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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A NOVEL MINIATURE MIXING DEVICE FOR POLYMERIC BLENDS AND COMPOUNDS
Polymeric compounds and blends are typically developed via a mechanical mixing process during which time the ingredients are subjected to both shear and extensional deformations. The overall integrity of said compounds strongly depends upon the shear and extensional rheological properties of the polymeric matrix. In addition, the rheological properties also control the final quality and commercial attractiveness of the final products. Often times when working with new experimental fillers and polymers, material quantities may be available in extremely limited amounts thereby constraining material compounding protocols and the physical property characterizations associated therewith. A new miniature mixer has been developed to monitor and optimize the preparation protocol of various polymeric compounds and blend systems. The effect of mixing time and other basic processing parameters on the shear and extensional rheological properties of said compounds is examined in order to understand the effect of undermixed and/or overmixed conditions on the rheological properties and thus the quality of the final products. Results from said new miniature mixer are compared with the results from other conventional mixing techniques in order to assess the scalability of the new mixing protocol.
THERMAL AND RHEOLOGICAL STABILITIES OF PE AND PP DUE TO REPEATED PELLETIZNG
It is known that polymers properties could change due to repeated exposure to high temperatures and shear during processing and recycling. In this research the rheological and thermal properties of polyethylene (PE) and polypropylene (PP) were investigated. A twin screw extruder (Farrel FTX20) was used to expose PE and PP to repeated thermal history during pelletization. PE and PP were exposed to thermal histories up to 12 times during pelletization and re-pelletization processes. The rheological and thermal properties of the virgin polymer were compared to the re-pelletized ones. It was noticed that the melt viscosity of PE increased and that of PP decreased as the polymer was exposed to repeated pelletization. Additionally, the evaluated thermal properties of those of PE were not significantly changed, whereas, those of PP were affected.
USING MELT FLOW INDEX TO CHARACTERIZE SOME RHEOLOGICAL USING MELT FLOW INDEX TO CHARACTERIZE SOME RHEOLOGICAL
This paper is a sequel to a previous publication that was presented at ANTEC '08. That paper addressed a variety of uses of the Melt Flow Index (MFI) equipment, which were achieved by changing the heating temperature, the dwell time, and load. Some of these conditions were used to judge the temperature and / or load sensitivity of polyethylene (PE) and polypropylene (PP).In the current paper we will show a new set of applications for the MFI equipment. Some of polyolefin's properties that are presented here and could be characterized by MFI equipment are; melt density, extrudate swell, and viscosity. These properties were measured and compared for high density PE (HDPE), linear low density PE (LLDPE), low density PE (LDPE), and PP.
MEASUREMENT OF THE ABRASION CAPACITY OF FLEXIBLE FOAMS FOR FINISHING CRUDE POTTERY
Ceramics processing industry employs foam materials in order to finish crude pottery because of its softness, elastic recovery, abrasion capacity, among others. At the moment, the ceramists in Colombia use marine sponge despite the increasing economic and environmental costs of this practice. This work explores the methods to produce a synthetic and feasible alternative for Colombian ceramic materials manufacturers based on morphologystructure- properties of the marine sponge and a comparison with thermoset and thermoplastic flexible foams. In addition, the abrasion capacity is calculated based on superficial quality in crude pottery by means of contact methods
WELDABILITY OF POLYLACTIC ACID SHEETS AND FILMS
In this work the weldability of PLA (Polylactic acid), a biodegradable polymer derived from corn starch was examined. Samples of biaxial oriented PLA films of various thicknesses were impulse and ultrasonic welded at various processing parameters. The results showed that relatively high weld strengths could be achieved with impulse welding over a relatively wide range of parameters. In addition, ultrasonic welding produced samples of relatively high strength too. However, while this process can be used with faster cycle times, it was less robust. In detail, ultrasonic welded samples of a thickness of 254 'm that were welded with a cycle time of 0.25 s had a average strength of approximately 160 N, while the results showed a standard deviation up to 50 N. In impulse welding samples of 100 'm thickness welded at 2 and 3 s had a strength of approximately 75 N, while the deviation was approximately 3 or 4 N. It was also seen that sample thickness affected the optimized welding parameters as well as ultimate strength. Having a thickness of 305 'm the weld of the samples had a strength of 80 N while the strength was 25-30 N at a thickness of 200 and 254 'm and a weld time of 0.15 s.
A STUDY ON LIGA NANOFABRICATION FOR SUB-WAVELENGTH OPTICS
This research focuses on the research and development to fabricate anti-reflection films within sub-micro features. The LIGA process was used to fabricate such structures in sub-micrometer scale. The e-beam writer defines the pattern of the X-ray mask. The golden absorber on the X-ray mask was fabricated by electroforming. After lithography and development, PMMA photoresistant with micro features was achieved.The micro master mold was then made by nickel electroforming. Finally, the anti-reflection films were formed by hot embossing. The micro-structures on thePMMA film were about 0.8 ?¬m wide and 5.1 ?¬m high.This film exhibited a better light anti-reflection effect.
POLYPROPYLENE - CUP CONVERSION FROM INJECTION MOLDING TO THERMOFORMING
Food containers such as cups can be made by injection molding (IM) or thermoforming (TF). Typical materials are high density polyethylene (HDPE), polypropylene (PP) and high impact polystyrene (HIPS). For many years the preferred choice for polypropylene cups was IM because it produces a high quality part with excellent part-to-part consistency. Conventional TF to make similar containers in PP results in wider dimensional tolerances. On the other hand, in-line, trimin- place thermoforming overcomes many of the limitations of conventional TF and allows for the production of high quality containers. This paper outlines the conversion from IM to trim-in-place for a 235-ml cup and compares the physical properties of cups from each process.
EXPERIMENTAL STUDY OF HOT PLATE WELDING OF POLYCARBONATE USING DISPLACEMENT VERSUS PRESSURE CONTROL
During hot plate welding the final forging phase can be controlled by either pressure or displacement. When using pressure control, the parts are placed under constant pressure thereby simultaneously squeezing and cooling the melt until the interface solidifies. In displacement control, the parts are pressed together until mechanical stops are reached and the weld cools further under no pressure. In this work, we studied contact hot plate welding of polycarbonate using low and high temperature hot plate with both pressure and displacement control. It was found that high temperature hot plate welding produced stronger joints than low temperature hot plate for both control methods.
INTEGRATION IN DESIGN AND MANUFACTURING OF POLYMER SMART DEVICES
Integration of functions in single components is pursued in order to manufacture smaller and smarter polymer micro devices at less cost, through e.g. less assembly steps. It requires integration on both product and production side. This paper addresses the use of molded interconnect device (MID) technology for the integration of electronic circuitry into polymer products. Shown will be new approaches of selective metallization for creating conductive tracks. The supply chain of MID parts is still seen as vulnerable, resulting in concerns on reliability of production and product. A solution is integration of processes in one production cell. Shown is the feasibility of integrating a surface patterning process into an injection molding tool.
ADHESION OF PROPYLENE-ETHYLENE COPOLYMERS TO POLYOLEFINS
The effect of ethylene content on the adhesion of two propylene-ethylene (P/E) copolymers to polypropylene (PP) and high density polyethylene (HDPE) was studied using microlayered coextruded tapes with tie-layer thicknesses varying from 0.1 ' 14 ?¬m. The two propyleneethylene copolymers were P/E859 (? = 0.859 g cm-3) and P/E876 (? = 0.876 g cm-3). P/E859 exhibited higher delamination toughness than P/E876 in the T-peel test and both P/E copolymers delaminated adhesively from the HDPE side. The delamination toughness of P/E859 tapes (tie-layer thickness > 0.8?¬m) increased linearly with the tie-layer thickness due to deformation of the entire tie-layer while the delamination toughness of P/E876 tapes (tielayer thickness > 0.8?¬m) was independent of the tie-layer thickness. This was attributed to the limited deformation of the tie-layer adjacent to the interface. A correlation was found between the damage zone morphology and the delamination toughness. The effect of temperature on the delamination toughness was also studied.
TRENDS IN RESEARCH ON POLYMER FOAMS
In recent years, concerns over environmental issues have led to a number of new regulations which have had a significant impact on the foams business in general and, in particular, for foams used in thermal insulation applications. Concerns over the depletion of the ozone layer and greenhouse gas emissions have led to the Montreal Protocol and measures to reduce the CO2 emissions. These regulatory issues in combination with traditional performance vs. cost issues are still driving changes in the global foams market today ' changes that are reflected both in the predictions of market growth as well as the technical demands placed on foamed products. In this paper, the expandable polystyrene (EPS) foam market is used to demonstrate the complex interactions of market forces versus technical progress when implementing successful foam products and processes for a wide-spread utilisation.
MISCIBILITY OF STATISTICAL AND BLOCK ETHYLENE-OCTENE COPOLYMER BLENDS
The miscibility of a statistical ethylene-octene copolymer (EO) with an ethylene-octene block copolymer (OBC) was studied. In general the EO/OBC blends were miscible if the octene content difference was less than about 7 mol% and immiscible above about 12 mol%. This contrasted to EO/EO blends where blends were miscible if the difference in octene content was less than about 10 mol% and immiscible above 13 mol%. Unexpectedly, OBC-rich blends (EO/OBC 30/70) displayed significantly more demixing than OBC-poor blends (70/30) even for constituents of about the same molecular weight. The octene content of the OBC soft block was varied in order to differentiate the effects of the average comonomer content from the effects of blockiness.
Comparison of Different Methods of Introducing Water as a Co-Blowing Agent in the Carbon Dioxide Extrusion Foaming Process for Polystyrene Thermal Insulation Foams
In this study, water is used as a co-blowing agent in the carbon dioxide (CO2) extrusion foaming process in a twin screw extruder. It acts as a co-blowing agent to generate larger cells and thus low density foams for thermal insulation applications. Different strategies have been studied in our group to introduce water into the foaming process. These methods include direct injection of water into the extruder with surfactants, the extrusion foaming of water expandable polystyrene (WEPS) beads, and feeding water containing activated carbon (WCAC)/polystyrene (PS) pellets. Morphology and properties of foams made by these processes are compared. It was found that WCAC/PS pellets provide the most stable and clean extrusion process, more uniform cell morphology, and better thermal insulation than other methods.
A COMPARISON OF LAYERED NANOFILLERS IN FLEXIBLE PVC
Previously, our group reported improved oxygen barrier in flexible PVC nanocomposites with 2 wt% Cloisite 30B, an organically modified montmorillonite nanofiller , and industrially relevant lead- and phthalate-free PVC / Cloisite 30B nanocomposite wire and cable formulations with enhanced acceptability . In this work, we begin with a flexible PVC formulation based on our wire and cable work but with all other fillers removed, and consider the effects of a constant loading level of 2 wt% of various commercial layered nanofillers on appearance, thermal stability and oxygen barrier. In addition to natural smectites and synthetic analogs, hydrotalcite nanofillers are investigated as well.
IMPROVING COMPATIBILITY OF BLENDS OF POLYSTYRENE AND POLY(METHYL METHACRYLATE) BY ORGANICALLY MODIFIED LAYERED-SILICATES
Equal volume fraction blends of high molecular weight PS and PMMA are thermodynamically unstable. In thin films supported on silicon, PMMA forms a continuous layer on the surface; while PS tends to move away from the surface and form discrete islands on top of the PMMA phase. The size of PS domains decreases with introduction of nanoparticles. For bulk blends, without nanoparticles, PS forms the matrix and PMMA forms the dispersed phase. For the case of 0.6 wt% silicate, in both thin film and bulk, the blend morphology converts from discrete to co-continuous.Electron micrographs reveal well dispersed silicate sheets locating at the interface between small PS domains in the PMMA phase.
ENCHANCEMENT OF SURFACE REPLICATION BY MICRO-GAS-INJECTION MOLDING
The quality of surface replication is very critical for polymeric micro fluidic devices. It, however, has been a great challenge to achieve perfect replication of micron or submicron features without creating sink marks in the injection molded parts. Gas assist injection molding (GAIM) has been employed to solve this problem with polypropylene and polymethylmethacrylate. This paper discusses the implementation of GAIM in these parts and replication as characterized using profilometry, scanning electron microscopy and confocal microscopy.
FOAMING BEHAVIOR OF MELT BLENDED POLYLACTIDE-CHITIN COMPOSITES
This study details the fabrication and foaming of melt blended polylactide (PLA) and chitin composites. The chitin used for compounding was as-received and in nano-whisker form, which were produced by an acidhydrolysis technique and their morphology was examined with Transmission Electron Microscopy. The composites were characterized for their thermal and rheological behavior. Chitin was found to decrease the thermal stability but increase the crystallinity of PLA. Addition of chitin was also found to reduce the viscosity of the composites even though chitin is a stiffer phase. The reason for this observation is believed to be due to the hydrolysis of PLA during melt blending of chitin in suspension. Foam samples were produced by a two step batch foaming technique and the expansion behavior was correlated with the visco-elastic observations.
ENHANCING THE GAS BARRIER PROPERTIES OF POLYLACTIC ACID BY MEANS OF ELECTROSPUN ULTRATHINZEIN FIBERS
Ultrathin fibers of 100-500 nm in diameter were obtained by electrospinning from an alcoholic solution of zein, a prolamine from maize. The ultrathin zein fibers generated were incorporated as a reinforcement to a poly(lactic acid)/polyethylene glycol (PLA/PEG) matrix by a proprietary method to generate a novel multilayer structure consisting of a zein fiber layer laminated in a sandwich to two PLA/PEG layers.As the zein nanofibers retained the ultrathin structure inside the resulting PLA/PEG matrix, the overall composite remained transparent and colorless. The incorporation of the zein did not significantly affect the thermal behaviour or the water permeability of the original PLA/PEG matrix, but surprisingly it did reduce the oxygen permeability of the matrix by ca. 70%. This technology could thus be potentially applied to obtain highly transparent PLA films with enhanced barrier properties of interest in for instance packaging applications.
CHARACTERIZATION OF POLYETHYLENE BLENDS IN CONSIDERATION OF EPE FOAMING
Blends of linear low density polyethylene (LLDPE), low density polyethylene (LDPE), and high density polyethylene (HDPE) have been characterized in this research work. The main purpose was to generate clear two-peaks from the expanded polyethylene (EPE) foam beads made out of these blends . The blends of 20 wt% of the minor components into LLDPE and a ternary blend of the three components were prepared in a twinscrew extruder at two levels of rotational speed: 5 and 50 rpm. The DSC measurement was carried out at two cooling rates, 5 and 50?§C/min. The results showed that blending with HDPE has a more noticeable effect on the DSC curve of LLDPE than with LDPE. Also, the rotational speed and the cooling rate affect the shape of the DSC curves and the percentage area below the onset point. DSC Characterization of the batch foamed blends revealed the existence of multiple peaks which may be mainly due to the annealing effect during the gas saturation process.
COMPARISON OF THE PREDICTED AND ACTUAL CELL DENSITIES IN STRUCTURAL FOAM MOLDING
There have been many studies on the cell nucleation behaviors in extrusion. In this paper, an effort is made to utilize the cell nucleation mechanism obtained from foam extrusion to describe that of the structural foam molding process. The mold pressure profile is recorded and used to determine the pressure drop (i.e., super-saturation) that is applied for cell nucleation during the structural foam molding process. The predicted data are compared to the actual obtained cell densities. The results indicate that a variety of cell nucleation technologies developed in extrusion foam can also be applicable to injection molding as long as cell deterioration is prevented.
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