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 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.
The Effect of Orientation on Perfluorosulfonate Ionomer Based IPMC Actuation
This paper discusses recent findings in the enhancement of actuation properties in ionic polymer metal composites through systematic manipulations of molecular organization and morphology. The preliminary results showed that there is a direct correlation between the morphology of the material and the mechanical properties.
Enhanced Performance and Processing Considerations of Modified PMMA Capstocks for Weatherable PVC Building Products
There is a need for superior weathering PVC profiles and sheet with a variety of colors and appearance. Capping PVC profiles and sheet with MODIFIED-PMMA provides many enhancements to a multi-layered PVC system, not just enhanced weatherability. This paper reviews many of the performance changes encountered from the use of MODIFIED-PMMA capstocks with PVC substrates and the variables that influence the system performance. In addition, processing considerations required for existing PVC extrusion operations are detailed as well as fabrication adjustments.
Preparation and Characterization of Polymeric Capsules Containing Functional Additives
In attempts to develop novel functional additives for thermoplastic and thermoset polymer coatings, various sizes of microcapsules containing a silicone fluid which could facilitate the release of the coating from a metallic substrate were prepared by in-situ polymerization. Fill content, size of capsules, wall-thickness, and surface morphology were observed by TGA, TEM, SEM, EDX, optical and NMR microscopy. The capsules were dispersed in polymeric coatings and the release of their content through mechanical means was followed microscopically.
Scratch Behavior of Model Polypropylene Thin Sheets
The effects of molecular weight (MW) and surface morphology on scratch behavior of model polypropylenes (PP) were investigated. The results suggest that scratch performance is improved when the MW and surface crystallinity of PP are high. Correlation between surface properties and scratch resistance of PP is established and discussed.
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