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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Modeling of Non-Isothermal Film Blowing Process by Using Variational Principles
A recently proposed model of the film blowing process (Zatloukal and Vlcek) was generalized and consequently applied to the case of high-stalk tubular film blowing of HMW-HDPE. It was found that the proposed model has a good capability to describe and predict the relevant experimental data. In the second part of the paper, a non-isothermal version of the film blowing model is developed and tested. Finally, a novel version of the generalized Newtonian model is proposed, which allows one to take into account the effect of extensional melt rhelogy.
Investigation of PPA Interactions with Polymer Melts in Coextrusion Flows
Recently proposed new slip model based on 'effective continuum methods' was developed and used for investigation of process aids interactions with polymer melts in single as well as multi-layer flows. Specific attention has been paid to understanding the role of process aids on stabilization of the zig-zag type of interfacial instabilities in film blowing coextrusion.
Modeling of Viscoelastic Multi-Layer Flows for Different Polymer Melts
Modified Leonov model has been employed in the modeling of the coextrusion flows with same as well as differerent polymer melts. Flow visualization measurements were used for verification of the used numerical scheme. Specific attention is paid here to the possible numerical difficulties which may occur during modeling of the merging area with different polymer materials. Both, measurements as well as FEM analysis of the coextrusion flows were discussed from the wave type of interfacial instabilities point of view.
Investigation of Advanced Constitutive Equations Under Different Flow Conditions
The predictive capabilities of three models (eXtended Pom-Pom, PTT- XPP and modified Leonov model) are tested for both, steady as well as transient shear and uniaxial extensional flows of LDPE. In the second part of the paper, the modified Leonov model is employed in FEM modeling of the abrupt contraction flow and predicted stress fields are compared with the stress measurements from the flow visualization cell.
The Elimination of Weld Line Witness Marks in Injection Moulding
The surface witness marks of weld lines in injection mouldings can be particularly unsightly in certain resin compounds. This paper will describe a method that offers the potential to eliminate weld line witness marks. The process involves the combination of selectively heating the mould surface and the application of melt shearing in the mould cavity.
Shape Memory Binary Blends: Compositionally Tailored Fixing and Recovery
Semicrystalline-amorphous blends exhibit shape memory due to (1) the elastomeric nature imparted by crystallites that act as physical crosslinks and (2) temporary shape fixing made possible by the vitrification of a continuous, miscible amorphous phase. PVDF-containing binary blends were studied using calorimetry and rheology in order to characterize the morphological control afforded by subjecting such materials to different thermal histories. The sensitivity of the aforementioned techniques to changes in blend morphology will also be discussed.
Fracture Behaviour of Injection Moulding Post-Consumer Wood/Plastic Composite Foams
This study investigates fibre reinforced microcellular foams produced via injection moulding using recycled polymers. The objective is to determine the effect of wood, blowing agent and coupling agent contents on impact and tensile properties. Birch wood fibres were blended with a post-consumer HDPE/PP matrix to produce the composites. Azodicarbonamide was used as a blowing agent while maleic anhydride polypropylene copolymer was used as a compatibilizer. Optimal results were obtained with 20 wt.% wood contents.
The Effect of Sharp Corners and Runner Length on Melt Flow Imbalances
This study revealed that the use of 90 degree sharp corners has virtually no effect on mold filling imbalance. The study also found that mold fill rates can have a significant impact on the shear induced imbalances found in multi-cavity molds. Further, the study found that increasing the length of the secondary runner will initially decrease the shear induced imbalance developed in the primary runner. Continuing to increase the length has a diminishing effect on the degree the imbalance decreases.
Replication of Injection Molded Parts with Micro-Scale Features
The effects of melt viscosity and molding conditions on the replication of microscopic v-groove features in injection molded parts were examined for polycarbonate (PC). A polarized Raman spectroscopy was used to characterize the microstructure of these molded parts. It has been found that high replication of micro-scale features can be achieved by higher mold temperature and higher melt temperature even with high viscosity PC. The difference of the molecular orientation at the inside of the injection molded v-groove was observed among the different molding conditions.
Geometrical Effect and Material Selelction in Multi-Component Molding (MCM) Development
Due to its complicated nature and the unclear physical mechanism for the Multi-Component Molding (MCM) processes, conventionally the trial-and-error method can not catch the crucial factors effectively. In this study, the product geometrical effect and material selection in MCM processes have been conducted. Results showed that the product geometries and molded materials will affect the final products significantly. In addition, it can be the good guidelines to help people understand the mechanism and make the proper design to fabricate the modern MCM products.
Film-Casting Behavior as a Function of Molecular Structure and Rheology
Polyethylene resins with different molecular structures and rheological properties are investigated in terms of their performance in film-casting. Four metallocene catalyzed polyethylene resins with different degrees of long-chain branching and two conventional polyethylene resins are analyzed in terms of their dimensional changes during film production. With an increase in long-chain branching, and thus strain hardening-behavior, an increase in the necking phenomenon is observed during film-casting.
Antimicrobial Additives in Medical Plastics Compounds
Bacterial infections in hospitals are a leading cause of death in the U.S. and can be caused by bacterial growth on plastic medical devices. The purpose of this paper is to identify effects of microorganisms on plastics, discuss pros and cons of antimicrobial additives in medical plastics.
Measurement of Surface Properties of Polymeric Materials Using Nanosphere Embedment Measurements
Here we report results from our ongoing investigation of the surface properties of polymers using a nanoparticle embedment method that was originally pioneered by Teichroeb and Forrest. We describe a viscoelastic contact mechanics solution that includes surface adhesive forces and a time dependent Poisson's ratio. The results show that, with properly designed experiments, both the surface adhesion properties and the surface rheological properties can be extracted from nanosphere embedment measurements.
A Test Method for Rolling Resistance of Rubber Compounds
A test method is described for measuring energy losses in rolling, using the damped oscillations of a pendulum. The amplitude of oscillation decays initially at a constant rate, and changes to a decreasing rate as the swings become small. In principle, the two processes provide separate measures of energy dissipation. The proposed method could be used for studying the effects of surface features of tire treads and roads on tire rolling resistance, in addition to characterizing the dissipative properties of tread compounds.
High Whiteness Masking Masterbatch for Film Applications
Repro" or recycled polymer waste has been utilized in the polymer industry for years. In the manufacture of polyethylene films it is desired to introduce repro (recycled film scrap etc.) back into the film process. The recycled resin stream often contains residual inks or colorants which adversely affects the desired color of the final product when producing white films. A new masterbatch "Reproclean" has been developed to help mask the color of the recycled resin in the final film product. Results indicate that Reproclean significantly improves the whiteness and brightness indices of white polymer films."
Mechanical Properties of Foamed PP Sheet
Mechanical properties of foamed polypropylene sheet having different foaming ratios (2.0, 2.4 and 3.0) were investigated. Tensile strengths and ultimate strains of polypropylene sheet with 3.0 foaming ratio were lower than those of polypropylene sheet with 2.0 and 2.4 foaming ratios. The ultimate strain increased with an increase in the aspect ratio of the cell shape in the polypropylene sheet. The ultimate strain of the foamed polypropylene sheet was affected by the cell shape.
Thermal and Morphological Properties of Polyethylene Crystals Formed in N-Pentane Under High Pressure
The thermal and morphological properties of PE crystals formed in n-pentane at selected pressures from 10 to 54 MPa were studied using DSC and SEM. The results show that the PE crystals that form from these high-pressure conditions display a plate-like morphology which tends to aggregate into ellipsoid-shape structures. DSC studies show that the PE crystals show higher crystallinity and display multiple melting peaks during the first heating scan. This process can be an alternative method for the thermal fractionation.
Blown Films From LDPE-Organoclay and Ionomer-Organoclay Nanocomposites
Mechanical and barrier properties of LDPE and poly(ethylene-co-methacrylic acid) ionomers were improved by melt mixing them with montmorillonite based organoclays. Organoclay structure was optimized to form nanocomposites with good exfoliation, from which films were blown under different conditions.
Modeling the Transient Rheology of a Polypropylene Melt Reinforced with Long And Short Glass Fibers
In this paper we investigate the transient shear rheology of a polypropylene containing long fibers (2.75 to 11 mm, L/D > 150) and short fibers (1 mm, L/D < 50). The objectives of this work are to determine the relationship between stress growth and relaxation behavior of fiber orientation and determine the feasibility of extending Doi's theory for the rheology of rod-like molecules to fiber reinforced materials.
Chemical Attack of UV-Cure Adhesives Involving Polycarbonate
UV-cure adhesives are commonly used to assemble a variety of devices molded out of polycarbonate. This paper investigates the effect of uncured or partially cured UV adhesives on elongation-to-break performance of polycarbonate samples, both stressed and unstressed. In addition, the effect of cure time and vapor exposure on elongation-to-break is also summarized.
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