition, new testing techniques had to be developed to allow quantitative measurements to be made on weld strength due to relatively small weld area. Micrographs of the resulting welds revealed evidence of ablation at high heat inputs. Finite element analysis of the mechanical tests showed that the localized weld strength approached the yield strength of polycarbonate.
Modeling Heat Flow for a Moving Heat Source to Describe Scan Micro-Laser Welding
Polymer use in micro-devices, especially in the medical industry has been rapidly increasing. During assembly of micro-devices it is desirable to produce weld joints that are about 100 ?m in width. This paper reviews the modeling of heat flow during through transmission infrared micro-welding of plastic using fiber coupled laser diodes. Two models were used to predict temperature distributions within welded samples. Both models were based on a moving heat source and moving coordinate system. For the simpler model a moving point heat source was used and for the more complex model a Gaussian distributed heat source was used. It was found that the distributed model can accurately predict temperature fields in plastic laser welds for all ranges of the parameters evaluated. However, the point heat source model was only able to accurately predict temperature fields with a relatively small laser focal spot (25 ?m). In addition it was found that for micro-welding of plastics, when the dimensionless distribution parameter is less than two, a point heat source model predicts similar widths to those predicted by a distributed heat source model.
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