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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RHEOLOGICAL EFFECTS ON FOAM PROCESSING IN ROTATIONAL MOLDING
Rheological properties of several polypropylene polymers were measured and the foam processing of these materials using chemical blowing agent was studied. Foaming was carried out in monolayer and skin-foam layer moldings. The uniaxial extensional viscosity was quantified and the foam characterized based on bulk density, bubble size, and bubble concentration. It was found that the foam processing window is determined and bounded by melt viscosity and melt elasticity. Melt strength and strain-hardening can substantially improve the foaming performance and play significant role in determining the developed morphological structure.
STUDY ON THE PROCESS PARAMETERS TO IMPROVE STRENGTH OF WPC PREPARED BY A NOVEL COMPRESSION MOLDING SYSTEM
It was found that compression molded Wood Plastic Composites (WPC) show lower strength than the extruded WPC which could be due to lower net alignment of the reinforcing fibers and lower inter-diffusion and alignment of the polymer chains due to the smaller net flow of material during processing. To test this hypothesis, a new compression molding system was developed where materials were forced to flow in one direction. Comparative strength studies of WPC, prepared by this novel compression molding system, have been presented at varying speed and temperature of die-press. The initials results seem to validate our hypothesis.
FILLER RE-AGGREGATION AND NETWORK FORMATION TIME SCALE IN EXTRUDED HIGH DENSITY POLYETHYLENE / MULTI-WALLED CARBON NANOTUBE COMPOSITES
Multi-walled carbon nanotube (MWNT) / high density polyethylene (HDPE) composites with varying amounts of carbon nanotubes were investigated and the effect of MWNT weight fraction on their electrical conductivity, crystallinity and mechanical properties is presented here. Samples were prepared by melt dilution of a HDPE masterbatch containing 20.2 wt% MWNT with varying amounts of neat HDPE. The effect of extrusion processing on the formation of an electrically conductive MWNT network in extruded samples was assessed by the addition of a low-shear annealing zone (shear rate 1-10 s-1) before final extrusion through a die and it is also discussed here.
INVESTIGATION OF THE RELATIONSHIP BETWEEN CELLULAR AND MECHANICAL PROPERTIES OF INJECTION FOAM MOLDED POLYMER COMPOSITES
Microcellular injection foam molding technology can bring a number of advantages to the existing conventional injection molded products such as lower density, material cost reduction, reduction of residual stress, better dimensional stability, reduction of cycle time, and better dispersion of fillers. However, the technology has not been fully employed yet, especially in the automotive sector, because injection foam molded parts, in general, experience a decrease in mechanical strengths. Therefore, this research studies the relationship between cellular and mechanical properties of the two common polymer composites in the automotive industry, which are glass-fiber reinforced plastics (GFRP) and wood-fiber polymer composites (WPC).
OXIDATIVE STABILITY OF VITAMIN E INFUSED, HIGHLY CROSSLINKED POLYETHYLENE FOR ORTHOPEDIC APPLICATIONS
In this paper, highly crosslinked and vitamin E infused (VITE) ultra-high molecular weight polyethylene is evaluated for mechanical properties, oxidation resistance, and wear. Testing included small punch mechanical properties, impact strength, a fatigue study, and knee wear simulator testing. The VITE material showed no evidence of oxidation and no decrease in the mechanical properties with accelerated aging. The VITE material showed an 86% reduction in wear over the control. The combination of crosslinking and vitamin E infusion produced a polyethylene material with improved wear properties and superior oxidation resistance suitable for use in orthopedic applications.
Application of Variational Asymptotical Method for Unit Cell Homogenization (VAMUCH) in the Prediction of Mechanical Properties for Microcellular Plastics
This study presents the application of Variational Asymptotical Method for Unit Cell Homogenization (VAMUCH) with a three-dimensional unit cell (UC) structure and finite element analysis for analyzing and predicting the effective elastic properties of microcellular injection molded plastics. A series of injection molded plastic samples with microcellular foamed structures were produced and their mechanical properties were compared with predicted values. The results show that for most material samples, the numerical prediction is in fairly good agreement with the experimental results, which suggests the applicability and reliability of VAMUCH in analyzing the mechanical properties of porous materials.
PRELIMINARY RESULTS IN RHEOLOGICALLY OBTAINING MODEL PARAMETERS FOR THE PURPOSE OF PREDICTING THE ORIENTATION OF CONCENTRATED LONG GLASS FIBERS IN PROCESSING FLOWS
The purpose of this research is to understand the transient fiber orientation of long glass fiber (> 1mm) reinforced polypropylene, in a well-defined simple shear flow (using a sliding plate), by determining unambiguous model parameters from rheological experiments, and to ultimately predict fiber orientation in complex processing flows. Two fiber orientation models were investigated. One model, the Folgar-Tucker model, has been particularly useful for short glass fiber systems and was used in this paper to assess its performance with long glass fibers. A second fiber orientation model, one that accounts for the flexibility of long fibers, was also investigated.
RHEOLOGICAL CHARACTERIZATION OF POLYPROPYLENE MIXED WITH SPECIALLY MODIFIED CALCIUM CARBONATE
The rheological properties of polypropylene filled with specially coated calcium carbonate were investigated in this study. CaCO3 fillers were coated in order to further improve the mechanical and flow properties of the filled polymer. A fluid energy mill (FEM) was used to simultaneously mill and coat the calcium carbonate particles. Both rotational and capillary rheometers were utilized to study the rheological impact of the coated particles. The rheological properties of the specially coated particles were compared with non-coated particles at similar concentration. Shear viscosity, dynamic viscosity and also melt flow index were determined at three different temperatures.
AGING DEPENDENT SLIP AGENT SURFACE MORPHOLOGY OF LLDPE FILMS
The ability to maintain stability of coefficient of friction (COF) for low density polyethylene (PE) films has been a persisting issue for the flexible food and specialty packaging industry. We conducted a systematic study monitoring the change on slip agent coverage and morphology change on PE film surfaces including films aged at room temperature and at elevated temperatures. We found significant change in slip agent morphology on the film surface over long aging time at room temperature. This paper describes our investigation on erucamide, a slip agent, surface coverage and its morphology changes with respect to aging time and temperatures.
RHEOLOGICAL CHARACTERIZATION OF POLYCARBONATE RESINS AND ITS APPLICATIONS
We show results of rheological testing of polycarbonate resind and its applications. Rheological characterization provides indirect measurements of materials properties, such as molar mass and molar mass distribution. Dynamic storage Gƒ?? and loss Gƒ? modulus represent elastic and viscous properties of the material. Viscosity curves give information about materials behavior under different temperatures and shear rates. Dynamic mudulus and zero shear viscosity can be used as qualitative parameters to characterize and distinguish different materials, and to predict materials performance. Rheological data can be used for process optimization and quality control.
ORDERING KINETICS OF BLOCK COPOLYMER SOLUTIONS DURING SOLVENT REMOVAL
The ordering kinetics of block copolymers in solution are studied during a solvent removal process. The kinetics of styrenic block copolymers in a neutral solvent, toluene, are tracked at various concentrations along a drying path to determine the effect of concentration on phase separation. The ordering process is modeled with the Avrami equation. Small angle X-ray scattering has been used to determine that the structures developing during solvent removal are cylinders. Scattering data also indicates that the concentrations studied by the rheology experiments are limited by the conditions under which samples are dried.
MODELING AVERAGE CAVITY TEMPERATURE USING ARTIFICIAL NEURAL NETWORKS
Average cavity temperature has been shown to be a suitable control variable in obtaining repeatable part quality. Existing control schemes for average cavity temperature use on-line and off-line identification techniques to formulate system models. These models are often linearized about a specific operating region and introduce inaccuracies in control due to process nonlinearities. This work presents an online artificial neural network black-box system identification routine to model the nonlinear dynamics of the average cavity temperature with respect to mold and process conditions.
LOW-DENSITY POLYETHYLENE COMPOSITES FILLED WITH CERAMIC FILLERS FOR ELECTRONIC PACKAGING APPLICATIONS
This study details the fabrication of linear low-density polythene (LLDPE)-based composite materials containing silicon carbide (SiC) and boron nitride (BN) filler particles. The composites were created by using a twin-screw compounder, and evaluated based on their morphology, as well as their thermal, electrical, and mechanical properties. Overall, the addition of ceramic fillers increased the thermal conductivity of the composites, without compromising the electrical resistivity, which is desirable for electronic packaging and heat management components in microelectronics.
THE MULTIFUNCTIONAL CHARACTERISTICS OF CARBONACEOUS FILLER-REINFORCED POLY(PHENYLENE SULFIDE) COMPOSITES
Poly(phenylene sulfide) (PPS) composites, reinforced by carbon fibers (CFs) and multiwall carbon nanotubes (MWCNTs), were fabricated through melt compounding. Their thermal, electrical, and mechanical properties were systematically studied as functions of filler contents and properties. The electrical percolation thresholds for CFs and MWCNTs were identified; however, the thermal percolation thresholds could not be achieved. This illustrates different requirements are needed in carbonaceous filler network to promote different functional performances of the composites.
MICROCRYSTALLINE CELLULOSE COMPOSITES OF POLY(LACTIC ACID)/POLY(ETHYLENE GLYCOL) OR POLYPROPYLENE CREATED VIA SOLID-STATE SHEAR PULVERIZATION
Hybrids of poly(lactic acid) (PLA) or polypropylene (PP) with microcrystalline cellulose (MCC) were created using solid-state shear pulverization (SSSP). For the PLA composite, this was followed with melt processing (MP) with added polyethylene glycol (PEG). We demonstrate a synergistic effect of MCC and PEG in enhancing the crystallization kinetics of PLA. Additionally, an SSSP processed 80/20 wt% PP/MCC composite was successfully injection molded into a bottle cap, which shows excellent MCC dispersion and stiffness.
SYNTHESIS AND CHARACTERIZATION OF A NOVEL, HIGHLY BROMINATED, FLAME RETARDANT POLYMER
A novel brominated polymer was synthesized from pentabromo-6-ethoxybenzene vinyl ether using cationic polymerization. The thermal and rheological properties of the polymer (i.e. PBrVE) were compared to the commercial brominated flame retardant, poly(pentabromobenzyl acrylate) (PBrBA). The glass transition temperature of PBrVE was determined to be 103 C which was 57 C lower than that of PBrBA. The higher molecular mobility of PBrVE resulted in lower melt viscosity in blends with PBT. Characterization of the PBT blends using transmission electron microscopy indicated higher compatibility between PBT and PBrVE as compared to PBT and PBrBA.
PROCESSING LINEAR POLYPROPYLENE-CLAY NANOCOMPOSITES WITH SILANE COUPLING AGENTS
Two different grades of organically modified montmorillonite were treated with several aminosilanes before compounding with a linear polypropylene (MFR=4) and a high molecular weight PP-g-MA in the same proportions in all cases. This treatment served to promote reactive coupling of the polymeric compatibilizer (PP-g-MA) to the nanolayer edges alone in some cases or to the nanolayer faces as well as edges in other cases. Edge coupling alone or coupling at the faces and edges give rise to different effects on the morphology and melt rheology ƒ??particularly strain hardening in extensional flow of the nanocomposites.
BARRIER PROPERTIES AND CHARACTERISTICS OF POLYGLYCOLIC ACID FOR UN-ORIENTED AND ORIENTED FILMS
Measurement of oxygen permeability of biodegradable polyglycolic acid (PGA) un-oriented amorphous and crystallized films, and oriented films showed superior values versus general barrier materials. The effect of orientation and crystallization was investigated, showing that oxygen permeability was dependent upon the polymer's free volume and its degree of crystallinity. By stretching an un-oriented amorphous film, PGA chains became highly oriented, resulting in increased temperatures of glass transition and tan?? peak. PGAƒ??s carbon dioxide barrier was tested using PET/PGA multilayer bottles, with 1 and 3wt% PGA bottles showing 1.5 and 2.5 times better gas barrier, respectively, versus a PET monolayer bottle.
PROPERTY RETENTION OF HIGH-FLOW MEDICAL-RESINS AFTER GAMMA-IRRADIATION
In this work, newly-introduced polycarbonate resins targeted for medical device applications, Makrolon Rx2435 and Makrolon 2258 were studied after sterilization with 30 kGy and 60 kGy gamma-irradiation. Despite characteristic color shifts and slight losses in molecular weights, the polycarbonate resins showed excellent retention of properties after irradiation up to 60 kGy. Although the polycarbonate color shifts were greater than what was observed for a medical copolyester, the copolyester yielded greater viscosity losses after sterilization. The color shifts for Makrolon point to the polycarbonate rearrangement reactions which occur upon irradiation.
CONFIRMATION AND QUANTIFICATION OF LINEAR LOW-DENSITY POLYETHYLENE (LLDPE) AND MALEATED LINEAR LOW-DENSITY POLYETHYLENE (LLDPE-g-MA) INFUSED WITH NANOCLAY IN SUPERCRITICAL CARBON DIOXIDE
Nanoclay fillers have the ability to enhance the thermo-mechanical, barrier and flame resistant properties of Linear Low-Density Polyethylene (LLDPE). One method employed to successfully disperse nanoclay powders into polymers that is both inexpensive and deemed environmentally friendly is supercritical carbon dioxide processing. With supercritical carbon dioxide processing, Cloisite 93A was infused into LLDPE and Maleated LLDPE (LLDPE-g-MA). The infusion of Cloisite 93A was confirmed by XRD and FTIR analysis. In addition, XRD analysis suggests that clay intercalation was achieved for select runs. And FTIR analysis was used to determine the amount of nanoclay infused into the polymer.
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