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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Gelation of Hydroxy Propyl Cellulose with Sodium Dodecyl Sulfate: Temperature, Frequency and HPC Concentration Effects
The gelation of hydroxypropyl cellulose (HPC) solutions with an anionic surfactant was investigated. First the influence of HPC concentration (1-8%) on viscosity of water was examined. This indicated a change from Newtonian to Non-Newtonian and the development of a biphasic system. A 2 and 8% solution mixed with an anionic surfactant, sodium dodecylsulfate (SDS), was then investigated. At concentrations below the critical micelle concentration of the SDS, a peak in viscosity-concentration was observed. The concentration corresponding to the peak was found to be frequency dependent. The introduction of the SDS into HPC eliminated the biphasic structure of HPC.
Microstructure Evolution during Flow Startup of a Thermotropic Liquid Crystalline Copolyester
The microstructure evolution and corresponding transient rheological behavior of a thermotropic liquid crystalline polymer (TLCP), Vectran V400P, is reported. The structure was characterized by using a Linkam CSS- 450 shearing/hot-stage mounting on a polarized microscope. Rheological characterization in the transient mode revealed that the transient shear stress exhibited two overshoots. We believe that the domain and defect rearrangement leads to the first shear stress overshoot. The relative magnitude of the second shear stress overshoot increases with increasing shear rate and with decreasing temperature.
Small-Scale Studies of Flowing Polymer Melts within Recirculation Flowcells
Two small scale (30g and 200g full charge) recirculation flow cells have been designed, manufactured and commissioned for the study of newly synthesised novel polymers. Full field stress and velocity measurements for a number of polymer melts through two abrupt contraction dies have been made utilising stress birefringence and particle tracking velocimetry techniques. These results have been compared with those through geometrically identical contractions mounted in flow cells on 38mm and 60mm extruders in order to quantify the effects of scale up. Complimentary small angle neutron scattering (SANS) and X-ray scattering (SAXS) studies on molecular configuration and shear induced crystallisation show the usefulness of these flow cells and brief results from these experiments will be presented.
Effect of Low Temperature Shift Factor Modeling on Predicted Part Quality
The effect of low temperature modeling of the time-temperature shift factor on the prediction of residual stress and warpage of injection-compression molded compact discs is studied for an optical grade polycarbonate. Predicted residual stress and warpage with WLF and Arrhenius shift factors truncated at different temperatures indicate that the truncation temperature has a significant effect on the predicted part qualities. A double domain approach is employed to fit the shift factor with WLF function above Tg and an asymptotic function below Tg, and the simulation results are compared with the experimental observations. The comparison shows that the double domain shift factor yields good model fit and part quality prediction of injection-compression molded compact discs.
Mechanical Hole Burning Spectroscopy: A Comparison of Two Scenarios
A mechanical hole-burning (MSHB) scheme was constructed to compare the analogous observations to those from dielectric non-resonant spectral hole burning (NSHB) for glass-forming liquids near their glass transitions. We used the framework of the BKZ and Bernstein-Shokooh nonlinear viscoelastic constitutive equations to examine the modified responses in a way that does not invoke an explicit heterogeneous or homogeneous nature for the relaxation response. From the BKZ model only partial hole-burning features are observed in the modified shear modulus. The Bernstein- Shokooh model used to calculate the modified compliance shows no evidence at all of a hole-burning event. These results suggest that in addition to showing potential as a probe of dynamic heterogeneity, MSHB may also a prove to be a sensitive test for the validity of nonlinear constitutive laws.
Electron-Beam Cross-Linking and Melting of UHMWPE for Hip and Knee Replacements
Wear and damage of polyethylene are the leading causes of in vivo failure of total hip and total knee arthroplasty. Increasing the resistance of polyethylene to wear and damage has been possible by radiation crosslinking and subsequent melting. Crosslinking improves the wear resistance of this polymer, while post-irradiation melting improves the long term oxidative stability, which is the primary precursor to polyethylene damage in vivo.
Continuous Process for Recycling of Polyurethane Foam
A continuous process for decrosslinking high resiliency polyurethane foam in an extruder with ultrasonic devices was developed. Rheological, structural and NMR relaxation and diffusion characterizations of decrosslinked foam were performed. The decrosslinked foam was blended with the virgin polyurethane rubber (PUR) and cured and the blend properties were investigated.
Study of the Processability of Post-Consumer and Post-Industrial Recycled High-Impact Polystyrene
In this work, the process of recycling high-impact polystyrene, both post-consumer and post-industrial, was studied. Blends of recycled/virgin materials were made and their MFI, mechanical properties and processability (thermoforming) were evaluated. Few differences in the behavior of the materials were found and their use as thermoformed packaging was ascertained.
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.
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